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118 lines
3.7 KiB
118 lines
3.7 KiB
#include "blaswrap.h"
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#include "f2c.h"
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/* Subroutine */ int dgesv_(integer *n, integer *nrhs, doublereal *a, integer
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*lda, integer *ipiv, doublereal *b, integer *ldb, integer *info)
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{
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/* -- LAPACK driver 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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DGESV computes the solution to a real system of linear equations
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A * X = B,
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where A is an N-by-N matrix and X and B are N-by-NRHS matrices.
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The LU decomposition with partial pivoting and row interchanges is
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used to factor A as
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A = P * L * U,
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where P is a permutation matrix, L is unit lower triangular, and U is
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upper triangular. The factored form of A is then used to solve the
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system of equations A * X = B.
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Arguments
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=========
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N (input) INTEGER
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The number of linear equations, i.e., the order of the
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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/output) DOUBLE PRECISION array, dimension (LDA,N)
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On entry, the N-by-N coefficient matrix A.
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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,N).
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IPIV (output) INTEGER array, dimension (N)
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The pivot indices that define the permutation matrix P;
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row i of the 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 N-by-NRHS matrix of right hand side matrix B.
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On exit, if INFO = 0, the N-by-NRHS 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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> 0: if INFO = i, U(i,i) is exactly zero. The factorization
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has been completed, but the factor U is exactly
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singular, so the solution could not be computed.
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=====================================================================
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Test the input parameters.
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Parameter adjustments */
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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 /* Subroutine */ int dgetrf_(integer *, integer *, doublereal *,
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integer *, integer *, integer *), xerbla_(char *, integer *), dgetrs_(char *, integer *, integer *, doublereal *,
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integer *, integer *, doublereal *, integer *, integer *);
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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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if (*n < 0) {
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*info = -1;
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} else if (*nrhs < 0) {
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*info = -2;
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} else if (*lda < max(1,*n)) {
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*info = -4;
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} else if (*ldb < max(1,*n)) {
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*info = -7;
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}
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if (*info != 0) {
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i__1 = -(*info);
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xerbla_("DGESV ", &i__1);
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return 0;
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}
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/* Compute the LU factorization of A. */
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dgetrf_(n, n, &a[a_offset], lda, &ipiv[1], info);
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if (*info == 0) {
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/* Solve the system A*X = B, overwriting B with X. */
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dgetrs_("No transpose", n, nrhs, &a[a_offset], lda, &ipiv[1], &b[
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b_offset], ldb, info);
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}
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return 0;
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/* End of DGESV */
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} /* dgesv_ */
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