/* -- translated by f2c (version 20100827).
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*/
#include "f2c.h"
/* Table of constant values */
static integer c__1 = 1;
static doublereal c_b8 = -1.;
/* > \brief \b DGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row
interchanges (unblocked algorithm).
=========== DOCUMENTATION ===========
Online html documentation available at
http://www.netlib.org/lapack/explore-html/
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Definition:
===========
SUBROUTINE DGETF2( M, N, A, LDA, IPIV, INFO )
INTEGER INFO, LDA, M, N
INTEGER IPIV( * )
DOUBLE PRECISION A( LDA, * )
> \par Purpose:
=============
>
> \verbatim
>
> DGETF2 computes an LU factorization of a general m-by-n matrix A
> using partial pivoting with row interchanges.
>
> The factorization has the form
> A = P * L * U
> where P is a permutation matrix, L is lower triangular with unit
> diagonal elements (lower trapezoidal if m > n), and U is upper
> triangular (upper trapezoidal if m < n).
>
> This is the right-looking Level 2 BLAS version of the algorithm.
> \endverbatim
Arguments:
==========
> \param[in] M
> \verbatim
> M is INTEGER
> The number of rows of the matrix A. M >= 0.
> \endverbatim
>
> \param[in] N
> \verbatim
> N is INTEGER
> The number of columns of the matrix A. N >= 0.
> \endverbatim
>
> \param[in,out] A
> \verbatim
> A is DOUBLE PRECISION array, dimension (LDA,N)
> On entry, the m by n matrix to be factored.
> On exit, the factors L and U from the factorization
> A = P*L*U; the unit diagonal elements of L are not stored.
> \endverbatim
>
> \param[in] LDA
> \verbatim
> LDA is INTEGER
> The leading dimension of the array A. LDA >= max(1,M).
> \endverbatim
>
> \param[out] IPIV
> \verbatim
> IPIV is INTEGER array, dimension (min(M,N))
> The pivot indices; for 1 <= i <= min(M,N), row i of the
> matrix was interchanged with row IPIV(i).
> \endverbatim
>
> \param[out] INFO
> \verbatim
> INFO is INTEGER
> = 0: successful exit
> < 0: if INFO = -k, the k-th argument had an illegal value
> > 0: if INFO = k, U(k,k) is exactly zero. The factorization
> has been completed, but the factor U is exactly
> singular, and division by zero will occur if it is used
> to solve a system of equations.
> \endverbatim
Authors:
========
> \author Univ. of Tennessee
> \author Univ. of California Berkeley
> \author Univ. of Colorado Denver
> \author NAG Ltd.
> \date September 2012
> \ingroup doubleGEcomputational
=====================================================================
Subroutine */ int igraphdgetf2_(integer *m, integer *n, doublereal *a, integer *
lda, integer *ipiv, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
doublereal d__1;
/* Local variables */
integer i__, j, jp;
extern /* Subroutine */ int igraphdger_(integer *, integer *, doublereal *,
doublereal *, integer *, doublereal *, integer *, doublereal *,
integer *), igraphdscal_(integer *, doublereal *, doublereal *, integer
*);
doublereal sfmin;
extern /* Subroutine */ int igraphdswap_(integer *, doublereal *, integer *,
doublereal *, integer *);
extern doublereal igraphdlamch_(char *);
extern integer igraphidamax_(integer *, doublereal *, integer *);
extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);
/* -- LAPACK computational routine (version 3.4.2) --
-- LAPACK is a software package provided by Univ. of Tennessee, --
-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
September 2012
=====================================================================
Test the input parameters.
Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--ipiv;
/* Function Body */
*info = 0;
if (*m < 0) {
*info = -1;
} else if (*n < 0) {
*info = -2;
} else if (*lda < max(1,*m)) {
*info = -4;
}
if (*info != 0) {
i__1 = -(*info);
igraphxerbla_("DGETF2", &i__1, (ftnlen)6);
return 0;
}
/* Quick return if possible */
if (*m == 0 || *n == 0) {
return 0;
}
/* Compute machine safe minimum */
sfmin = igraphdlamch_("S");
i__1 = min(*m,*n);
for (j = 1; j <= i__1; ++j) {
/* Find pivot and test for singularity. */
i__2 = *m - j + 1;
jp = j - 1 + igraphidamax_(&i__2, &a[j + j * a_dim1], &c__1);
ipiv[j] = jp;
if (a[jp + j * a_dim1] != 0.) {
/* Apply the interchange to columns 1:N. */
if (jp != j) {
igraphdswap_(n, &a[j + a_dim1], lda, &a[jp + a_dim1], lda);
}
/* Compute elements J+1:M of J-th column. */
if (j < *m) {
if ((d__1 = a[j + j * a_dim1], abs(d__1)) >= sfmin) {
i__2 = *m - j;
d__1 = 1. / a[j + j * a_dim1];
igraphdscal_(&i__2, &d__1, &a[j + 1 + j * a_dim1], &c__1);
} else {
i__2 = *m - j;
for (i__ = 1; i__ <= i__2; ++i__) {
a[j + i__ + j * a_dim1] /= a[j + j * a_dim1];
/* L20: */
}
}
}
} else if (*info == 0) {
*info = j;
}
if (j < min(*m,*n)) {
/* Update trailing submatrix. */
i__2 = *m - j;
i__3 = *n - j;
igraphdger_(&i__2, &i__3, &c_b8, &a[j + 1 + j * a_dim1], &c__1, &a[j + (
j + 1) * a_dim1], lda, &a[j + 1 + (j + 1) * a_dim1], lda);
}
/* L10: */
}
return 0;
/* End of DGETF2 */
} /* igraphdgetf2_ */