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/* dgetf2.f -- translated by f2c (version 19991025).
You must link the resulting object file with the libraries:
-lf2c -lm (in that order)
*/
#include "f2c.h"
/* Table of constant values */
static integer c__1 = 1;
static doublereal c_b6 = -1.;
/* Subroutine */ int dgetf2_(m, n, a, lda, ipiv, info)
integer *m, *n;
doublereal *a;
integer *lda, *ipiv, *info;
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
doublereal d__1;
/* Local variables */
extern /* Subroutine */ int dger_();
static integer j;
extern /* Subroutine */ int mMdscal_(), mMdswap_();
static integer jp;
extern integer idamax_();
extern /* Subroutine */ int xerbla_();
/* -- LAPACK ROUTINE (VERSION 1.0B) -- */
/* UNIV. OF TENNESSEE, UNIV. OF CALIFORNIA BERKELEY, NAG LTD., */
/* COURANT INSTITUTE, ARGONNE NATIONAL LAB, AND RICE UNIVERSITY */
/* JUNE 30, 1992 */
/* .. SCALAR ARGUMENTS .. */
/* .. */
/* .. ARRAY ARGUMENTS .. */
/* .. */
/* PURPOSE */
/* ======= */
/* 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. */
/* ARGUMENTS */
/* ========= */
/* M (INPUT) INTEGER */
/* THE NUMBER OF ROWS OF THE MATRIX A. M >= 0. */
/* N (INPUT) INTEGER */
/* THE NUMBER OF COLUMNS OF THE MATRIX A. N >= 0. */
/* A (INPUT/OUTPUT) 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. */
/* LDA (INPUT) INTEGER */
/* THE LEADING DIMENSION OF THE ARRAY A. LDA >= MAX(1,M). */
/* IPIV (OUTPUT) 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). */
/* INFO (OUTPUT) 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. */
/* ===================================================================== */
/* .. PARAMETERS .. */
/* .. */
/* .. LOCAL SCALARS .. */
/* .. */
/* .. EXTERNAL FUNCTIONS .. */
/* .. */
/* .. EXTERNAL SUBROUTINES .. */
/* .. */
/* .. INTRINSIC FUNCTIONS .. */
/* .. */
/* .. EXECUTABLE STATEMENTS .. */
/* TEST THE INPUT PARAMETERS. */
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1 * 1;
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);
xerbla_("DGETF2", &i__1, (ftnlen)6);
return 0;
}
/* QUICK RETURN IF POSSIBLE */
if (*m == 0 || *n == 0) {
return 0;
}
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 + idamax_(&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) {
mMdswap_(n, &a[j + a_dim1], lda, &a[jp + a_dim1], lda);
}
/* COMPUTE ELEMENTS J+1:M OF J-TH COLUMN. */
if (j < *m) {
i__2 = *m - j;
d__1 = 1. / a[j + j * a_dim1];
mMdscal_(&i__2, &d__1, &a[j + 1 + j * a_dim1], &c__1);
}
} else if (*info == 0) {
*info = j;
}
if (j < min(*m,*n)) {
/* UPDATE TRAILING SUBMATRIX. */
i__2 = *m - j;
i__3 = *n - j;
dger_(&i__2, &i__3, &c_b6, &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 */
} /* dgetf2_ */
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