119 lines
3.1 KiB
C
119 lines
3.1 KiB
C
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/*! @file clangs.c
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* \brief Returns the value of the one norm
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*
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* <pre>
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* -- SuperLU routine (version 2.0) --
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* Univ. of California Berkeley, Xerox Palo Alto Research Center,
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* and Lawrence Berkeley National Lab.
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* November 15, 1997
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*
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* Modified from lapack routine CLANGE
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* </pre>
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*/
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/*
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* File name: clangs.c
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* History: Modified from lapack routine CLANGE
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*/
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#include <math.h>
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#include "slu_cdefs.h"
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/*! \brief
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*
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* <pre>
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* Purpose
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* =======
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*
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* CLANGS returns the value of the one norm, or the Frobenius norm, or
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* the infinity norm, or the element of largest absolute value of a
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* real matrix A.
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*
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* Description
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* ===========
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*
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* CLANGE returns the value
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*
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* CLANGE = ( max(abs(A(i,j))), NORM = 'M' or 'm'
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* (
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* ( norm1(A), NORM = '1', 'O' or 'o'
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* (
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* ( normI(A), NORM = 'I' or 'i'
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* (
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* ( normF(A), NORM = 'F', 'f', 'E' or 'e'
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*
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* where norm1 denotes the one norm of a matrix (maximum column sum),
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* normI denotes the infinity norm of a matrix (maximum row sum) and
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* normF denotes the Frobenius norm of a matrix (square root of sum of
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* squares). Note that max(abs(A(i,j))) is not a matrix norm.
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*
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* Arguments
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* =========
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*
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* NORM (input) CHARACTER*1
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* Specifies the value to be returned in CLANGE as described above.
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* A (input) SuperMatrix*
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* The M by N sparse matrix A.
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*
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* =====================================================================
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* </pre>
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*/
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float clangs(char *norm, SuperMatrix *A)
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{
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/* Local variables */
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NCformat *Astore;
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complex *Aval;
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int i, j, irow;
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float value, sum;
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float *rwork;
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Astore = A->Store;
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Aval = Astore->nzval;
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if ( SUPERLU_MIN(A->nrow, A->ncol) == 0) {
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value = 0.;
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} else if (lsame_(norm, "M")) {
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/* Find max(abs(A(i,j))). */
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value = 0.;
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for (j = 0; j < A->ncol; ++j)
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for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; i++)
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value = SUPERLU_MAX( value, c_abs( &Aval[i]) );
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} else if (lsame_(norm, "O") || *(unsigned char *)norm == '1') {
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/* Find norm1(A). */
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value = 0.;
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for (j = 0; j < A->ncol; ++j) {
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sum = 0.;
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for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; i++)
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sum += c_abs( &Aval[i] );
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value = SUPERLU_MAX(value,sum);
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}
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} else if (lsame_(norm, "I")) {
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/* Find normI(A). */
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if ( !(rwork = (float *) SUPERLU_MALLOC(A->nrow * sizeof(float))) )
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ABORT("SUPERLU_MALLOC fails for rwork.");
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for (i = 0; i < A->nrow; ++i) rwork[i] = 0.;
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for (j = 0; j < A->ncol; ++j)
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for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; i++) {
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irow = Astore->rowind[i];
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rwork[irow] += c_abs( &Aval[i] );
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}
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value = 0.;
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for (i = 0; i < A->nrow; ++i)
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value = SUPERLU_MAX(value, rwork[i]);
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SUPERLU_FREE (rwork);
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} else if (lsame_(norm, "F") || lsame_(norm, "E")) {
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/* Find normF(A). */
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ABORT("Not implemented.");
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} else
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ABORT("Illegal norm specified.");
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return (value);
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} /* clangs */
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