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158 lines
4.2 KiB
158 lines
4.2 KiB
#include "blaswrap.h"
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#include "f2c.h"
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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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/* -- LAPACK routine (version 3.0) --
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Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
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Courant Institute, Argonne National Lab, and Rice University
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June 30, 1992
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Purpose
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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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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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This is the right-looking Level 2 BLAS version of the algorithm.
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Arguments
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=========
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M (input) INTEGER
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The number of rows of the matrix A. M >= 0.
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N (input) INTEGER
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The number of columns of the matrix A. N >= 0.
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A (input/output) 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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LDA (input) INTEGER
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The leading dimension of the array A. LDA >= max(1,M).
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IPIV (output) 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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INFO (output) 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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=====================================================================
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Test the input parameters.
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Parameter adjustments */
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/* Table of constant values */
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static integer c__1 = 1;
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static doublereal c_b6 = -1.;
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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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extern /* Subroutine */ int dger_(integer *, integer *, doublereal *,
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doublereal *, integer *, doublereal *, integer *, doublereal *,
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integer *);
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static integer j;
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extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *,
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integer *), dswap_(integer *, doublereal *, integer *, doublereal
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*, integer *);
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static integer jp;
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extern integer idamax_(integer *, doublereal *, integer *);
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extern /* Subroutine */ int xerbla_(char *, integer *);
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#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]
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a_dim1 = *lda;
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a_offset = 1 + a_dim1 * 1;
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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_("DGETF2", &i__1);
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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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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_ref(j, j), &c__1);
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ipiv[j] = jp;
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if (a_ref(jp, j) != 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_ref(j, 1), lda, &a_ref(jp, 1), 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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i__2 = *m - j;
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d__1 = 1. / a_ref(j, j);
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dscal_(&i__2, &d__1, &a_ref(j + 1, j), &c__1);
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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_b6, &a_ref(j + 1, j), &c__1, &a_ref(j, j +
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1), lda, &a_ref(j + 1, j + 1), 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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#undef a_ref
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