umf_scale.c
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/* ========================================================================== */
/* === UMF_scale ============================================================ */
/* ========================================================================== */
/* -------------------------------------------------------------------------- */
/* UMFPACK Copyright (c) Timothy A. Davis, CISE, */
/* Univ. of Florida. All Rights Reserved. See ../Doc/License for License. */
/* web: http://www.cise.ufl.edu/research/sparse/umfpack */
/* -------------------------------------------------------------------------- */
/* Divide a vector of stride 1 by the pivot value. */
#include "umf_internal.h"
GLOBAL void UMF_scale
(
Int n,
Entry pivot,
Entry X [ ]
)
{
Entry x ;
double s ;
Int i ;
/* ---------------------------------------------------------------------- */
/* compute the approximate absolute value of the pivot, and select method */
/* ---------------------------------------------------------------------- */
APPROX_ABS (s, pivot) ;
if (s < RECIPROCAL_TOLERANCE || IS_NAN (pivot))
{
/* ------------------------------------------------------------------ */
/* tiny, or zero, pivot case */
/* ------------------------------------------------------------------ */
/* The pivot is tiny, or NaN. Do not divide zero by the pivot value,
* and do not multiply by 1/pivot, either. */
for (i = 0 ; i < n ; i++)
{
/* X [i] /= pivot ; */
x = X [i] ;
#ifndef NO_DIVIDE_BY_ZERO
if (IS_NONZERO (x))
{
DIV (X [i], x, pivot) ;
}
#else
/* Do not divide by zero */
if (IS_NONZERO (x) && IS_NONZERO (pivot))
{
DIV (X [i], x, pivot) ;
}
#endif
}
}
else
{
/* ------------------------------------------------------------------ */
/* normal case */
/* ------------------------------------------------------------------ */
/* The pivot is not tiny, and is not NaN. Don't bother to check for
* zeros in the pivot column, X. This is slightly more accurate than
* multiplying by 1/pivot (but slightly slower), particularly if the
* pivot column consists of only IEEE subnormals. */
for (i = 0 ; i < n ; i++)
{
/* X [i] /= pivot ; */
x = X [i] ;
DIV (X [i], x, pivot) ;
}
}
}