267 lines
7.3 KiB
C++
267 lines
7.3 KiB
C++
/* fortran/dgetf2.f -- translated by f2c (version 20200916).
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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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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "lmp_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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/* .. Scalar Arguments .. */
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/* INTEGER INFO, LDA, M, N */
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/* .. */
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/* .. Array Arguments .. */
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/* INTEGER IPIV( * ) */
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/* DOUBLE PRECISION A( LDA, * ) */
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/* .. */
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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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/* > \ingroup doubleGEcomputational */
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/* ===================================================================== */
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/* Subroutine */ int dgetf2_(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 dger_(integer *, integer *, doublereal *,
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doublereal *, integer *, doublereal *, integer *, doublereal *,
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integer *), dscal_(integer *, doublereal *, doublereal *, integer
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*);
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doublereal sfmin;
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extern /* Subroutine */ int dswap_(integer *, doublereal *, integer *,
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doublereal *, integer *);
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extern doublereal dlamch_(char *, ftnlen);
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extern integer idamax_(integer *, doublereal *, integer *);
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extern /* Subroutine */ int xerbla_(char *, integer *, ftnlen);
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/* -- LAPACK computational routine -- */
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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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/* .. Scalar Arguments .. */
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/* .. */
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/* .. Array Arguments .. */
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/* .. */
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/* ===================================================================== */
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/* .. Parameters .. */
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/* .. */
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/* .. Local Scalars .. */
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/* .. */
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/* .. External Functions .. */
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/* .. */
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/* .. External Subroutines .. */
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/* .. */
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/* .. Intrinsic Functions .. */
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/* .. */
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/* .. Executable Statements .. */
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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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xerbla_((char *)"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 = dlamch_((char *)"S", (ftnlen)1);
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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 + idamax_(&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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dswap_(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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dscal_(&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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dger_(&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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} /* dgetf2_ */
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#ifdef __cplusplus
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}
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#endif
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