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160 lines
4.4 KiB
160 lines
4.4 KiB
#include "blaswrap.h"
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#include "f2c.h"
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/* Subroutine */ int dgetrs_(char *trans, integer *n, integer *nrhs,
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doublereal *a, integer *lda, integer *ipiv, doublereal *b, integer *
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ldb, 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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March 31, 1993
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Purpose
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=======
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DGETRS solves a system of linear equations
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A * X = B or A' * X = B
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with a general N-by-N matrix A using the LU factorization computed
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by DGETRF.
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Arguments
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=========
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TRANS (input) CHARACTER*1
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Specifies the form of the system of equations:
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= 'N': A * X = B (No transpose)
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= 'T': A'* X = B (Transpose)
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= 'C': A'* X = B (Conjugate transpose = Transpose)
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N (input) INTEGER
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The order of the matrix A. N >= 0.
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NRHS (input) INTEGER
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The number of right hand sides, i.e., the number of columns
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of the matrix B. NRHS >= 0.
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A (input) DOUBLE PRECISION array, dimension (LDA,N)
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The factors L and U from the factorization A = P*L*U
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as computed by DGETRF.
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LDA (input) INTEGER
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The leading dimension of the array A. LDA >= max(1,N).
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IPIV (input) INTEGER array, dimension (N)
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The pivot indices from DGETRF; for 1<=i<=N, row i of the
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matrix was interchanged with row IPIV(i).
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B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
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On entry, the right hand side matrix B.
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On exit, the solution matrix X.
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LDB (input) INTEGER
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The leading dimension of the array B. LDB >= max(1,N).
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INFO (output) INTEGER
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= 0: successful exit
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< 0: if INFO = -i, the i-th argument had an illegal value
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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_b12 = 1.;
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static integer c_n1 = -1;
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/* System generated locals */
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integer a_dim1, a_offset, b_dim1, b_offset, i__1;
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/* Local variables */
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extern logical lsame_(char *, char *);
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extern /* Subroutine */ int dtrsm_(char *, char *, char *, char *,
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integer *, integer *, doublereal *, doublereal *, integer *,
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doublereal *, integer *), xerbla_(
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char *, integer *), dlaswp_(integer *, doublereal *,
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integer *, integer *, integer *, integer *, integer *);
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static logical notran;
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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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b_dim1 = *ldb;
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b_offset = 1 + b_dim1 * 1;
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b -= b_offset;
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/* Function Body */
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*info = 0;
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notran = lsame_(trans, "N");
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if (! notran && ! lsame_(trans, "T") && ! lsame_(
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trans, "C")) {
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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 (*nrhs < 0) {
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*info = -3;
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} else if (*lda < max(1,*n)) {
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*info = -5;
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} else if (*ldb < max(1,*n)) {
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*info = -8;
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}
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if (*info != 0) {
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i__1 = -(*info);
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xerbla_("DGETRS", &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 (*n == 0 || *nrhs == 0) {
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return 0;
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}
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if (notran) {
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/* Solve A * X = B.
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Apply row interchanges to the right hand sides. */
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dlaswp_(nrhs, &b[b_offset], ldb, &c__1, n, &ipiv[1], &c__1);
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/* Solve L*X = B, overwriting B with X. */
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dtrsm_("Left", "Lower", "No transpose", "Unit", n, nrhs, &c_b12, &a[
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a_offset], lda, &b[b_offset], ldb);
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/* Solve U*X = B, overwriting B with X. */
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dtrsm_("Left", "Upper", "No transpose", "Non-unit", n, nrhs, &c_b12, &
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a[a_offset], lda, &b[b_offset], ldb);
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} else {
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/* Solve A' * X = B.
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Solve U'*X = B, overwriting B with X. */
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dtrsm_("Left", "Upper", "Transpose", "Non-unit", n, nrhs, &c_b12, &a[
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a_offset], lda, &b[b_offset], ldb);
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/* Solve L'*X = B, overwriting B with X. */
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dtrsm_("Left", "Lower", "Transpose", "Unit", n, nrhs, &c_b12, &a[
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a_offset], lda, &b[b_offset], ldb);
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/* Apply row interchanges to the solution vectors. */
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dlaswp_(nrhs, &b[b_offset], ldb, &c__1, n, &ipiv[1], &c_n1);
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}
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return 0;
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/* End of DGETRS */
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} /* dgetrs_ */
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