Abdelrahman Said
245 lines
6.9 KiB
C
245 lines
6.9 KiB
C
/* -- translated by f2c (version 20240504).
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You must link the resulting object file with libf2c:
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on Microsoft Windows system, link with libf2c.lib;
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on Linux or Unix systems, link with .../path/to/libf2c.a -lm
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or, if you install libf2c.a in a standard place, with -lf2c -lm
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-- in that order, at the end of the command line, as in
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cc *.o -lf2c -lm
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Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
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http://www.netlib.org/f2c/libf2c.zip
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*/
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#include "f2c.h"
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/* Table of constant values */
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static integer c__1 = 1;
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static doublereal c_b8 = -1.;
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/* > \brief \b DGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row
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interchanges (unblocked algorithm).
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=========== DOCUMENTATION ===========
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Online html documentation available at
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http://www.netlib.org/lapack/explore-html/
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> \htmlonly
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> Download DGETF2 + dependencies
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dgetf2.
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f">
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> [TGZ]</a>
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dgetf2.
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f">
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> [ZIP]</a>
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dgetf2.
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f">
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> [TXT]</a>
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> \endhtmlonly
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Definition:
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===========
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SUBROUTINE DGETF2( M, N, A, LDA, IPIV, INFO )
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INTEGER INFO, LDA, M, N
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INTEGER IPIV( * )
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DOUBLE PRECISION A( LDA, * )
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> \par Purpose:
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=============
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>
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> \verbatim
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>
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> DGETF2 computes an LU factorization of a general m-by-n matrix A
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> using partial pivoting with row interchanges.
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>
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> The factorization has the form
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> A = P * L * U
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> where P is a permutation matrix, L is lower triangular with unit
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> diagonal elements (lower trapezoidal if m > n), and U is upper
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> triangular (upper trapezoidal if m < n).
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>
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> This is the right-looking Level 2 BLAS version of the algorithm.
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> \endverbatim
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Arguments:
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==========
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> \param[in] M
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> \verbatim
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> M is INTEGER
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> The number of rows of the matrix A. M >= 0.
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> \endverbatim
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>
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> \param[in] N
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> \verbatim
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> N is INTEGER
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> The number of columns of the matrix A. N >= 0.
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> \endverbatim
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>
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> \param[in,out] A
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> \verbatim
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> A is DOUBLE PRECISION array, dimension (LDA,N)
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> On entry, the m by n matrix to be factored.
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> On exit, the factors L and U from the factorization
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> A = P*L*U; the unit diagonal elements of L are not stored.
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> \endverbatim
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>
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> \param[in] LDA
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> \verbatim
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> LDA is INTEGER
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> The leading dimension of the array A. LDA >= max(1,M).
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> \endverbatim
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>
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> \param[out] IPIV
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> \verbatim
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> IPIV is INTEGER array, dimension (min(M,N))
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> The pivot indices; for 1 <= i <= min(M,N), row i of the
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> matrix was interchanged with row IPIV(i).
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> \endverbatim
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>
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> \param[out] INFO
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> \verbatim
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> INFO is INTEGER
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> = 0: successful exit
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> < 0: if INFO = -k, the k-th argument had an illegal value
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> > 0: if INFO = k, U(k,k) is exactly zero. The factorization
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> has been completed, but the factor U is exactly
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> singular, and division by zero will occur if it is used
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> to solve a system of equations.
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> \endverbatim
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Authors:
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========
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> \author Univ. of Tennessee
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> \author Univ. of California Berkeley
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> \author Univ. of Colorado Denver
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> \author NAG Ltd.
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> \date September 2012
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> \ingroup doubleGEcomputational
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=====================================================================
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Subroutine */ int igraphdgetf2_(integer *m, integer *n, doublereal *a, integer *
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lda, integer *ipiv, integer *info)
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{
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2, i__3;
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doublereal d__1;
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/* Local variables */
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integer i__, j, jp;
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extern /* Subroutine */ int igraphdger_(integer *, integer *, doublereal *,
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doublereal *, integer *, doublereal *, integer *, doublereal *,
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integer *), igraphdscal_(integer *, doublereal *, doublereal *, integer
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*);
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doublereal sfmin;
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extern /* Subroutine */ int igraphdswap_(integer *, doublereal *, integer *,
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doublereal *, integer *);
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extern doublereal igraphdlamch_(char *);
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extern integer igraphidamax_(integer *, doublereal *, integer *);
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extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);
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/* -- LAPACK computational routine (version 3.4.2) --
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-- LAPACK is a software package provided by Univ. of Tennessee, --
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-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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September 2012
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=====================================================================
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Test the input parameters.
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Parameter adjustments */
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a_dim1 = *lda;
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a_offset = 1 + a_dim1;
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a -= a_offset;
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--ipiv;
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/* Function Body */
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*info = 0;
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if (*m < 0) {
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*info = -1;
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} else if (*n < 0) {
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*info = -2;
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} else if (*lda < max(1,*m)) {
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*info = -4;
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}
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if (*info != 0) {
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i__1 = -(*info);
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igraphxerbla_("DGETF2", &i__1, (ftnlen)6);
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return 0;
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}
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/* Quick return if possible */
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if (*m == 0 || *n == 0) {
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return 0;
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}
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/* Compute machine safe minimum */
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sfmin = igraphdlamch_("S");
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i__1 = min(*m,*n);
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for (j = 1; j <= i__1; ++j) {
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/* Find pivot and test for singularity. */
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i__2 = *m - j + 1;
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jp = j - 1 + igraphidamax_(&i__2, &a[j + j * a_dim1], &c__1);
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ipiv[j] = jp;
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if (a[jp + j * a_dim1] != 0.) {
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/* Apply the interchange to columns 1:N. */
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if (jp != j) {
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igraphdswap_(n, &a[j + a_dim1], lda, &a[jp + a_dim1], lda);
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}
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/* Compute elements J+1:M of J-th column. */
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if (j < *m) {
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if ((d__1 = a[j + j * a_dim1], abs(d__1)) >= sfmin) {
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i__2 = *m - j;
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d__1 = 1. / a[j + j * a_dim1];
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igraphdscal_(&i__2, &d__1, &a[j + 1 + j * a_dim1], &c__1);
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} else {
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i__2 = *m - j;
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for (i__ = 1; i__ <= i__2; ++i__) {
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a[j + i__ + j * a_dim1] /= a[j + j * a_dim1];
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/* L20: */
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}
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}
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}
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} else if (*info == 0) {
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*info = j;
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}
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if (j < min(*m,*n)) {
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/* Update trailing submatrix. */
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i__2 = *m - j;
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i__3 = *n - j;
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igraphdger_(&i__2, &i__3, &c_b8, &a[j + 1 + j * a_dim1], &c__1, &a[j + (
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j + 1) * a_dim1], lda, &a[j + 1 + (j + 1) * a_dim1], lda);
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}
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/* L10: */
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}
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return 0;
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/* End of DGETF2 */
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} /* igraphdgetf2_ */
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