trunk/blas/idamax.f

C  idamax.f
C  is freely available from netlib. It is not subject to any GNU License
C  set by the authors of the ASCEND math programming system.
C  $Date: 1996/04/30 18:14:08 $ $Revision: 1.1.1.1 $
C
      integer function idamax(n,dx,incx)
c
c     finds the index of element having max. absolute value.
c     jack dongarra, linpack, 3/11/78.
c     modified to correct problem with negative increment, 8/21/90.
c
      double precision dx(*),dmax
      integer i,incx,ix,n
c
      idamax = 0
      if( n .lt. 1 ) return
      idamax = 1
      if(n.eq.1)return
      if(incx.eq.1)go to 20
c
c        code for increment not equal to 1
c
      ix = 1
      if(incx.lt.0)ix = (-n+1)*incx + 1
      dmax = dabs(dx(ix))
      ix = ix + incx
      do 10 i = 2,n
         if(dabs(dx(ix)).le.dmax) go to 5
         idamax = i
         dmax = dabs(dx(ix))
    5    ix = ix + incx
   10 continue
      return
c
c        code for increment equal to 1
c
   20 dmax = dabs(dx(1))
      do 30 i = 2,n
         if(dabs(dx(i)).le.dmax) go to 30
         idamax = i
         dmax = dabs(dx(i))
   30 continue
      return
      end
1	C idamax.f
2	C is freely available from netlib. It is not subject to any GNU License
3	C set by the authors of the ASCEND math programming system.
4	C $Date: 1996/04/30 18:14:08 $ $Revision: 1.1.1.1 $
5	C
6	integer function idamax(n,dx,incx)
7	c
8	c finds the index of element having max. absolute value.
9	c jack dongarra, linpack, 3/11/78.
10	c modified to correct problem with negative increment, 8/21/90.
11	c
12	double precision dx(*),dmax
13	integer i,incx,ix,n
14	c
15	idamax = 0
16	if( n .lt. 1 ) return
17	idamax = 1
18	if(n.eq.1)return
19	if(incx.eq.1)go to 20
20	c
21	c code for increment not equal to 1
22	c
23	ix = 1
24	if(incx.lt.0)ix = (-n+1)*incx + 1
25	dmax = dabs(dx(ix))
26	ix = ix + incx
27	do 10 i = 2,n
28	if(dabs(dx(ix)).le.dmax) go to 5
29	idamax = i
30	dmax = dabs(dx(ix))
31	5 ix = ix + incx
32	10 continue
33	return
34	c
35	c code for increment equal to 1
36	c
37	20 dmax = dabs(dx(1))
38	do 30 i = 2,n
39	if(dabs(dx(i)).le.dmax) go to 30
40	idamax = i
41	dmax = dabs(dx(i))
42	30 continue
43	return
44	end