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112 lines
2.9 KiB
112 lines
2.9 KiB
15 years ago
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#include "clapack.h"
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/* Subroutine */ int spotri_(char *uplo, integer *n, real *a, integer *lda,
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integer *info)
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{
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/* System generated locals */
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integer a_dim1, a_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 xerbla_(char *, integer *), slauum_(
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char *, integer *, real *, integer *, integer *), strtri_(
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char *, char *, integer *, real *, integer *, 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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/* SPOTRI computes the inverse of a real symmetric positive definite */
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/* matrix A using the Cholesky factorization A = U**T*U or A = L*L**T */
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/* 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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/* A (input/output) REAL array, dimension (LDA,N) */
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/* On entry, the triangular factor U or L from the Cholesky */
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/* factorization A = U**T*U or A = L*L**T, as computed by */
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/* SPOTRF. */
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/* On exit, the upper or lower triangle of the (symmetric) */
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/* inverse of A, overwriting the input factor U or L. */
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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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/* 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, the (i,i) element of the factor U or L is */
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/* zero, and the inverse could not be computed. */
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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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/* Function Body */
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*info = 0;
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if (! lsame_(uplo, "U") && ! 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 (*lda < max(1,*n)) {
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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_("SPOTRI", &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) {
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return 0;
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}
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/* Invert the triangular Cholesky factor U or L. */
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strtri_(uplo, "Non-unit", n, &a[a_offset], lda, info);
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if (*info > 0) {
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return 0;
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}
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/* Form inv(U)*inv(U)' or inv(L)'*inv(L). */
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slauum_(uplo, n, &a[a_offset], lda, info);
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return 0;
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/* End of SPOTRI */
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} /* spotri_ */
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