152 lines
3.9 KiB
C
152 lines
3.9 KiB
C
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#include "clapack.h"
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/* Table of constant values */
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static real c_b9 = 1.f;
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/* Subroutine */ int spotrs_(char *uplo, integer *n, integer *nrhs, real *a,
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integer *lda, real *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 logical lsame_(char *, char *);
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logical upper;
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extern /* Subroutine */ int strsm_(char *, char *, char *, char *,
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integer *, integer *, real *, real *, integer *, real *, integer *
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), xerbla_(char *, integer *);
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/* -- LAPACK 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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/* SPOTRS solves a system of linear equations A*X = B with a symmetric */
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/* positive definite matrix A using the Cholesky factorization */
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/* A = U**T*U or A = L*L**T computed by SPOTRF. */
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/* Arguments */
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/* ========= */
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/* UPLO (input) CHARACTER*1 */
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/* = 'U': Upper triangle of A is stored; */
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/* = 'L': Lower triangle of A is stored. */
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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) REAL array, dimension (LDA,N) */
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/* The triangular factor U or L from the Cholesky factorization */
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/* A = U**T*U or A = L*L**T, as computed by SPOTRF. */
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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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/* B (input/output) REAL 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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/* .. Parameters .. */
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/* .. */
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/* .. Local Scalars .. */
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/* .. */
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/* .. External Functions .. */
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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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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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upper = lsame_(uplo, "U");
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if (! upper && ! lsame_(uplo, "L")) {
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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 = -7;
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}
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if (*info != 0) {
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i__1 = -(*info);
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xerbla_("SPOTRS", &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 (upper) {
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/* Solve A*X = B where A = U'*U. */
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/* Solve U'*X = B, overwriting B with X. */
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strsm_("Left", "Upper", "Transpose", "Non-unit", n, nrhs, &c_b9, &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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strsm_("Left", "Upper", "No transpose", "Non-unit", n, nrhs, &c_b9, &
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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 where A = L*L'. */
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/* Solve L*X = B, overwriting B with X. */
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strsm_("Left", "Lower", "No transpose", "Non-unit", n, nrhs, &c_b9, &
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a[a_offset], lda, &b[b_offset], ldb);
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/* Solve L'*X = B, overwriting B with X. */
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strsm_("Left", "Lower", "Transpose", "Non-unit", n, nrhs, &c_b9, &a[
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a_offset], lda, &b[b_offset], ldb);
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}
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return 0;
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/* End of SPOTRS */
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} /* spotrs_ */
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