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C idamax.f |
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C is freely available from netlib. It is not subject to any GNU License |
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C set by the authors of the ASCEND math programming system. |
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C $Date: 1996/04/30 18:14:08 $ $Revision: 1.1.1.1 $ |
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C |
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integer function idamax(n,dx,incx) |
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c |
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c finds the index of element having max. absolute value. |
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c jack dongarra, linpack, 3/11/78. |
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c modified to correct problem with negative increment, 8/21/90. |
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c |
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double precision dx(*),dmax |
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integer i,incx,ix,n |
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c |
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idamax = 0 |
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if( n .lt. 1 ) return |
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idamax = 1 |
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if(n.eq.1)return |
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if(incx.eq.1)go to 20 |
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c |
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c code for increment not equal to 1 |
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c |
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ix = 1 |
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if(incx.lt.0)ix = (-n+1)*incx + 1 |
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dmax = dabs(dx(ix)) |
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ix = ix + incx |
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do 10 i = 2,n |
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if(dabs(dx(ix)).le.dmax) go to 5 |
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idamax = i |
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dmax = dabs(dx(ix)) |
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5 ix = ix + incx |
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10 continue |
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return |
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c |
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c code for increment equal to 1 |
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c |
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20 dmax = dabs(dx(1)) |
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do 30 i = 2,n |
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if(dabs(dx(i)).le.dmax) go to 30 |
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idamax = i |
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dmax = dabs(dx(i)) |
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30 continue |
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return |
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end |
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