generic/compiler/relation_util.c

/*  ASCEND modelling environment
    Copyright (C) 1997, 2006 Carnegie Mellon University
    Copyright (C) 1993, 1994 Joseph James Zaher, Benjamin Andrew Allan
    Copyright (C) 1993 Joseph James Zaher
    Copyright (C) 1990 Thomas Guthrie Epperly, Karl Michael Westerberg

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2, or (at your option)
    any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330,
    Boston, MA 02111-1307, USA.
*//**
    @file
    Relation utility functions for Ascend

    This module defines the dimensionality checking and some other
    relation auxillaries for ASCEND.
*//*
    Last in CVS: $Revision: 1.44 $ $Date: 1998/04/23 23:51:09 $ $Author: ballan $
*/

#include <math.h>
#include <errno.h>
#include <stdarg.h>

#include "relation_util.h"

#include <utilities/ascMalloc.h>
#include <utilities/ascPanic.h>
#include <general/mathmacros.h>
#include <general/list.h>
#include <general/dstring.h>
#include "symtab.h"
#include "vlist.h"
#include "dimen_io.h"
#include "instance_enum.h"
#include "bintoken.h"
#include "find.h"
#include "atomvalue.h"
#include "instance_name.h"
#include "rel_blackbox.h"
#include "relation.h"
#include "instance_io.h"
#include "instquery.h"
#include "visitinst.h"
#include "mathinst.h"
#include "rootfind.h"
#include "func.h"
#include "parentchild.h"

#ifndef NDEBUG
#include "relation_io.h"
#endif

/*------------------------------------------------------------------------------
  DATA TYPES AND GLOBAL VARS
*/

int g_check_dimensions_noisy = 1;
#define GCDN g_check_dimensions_noisy

/** global relation pointer to avoid passing a relation recursively */
static struct relation *glob_rel;

/**
    The following global variables are used thoughout the
    functions called by RelationFindroot.

    These should probably be located at the top of this
    file alonge with glob_rel. [OK, let it be so then. -- JP]
*/
static unsigned long glob_varnum;
static int glob_done;

/* some data structurs...*/

struct dimnode {
   dim_type d;
   enum Expr_enum type;
   short int_const;
   double real_const;
   struct fraction power;
};

struct ds_soln_list {
   int length,capacity;
   double *soln;
};

/*
    Define the following if you want ASCEND to panic when it hits a
    relation error in this file. This will help with debugging (GDB).

    Comment it out for ERROR_REPORTER to be used instead.
*/
#define RELUTIL_CHECK_ABORT

/*------------------------------------------------------------------------------
  forward declarations
*/

static struct fraction real_to_frac(double real);
int ArgsForRealToken(enum Expr_enum type);
static int IsZero(struct dimnode *node);

/* bunch of support functions for RelationFindRoots */
static double RootFind(struct relation *rel, double *lower_bound, double *upper_bound,
    double *nominal,double *tolerance,unsigned long varnum,int *status);
static int CalcResidGivenValue(int *mode, int *m, unsigned long *varnum,double *val, double *u, double *f, double *g);
int RelationInvertTokenTop(struct ds_soln_list *soln_list);
int RelationInvertToken(struct relation_term **term,struct ds_soln_list *soln_list,enum safe_err *not_safe);
static void SetUpInvertTokenTop(struct relation_term **invert_side,double *value);
static int SetUpInvertToken(struct relation_term *term,struct relation_term **invert_side,double *value);
static int SearchEval_Branch(struct relation_term *term);
static void InsertBranchResult(struct relation_term *term, double value);
static void remove_soln( struct ds_soln_list *sl, int ndx);
static void append_soln( struct ds_soln_list *sl, double soln);
static struct relation *RelationTmpTokenCopy(CONST struct relation *src);
static int RelationTmpCopySide(union RelationTermUnion *old,unsigned long len,union RelationTermUnion *arr);
static struct relation *RelationCreateTmp(unsigned long lhslen, unsigned long rhslen, enum Expr_enum relop);

/* the following appear only to be used locally, so I've made them static  -- JP */

static int RelationCalcDerivative(struct Instance *i, unsigned long vindex, double *grad);
/**<
 *  This calculates the derivative of the relation df/dx (f = lhs-rhs)
 *  where x is the VINDEX-th entry in the relation's var list.
 *  The var list is a gl_list_t indexed from 1 to length.
 *  Non-zero return value implies a problem.<br><br>
 *
 *  Notes: This function is a possible source of floating point
 *         exceptions and should not be used during compilation.
 */

static enum safe_err
RelationCalcDerivativeSafe(struct Instance *i, unsigned long vindex, double *grad);
/**<
 *  Calculates the derivative safely.
 *  Non-zero return value implies a problem.
 */

#ifndef NDEBUG
static int  relutil_check_inst_and_res(struct Instance *i, double *res);
#endif

#ifndef NDEBUG
# define CHECK_INST_RES(i,res,retval) if(!relutil_check_inst_and_res(i,res)){return retval;}
#else
# define CHECK_INST_RES(i,res,retval) ((void)0)
#endif

/*------------------------------------------------------------------------------
  SOME STUFF TO DO WITH DIMENSIONS
*/

/*
    @TODO what this does needs to be documented here
*/
static void apply_term_dimensions(CONST struct relation *rel,
        struct relation_term *rt,
        struct dimnode *first,
        struct dimnode *second,
        int *con,
        int *wild
){
   enum Expr_enum type;

   switch(type=RelationTermType(rt)) {
      case e_zero:
         CopyDimensions(WildDimension(),&(first->d));
         first->real_const = 0.0;
         first->type = type;
         break;

      case e_int:
         CopyDimensions(Dimensionless(),&(first->d));
         first->int_const = (short)TermInteger(rt);
         first->type = type;
         break;

      case e_real:
         CopyDimensions(TermDimensions(rt),&(first->d));
         first->real_const = TermReal(rt);
         first->type = type;
         break;

      case e_var: {
         struct Instance *var = RelationVariable(rel,TermVarNumber(rt));
         CopyDimensions(RealAtomDims(var),&(first->d));
         first->type = type;
         break;
      }
      case e_func: {
         enum Func_enum id = FuncId(TermFunc(rt));
         switch( id ) {
            case F_ABS:
            case F_HOLD:
               /* no checking or scaling */
               break;

            case F_SQR:
               /* no checking, just simple scaling */
               first->d = ScaleDimensions(&(first->d),CreateFraction(2,1));
               break;

            case F_CUBE:
               /* no checking, just simple scaling */
               first->d = ScaleDimensions(&(first->d),CreateFraction(3,1));
               break;

            case F_SQRT:
               /* no checking, just simple scaling */
               first->d = ScaleDimensions(&(first->d),CreateFraction(1,2));
               break;

            case F_CBRT:
               /* no checking, just simple scaling */
               first->d = ScaleDimensions(&(first->d),CreateFraction(1,3));
               break;

            case F_EXP:
            case F_LN:
            case F_LNM:
            case F_LOG10:
#ifdef HAVE_ERF
            case F_ERF:
#endif /* HAVE_ERF */
            case F_SINH:
            case F_COSH:
            case F_TANH:
            case F_ARCSINH:
            case F_ARCCOSH:
            case F_ARCTANH:
               /**
                ***  first must now be dimensionless.  It will
                ***  end up dimensionless as well.
                **/
               if( IsWild(&(first->d)) && !IsZero(first) ) {
                  if( !*wild ) *wild = TRUE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR:  Relation has wild dimensions\n");
                    FPRINTF(ASCERR,"        in function %s.\n",
                      FuncName(TermFunc(rt)));
                  }
               } else if( !IsWild(&(first->d)) &&
                         CmpDimen(&(first->d),Dimensionless()) ) {
                  if( *con ) *con = FALSE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR:  Function %s called with\n",
                      FuncName(TermFunc(rt)));
                    FPRINTF(ASCERR,"        dimensions ");
                    WriteDimensions(ASCERR,&(first->d));
                    FPRINTF(ASCERR,".\n");
                  }
               }
               CopyDimensions(Dimensionless(),&(first->d));
               break;

            case F_SIN:
            case F_COS:
            case F_TAN: {
               /**
                ***  first must now be of dimension D_PLANE_ANGLE.
                ***  It will then be made dimensionless.
                **/
               if( IsWild(&(first->d)) && !IsZero(first) ) {
                  if( !*wild ) *wild = TRUE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR:  Relation has wild dimensions\n");
                    FPRINTF(ASCERR,"        in function %s.\n",
                      FuncName(TermFunc(rt)) );
                  }
               }else{
                 if( !IsWild(&(first->d)) &&
                         CmpDimen(&(first->d),TrigDimension()) ) {
                  if( *con ) *con = FALSE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR:  Function %s called with\n",
                      FuncName(TermFunc(rt)));
                    FPRINTF(ASCERR,"        dimensions ");
                    WriteDimensions(ASCERR,&(first->d));
                    FPRINTF(ASCERR,".\n");
                  }
                 }
               }
               CopyDimensions(Dimensionless(),&(first->d));
               break;
            }

            case F_ARCSIN:
            case F_ARCCOS:
            case F_ARCTAN:
               /**
                ***  first must now be dimensionless.  It will
                ***  end up with dimension D_PLANE_ANGLE
                **/
               if( IsWild(&(first->d)) && !IsZero(first) ) {
                  if( !*wild ) *wild = TRUE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR:  Relation has wild dimensions\n");
                    FPRINTF(ASCERR,"        in function %s.\n",
                      FuncName(TermFunc(rt)));
                  }
               } else if( !IsWild(&(first->d)) &&
                         CmpDimen(&(first->d),Dimensionless()) ) {
                  if( *con ) *con = FALSE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR:  Function %s called with\n",
                      FuncName(TermFunc(rt)));
                    FPRINTF(ASCERR,"        dimensions ");
                    WriteDimensions(ASCERR,&(first->d));
                    FPRINTF(ASCERR,".\n");
                  }
               }
               CopyDimensions(TrigDimension(),&(first->d));
               break;
         }
         first->type = type;
         break;
      }

      case e_uminus:
         first->type = type;
         break;

      case e_times:
         first->d = AddDimensions(&(first->d),&(second->d));
         first->type = type;
         break;

      case e_divide:
         first->d = SubDimensions(&(first->d),&(second->d));
         first->type = type;
         break;

      case e_power: /* fix me and add ipower */
         if( IsWild(&(second->d)) && !IsZero(second) ) {
            if( !*wild ) *wild = TRUE;
            if (GCDN) {
              FPRINTF(ASCERR,"ERROR:  Relation has wild dimensions\n");
              FPRINTF(ASCERR,"        in exponent.\n");
            }
         } else if( !IsWild(&(second->d)) &&
                   CmpDimen(&(second->d),Dimensionless()) ) {
            if( *con ) *con = FALSE;
            if (GCDN) {
              FPRINTF(ASCERR,"ERROR:  Exponent has dimensions ");
              WriteDimensions(ASCERR,&(second->d));
              FPRINTF(ASCERR,".\n");
            }
         }
         CopyDimensions(Dimensionless(),&(second->d));
         switch( second->type ) {
            case e_int:
               if( !IsWild(&(first->d)) &&
                  CmpDimen(&(first->d),Dimensionless()) ) {
                  struct fraction power;
                  power = CreateFraction(second->int_const,1);
                  first->d = ScaleDimensions(&(first->d),power);
               }
               break;

            case e_real:
               if( !IsWild(&(first->d)) &&
                  CmpDimen(&(first->d),Dimensionless()) ) {
                  struct fraction power;
                  power = real_to_frac(second->real_const);
                  first->d = ScaleDimensions(&(first->d),power);
               }
               break;

            /* what about e_zero? */
            default:
               if( IsWild(&(first->d)) && !IsZero(first) ) {
                  if( !*wild ) *wild = TRUE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR: Relation has wild dimensions\n");
                    FPRINTF(ASCERR,"       raised to a non-constant power.\n");
                  }
               } else if( !IsWild(&(first->d)) &&
                         CmpDimen(&(first->d),Dimensionless()) ) {
                  if( *con ) *con = FALSE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR:  Dimensions ");
                    WriteDimensions(ASCERR,&(first->d));
                    FPRINTF(ASCERR," are\n");
                    FPRINTF(ASCERR,"       raised to a non-constant power.\n");
                  }
               }
               CopyDimensions(Dimensionless(),&(first->d));
               break;

         }
         first->type = type;
         break;

      case e_plus:
      case e_minus:
         if( IsWild(&(first->d)) && IsZero(first) ) {
            /* first wild zero */
            CopyDimensions(&(second->d),&(first->d));
            first->type = second->type;
            if( second->type==e_int )
               first->int_const = second->int_const;
            if( second->type==e_real )
               first->real_const = second->real_const;
         } else if( IsWild(&(first->d)) && !IsZero(first) ) {
            /* first wild non-zero */
            if( IsWild(&(second->d)) && !IsZero(second) ) {
               /* second wild non-zero */
               if( !*wild ) *wild = TRUE;
               if (GCDN) {
                 FPRINTF(ASCERR,"ERROR:  %s has wild dimensions on\n",
                       type==e_plus ? "Addition":"Subtraction");
                 FPRINTF(ASCERR,"        left and right hand sides.\n");
               }
               first->type = type;
            } else if( !IsWild(&(second->d)) ) {
               /* second not wild */
               if( !*wild ) *wild = TRUE;
               if (GCDN) {
                 FPRINTF(ASCERR,"ERROR:  %s has wild dimensions on\n",
                       type==e_plus ? "Addition":"Subtraction");
                 FPRINTF(ASCERR,"        left hand side.\n");
               }
               CopyDimensions(&(second->d),&(first->d));
               first->type = type;
            }
         } else if( !IsWild(&(first->d)) ) {
            /* first not wild */
            if( IsWild(&(second->d)) && !IsZero(second) ) {
               /* second wild non-zero */
               if( !*wild ) *wild = TRUE;
               if (GCDN) {
                 FPRINTF(ASCERR,"ERROR:  %s has wild dimensions on\n",
                       type==e_plus ? "Addition":"Subtraction");
                 FPRINTF(ASCERR,"        right hand side.\n");
               }
               first->type = type;
            } else if ( !IsWild(&(second->d)) ) {
               /* second not wild */
               if( CmpDimen(&(first->d),&(second->d)) ) {
                  if( *con ) *con = FALSE;
                  if (GCDN) {
                    FPRINTF(ASCERR,"ERROR:  %s has dimensions ",
                      type==e_plus ? "Addition":"Subtraction");
                    WriteDimensions(ASCERR,&(first->d));
                    FPRINTF(ASCERR," on left\n");
                    FPRINTF(ASCERR,"        and dimensions ");
                    WriteDimensions(ASCERR,&(second->d));
                    FPRINTF(ASCERR," on right.\n");
                  }
               }
               first->type = type;
            }
         }
         break;

      default:
         FPRINTF(ASCERR,"ERROR:  Unknown relation term type.\n");
         if( *con ) *con = FALSE;
         first->type = type;
         break;
   }
}

/**
    @TODO what this does needs to be documented here
*/
int RelationCheckDimensions(struct Instance *relinst, dim_type *dimens)
{
  CONST struct relation *rel;
  enum Expr_enum reltype= 0;
  struct dimnode *stack, *sp;
  CONST dim_type* lhsdim;
  struct Instance * lhs;
  int consistent = TRUE;
  int wild = FALSE;
  unsigned long c, len;

  rel = GetInstanceRelation(relinst, &reltype);
  if ( !IsWild(RelationDim(rel)) ) { /* don't do this twice */
    CopyDimensions(RelationDim(rel),dimens);
    return 2;
  }
  if (reltype == e_glassbox || reltype == e_opcode) {
    return 0;
  }
  if (reltype == e_blackbox) {
    lhs = BlackBoxGetOutputVar(rel);
    lhsdim = RealAtomDims(lhs);
    CopyDimensions(lhsdim,dimens);
    return( !IsWild(dimens) );
  }
  /* else token relation */
  sp = stack = (struct dimnode *)
    ascmalloc(RelationDepth(rel)*sizeof(struct dimnode));
  switch( RelationRelop(rel) ) {
  case e_less:
  case e_lesseq:
  case e_greater:
  case e_greatereq:
  case e_equal:
  case e_notequal:
     /* Working on the left-hand-side */
    len = RelationLength(rel,TRUE);
    for( c = 1; c <= len; c++ ) {
      struct relation_term *rt;
      rt = (struct relation_term *)RelationTerm(rel,c,TRUE);
      sp += 1-ArgsForRealToken(RelationTermType(rt));
      apply_term_dimensions(rel,rt,sp-1,sp,&consistent,&wild);
    } /* stack[0].d contains the dimensions of the lhs expression */

    /* Now working on the right-hand_side */
    len = RelationLength(rel,FALSE);
    for( c = 1; c <= len; c++ ) {
      struct relation_term *rt;
      rt = (struct relation_term *) RelationTerm(rel,c,FALSE);
      sp += 1-ArgsForRealToken(RelationTermType(rt));
      apply_term_dimensions(rel,rt,sp-1,sp,&consistent,&wild);
    } /* stack[1].d contains the dimensions of the rhs expression */

    if( IsWild(&(stack[0].d)) || IsWild(&(stack[1].d)) ) {
      if( IsWild(&(stack[0].d)) && !IsZero(&(stack[0])) ) {
        if( !wild ) wild = TRUE;
        if (GCDN) {
          FPRINTF(ASCERR,"ERROR:  Relation has wild dimensions\n");
          FPRINTF(ASCERR,"        on left hand side.\n");
        }
      }
      if( IsWild(&(stack[1].d)) && !IsZero(&(stack[1])) ) {
        if( !wild ) wild = TRUE;
        if (GCDN) {
          FPRINTF(ASCERR,"ERROR:  Relation has wild dimensions\n");
          FPRINTF(ASCERR,"        on right hand side.\n");
        }
      }
    }else{
      if( CmpDimen(&(stack[0].d),&(stack[1].d)) ) {
        if( consistent ) consistent = FALSE;
        if (GCDN) {
          FPRINTF(ASCERR,"ERROR:  Relation has dimensions ");
          WriteDimensions(ASCERR,&(stack[0].d));
          FPRINTF(ASCERR," on left\n");
          FPRINTF(ASCERR,"        and dimensions ");
          WriteDimensions(ASCERR,&(stack[1].d));
          FPRINTF(ASCERR," on right.\n");
        }
      }
    }
    break;
  case e_maximize:
  case e_minimize:
    /* Working on the left-hand-side */
    len = RelationLength(rel,TRUE);
    for( c = 1; c <= len; c++ ) {
      struct relation_term *rt;
      rt = (struct relation_term *) RelationTerm(rel,c,TRUE);
      sp += 1-ArgsForRealToken(RelationTermType(rt));
      apply_term_dimensions(rel,rt,sp-1,sp,&consistent,&wild);
    } /* stack[0].d contains the dimensions of the lhs expression */

    if( IsWild(&(stack[0].d)) && !IsZero(&(stack[0])) ) {
      if( !wild ) wild = TRUE;
      if (GCDN) {
        FPRINTF(ASCERR,"ERROR:  Objective has wild dimensions.\n");
      }
    }
    break;

  default:
    FPRINTF(ASCERR,"ERROR:  Unknown relation type.\n");
    if( consistent ) consistent = FALSE;
    break;
  }
  CopyDimensions(&(stack[0].d),dimens);
  ascfree(stack);
  return( consistent && !wild );
}

/*------------------------------------------------------------------------------
  CALCULATION FUNCTIONS
*/

/** @NOTE ANY function calling RelationBranchEvaluator should set
   glob_rel to point at the relation being evaluated.  The calling
   function should also set glob_rel = NULL when it is done.
*/
static double RelationBranchEvaluator(struct relation_term *term)
{
  assert(term != NULL);
  switch(RelationTermType(term)) {
  case e_func:
     /* CONSOLE_DEBUG("Evaluating term using FuncEval..."); */
    return FuncEval(TermFunc(term),
      RelationBranchEvaluator(TermFuncLeft(term)) );
  case e_var:
    return TermVariable(glob_rel , term);
  case e_int:
    return (double)TermInteger(term);
  case e_real:
    return TermReal(term);
  case e_zero:
    return 0.0;
  case e_plus:
    return (RelationBranchEvaluator(TermBinLeft(term)) +
      RelationBranchEvaluator(TermBinRight(term)));
  case e_minus:
    return (RelationBranchEvaluator(TermBinLeft(term)) -
      RelationBranchEvaluator(TermBinRight(term)));
  case e_times:
    return (RelationBranchEvaluator(TermBinLeft(term)) *
      RelationBranchEvaluator(TermBinRight(term)));
  case e_divide:
    return (RelationBranchEvaluator(TermBinLeft(term)) /
      RelationBranchEvaluator(TermBinRight(term)));
  case e_power:
  case e_ipower:
    return pow( RelationBranchEvaluator(TermBinLeft(term)) ,
               RelationBranchEvaluator(TermBinRight(term)) );
  case e_uminus:
    return - RelationBranchEvaluator(TermBinLeft(term));
  default:
    FPRINTF(ASCERR, "error in RelationBranchEvaluator routine\n");
    FPRINTF(ASCERR, "relation term type not recognized\n");
    return 0.0;
  }
}

/**
    This function is passed a relation pointer, r, a pointer, pos, to a
    position in the postfix version of the relation (0<=pos<length), and
    a flag, lhs, telling whether we are interested in the left(=1) or
    right(=0) side of the relation.  This function will tranverse and
    evaluate the subtree rooted at pos and will return the value as a
    double.  To do its evaluation, this function goes backwards through
    the postfix representation of relation and calls itself at each
    node--creating a stack of function calls.

    @NOTE: This function changes the value of pos---to the position of
    the deepest leaf visited
*/
static double
RelationEvaluatePostfixBranch(CONST struct relation *r,
                              unsigned long *pos,
                              int lhs)
{
  CONST struct relation_term *term; /* the current term */
  CONST struct Func *funcptr;       /* a pointer to a function */
  double x, y;                      /* temporary values */

  term = NewRelationTerm(r, *pos, lhs);
  assert(term != NULL);
  switch( RelationTermType(term) ) {
  case e_zero:
  case e_real:
    return TermReal(term);
  case e_int:
    return TermInteger(term);
  case e_var:
    return TermVariable(r, term);
  case e_plus:
    (*pos)--;
    y = RelationEvaluatePostfixBranch(r, pos, lhs); /* y==right-side of '+' */
    (*pos)--;
    return RelationEvaluatePostfixBranch(r, pos, lhs) + y;
  case e_minus:
    (*pos)--;
    y = RelationEvaluatePostfixBranch(r, pos, lhs); /* y==right-side of '-' */
    (*pos)--;
    return RelationEvaluatePostfixBranch(r, pos, lhs) - y;
  case e_times:
    (*pos)--;
    y = RelationEvaluatePostfixBranch(r, pos, lhs); /* y==right-side of '*' */
    (*pos)--;
    return RelationEvaluatePostfixBranch(r, pos, lhs) * y;
  case e_divide:
    (*pos)--;
    y = RelationEvaluatePostfixBranch(r, pos, lhs); /* y is the divisor */
    (*pos)--;
    return RelationEvaluatePostfixBranch(r, pos, lhs) / y;
  case e_power:
    (*pos)--;
    y = RelationEvaluatePostfixBranch(r, pos, lhs); /* y is the power */
    (*pos)--;
    x = RelationEvaluatePostfixBranch(r, pos, lhs); /* x is the base */
    return pow(x, y);
  case e_ipower:
    (*pos)--;
    y = RelationEvaluatePostfixBranch(r, pos, lhs); /* y is the power */
    (*pos)--;
    x = RelationEvaluatePostfixBranch(r, pos, lhs); /* x is the base */
    return asc_ipow(x, (int)y);
  case e_uminus:
    (*pos)--;
    return -1.0 * RelationEvaluatePostfixBranch(r, pos, lhs);
  case e_func:
    funcptr = TermFunc(term);
    (*pos)--;
    return FuncEval(funcptr, RelationEvaluatePostfixBranch(r, pos, lhs));
  default:
    ASC_PANIC("unrecognised relation type");
    break;
  }
}

#define RECURSE RelationEvaluatePostfixBranchSafe
static double
RelationEvaluatePostfixBranchSafe(CONST struct relation *r,
                                  unsigned long *pos,
                                  int lhs,
                                  enum safe_err *serr
){
  CONST struct relation_term *term; /* the current term */
  double x, y;                      /* temporary values */

  term = NewRelationTerm(r, *pos, lhs);
  assert(term != NULL);
  switch( RelationTermType(term) ) {
  case e_zero:
  case e_real:
    return TermReal(term);
  case e_int:
    return TermInteger(term);
  case e_var:
    return TermVariable(r, term);
  case e_plus:
    (*pos)--; y = RECURSE(r, pos, lhs, serr); /* = RHS of '+' */
    (*pos)--; return safe_add_D0(RECURSE(r,pos,lhs,serr), y, serr);
  case e_minus:
    (*pos)--; y = RECURSE(r, pos, lhs, serr); /* = RHS of '-' */
    (*pos)--; return safe_sub_D0(RECURSE(r,pos,lhs,serr), y, serr);
  case e_times:
    (*pos)--; y = RECURSE(r, pos, lhs, serr); /* = RHS of '*' */
    (*pos)--; return safe_mul_D0(RECURSE(r,pos,lhs,serr), y, serr);
  case e_divide:
    (*pos)--; y = RECURSE(r, pos, lhs, serr); /* = the divisor (RHS of '/') */
    (*pos)--; return safe_div_D0(RECURSE(r,pos,lhs,serr), y, serr);
  case e_power:
    (*pos)--; y = RECURSE(r, pos, lhs, serr); /* = the power (RHS of '^') */
    (*pos)--; x = RECURSE(r, pos, lhs, serr); /* = the base */
    return safe_pow_D0(x, y, serr);
  case e_ipower:
    (*pos)--; y = RECURSE(r, pos, lhs, serr); /* y is the power (RHS of '^') */
    (*pos)--; x = RECURSE(r, pos, lhs, serr); /* x is the base */
    return safe_ipow_D0(x, (int)y, serr);
  case e_uminus:
    (*pos)--; return -1.0 * RECURSE(r, pos, lhs, serr);
  case e_func:
    (*pos)--; return FuncEvalSafe(TermFunc(term),RECURSE(r,pos,lhs,serr),serr);
  default:
    ASC_PANIC("Unknown relation term type");
  }
}
#undef RECURSE

/**
    Yet another function for calculating the residual of a relation.
    This function also uses the postfix version of the relations, but it
    manages a stack(array) of doubles and calculates the residual in this
    stack; therefore the function is not recursive.  If the funtion
    cannot allocate memory for its stack, it returns 0.0, so there is
    currently no way of knowing if this function failed.
*/
static double
RelationEvaluateResidualPostfix(CONST struct relation *r)
{
  unsigned long t;       /* the current term in the relation r */
  int lhs;               /* looking at left(=1) or right(=0) hand side */
  double *res_stack;     /* the stack we use for evaluating the residual */
  long s = -1;           /* the top position in the stacks */
  unsigned long length_lhs, length_rhs;
  CONST struct relation_term *term;
  CONST struct Func *funcptr;


  length_lhs = RelationLength(r, 1);
  length_rhs = RelationLength(r, 0);
  if( (length_lhs+length_rhs) == 0 ) return 0.0;

  /* create the stacks */
  res_stack = tmpalloc_array((1+MAX(length_lhs,length_rhs)),double);
  if( res_stack == NULL ) return 0.0;

  lhs = 1;
  t = 0;
  while (1) {
    if( lhs && (t >= length_lhs) ) {
      /* finished processing left hand side, switch to right if it exists */
      if( length_rhs ) {
        lhs = t = 0;
      }
      else {
        /* do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_rhs==0), the
         * length_lhs must be > 0, thus s>=0
         */
        return (res_stack[s]);
      }
    }
    else if( (!lhs) && (t >= length_rhs) ) {
      /* finished processing right hand side */
      if( length_lhs ) {
        /* we know length_lhs and length_rhs are both > 0, since if
         * length_rhs == 0, we would have exited above.
         */
        return (res_stack[s-1] - res_stack[s]);
      }
      else {
        /* do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_lhs==0), the
         * length_rhs must be > 0, thus s>=0
         */
        return (-1.0 * res_stack[s]);
      }
    }

    term = NewRelationTerm(r, t++, lhs);
    switch( RelationTermType(term) ) {
    case e_zero:
      s++;  res_stack[s] = 0.0;  break;
    case e_real:
      s++;  res_stack[s] = TermReal(term);  break;
    case e_int:
      s++;  res_stack[s] = TermInteger(term);  break;
    case e_var:
      s++;  res_stack[s] = TermVariable(r, term);  break;
    case e_plus:
      res_stack[s-1] += res_stack[s];  s--;  break;
    case e_minus:
      res_stack[s-1] -= res_stack[s];  s--;  break;
    case e_times:
      res_stack[s-1] *= res_stack[s];  s--;  break;
    case e_divide:
      res_stack[s-1] /= res_stack[s];  s--;  break;
    case e_uminus:
      res_stack[s] *= -1.0;  break;
    case e_power:
    case e_ipower:
      res_stack[s-1] = pow(res_stack[s-1], res_stack[s]);  s--;  break;
    case e_func:
      funcptr = TermFunc(term);
      res_stack[s] = FuncEval(funcptr, res_stack[s]);
      break;
    default:
      ASC_PANIC("Unknown relation term type");
    }
  }
}

/*------------------------------------------------------------------------------
  GRADIENT AND DERIVATIVE CALCULATIONS
*/

/**
    Compute residuals and gradients for a relation (compiler-side routine)

    @param r relation for which residual and gradients are to be calculated.
    @param residual pointer to a double in which the residual shall be stored (must have already been allocated)
    @param gradient pointer to an array of doubles where the gradients can be stored (must already have been allocated)

    @return 0 on success, 1 on out-of-memeory.

    Computes the gradients by maintaining n stacks, where
        n = (number-of-variables-in-r + 1)
    The +1 is for the residual.  The stacks come from a single array which
    this function gets by calling tmpalloc_array.  Two macros are defined
    to make referencing this array easier.
*/
static int
RelationEvaluateResidualGradient(CONST struct relation *r,
                                 double *residual,
                                 double *gradient)
{
  unsigned long t;       /* the current term in the relation r */
  unsigned long num_var; /* the number of variables in the relation r */
  unsigned long v;       /* the index of the variable we are looking at */
  int lhs;               /* looking at left(=1) or right(=0) hand side of r */
  double *stacks;        /* the memory for the stacks */
  unsigned long stack_height; /* height of each stack */
  long s = -1;           /* the top position in the stacks */
  double temp, temp2;    /* temporary variables to speed gradient calculatns */
  unsigned long length_lhs, length_rhs;
  CONST struct relation_term *term;
  CONST struct Func *fxnptr;

  num_var = NumberVariables(r);
  length_lhs = RelationLength(r, 1);
  length_rhs = RelationLength(r, 0);
  if( (length_lhs + length_rhs) == 0 ) {
    for( v = 0; v < num_var; v++ ) gradient[v] = 0.0;
    ERROR_REPORTER_HERE(ASC_PROG_WARNING,"Relation with no LHS and no RHS: returning residual 0");
    *residual = 0.0;
    return 0;
  }
  else {
    stack_height = 1 + MAX(length_lhs,length_rhs);
  }

  /* create the stacks */
  stacks = tmpalloc_array(((num_var+1)*stack_height),double);
  if( stacks == NULL ) return 1;

#define res_stack(s)    stacks[(s)]
#define grad_stack(v,s) stacks[((v)*stack_height)+(s)]

  lhs = 1;
  t = 0;
  while(1) {
    if( lhs && (t >= length_lhs) ) {
      /* need to switch to the right hand side--if it exists */
      if( length_rhs ) {
        lhs = t = 0;
      }
      else {
        /* Set the pointers we were passed to the tops of the stacks.
         * We do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_rhs==0), the
         * length_lhs must be > 0, thus s>=0
         */
        for( v = 1; v <= num_var; v++ ) gradient[v-1] = grad_stack(v,s);
        *residual = res_stack(s);
        return 0;
      }
    }
    else if( (!lhs) && (t >= length_rhs) ) {
      /* we have processed both sides, quit */
      if( length_lhs ) {
        /* Set the pointers we were passed to lhs - rhs
         * We know length_lhs and length_rhs are both > 0, since if
         * length_rhs == 0, we would have exited above.
         */
        for( v = 1; v <= num_var; v++ ) {
          gradient[v-1] = grad_stack(v,s-1) - grad_stack(v,s);
        }
        *residual = res_stack(s-1) - res_stack(s);
        return 0;
      }
      else {
        /* Set the pointers we were passed to -1.0 * top of stacks.
         * We do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_lhs==0), the
         * length_rhs must be > 0, thus s>=0
         */
        for( v = 1; v <= num_var; v++ ) {
          gradient[v-1] = -grad_stack(v,s);
        }
        *residual = -res_stack(s);
        return 0;
      }
    }

    term = NewRelationTerm(r, t++, lhs);
    switch( RelationTermType(term) ) {
    case e_zero:
      s++;
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = 0.0;
      res_stack(s) = 0.0;
      break;
    case e_real:
      s++;
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = 0.0;
      res_stack(s) = TermReal(term);
      break;
    case e_int:
      s++;
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = 0.0;
      res_stack(s) = TermInteger(term);
      break;
    case e_var:
      s++;
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = 0.0;
      grad_stack(TermVarNumber(term),s) = 1.0;
      res_stack(s) = TermVariable(r, term);
      break;
    case e_plus:
      /* d(u+v) = du + dv */
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s-1) += grad_stack(v,s);
      res_stack(s-1) += res_stack(s);
      s--;
      break;
    case e_minus:
      /* d(u-v) = du - dv */
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s-1) -= grad_stack(v,s);
      res_stack(s-1) -= res_stack(s);
      s--;
      break;
    case e_times:
      /* d(u*v) = u*dv + v*du */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1) = ((res_stack(s-1) * grad_stack(v,s)) +
                             (res_stack(s) * grad_stack(v,s-1)));
      }
      res_stack(s-1) *= res_stack(s);
      s--;
      break;
    case e_divide:
      /*  d(u/v) = du/v - u*dv/(v^2) = (1/v) * [du - (u/v)*dv]  */
      res_stack(s) = 1.0 / res_stack(s);      /*  1/v  */
      res_stack(s-1) *= res_stack(s);         /*  u/v  */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1) = (res_stack(s) *
                             (grad_stack(v,s-1) -
                              (res_stack(s-1) * grad_stack(v,s))));
      }
      s--;
      break;
    case e_uminus:
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = -grad_stack(v,s);
      res_stack(s) = -res_stack(s);
      break;
    case e_power:
      /*  d(u^v) = v * u^(v-1) * du + ln(u) * u^v * dv  */
      /*  First compute:  v*u^(v-1)  */
      temp = res_stack(s) * pow( res_stack(s-1), (res_stack(s) - 1.0) );
      /*  Now compute:  ln(u)  */
      temp2 = FuncEval( LookupFuncById(F_LN), res_stack(s-1) );
      /*  Next compute:  u^v  */
      res_stack(s-1) = pow(res_stack(s-1), res_stack(s));
      /*  Compute:  [ln(u)] * [u^v]  */
      temp2 *= res_stack(s-1);
      /*  Finally, compute:  [v*u^(v-1)] * [du] + [ln(u)*u^v] * [dv]  */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1) = ((temp * grad_stack(v,s-1)) +
                             (temp2 * grad_stack(v,s)));
      }
      s--;
      break;
    case e_ipower:
      /*  d(u^v) = v * u^(v-1) * du + ln(u) * u^v * dv  */
      /*  First compute:  v*u^(v-1)  */
      temp = asc_d1ipow( res_stack(s-1), ((int)res_stack(s)) );
      /*  Now compute:  ln(u)  */
      temp2 = FuncEval( LookupFuncById(F_LN), res_stack(s-1) );
      /*  Next compute:  u^v  */
      res_stack(s-1) = asc_ipow( res_stack(s-1), ((int)res_stack(s)) );
      /*  Compute:  [ln(u)] * [u^v]  */
      temp2 *= res_stack(s-1);
      /*  Finally, compute:  [v*u^(v-1)] * [du] + [ln(u)*u^v] * [dv]  */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1) = ((temp * grad_stack(v,s-1)) +
                             (temp2 * grad_stack(v,s)));
      }
      s--;
      break;
    case e_func:
      /*
      funcptr = TermFunc(term);
      for (v = 0; v < num_var; v++) {
        grad_stack(v,s) = FuncDeriv(funcptr, grad_stack(v,s));
      }
      res_stack(s) = FuncEval(funcptr, res_stack(s));  */
      fxnptr = TermFunc(term);
      temp = FuncDeriv( fxnptr, res_stack(s) );
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) *= temp;
      res_stack(s) = FuncEval( fxnptr, res_stack(s) );
      break;
    default:
      ASC_PANIC("Unknown relation term type");
      break;
    }
  }
#undef grad_stack
#undef res_stack
}

static int
RelationEvaluateResidualGradientSafe(CONST struct relation *r,
                                     double *residual,
                                     double *gradient,
                                     enum safe_err *serr)
{
  unsigned long t;       /* the current term in the relation r */
  unsigned long num_var; /* the number of variables in the relation r */
  unsigned long v;       /* the index of the variable we are looking at */
  int lhs;               /* looking at left(=1) or right(=0) hand side of r */
  double *stacks;        /* the memory for the stacks */
  unsigned long stack_height; /* height of each stack */
  long s = -1;           /* the top position in the stacks */
  double temp, temp2;    /* temporary variables to speed gradient calculatns */
  unsigned long length_lhs, length_rhs;
  CONST struct relation_term *term;
  CONST struct Func *fxnptr;

  num_var = NumberVariables(r);
  length_lhs = RelationLength(r, 1);
  length_rhs = RelationLength(r, 0);
  if( (length_lhs + length_rhs) == 0 ) {
    for( v = 0; v < num_var; v++ ) gradient[v] = 0.0;
    *residual = 0.0;
    return 0;
  }
  else {
    stack_height = 1 + MAX(length_lhs,length_rhs);
  }

  /* create the stacks */
  stacks = tmpalloc_array(((num_var+1)*stack_height),double);
  if( stacks == NULL ) return 1;

#define res_stack(s)    stacks[(s)]
#define grad_stack(v,s) stacks[((v)*stack_height)+(s)]

  lhs = 1;
  t = 0;
  while(1) {
    if( lhs && (t >= length_lhs) ) {
      /* need to switch to the right hand side--if it exists */
      if( length_rhs ) {
        lhs = t = 0;
      }
      else {
        /* Set the pointers we were passed to the tops of the stacks.
         * We do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_rhs==0), the
         * length_lhs must be > 0, thus s>=0
         */
        for( v = 1; v <= num_var; v++ ) gradient[v-1] = grad_stack(v,s);
        *residual = res_stack(s);
        return 0;
      }
    }
    else if( (!lhs) && (t >= length_rhs) ) {
      /* we have processed both sides, quit */
      if( length_lhs ) {
        /* Set the pointers we were passed to lhs - rhs
         * We know length_lhs and length_rhs are both > 0, since if
         * length_rhs == 0, we would have exited above.
         */
        for( v = 1; v <= num_var; v++ ) {
          gradient[v-1] = safe_sub_D0(grad_stack(v,s-1),grad_stack(v,s),serr);
        }
        *residual = safe_sub_D0(res_stack(s-1), res_stack(s), serr);
        return 0;
      }
      else {
        /* Set the pointers we were passed to -1.0 * top of stacks.
         * We do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_lhs==0), the
         * length_rhs must be > 0, thus s>=0
         */
        for( v = 1; v <= num_var; v++ ) {
          gradient[v-1] = -grad_stack(v,s);
        }
        *residual = -res_stack(s);
        return 0;
      }
    }

    term = NewRelationTerm(r, t++, lhs);
    switch( RelationTermType(term) ) {
    case e_zero:
      s++;
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = 0.0;
      res_stack(s) = 0.0;
      break;
    case e_real:
      s++;
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = 0.0;
      res_stack(s) = TermReal(term);
      break;
    case e_int:
      s++;
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = 0.0;
      res_stack(s) = TermInteger(term);
      break;
    case e_var:
      s++;
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = 0.0;
      grad_stack(TermVarNumber(term),s) = 1.0;
      res_stack(s) = TermVariable(r, term);
      break;
    case e_plus:
      /* d(u+v) = du + dv */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1)=safe_add_D0(grad_stack(v,s-1),grad_stack(v,s),serr);
      }
      res_stack(s-1) = safe_add_D0(res_stack(s-1),res_stack(s),serr);
      s--;
      break;
    case e_minus:
      /* d(u-v) = du - dv */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1)=safe_sub_D0(grad_stack(v,s-1),grad_stack(v,s),serr);
      }
      res_stack(s-1) = safe_sub_D0(res_stack(s-1),res_stack(s),serr);
      s--;
      break;
    case e_times:
      /* d(u*v) = u*dv + v*du */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1) =
          safe_add_D0(safe_mul_D0(res_stack(s-1),grad_stack(v,s),serr),
                      safe_mul_D0(res_stack(s),grad_stack(v,s-1),serr),
                      serr);
      }
      res_stack(s-1) = safe_mul_D0(res_stack(s-1),res_stack(s),serr);
      s--;
      break;
    case e_divide:
      /*  d(u/v) = du/v - u*dv/(v^2) = (1/v) * [du - (u/v)*dv]  */
      res_stack(s) = safe_rec(res_stack(s),serr);                     /* 1/v */
      res_stack(s-1) = safe_mul_D0(res_stack(s-1),res_stack(s),serr); /* u/v */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1) =
          safe_mul_D0(res_stack(s),
                      safe_sub_D0(grad_stack(v,s-1),
                                  safe_mul_D0(res_stack(s-1),
                                              grad_stack(v,s),
                                              serr),serr),serr);
      }
      s--;
      break;
    case e_uminus:
      for( v = 1; v <= num_var; v++ ) grad_stack(v,s) = -grad_stack(v,s);
      res_stack(s) = -res_stack(s);
      break;
    case e_power:
      /*  d(u^v) = v * u^(v-1) * du + ln(u) * u^v * dv  */
      /*  v*u^(v-1)  */
      temp = safe_pow_D1( res_stack(s-1), res_stack(s), 0, serr );
      /*  ln(u)*u^v  */
      temp2 = safe_pow_D1( res_stack(s-1), res_stack(s), 1, serr );
      /*  Compute:  [v*u^(v-1)] * [du] + [ln(u)*u^v] * [dv]  */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1) =
          safe_add_D0(safe_mul_D0(temp, grad_stack(v,s-1), serr),
                      safe_mul_D0(temp2, grad_stack(v,s), serr), serr);
      }
      /*  u^v  */
      res_stack(s-1) = safe_pow_D0( res_stack(s-1), res_stack(s), serr );
      s--;
      break;
    case e_ipower:
      /*  d(u^v) = v * u^(v-1) * du + ln(u) * u^v * dv  */
      /*  v*u^(v-1)  */
      temp = safe_ipow_D1( res_stack(s-1), res_stack(s), 0, serr );
      /*  ln(u)*u^v */
      temp2 = safe_ipow_D1( res_stack(s-1), res_stack(s), 1, serr );
      /*  Compute:  [v*u^(v-1)] * [du] + [ln(u)*u^v] * [dv]  */
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s-1) =
          safe_add_D0(safe_mul_D0(temp, grad_stack(v,s-1), serr),
                      safe_mul_D0(temp2, grad_stack(v,s), serr), serr);
      }
      /*  Next compute:  u^v  */
      res_stack(s-1) = safe_ipow_D0( res_stack(s-1), res_stack(s), serr );
      s--;
      break;
    case e_func:
      fxnptr = TermFunc(term);
      temp = FuncDerivSafe( fxnptr, res_stack(s), serr);
      for( v = 1; v <= num_var; v++ ) {
        grad_stack(v,s) = safe_mul_D0( grad_stack(v,s), temp, serr );
      }
      res_stack(s) = FuncEvalSafe( fxnptr, res_stack(s), serr);
      break;
    default:
      ASC_PANIC("Unknown relation term type");
    }
  }
#undef grad_stack
#undef res_stack
}

/**
    This function evaluates and returns the derivative of the
    relation r with respect to the variable whose index is pos.
    This function assumes r exists and that pos is within the proper range.
    The function computes the gradients by maintaining 2 stacks, one for
    the residual and one for the derivative.  The stacks come from a
    single array which this gets by calling tmpalloc_array.  Two macros
    are defined to make referencing this array easier.  Of the malloc fails,
    this function returns 0.0, so there is currently no way to know if
    the function failed.
*/
static double
RelationEvaluateDerivative(CONST struct relation *r,
                           unsigned long pos)
{
  unsigned long t;       /* the current term in the relation r */
  int lhs;               /* looking at left(=1) or right(=0) hand side of r */
  double *stacks;        /* the memory for the stacks */
  unsigned long stack_height; /* height of each stack */
  long s = -1;           /* the top position in the stacks */
  unsigned long length_lhs, length_rhs;
  CONST struct relation_term *term;
  CONST struct Func *fxnptr;

  length_lhs = RelationLength(r, 1);
  length_rhs = RelationLength(r, 0);
  if( (length_lhs + length_rhs) == 0 ) {
    return 0.0;
  }
  else {
    stack_height = 1 + MAX(length_lhs,length_rhs);
  }

  /* create the stacks */
  stacks = tmpalloc_array((2*stack_height),double);
  if( stacks == NULL ) return 0.0;

#define res_stack(s)  stacks[(s)]
#define grad_stack(s) stacks[stack_height+(s)]

  lhs = 1;
  t = 0;
  while(1) {
    if( lhs && (t >= length_lhs) ) {
      /* need to switch to the right hand side--if it exists */
      if( length_rhs ) {
        lhs = t = 0;
      }
      else {
        /* do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_rhs==0), the
         * length_lhs must be > 0, thus s>=0
         */
        return grad_stack(s);
      }
    }
    else if( (!lhs) && (t >= length_rhs) ) {
      /* we have processed both sides, quit */
      if( length_lhs ) {
        /* we know length_lhs and length_rhs are both > 0, since if
         * length_rhs == 0, we would have exited above.
         */
        return (grad_stack(s-1) - grad_stack(s));
      }
      else {
        /* do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_lhs==0), the
         * length_rhs must be > 0, thus s>=0
         */
        return (-1.0 * grad_stack(s));
      }
    }

    term = NewRelationTerm(r, t++, lhs);
    switch( RelationTermType(term) ) {
    case e_zero:
      s++;
      grad_stack(s) = res_stack(s) = 0.0;
      break;
    case e_real:
      s++;
      grad_stack(s) = 0.0;
      res_stack(s) = TermReal(term);
      break;
    case e_int:
      s++;
      grad_stack(s) = 0.0;
      res_stack(s) = TermInteger(term);
      break;
    case e_var:
      s++;
      grad_stack(s) = ( (pos == TermVarNumber(term)) ? 1.0 : 0.0 );
      res_stack(s) = TermVariable(r, term);
      break;
    case e_plus:
      /* d(u+v) = du + dv */
      grad_stack(s-1) += grad_stack(s);
      res_stack(s-1) += res_stack(s);
      s--;
      break;
    case e_minus:
      /* d(u-v) = du - dv */
      grad_stack(s-1) -= grad_stack(s);
      res_stack(s-1) -= res_stack(s);
      s--;
      break;
    case e_times:
      /* d(u*v) = u*dv + v*du */
      grad_stack(s-1) = ((res_stack(s-1) * grad_stack(s)) +
                         (res_stack(s) * grad_stack(s-1)));
      res_stack(s-1) *= res_stack(s);
      s--;
      break;
    case e_divide:
      /*  d(u/v) = du/v - u*dv/(v^2) = [du - (u/v)*dv]/v  */
      res_stack(s-1) = res_stack(s-1) / res_stack(s);
      grad_stack(s-1) = ((grad_stack(s-1) - (res_stack(s-1) * grad_stack(s))) /
                         res_stack(s));
      s--;
      break;
    case e_uminus:
      grad_stack(s) = -grad_stack(s);
      res_stack(s) = -res_stack(s);
      break;
    case e_power:
      /*  d(u^v) = v * u^(v-1) * du + ln(u) * u^v * dv  */
      /*  First we compute:  v*u^(v-1)*du  */
      grad_stack(s-1) *= (pow(res_stack(s-1), (res_stack(s) - 1.0)) *
                          res_stack(s));
      /*  Now compute:  ln(u)*dv  */
      grad_stack(s) *= FuncEval( LookupFuncById(F_LN), res_stack(s-1) );
      /*  Next compute:  u^v  */
      res_stack(s-1) = pow( res_stack(s-1), res_stack(s) );
      /*  Finally, compute:  [v*u^(v-1)*du] + [u^v] * [ln(u)*dv]  */
      grad_stack(s-1) += (res_stack(s-1) * grad_stack(s));
      s--;
      break;
    case e_ipower:
      /*  d(x^y) = y * dx * x^(y-1) + ln(x) * dy * x^y  */
      /*  First we compute:  v*u^(v-1)*du  */
      grad_stack(s-1) *= asc_d1ipow( res_stack(s-1), ((int)res_stack(s)) );
      /*  Now compute:  ln(u)*dv  */
      grad_stack(s) *= FuncEval( LookupFuncById(F_LN), res_stack(s-1) );
      /*  Next compute:  u^v  */
      res_stack(s-1) = asc_ipow( res_stack(s-1), ((int)res_stack(s)) );
      /*  Finally, compute:  [v*u^(v-1)*du] + [u^v] * [ln(u)*dv]  */
      grad_stack(s-1) += (res_stack(s-1) * grad_stack(s));
      s--;
      break;
    case e_func:
      fxnptr = TermFunc(term);
      grad_stack(s) *= FuncDeriv( fxnptr, res_stack(s) );
      res_stack(s) = FuncEval( fxnptr, res_stack(s) );
      break;
    default:
      ASC_PANIC("Unknown relation term type");
      break;
    }
  }
#undef grad_stack
#undef res_stack
}

static double
RelationEvaluateDerivativeSafe(CONST struct relation *r,
                               unsigned long pos,
                               enum safe_err *serr)
{
  unsigned long t;       /* the current term in the relation r */
  int lhs;               /* looking at left(=1) or right(=0) hand side of r */
  double *stacks;        /* the memory for the stacks */
  unsigned long stack_height; /* height of each stack */
  long s = -1;           /* the top position in the stacks */
  unsigned long length_lhs, length_rhs;
  CONST struct relation_term *term;
  CONST struct Func *fxnptr;

  length_lhs = RelationLength(r, 1);
  length_rhs = RelationLength(r, 0);
  if( (length_lhs + length_rhs) == 0 ) {
    return 0.0;
  }
  else {
    stack_height = 1 + MAX(length_lhs,length_rhs);
  }

  /* create the stacks */
  stacks = tmpalloc_array((2*stack_height),double);
  if( stacks == NULL ) return 0.0;

#define res_stack(s)  stacks[(s)]
#define grad_stack(s) stacks[stack_height+(s)]

  lhs = 1;
  t = 0;
  while(1) {
    if( lhs && (t >= length_lhs) ) {
      /* need to switch to the right hand side--if it exists */
      if( length_rhs ) {
        lhs = t = 0;
      }
      else {
        /* do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_rhs==0), the
         * length_lhs must be > 0, thus s>=0
         */
        return grad_stack(s);
      }
    }
    else if( (!lhs) && (t >= length_rhs) ) {
      /* we have processed both sides, quit */
      if( length_lhs ) {
        /* we know length_lhs and length_rhs are both > 0, since if
         * length_rhs == 0, we would have exited above.
         */
        return safe_sub_D0(grad_stack(s-1), grad_stack(s), serr);
      }
      else {
        /* do not need to check for s>=0, since we know that
         * (length_lhs+length_rhs>0) and that (length_lhs==0), the
         * length_rhs must be > 0, thus s>=0
         */
        return (-grad_stack(s));
      }
    }

    term = NewRelationTerm(r, t++, lhs);
    switch( RelationTermType(term) ) {
    case e_zero:
      s++;
      grad_stack(s) = res_stack(s) = 0.0;
      break;
    case e_real:
      s++;
      grad_stack(s) = 0.0;
      res_stack(s) = TermReal(term);
      break;
    case e_int:
      s++;
      grad_stack(s) = 0.0;
      res_stack(s) = TermInteger(term);
      break;
    case e_var:
      s++;
      grad_stack(s) = ( (pos == TermVarNumber(term)) ? 1.0 : 0.0 );
      res_stack(s) = TermVariable(r, term);
      break;
    case e_plus:
      /* d(u+v) = du + dv */
      grad_stack(s-1) = safe_add_D0( grad_stack(s-1), grad_stack(s), serr );
      res_stack(s-1) = safe_add_D0( res_stack(s-1), res_stack(s), serr );
      s--;
      break;
    case e_minus:
      /* d(u-v) = du - dv */
      grad_stack(s-1) = safe_sub_D0( grad_stack(s-1), grad_stack(s), serr );
      res_stack(s-1) = safe_sub_D0( res_stack(s-1), res_stack(s), serr );
      s--;
      break;
    case e_times:
      /* d(u*v) = u*dv + v*du */
      grad_stack(s-1) =
        safe_add_D0(safe_mul_D0( res_stack(s-1), grad_stack(s), serr),
                    safe_mul_D0( res_stack(s), grad_stack(s-1), serr), serr);
      res_stack(s-1) = safe_mul_D0( res_stack(s-1), res_stack(s), serr );
      s--;
      break;
    case e_divide:
      /*  d(u/v) = du/v - u*dv/(v^2) = [du - (u/v)*dv]/v  */
      res_stack(s-1) = safe_div_D0( res_stack(s-1), res_stack(s), serr);
      grad_stack(s-1) =
        safe_div_D0(safe_sub_D0(grad_stack(s-1),
                                safe_mul_D0(res_stack(s-1),grad_stack(s),serr),
                                serr),
                    res_stack(s),serr);
      s--;
      break;
    case e_uminus:
      grad_stack(s) = -grad_stack(s);
      res_stack(s) = -res_stack(s);
      break;
    case e_power:
      /*  d(u^v) = v * u^(v-1) * du + ln(u) * u^v * dv  */
      grad_stack(s-1) =
        safe_add_D0(safe_mul_D0(safe_pow_D1(res_stack(s-1),
                                            res_stack(s),0,serr),
                                grad_stack(s-1), serr),
                    safe_mul_D0(safe_pow_D1(res_stack(s-1),
                                            res_stack(s),1,serr),
                                grad_stack(s),serr), serr);
      /*  u^v  */
      res_stack(s-1) = safe_pow_D0( res_stack(s-1), res_stack(s), serr);
      s--;
      break;
    case e_ipower:
      /*  d(x^y) = y * dx * x^(y-1) + ln(x) * dy * x^y  */
      grad_stack(s-1) =
        safe_add_D0(safe_mul_D0(safe_ipow_D1(res_stack(s-1),
                                             res_stack(s),0,serr),
                                grad_stack(s-1), serr),
                    safe_mul_D0(safe_ipow_D1(res_stack(s-1),
                                             res_stack(s),1,serr),
                                grad_stack(s),serr), serr);
      /*  u^v  */
      res_stack(s-1) = safe_ipow_D0( res_stack(s-1), res_stack(s), serr);
      s--;
      break;
    case e_func:
      fxnptr = TermFunc(term);
      grad_stack(s) = safe_mul_D0(FuncDerivSafe( fxnptr, res_stack(s), serr ),
                                  grad_stack(s), serr);
      res_stack(s) = FuncEvalSafe( fxnptr, res_stack(s), serr);
      break;
    default:
      ASC_PANIC("Unknown relation term type");
    }
  }
#undef grad_stack
#undef res_stack
}

/*------------------------------------------------------------------------------
  RELATION & RELATION TERM QUERIES FUNCTIONS (FOR USE BY EXTERNAL CODE)
*/

/**
    @return =, <, >, etc, etc. not e_token, e_glassbox, etc
*/
enum Expr_enum RelationRelop(CONST struct relation *rel)
{
  AssertAllocatedMemory(rel,sizeof(struct relation));
  return rel->share->s.relop;
}

/**
    This query only applies to TokenRelations and OpcodeRelations.
*/
unsigned long RelationLength(CONST struct relation *rel, int lhs){
  assert(rel!=NULL);
  AssertAllocatedMemory(rel,sizeof(struct relation));
  if(lhs){
    if(RTOKEN(rel).lhs){
      asc_assert(RTOKEN(rel).lhs_len >= 0);
      return RTOKEN(rel).lhs_len;
    }
    return 0;
  }
  if(RTOKEN(rel).rhs){
    asc_assert(RTOKEN(rel).rhs_len >= 0);
    return RTOKEN(rel).rhs_len;
  }
  return 0;
}

struct gl_list_t *RelationBlackBoxArgNames(CONST struct relation *rel)
{
  assert(rel!=NULL);
  return RelationBlackBoxCache(rel)->argListNames;
}

struct Name *RelationBlackBoxDataName(CONST struct relation *rel)
{
  assert(rel!=NULL);
  return RelationBlackBoxCache(rel)->dataName;
}

struct BlackBoxCache * RelationBlackBoxCache(CONST struct relation *rel)
{
  assert(rel!=NULL);
  AssertAllocatedMemory(rel,sizeof(struct relation));
  return ((struct BlackBoxData *) (rel->externalData))->common;
}

struct BlackBoxData * RelationBlackBoxData(CONST struct relation *rel)
{
  assert(rel!=NULL);
  AssertAllocatedMemory(rel,sizeof(struct relation));
  return (struct BlackBoxData *) rel->externalData;
}

/*
    This query only applies to TokenRelations. It assumes the
    user still thinks tokens number from [1..len].
*/
CONST struct relation_term *RelationTerm(CONST struct relation *rel,
                         unsigned long int pos, int lhs)
{
  assert(rel!=NULL);
  AssertAllocatedMemory(rel,sizeof(struct relation));
  if (lhs){
    if (RTOKEN(rel).lhs)
      return A_TERM(&(RTOKEN(rel).lhs[pos-1]));
    else return NULL;
  }
  else{
    if (RTOKEN(rel).rhs)
      return A_TERM(&(RTOKEN(rel).rhs[pos-1]));
    else return NULL;
  }
}

/**
    This query only applies to TokenRelations. It assumes the
    clued user thinks tokens number from [0..len-1], which they do.
*/
CONST struct relation_term
*NewRelationTermF(CONST struct relation *rel, unsigned long pos, int lhs)
{
  assert(rel!=NULL);
  AssertAllocatedMemory(rel,sizeof(struct relation));
  if (lhs){
    if (RTOKEN(rel).lhs != NULL)
      return A_TERM(&(RTOKEN(rel).lhs[pos]));
    else return NULL;
  }else{
    if (RTOKEN(rel).rhs != NULL)
      return A_TERM(&(RTOKEN(rel).rhs[pos]));
    else return NULL;
  }
}

/**
    This query only applies to sides from TokenRelations. It assumes the
    clued user thinks tokens number from [0..len-1], which they do,
    and that the side came from a token relation instance.
*/
CONST struct relation_term
*RelationSideTermF(CONST union RelationTermUnion *side, unsigned long pos)
{
  assert(side!=NULL);
  return A_TERM(&(side[pos]));
}

/**
    This query only applies to TokenRelations. It assumes the
    clued user thinks tokens number from [0..len-1], which they do.
*/
enum Expr_enum RelationTermTypeF(CONST struct relation_term *term)
{
  AssertMemory(term);
  return term->t;
}

unsigned long TermVarNumber(CONST struct relation_term *term)
{
  assert(term&&term->t == e_var);
  AssertMemory(term);
  return V_TERM(term)->varnum;
}

long TermInteger(CONST struct relation_term *term){
  assert(term&&(term->t==e_int));
  AssertMemory(term);
  return I_TERM(term)->ivalue;
}

double TermReal(CONST struct relation_term *term){
  assert(term&&( term->t==e_real || term->t==e_zero));
  AssertMemory(term);
  return R_TERM(term)->value;
}

double
TermVariable(CONST struct relation *rel, CONST struct relation_term *term){
  return
    RealAtomValue((struct Instance*)RelationVariable(rel,TermVarNumber(term)));
}

CONST dim_type *TermDimensions(CONST struct relation_term *term){
  assert( term && (term->t==e_real || term->t == e_int || term->t == e_zero) );
  AssertMemory(term);
  if (term->t==e_real) return R_TERM(term)->dimensions;
  if (term->t==e_int) return Dimensionless();
  if (term->t==e_zero) return WildDimension();
  return NULL;
}

CONST struct Func *TermFunc(CONST struct relation_term *term){
  assert(term&&(term->t == e_func));
  AssertMemory(term);
  return F_TERM(term)->fptr;
}

struct relation_term *RelationINF_Lhs(CONST struct relation *rel){
  return RTOKEN(rel).lhs_term;
}

struct relation_term *RelationINF_Rhs(CONST struct relation *rel){
  return RTOKEN(rel).rhs_term;
}

struct ExternalFunc *RelationBlackBoxExtFunc(CONST struct relation *rel)
{
  assert(rel!=NULL);
  return RelationBlackBoxCache(rel)->efunc;
}

/*------------------------------------------------------------------------------
  GLASSBOX RELATION QUERIES

  For picking apart a GlassBox relation.
*/

struct ExternalFunc *RelationGlassBoxExtFunc(CONST struct relation *rel){
  assert(rel!=NULL);
  return RGBOX(rel).efunc;
}

int GlassBoxRelIndex(CONST struct relation *rel){
  assert(rel!=NULL);
  return RGBOX(rel).index;
}

int *GlassBoxArgs(CONST struct relation *rel){
  assert(rel!=NULL);
  return RGBOX(rel).args;
}


/*------------------------------------------------------------------------------
  GENERAL RELATION QUERIES

    Not all of these queries may be applied to all relation types.
    Those that cannot be are so marked.
*/

CONST struct gl_list_t *RelationVarList(CONST struct relation *rel){
  return (CONST struct gl_list_t *)rel->vars;
}

dim_type *RelationDim(CONST struct relation *rel){
  assert(rel!=NULL);
  return rel->d;
}

int SetRelationDim(struct relation *rel, CONST dim_type *d)
{
  if (!rel) return 1;
  rel->d = (dim_type*)d;
  return 0;
}

double RelationResidual(CONST struct relation *rel){
  assert(rel!=NULL);
  return rel->residual;
}

void SetRelationResidual(struct relation *rel, double value){
  assert(rel!=NULL);
  rel->residual = value;
}

double RelationMultiplier(CONST struct relation *rel){
  assert(rel!=NULL);
  return rel->multiplier;
}

void SetRelationMultiplier(struct relation *rel, double value){
  assert(rel!=NULL);
  rel->multiplier = value;
}

double RelationNominal(CONST struct relation *rel){
  assert(rel!=NULL);
  return rel->nominal;
}

void SetRelationNominal(struct relation *rel, double value){
  assert(rel!=NULL);
  rel->nominal = (fabs(value) > 0.0) ? fabs(value) : rel->nominal;
}


int RelationIsCond(CONST struct relation *rel){
  if ( rel != NULL) {
    return rel->iscond;
  }
  return 0;
}

void SetRelationIsCond(struct relation *rel){
  if ( rel != NULL) {
    rel->iscond = 1;
  }else{
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"NULL relation");
  }
}

unsigned long NumberVariables(CONST struct relation *rel)
{
  unsigned long n;
  assert(rel!=NULL);
  n = (rel->vars!=NULL) ? gl_length(rel->vars) : 0;
  return n;
}

struct Instance *RelationVariable(CONST struct relation *rel,
        unsigned long int varnum
){
  assert(rel!=NULL);
  return (struct Instance *)gl_fetch(rel->vars,varnum);
}

static void CalcDepth(CONST struct relation *rel,
        int lhs,
        unsigned long int *depth,
        unsigned long int *maxdepth
){
  unsigned long c,length;
  CONST struct relation_term *term;
  length = RelationLength(rel,lhs);
  for(c=0;c<length;c++){
    term = NewRelationTerm(rel,c,lhs);
    switch(RelationTermType(term)){
    case e_zero:
    case e_int:
    case e_real:
    case e_var:
      if (++(*depth) > *maxdepth) *maxdepth = *depth;
      break;
    case e_func:
    case e_uminus:
      break;
    case e_plus:
    case e_minus:
    case e_times:
    case e_divide:
    case e_power:
    case e_ipower:
      (*depth)--;
      break;
    default:
      ASC_PANIC("Unknown relation term type");
    }
  }
}

unsigned long RelationDepth(CONST struct relation *rel){
  unsigned long depth=0,maxdepth=0;
  switch(RelationRelop(rel)){
  case e_equal:
  case e_notequal:
  case e_less:
  case e_greater:
  case e_lesseq:
  case e_greatereq:
    CalcDepth(rel,1,&depth,&maxdepth);
    CalcDepth(rel,0,&depth,&maxdepth);
    assert(depth == 2);
    break;
  case e_maximize:
  case e_minimize:
    CalcDepth(rel,1,&depth,&maxdepth);
    assert(depth == 1);
    break;
  default:
      ASC_PANIC("Unknown relation term type");
  }
  return maxdepth;
}

/*------------------------------------------------------------------------------
  EQUATION SCALING

  "Documentation will be added at a later date" -- someone last century
*/

static double FindMaxAdditiveTerm(struct relation_term *s){
  enum safe_err serr;
  double lhs, rhs;

  switch (RelationTermType(s)) {
  case e_plus:
  case e_minus:
    /** note these used to be inlined with max, but a bug in gcc323 caused it to be split out. */
    lhs = FindMaxAdditiveTerm(TermBinLeft(s));
    rhs = FindMaxAdditiveTerm(TermBinRight(s));
    return MAX(fabs(lhs), fabs(rhs));
  case e_uminus:
    return (FindMaxAdditiveTerm(TermUniLeft(s)));
  case e_times:
    return (FindMaxAdditiveTerm(TermBinLeft(s))*
      FindMaxAdditiveTerm(TermBinRight(s)));
  case e_divide:
    /* bug patch / 0 */
    return safe_div_D0(FindMaxAdditiveTerm(TermBinLeft(s)) ,
      RelationBranchEvaluator(TermBinRight(s)),&serr);
  default:
    return RelationBranchEvaluator(s);
  }
}

static double FindMaxFromTop(struct relation *s){
  double lhs;
  double rhs;
  if (s == NULL) {
    return 0;
  }
  /** note these used to be inlined with max, but a bug in gcc323 caused it to be split out. */
  lhs = FindMaxAdditiveTerm(Infix_LhsSide(s));
  rhs = FindMaxAdditiveTerm(Infix_RhsSide(s));
  return MAX(fabs(lhs), fabs(rhs));
}

/* send in relation */
double CalcRelationNominal(struct Instance *i){
  enum Expr_enum reltype;
  struct Instance *c , *p;
  symchar *nomname;

  char *iname;
  iname = WriteInstanceNameString(i,NULL);
  ascfree(iname);

  glob_rel = NULL;
  if (i == NULL){
    FPRINTF(ASCERR, "error in CalcRelationNominal routine\n");
    return (double)0;
  }
  if (InstanceKind(i) != REL_INST) {
    FPRINTF(ASCERR, "error in CalcRelationNominal routine\n");
    return (double)0;
  }
  glob_rel = (struct relation *)GetInstanceRelation(i,&reltype);
  if (glob_rel == NULL) {
    FPRINTF(ASCERR, "error in CalcRelationNominal routine\n");
    return (double)0;
  }

  if (reltype == e_token) {
    double temp;
    temp = FindMaxFromTop(glob_rel);
    if (asc_isnan(temp) || !asc_finite(temp)) {
      glob_rel = NULL;
      return (double)1;
    }
    if ( temp > 0) { /* this could return some really small numbers */
      glob_rel = NULL;
      return temp;
    }
  }
  if (reltype == e_blackbox){
    p = BlackBoxGetOutputVar(glob_rel);
    nomname = AddSymbolL("nominal",7);
    glob_rel = NULL;
    c = ChildByChar(p,nomname);
    if (c == NULL) {
      ERROR_REPORTER_HERE(ASC_PROG_ERR,"nominal missing from standard var definition (assuming 1.0) (%s)",__FUNCTION__);
      return 1.0;
    } else {
      return( RealAtomValue(c) );
    }
  }
  if (reltype == e_glassbox){
    p = BlackBoxGetOutputVar(glob_rel);
    nomname = AddSymbolL("nominal",7);
    glob_rel = NULL;
    c = ChildByChar(p,nomname);
    if (c == NULL) {
      ERROR_REPORTER_HERE(ASC_PROG_ERR,"nominal missing from standard var definition (assuming 1.0) (%s)",__FUNCTION__);
      return 1.0;
    } else {
      return( RealAtomValue(c) );
    }
  }
  if (reltype == e_opcode){
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"opcode not supported (%s)",__FUNCTION__);
  }
  glob_rel = NULL;
  return (double)1;
}

void PrintScale(struct Instance *i){
  if (InstanceKind(i) == REL_INST) {
    double j;
    j = CalcRelationNominal(i);
    PRINTF(" scale constant = %g\n", j);
  }
}

void PrintRelationNominals(struct Instance *i){
  VisitInstanceTree(i,PrintScale, 0, 0);
}

/*------------------------------------------------------------------------------
  CALCULATION ROUTINES
*/

/**
 * Load ATOM values into an array of doubles.
 * The array of doubles is indexed from 0 while the
 * var list is indexed from 1. The ultimate client of
 * the array calling this function thinks vars index from 0.
 */
static
void RelationLoadDoubles(struct gl_list_t *varlist, double *vars){
  unsigned long c;
  vars--; /* back up the pointer so indexing from 1 puts data right */
  for (c= gl_length(varlist); c > 0; c--) {
    vars[c] = RealAtomValue((struct Instance *)gl_fetch(varlist,c));
  }
}

/**
    only called on token relations.
*/
int RelationCalcResidualBinary(CONST struct relation *r, double *res){
  double *vars;
  double tres;
  int old_errno;

  if (r == NULL || res == NULL) {
    return 1;
  }
  vars = tmpalloc_array(gl_length(r->vars),double);
  if (vars == NULL) {
    return 1;
  }
  RelationLoadDoubles(r->vars,vars);
  old_errno = errno; /* push C global errno */
  errno = 0;
  if (BinTokenCalcResidual(RTOKEN(r).btable,RTOKEN(r).bindex,vars,&tres)) {
    if (errno == 0) { /* pop if unchanged */
      errno = old_errno;
    }
    return 1;
  }
  if (!asc_finite(tres) || errno == EDOM || errno == ERANGE ) {
    if (errno == 0) { /* pop if unchanged */
      errno = old_errno;
    }
    return 1;
  }
  if (errno == 0) { /* pop if unchanged */
    errno = old_errno;
  }
  *res = tres;
  return 0;
}

enum safe_err
RelationCalcResidualPostfixSafe(struct Instance *i, double *res){
  struct relation *r;
  enum Expr_enum reltype;
  enum safe_err status = safe_ok;
  unsigned long length_lhs, length_rhs;

  CHECK_INST_RES(i,res,1);

  r = (struct relation *)GetInstanceRelation(i, &reltype);

  if( r == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null relation");
    return safe_problem;
  }

  switch(reltype){
    case e_token:
      length_lhs = RelationLength(r, 1);
      length_rhs = RelationLength(r, 0);

      if(length_lhs){
        length_lhs--;
        *res = RelationEvaluatePostfixBranchSafe(r, &length_lhs, 1,&status);
      }else{
        *res = 0.0;
      }

      if(length_rhs){
        length_rhs--;
        *res -= RelationEvaluatePostfixBranchSafe(r, &length_rhs, 0,&status);
      }

      safe_error_to_stderr(&status);
      break;
    case e_blackbox:
      if ( RelationCalcResidualPostfix(i,res) != 0) {
        CONSOLE_DEBUG("Problem evalutating Blackbox residual");
        status = safe_problem;
        safe_error_to_stderr(&status);
      }
      break;
    case e_glassbox:
      ERROR_REPORTER_HERE(ASC_PROG_ERR,"'e_glassbox' relation not supported");
      status = safe_problem;
      break;
    case e_opcode:
      ERROR_REPORTER_HERE(ASC_PROG_ERR,"'e_opcode' relation not supported");
      status = safe_problem;
      break;
    default:
      if(reltype >= TOK_REL_TYPE_LOW && reltype <= TOK_REL_TYPE_HIGH){
        status = safe_problem;
      }else{
          ASC_PANIC("Reached end of routine!");
      }
  }
  return status;
}

/* return 0 on success */
int
RelationCalcResidualPostfix(struct Instance *i, double *res){
  struct relation *r;
  enum Expr_enum reltype;
  unsigned long length_lhs, length_rhs;

  CHECK_INST_RES(i,res,1);

  r = (struct relation *)GetInstanceRelation(i, &reltype);
  if(r == NULL){
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null relation\n");
    return 1;
  }

  /*
  struct Instance *p;
  p = InstanceParent(i,1);
  char *tmp;
  tmp = WriteRelationString(i,p,NULL,NULL,relio_ascend,NULL);
  CONSOLE_DEBUG("Evaluating residual for '%s'",tmp);
  ASC_FREE(tmp);
  */

  switch(reltype){
    case e_token:
      length_lhs = RelationLength(r, 1);
      length_rhs = RelationLength(r, 0);
      if(length_lhs > 0){
        length_lhs--;
        *res = RelationEvaluatePostfixBranch(r, &length_lhs, 1);
      }else{
        *res = 0.0;
      }
      if(length_rhs > 0){
        length_rhs--;
        *res -= RelationEvaluatePostfixBranch(r, &length_rhs, 0);
      }
      return 0;

    case e_blackbox:
      return BlackBoxCalcResidual(i, res, r);

    case e_glassbox:
    case e_opcode:
      ERROR_REPORTER_HERE(ASC_PROG_ERR,"opcode/glassbox not supported");
      return 1;

    default: break;
  }

  ERROR_REPORTER_HERE(ASC_PROG_ERR,"invalid relation type");
  return 1;
}

int RelationCalcExceptionsInfix(struct Instance *i){
  enum Expr_enum reltype;
  double res;
  int result = 0;
  int old_errno;

  glob_rel = NULL;

  CHECK_INST_RES(i,&res,-1);

  glob_rel = (struct relation *)GetInstanceRelation(i, &reltype);
  if( glob_rel == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"NULL relation");
    return -1;
  }
  if( reltype == e_token ) {
    if (Infix_LhsSide(glob_rel) != NULL) {
      old_errno = errno;
      errno = 0; /* save the last errno, because we don't know why */
      res = RelationBranchEvaluator(Infix_LhsSide(glob_rel));
      if (!asc_finite(res) || errno == EDOM || errno == ERANGE) {
        result |= RCE_ERR_LHS;
        if (asc_isnan(res)) {
          result |= RCE_ERR_LHSNAN;
        }else{
          if (!asc_finite(res)) {
            result |= RCE_ERR_LHSINF;
          }
        }
      }
      if (errno == 0) {
        errno = old_errno;
      } /* else something odd happened in evaluation */
    }
    if(Infix_RhsSide(glob_rel) != NULL) {
      res = RelationBranchEvaluator(Infix_RhsSide(glob_rel));
      if (!asc_finite(res)) {
        result |= RCE_ERR_RHS;
        if (asc_isnan(res)) {
          result |= RCE_ERR_RHSNAN;
        }else{
          if (!asc_finite(res)) {
            result |= RCE_ERR_LHSINF;
          }
        }
      }
    }
    glob_rel = NULL;
    return result;
  }else if (reltype >= TOK_REL_TYPE_LOW && reltype <= TOK_REL_TYPE_HIGH) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"relation type not implemented (%s)",__FUNCTION__);
    glob_rel = NULL;
    return -1;
  }

  ASC_PANIC("reached end of routine");
}


int RelationCalcResidualInfix(struct Instance *i, double *res){
  enum Expr_enum reltype;
  glob_rel = NULL;

  CHECK_INST_RES(i,res,1);

  glob_rel = (struct relation *)GetInstanceRelation(i, &reltype);
  if( glob_rel == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"NULL relation\n");
    return 1;
  }
  if( reltype == e_token ) {
    if(Infix_LhsSide(glob_rel) != NULL) {
      *res = RelationBranchEvaluator(Infix_LhsSide(glob_rel));
    }else{
      *res = 0.0;
    }
    if(Infix_RhsSide(glob_rel) != NULL) {
      *res -= RelationBranchEvaluator(Infix_RhsSide(glob_rel));
    }
    glob_rel = NULL;
    return 0;
  }else if (reltype >= TOK_REL_TYPE_LOW && reltype <= TOK_REL_TYPE_HIGH) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"reltype not implemented (%s)",__FUNCTION__);
    glob_rel = NULL;
    return 1;
  }

  ASC_PANIC("reached end of routine");
}


/*
    There used to be a stoopid comment here so I removed it.
*/
int
RelationCalcResidualPostfix2(struct Instance *i, double *res){
  struct relation *r;
  enum Expr_enum reltype;

  CHECK_INST_RES(i,res,1);

  r = (struct relation *)GetInstanceRelation(i, &reltype);
  if( r == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null relation\n");
    return 1;
  }

  if( reltype == e_token ){
    *res = RelationEvaluateResidualPostfix(r);
    return 0;
  }else if (reltype >= TOK_REL_TYPE_LOW && reltype <= TOK_REL_TYPE_HIGH){
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"reltype not implemented (%s)",__FUNCTION__);
    return 1;
  }

  ASC_PANIC("reached end of routine");
}


/*
    simply call the version that calculates the gradient and the residual,
    then ignore the residual
*/
int
RelationCalcGradient(struct Instance *r, double *grad){
  double residual;
  return RelationCalcResidGrad(r, &residual, grad);
}

/*
    simply call the version that calculates the gradient and the residual,
    then ignore the residual

    return 0 on success (as 'safe_ok' enum)
*/
enum safe_err
RelationCalcGradientSafe(struct Instance *r, double *grad){
  double residual;

  return RelationCalcResidGradSafe(r, &residual, grad);
}

/* return 0 on success, 1 on error */
int
RelationCalcResidGrad(struct Instance *i, double *residual, double *gradient){
  struct relation *r;
  enum Expr_enum reltype;

  CHECK_INST_RES(i,residual,1);
  CHECK_INST_RES(i,residual,1);

  r = (struct relation *)GetInstanceRelation(i, &reltype);
  if( r == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null relation");
    return 1;
  }

  if(reltype == e_token ){
    return RelationEvaluateResidualGradient(r, residual, gradient);
  }

  if(reltype == e_blackbox){
    return BlackBoxCalcResidGrad(i, residual, gradient, r);
  }

  assert(reltype >= TOK_REL_TYPE_LOW && reltype <= TOK_REL_TYPE_HIGH);
  ERROR_REPORTER_HERE(ASC_PROG_ERR,"reltype %d not implemented",reltype);
  return 1;
}

enum safe_err
RelationCalcResidGradSafe(struct Instance *i
        , double *residual, double *gradient
){
  struct relation *r;
  enum Expr_enum reltype;
  enum safe_err not_safe = safe_ok;
  int dummy_int;

#ifndef NDEBUG
  if( i == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null instance\n");
    not_safe = safe_problem;
    return not_safe;
  }
  if( residual == NULL || gradient == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null pointer\n");
    not_safe = safe_problem;
    return not_safe;
  }
  if( InstanceKind(i) != REL_INST ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"not relation\n");
    not_safe = safe_problem;
    return not_safe;
  }
#endif
  r = (struct relation *)GetInstanceRelation(i, &reltype);
  if( r == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null relation\n");
    not_safe = safe_problem;
    return not_safe;
  }

  if( reltype == e_token ) {
    dummy_int =
      RelationEvaluateResidualGradientSafe(r, residual, gradient, &not_safe);
    return not_safe;
  }
  if (reltype == e_blackbox){
    if (BlackBoxCalcResidGrad(i, residual, gradient, r) ) {
      not_safe = safe_problem;
    }
    return not_safe;
  }
  if (reltype >= TOK_REL_TYPE_LOW && reltype <= TOK_REL_TYPE_HIGH) {
    if (reltype == e_glassbox){
      ERROR_REPORTER_HERE(ASC_PROG_ERR,"glassbox not implemented yet (%s)",__FUNCTION__);
    }
    if (reltype == e_opcode){
      ERROR_REPORTER_HERE(ASC_PROG_ERR,"opcode not supported (%s)",__FUNCTION__);
    }
    not_safe = safe_problem;
    return not_safe;
  }

  ASC_PANIC( "reached end of routine");
}


/*
    calculate the derivative with respect to a single variable
    whose index is index, where 1<=index<=NumberVariables(r)

    @TODO this appears only to be used in PrintGradients
*/
int
RelationCalcDerivative(struct Instance *i,
                       unsigned long vindex,
                       double *gradient)
{
  struct relation *r;
  enum Expr_enum reltype;

  CHECK_INST_RES(i,gradient,1);

  r = (struct relation *)GetInstanceRelation(i, &reltype);
  if( r == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null relation\n");
    return 1;
  }
  if( (vindex < 1) || (vindex > NumberVariables(r)) ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"index out of bounds\n");
    return 1;
  }

  if( reltype == e_token ) {
    *gradient = RelationEvaluateDerivative(r, vindex);
    return 0;
  }
  else if (reltype >= TOK_REL_TYPE_LOW && reltype <= TOK_REL_TYPE_HIGH) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"reltype not supported (%s)",__FUNCTION__);
    return 1;
  }
  ASC_PANIC( "reached end of routine");
}

enum safe_err
RelationCalcDerivativeSafe(struct Instance *i,
                           unsigned long vindex,
                           double *gradient)
{
  struct relation *r;
  enum Expr_enum reltype;
  enum safe_err not_safe = safe_ok;

#ifndef NDEBUG
  if(!relutil_check_inst_and_res(i,gradient)){
    not_safe = safe_problem;
    return not_safe;
  }
#endif
  r = (struct relation *)GetInstanceRelation(i, &reltype);
  if( r == NULL ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"null relation\n");
    not_safe = safe_problem;
    return not_safe;
  }
  if( (vindex < 1) || (vindex > NumberVariables(r)) ) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"index out of bounds\n");
    not_safe = safe_problem;
    return not_safe;
  }

  if( reltype == e_token ) {
    *gradient = RelationEvaluateDerivativeSafe(r, vindex, &not_safe);
    return not_safe;
  }
  else if (reltype >= TOK_REL_TYPE_LOW && reltype <= TOK_REL_TYPE_HIGH) {
    ERROR_REPORTER_HERE(ASC_PROG_ERR,"reltype not supported (%s)",__FUNCTION__);
    not_safe = safe_problem;
    return not_safe;
  }

  ASC_PANIC( "reached end of routine");
}

/**
    Function for testing residual and gradient calulations
*/
void PrintGradients(struct Instance *i){
  if (InstanceKind(i) == REL_INST) {
    double res, grads[1000];
    unsigned long vars, v;
    enum Expr_enum type;
    enum safe_err safe;

    vars = NumberVariables((struct relation *)GetInstanceRelation(i,&type));

    /*****  use the non safe versions  *****/
    for( v = 0; v < vars; v++ ) {
      if( ! RelationCalcDerivative(i, v+1, &res) ) {
        PRINTF("derivative in%5ld =\t%g\n", v+1, res);
      }
      else {
        PRINTF("**** RelationCalcDerivative returned nonzero status\n");
      }
    }

    if( ! RelationCalcResidGrad(i,&res,grads) ) {
      for (v = 0; v < vars; v++) {
        PRINTF("gradient in %6ld =\t%g\n", v+1, grads[v]);
      }
      PRINTF("residual from grad =\t%g\n", res);
    }
    else {
      PRINTF("**** RelationCalcResidGrad returned nonzero status\n");
    }

    if( !RelationCalcResidualInfix(i,&res) ) {
      PRINTF("    infix residual =\t%g\n", res);
    }
    else {
      PRINTF("**** RelationCalcResidualInfix returned nonzero status\n");
    }

    if( !RelationCalcResidualPostfix(i,&res) ) {
      PRINTF("  postfix residual =\t%g\n", res);
    }
    else {
      PRINTF("**** RelationCalcResidualPostfix returned nonzero status\n");
    }

    if( !RelationCalcResidualPostfix2(i,&res) ) {
      PRINTF(" postfix2 residual =\t%g\n", res);
    }
    else {
      PRINTF("**** RelationCalcResidualPostfix2 returned nonzero status\n");
    }

    /*****  use the safe versions  *****/
    for( v = 0; v < vars; v++ ) {
      if(safe_ok == (safe = RelationCalcDerivativeSafe(i, v+1, &res)) ) {
        PRINTF("safe deriv in%5ld =\t%g\n", v+1, res);
      }
      else {
        PRINTF("**** RelationCalcDerivativeSafe returned nonzero: %d\n", safe);
      }
    }

    if(safe_ok == (safe = RelationCalcResidGradSafe(i,&res,grads)) ) {
      for (v = 0; v < vars; v++) {
        PRINTF("safe grad in%6ld =\t%g\n", v+1, grads[v]);
      }
      PRINTF("safe resid ala grad=\t%g\n", res);
    }
    else {
      PRINTF("**** RelationCalcResidGradSafe returned nonzero: %d\n", safe);
    }

  /*****  not implemented
    if( ! (safe = RelationCalcResidualInfixSafe(i,&res)) ) {
      PRINTF("safe infix residual=\t%g\n", res);
    }
    else {
      PRINTF("**** RelationCalcResidualInfixSafe returned nonzero: %d\n",
             safe);
    }
  *****/

    if(safe_ok == (safe = RelationCalcResidualPostfixSafe(i,&res)) ) {
      PRINTF("safe postfix resid =\t%g\n", res);
    }
    else {
      PRINTF("**** RelationCalcResidualPostfixSafe returned nonzero: %d\n",
             safe);
    }

  /*****  not implemented
    if( ! (safe = RelationCalcResidualPostfix2Safe(i,&res)) ) {
      PRINTF("safe postfix2 resd =\t%g\n", res);
    }
    else {
      PRINTF("**** RelationCalcResidualPostfix2Safe returned nonzero: %d\n",
             safe);
    }
  *****/

    PRINTF("\n");
  }
}
void PrintRelationGradients(struct Instance *i)
{
  VisitInstanceTree(i,PrintGradients, 0, 0);
}

/* this function may make an fpe for method 2 or 3.
 * list must be of nonnull struct relation * for
 * meth = m_BIN and struct Instance * for 1-3.
 */
#define m_BIN 0
#define m_PFS 1
#define m_PF  2
#define m_IF  3
void TimeCalcResidual(struct gl_list_t *rlist,int method){
  unsigned long c,len;
  double res;

  if (rlist==NULL) return;
  switch (method) {
  case m_BIN:
    for (c=1,len=gl_length(rlist); c <= len; c++) {
      RelationCalcResidualBinary(gl_fetch(rlist,c),&res);
    }
    break;
  case m_PFS:
    for (c=1,len=gl_length(rlist); c <= len; c++) {
      RelationCalcResidualPostfixSafe(gl_fetch(rlist,c),&res);
    }
    break;
  case m_PF:
    for (c=1,len=gl_length(rlist); c <= len; c++) {
      RelationCalcResidualPostfix(gl_fetch(rlist,c),&res);
    }
    break;
  case m_IF:
    for (c=1,len=gl_length(rlist); c <= len; c++) {
      RelationCalcResidualInfix(gl_fetch(rlist,c),&res);
    }
    break;
  default:
   break;
  }
  return;
}

void PrintResidual(struct Instance *i){
  enum safe_err se;
  struct relation *rel;
  enum Expr_enum reltype;
  int errb;
#ifndef M_PI
#define M_PIE 3.141590271828
#else
#define M_PIE M_PI
#endif
  double post=M_PIE,in=M_PIE,postsafe=M_PIE,binary=M_PIE;

  if (InstanceKind(i) == REL_INST) {
    rel = (struct relation *)GetInstanceRelation(i,&reltype);
    if (reltype == e_token) {
      errb = RelationCalcResidualBinary(rel,&(binary));
    }else{
      errb = 1;
    }
    se = RelationCalcResidualPostfixSafe(i,&(postsafe));
    if (errb || se != safe_ok) {
      FPRINTF(ASCERR,"Skipping Postfix,Infix\n");
    }else{
      RelationCalcResidualPostfix(i,&(post));
      RelationCalcResidualInfix(i,&(in));
    }
    PRINTF("binary residual  = %.18g\n",binary);
    PRINTF("postfix safe res = %.18g\n",postsafe);
    if (errb||se!= safe_ok) {
      PRINTF("postfix residual = %.18g\n",post);
      PRINTF("  infix residual = %.18g\n",in);
    }
    if(binary != postsafe) {
      PRINTF("!!!!!!!ERROR!!!!!!! %g \n", binary-post);
    }
    PRINTF("(Unchanged residuals = %.18g\n\n",M_PIE);
  }
}

void PrintRelationResiduals(struct Instance *i){
  VisitInstanceTree(i,PrintResidual, 0, 0);
}

/*==============================================================================
  'RELATIONFINDROOTS' AND SUPPORT FUNCTIONS

    The following functions support RelationFindRoots which
    is the compiler-side implementation of our old solver-side DirectSolve
    function.
*/

double *RelationFindRoots(struct Instance *i,
        double lower_bound, double upper_bound,
        double nominal,
        double tolerance,
        unsigned long *varnum,
        int *able,
        int *nsolns
){
  struct relation *rel;
  double sideval;
  enum Expr_enum reltype;
  static struct ds_soln_list soln_list = {0,0,NULL};
  CONST struct gl_list_t *list;

  /* check for recycle shutdown */
  if (i==NULL && varnum == NULL && able == NULL && nsolns == NULL) {
    if (soln_list.soln != NULL) {
      ascfree(soln_list.soln);
      soln_list.soln = NULL;
      soln_list.length = soln_list.capacity = 0;
    }
    RootFind(NULL,NULL,NULL,NULL,NULL,0L,NULL); /*clear brent recycle */
    RelationCreateTmp(0,0,e_nop); /* clear tmprelation recycle */
    return NULL;
  }
  /* check assertions */
#ifndef NDEBUG
  if( i == NULL ) {
    FPRINTF(ASCERR, "error in RelationFindRoot: NULL instance\n");
    glob_rel = NULL;
    return NULL;
  }
  if (able == NULL){
    FPRINTF(ASCERR,"error in RelationFindRoot: NULL able ptr\n");
    glob_rel = NULL;
    return NULL;
  }
  if (varnum == NULL){
    FPRINTF(ASCERR,"error in RelationFindRoot: NULL varnum\n");
    glob_rel = NULL;
    return NULL;
  }
  if( InstanceKind(i) != REL_INST ) {
    FPRINTF(ASCERR, "error in RelationFindRoot: not relation\n");
    glob_rel = NULL;
    return NULL;
  }
#endif

  *able = FALSE;
  *nsolns = -1;     /* nsolns will be -1 for a very unhappy root-finder */
  glob_rel = NULL;
  glob_done = 0;
  soln_list.length = 0; /* reset len to 0. if NULL to start, append mallocs */
  append_soln(&soln_list,0.0);
  rel = (struct relation *)GetInstanceRelation(i, &reltype);
  if( rel == NULL ) {
    FPRINTF(ASCERR, "error in RelationFindRoot: NULL relation\n");
    glob_rel = NULL; return NULL;
  }
  /* here we should switch and handle all types. at present we don't
   * handle anything except e_token
   */
  if( reltype != e_token ) {
    FPRINTF(ASCERR, "error in RelationFindRoot: non-token relation\n");
    glob_rel = NULL;
    return NULL;
  }

  if (RelationRelop(rel) == e_equal){
    glob_rel = RelationTmpTokenCopy(rel);
    assert(glob_rel!=NULL);
    glob_done = 0;
    list = RelationVarList(glob_rel);
    if( *varnum >= 1 && *varnum <= gl_length(list)){
      glob_done = 1;
    }
    if (!glob_done) {
      FPRINTF(ASCERR, "error in FindRoot: var not found\n");
      glob_rel = NULL;
      return NULL;
    }

    glob_varnum = *varnum;
    glob_done = 0;
    assert(Infix_LhsSide(glob_rel) != NULL);
    /* In the following if statements we look for the target variable
     * to the left and right, evaluating all branches without the
     * target.
     */
    if (SearchEval_Branch(Infix_LhsSide(glob_rel)) < 1) {
      /* CONSOLE_DEBUG("SearchEval_Branch(Infix_LhsSide(glob_rel)) gave < 1..."); */
      sideval = RelationBranchEvaluator(Infix_LhsSide(glob_rel));
      if (asc_finite(sideval)) {
        /* CONSOLE_DEBUG("LHS is finite"); */
        InsertBranchResult(Infix_LhsSide(glob_rel),sideval);
      }else{
        /* CONSOLE_DEBUG("LHS is INFINITE"); */
        FPRINTF(ASCERR,"Inequality in RelationFindRoots. Infinite RHS.\n");
        glob_rel = NULL;
        return NULL;
      }
    }
    assert(Infix_RhsSide(glob_rel) != NULL);
    if (SearchEval_Branch(Infix_RhsSide(glob_rel)) < 1) {
        /* CONSOLE_DEBUG("SearchEval_Branch(Infix_RhsSide(glob_rel)) gave < 1..."); */
        sideval = RelationBranchEvaluator(Infix_RhsSide(glob_rel));
        if (asc_finite(sideval)) {
          /* CONSOLE_DEBUG("RHS is finite"); */
          InsertBranchResult(Infix_RhsSide(glob_rel),sideval);
        }else{
          /* CONSOLE_DEBUG("RHS is INFINITE"); */
          FPRINTF(ASCERR,"Inequality in RelationFindRoots. Infinite LHS.\n");
          glob_rel = NULL;
          return NULL;
        }
    }
    if (glob_done < 1) {
      /* CONSOLE_DEBUG("RelationInvertToken never found variable"); */
      /* RelationInvertToken never found variable */
      glob_done = 0;
      *able = FALSE;
      return soln_list.soln;
    }
    if (glob_done == 1) {
      /* set to 0 so while loop in RelationInvertToken will work */
      glob_done = 0;
      /* CONSOLE_DEBUG("Calling 'RelationInvertToken'..."); */
      glob_done = RelationInvertTokenTop(&(soln_list));
    }
    if (glob_done == 1) { /* if still one, token inversions successful */
        /* CONSOLE_DEBUG("INVERSION was successful"); */
      glob_done = 0;
      *nsolns= soln_list.length;
      *able = TRUE;
      return soln_list.soln;
    }
    /* CALL ITERATIVE SOLVER */
    *soln_list.soln = RootFind(glob_rel,&(lower_bound),
                       &(upper_bound),&(nominal),
                       &(tolerance),
                       glob_varnum,able);

    glob_done = 0;
    if(*able == 0) { /* Root-Find returns 0 for success*/
      *nsolns = 1;
      *able = TRUE;
    }else{
      CONSOLE_DEBUG("Single-equation iterative solver was unable to find a solution.");
      *able = FALSE;
    }
    return soln_list.soln;

  }
  ERROR_REPORTER_HERE(ASC_PROG_ERR,"Inequality: can't find roots.");
  *able = FALSE;
  return soln_list.soln;
}

/*------------------------------------------------------------------------------
  MEMORY MANAGEMENT AND COPYING FUNCTIONS
  to support the RelationFindRoots function.
*/

/**
    @see RelationFindRoots

    Create a struct relation of type e_token
    and passes back a pointer to the relation.

    The lengths of
    the right and left sides (lhslen and rhslen) of the relation
    are supplied by the calling function.

    User is responsible for setting RTOKEN(return).*_len.

    Basically, all this does is manage memory nicely.

    IF called with all 0/NULL, frees internal recycles.
*/
static struct relation *RelationCreateTmp(
        unsigned long lhslen, unsigned long rhslen,
        enum Expr_enum relop
){
  static struct relation *rel=NULL;
  static unsigned long lhscap=0, rhscap=0;

  /* check for recycle clear and free things if needed. */
  if (lhslen==0 && rhslen == 0 && relop == e_nop) {
    if (rel != NULL) {
      if (rel->share != NULL) {
        if (RTOKEN(rel).lhs!=NULL) {
          ascfree(RTOKEN(rel).lhs);
        }
        if (RTOKEN(rel).rhs!=NULL)  {
          ascfree(RTOKEN(rel).rhs);
        }
        ascfree(rel->share);
      }
      ascfree(rel);
      rel = NULL;
    }
    lhscap = rhscap = 0;
    return NULL;
  }
  if (rel == NULL) {
    rel = CreateRelationStructure(relop,crs_NEWUNION);
  }
  if (lhscap < lhslen) {
    lhscap = lhslen;
    if ( RTOKEN(rel).lhs != NULL) {
      ascfree(RTOKEN(rel).lhs);
    }
    RTOKEN(rel).lhs = ASC_NEW_ARRAY(union RelationTermUnion,lhscap);
  }
  if (rhscap < rhslen) {
    rhscap = rhslen;
    if ( RTOKEN(rel).rhs != NULL) {
      ascfree(RTOKEN(rel).rhs);
    }
    RTOKEN(rel).rhs = ASC_NEW_ARRAY(union RelationTermUnion,rhscap);
  }
  return rel;
}

/**
    @see RelationFindRoots

    Full-blown relation copy (not copy by reference)

    We can now just do a memcopy and the infix pointers
    all adjust by the difference between the token
    arrays that the gl_lists are hiding. Cool, eh?

    @NOTE if any turkey ever tries to delete an individual
    token from these gl_lists AND deallocate it,
    they will get a severe headache. Ooo scary.

    This is a full blown copy and not copy by reference.
    You do not need to remake the infix pointers after
    calling this function. return 0 if ok, 1 if error.

    @NOTE RelationTmpCopySide and RelationTmpCopyToken are reimplimentations
    of functions from the v. old 'exprman' file.
*/
static int RelationTmpCopySide(union RelationTermUnion *old,
        unsigned long len,
        union RelationTermUnion *arr
){
  struct relation_term *term;
  unsigned long c;
  long int delta;

  if (old==NULL || !len) return 1;
  if (arr==NULL) {
    FPRINTF(ASCERR,"RelationTmpCopySide: null RelationTermUnion :-(.\n");
    return 1;
  }
  memcpy( (VOIDPTR)arr, (VOIDPTR)old, len*sizeof(union RelationTermUnion));
 /*
  *  Difference in chars between old and arr ptrs. It should me a multiple
  *  of sizeof(double) but may not be a multiple of sizeof(union RTU).
  *  Delta may easily be negative.
  *  Normally, though arr > old.
  */
  delta = (char *)arr - (char *)old;
#ifdef ADJPTR
#undef ADJPTR
#endif
#define ADJPTR(p) ( (p) = A_TERM((char *)(p)+delta) )
  for (c=0;c<len;c++) {
    term = A_TERM(&(arr[c]));
    switch (term->t) {
    /* unary terms */
    case e_uminus:
      ADJPTR(U_TERM(term)->left);
      break;
    /* binary terms */
    case e_plus:
    case e_minus: case e_times:
    case e_divide: case e_power: case e_ipower:
      ADJPTR(B_TERM(term)->left);
      ADJPTR(B_TERM(term)->right);
      break;
    case e_zero:
    case e_var:         /* the var number will be correct */
    case e_int:
    case e_real:
      break;
    case e_func:
      ADJPTR(F_TERM(term)->left);
      break;
    /* don't know how to deal with the following relation operators.
       they may be binary or unary, but InfixArr_MakeSide never set them. */
    case e_maximize: case e_minimize:
    case e_equal: case e_notequal: case e_less:
    case e_greater: case e_lesseq: case e_greatereq:
    default:
      ASC_PANIC("Unknown term type");
      break;
    }
  }
#undef ADJPTR

  return 0;
}

/**
    @see RelationFindRoots

    Copy tmp token for a relation (guess -- JP)

    The relation returned by this function should have
    NO persistent pointers made to it, as it is still
    our property. The vars in the relation do not
    know about these references to them, as this is
    a tmp rel.

    @NOTE RelationTmpCopySide and RelationTmpCopyToken are reimplimentations
    of functions from the v. old 'exprman' file.
*/
static struct relation *RelationTmpTokenCopy(CONST struct relation *src){
  struct relation *result;
  long int delta;
  assert(src!=NULL);

  result = RelationCreateTmp(RTOKEN(src).lhs_len,RTOKEN(src).rhs_len,
                             RelationRelop(src));

  if(RelationTmpCopySide(RTOKEN(src).lhs,RTOKEN(src).lhs_len,
                RTOKEN(result).lhs) == 0) {
    delta = UNION_TERM(RTOKEN(src).lhs_term) - RTOKEN(src).lhs;
    RTOKEN(result).lhs_term = A_TERM(RTOKEN(result).lhs+delta);
    RTOKEN(result).lhs_len = RTOKEN(src).lhs_len;
  }else{
    RTOKEN(result).lhs_term = NULL;
    RTOKEN(result).lhs_len = 0;
  }

  if( RelationTmpCopySide(RTOKEN(src).rhs,RTOKEN(src).rhs_len,
                  RTOKEN(result).rhs) == 0) {
    delta = UNION_TERM(RTOKEN(src).rhs_term) - RTOKEN(src).rhs;
    RTOKEN(result).rhs_term = A_TERM(RTOKEN(result).rhs+delta);
    RTOKEN(result).rhs_len = RTOKEN(src).rhs_len;
  }else{
    RTOKEN(result).rhs_term = NULL;
    RTOKEN(result).rhs_len = 0;
  }
  result->vars = src->vars;
  result->d = src->d;
  result->residual = src->residual;
  result->multiplier = src->multiplier;
  result->nominal = src->nominal;
  result->iscond = src->iscond;
  return result;
}

#define alloc_array(nelts,type) ((nelts) > 0 ? ASC_NEW_ARRAY(type,nelts) : NULL)
#define copy_nums(from,too,nnums)  \
   asc_memcpy((from),(too),(nnums)*sizeof(double))

/**
    @see RelationFindRoots

    Appends the solution onto the solution list
*/
static void append_soln( struct ds_soln_list *sl, double soln){
  if( sl->length == sl->capacity ) {
    int newcap;
    double *newlist;

    newcap = sl->capacity + 10;
    newlist = alloc_array(newcap,double);
    copy_nums((char *)sl->soln,(char *)newlist,sl->length);
    if( sl->soln != NULL ) {
      ascfree(sl->soln);
    }
    sl->soln = newlist;
    sl->capacity = newcap;
  }

  sl->soln[sl->length++] = soln;
}

/**
    @see RelationFindRoots

    Removes solution at given index from solution list.
*/
static void remove_soln( struct ds_soln_list *sl, int ndx){
  copy_nums((char *)(sl->soln+ndx+1),
            (char *)(sl->soln+ndx), --(sl->length) - ndx);
}

/*------------------------------------------------------------------------------
  DIRECT SOLVE FUNCTIONS
  to support the RelationFindRoots function.
*/

/**
    @see RelationFindRoots

    Change a relation term type to e_real and fill the value field of this term.

    In subsequent passes of the RelationBranchEvaluator the term will be
    considered to be a leaf.
 */
static void InsertBranchResult(struct relation_term *term, double value){
  assert(term!=NULL);
  term->t = e_real;
  R_TERM(term)->value = value;
}

/**
    @see RelationFindRoots

    Simplify branches of a relation (the relation pointed to by glob_rel).

    Only terms of type e_real, e_int, e_zero, and e_var are left
    hanging off the operators on the path to the
    variable (with varnum = glob_varnum) being direct
    solved for.

    @TODO This may need to be changed to only leave e_reals
    so that the inversion routine can make faster decisions???
    Probably not.

    @return >= 1 if glob_varnum spotted, else 0 (or at least <1).
*/
static int SearchEval_Branch(struct relation_term *term){
  int result = 0;