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126 lines
3.8 KiB
C
126 lines
3.8 KiB
C
#include "clapack.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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/* 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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/* -- LAPACK driver routine (version 3.1) -- */
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/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
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/* November 2006 */
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/* .. Scalar Arguments .. */
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/* .. */
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/* .. Array Arguments .. */
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/* .. */
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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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/* .. External Subroutines .. */
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/* .. */
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/* .. Intrinsic Functions .. */
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/* .. */
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/* .. Executable Statements .. */
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/* Test the input parameters. */
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/* Parameter adjustments */
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a_dim1 = *lda;
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a_offset = 1 + a_dim1;
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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;
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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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