Mercurial > octave-nkf
view liboctave/UMFPACK/UMFPACK/Source/umf_scale.c @ 5164:57077d0ddc8e
[project @ 2005-02-25 19:55:24 by jwe]
author | jwe |
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date | Fri, 25 Feb 2005 19:55:28 +0000 |
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/* ========================================================================== */ /* === UMF_scale ============================================================ */ /* ========================================================================== */ /* -------------------------------------------------------------------------- */ /* UMFPACK Version 4.4, Copyright (c) 2005 by Timothy A. Davis. CISE Dept, */ /* 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. select the x/pivot or x * (1/pivot) method */ /* ------------------------------------------------------------------ */ /* The pivot is not tiny, and is not NaN. Don't bother to check for * zeros in the pivot column, X. */ #if !defined (NRECIPROCAL) && !(defined (__GNUC__) && defined (COMPLEX)) /* -------------------------------------------------------------- */ /* multiply x by (1/pivot) */ /* -------------------------------------------------------------- */ /* Slightly less accurate, but faster. It allows the use of * the level-1 BLAS dscal or zscal routine. This not used when * UMFPACK is used in MATLAB (either as a built-in routine, or as * a mexFunction). * * Using gcc version 3.2 can cause the following code to fail for * some complex matrices (not all), with or without the BLAS. This * was found in Red Hat Linux 7.3 on a Dell Latitude C840 with a * Pentium 4M. Thus, this code is not used when gcc is used, for * the complex case. * * It works just fine with Intel's icc compiler, version 7.0. */ /* pivot = 1 / pivot */ RECIPROCAL (pivot) ; #if defined (USE_NO_BLAS) for (i = 0 ; i < n ; i++) { /* X [i] *= pivot ; */ x = X [i] ; MULT (X [i], x, pivot) ; } #else BLAS_SCAL (n, pivot, X) ; #endif #else /* -------------------------------------------------------------- */ /* divide x by the pivot */ /* -------------------------------------------------------------- */ /* This is slightly more accurate, particularly if the pivot column * consists of only IEEE subnormals. Always do this if UMFPACK is * being compiled as a built-in routine or mexFunction in MATLAB, * or if gcc is being used with complex matrices. */ for (i = 0 ; i < n ; i++) { /* X [i] /= pivot ; */ x = X [i] ; DIV (X [i], x, pivot) ; } #endif } }