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/* ../netlib/sposv.f -- translated by f2c (version 20100827). You must link the resulting object file with libf2c: on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm or, if you install libf2c.a in a standard place, with -lf2c -lm -- in that order, at the end of the command line, as in cc *.o -lf2c -lm Source for libf2c is in /netlib/f2c/libf2c.zip, e.g., http://www.netlib.org/f2c/libf2c.zip */
#include "FLA_f2c.h" /* > \brief <b> SPOSV computes the solution to system of linear equations A * X = B for PO matrices</b> */
/* =========== DOCUMENTATION =========== */
/* Online html documentation available at */
/* http://www.netlib.org/lapack/explore-html/ */
/* > \htmlonly */
/* > Download SPOSV + dependencies */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/sposv.f "> */
/* > [TGZ]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/sposv.f "> */
/* > [ZIP]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/sposv.f "> */
/* > [TXT]</a> */
/* > \endhtmlonly */
/* Definition: */
/* =========== */
/* SUBROUTINE SPOSV( UPLO, N, NRHS, A, LDA, B, LDB, INFO ) */
/* .. Scalar Arguments .. */
/* CHARACTER UPLO */
/* INTEGER INFO, LDA, LDB, N, NRHS */
/* .. */
/* .. Array Arguments .. */
/* REAL A( LDA, * ), B( LDB, * ) */
/* .. */
/* > \par Purpose: */
/* ============= */
/* > */
/* > \verbatim */
/* > */
/* > SPOSV computes the solution to a real system of linear equations */
/* > A * X = B, */
/* > where A is an N-by-N symmetric positive definite matrix and X and B */
/* > are N-by-NRHS matrices. */
/* > */
/* > The Cholesky decomposition is used to factor A as */
/* > A = U**T* U, if UPLO = 'U', or */
/* > A = L * L**T, if UPLO = 'L', */
/* > where U is an upper triangular matrix and L is a lower triangular */
/* > matrix. The factored form of A is then used to solve the system of */
/* > equations A * X = B. */
/* > \endverbatim */
/* Arguments: */
/* ========== */
/* > \param[in] UPLO */
/* > \verbatim */
/* > UPLO is CHARACTER*1 */
/* > = 'U': Upper triangle of A is stored;
*/
/* > = 'L': Lower triangle of A is stored. */
/* > \endverbatim */
/* > */
/* > \param[in] N */
/* > \verbatim */
/* > N is INTEGER */
/* > The number of linear equations, i.e., the order of the */
/* > matrix A. N >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in] NRHS */
/* > \verbatim */
/* > NRHS is INTEGER */
/* > The number of right hand sides, i.e., the number of columns */
/* > of the matrix B. NRHS >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in,out] A */
/* > \verbatim */
/* > A is REAL array, dimension (LDA,N) */
/* > On entry, the symmetric matrix A. If UPLO = 'U', the leading */
/* > N-by-N upper triangular part of A contains the upper */
/* > triangular part of the matrix A, and the strictly lower */
/* > triangular part of A is not referenced. If UPLO = 'L', the */
/* > leading N-by-N lower triangular part of A contains the lower */
/* > triangular part of the matrix A, and the strictly upper */
/* > triangular part of A is not referenced. */
/* > */
/* > On exit, if INFO = 0, the factor U or L from the Cholesky */
/* > factorization A = U**T*U or A = L*L**T. */
/* > \endverbatim */
/* > */
/* > \param[in] LDA */
/* > \verbatim */
/* > LDA is INTEGER */
/* > The leading dimension of the array A. LDA >= max(1,N). */
/* > \endverbatim */
/* > */
/* > \param[in,out] B */
/* > \verbatim */
/* > B is REAL array, dimension (LDB,NRHS) */
/* > On entry, the N-by-NRHS right hand side matrix B. */
/* > On exit, if INFO = 0, the N-by-NRHS solution matrix X. */
/* > \endverbatim */
/* > */
/* > \param[in] LDB */
/* > \verbatim */
/* > LDB is INTEGER */
/* > The leading dimension of the array B. LDB >= max(1,N). */
/* > \endverbatim */
/* > */
/* > \param[out] INFO */
/* > \verbatim */
/* > INFO is INTEGER */
/* > = 0: successful exit */
/* > < 0: if INFO = -i, the i-th argument had an illegal value */
/* > > 0: if INFO = i, the leading minor of order i of A is not */
/* > positive definite, so the factorization could not be */
/* > completed, and the solution has not been computed. */
/* > \endverbatim */
/* Authors: */
/* ======== */
/* > \author Univ. of Tennessee */
/* > \author Univ. of California Berkeley */
/* > \author Univ. of Colorado Denver */
/* > \author NAG Ltd. */
/* > \date November 2011 */
/* > \ingroup realPOsolve */
/* ===================================================================== */
/* Subroutine */
int sposv_(char *uplo, integer *n, integer *nrhs, real *a, integer *lda, real *b, integer *ldb, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, b_dim1, b_offset, i__1;
/* Local variables */
extern logical lsame_(char *, char *);
extern /* Subroutine */
int xerbla_(char *, integer *), spotrf_( char *, integer *, real *, integer *, integer *), spotrs_( char *, integer *, integer *, real *, integer *, real *, integer * , integer *);
/* -- LAPACK driver routine (version 3.4.0) -- */
/* -- LAPACK is a software package provided by Univ. of Tennessee, -- */
/* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */
/* November 2011 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* ===================================================================== */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input parameters. */
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
b_dim1 = *ldb;
b_offset = 1 + b_dim1;
b -= b_offset;
/* Function Body */
*info = 0;
if (! lsame_(uplo, "U") && ! lsame_(uplo, "L"))
{
*info = -1;
}
else if (*n < 0)
{
*info = -2;
}
else if (*nrhs < 0)
{
*info = -3;
}
else if (*lda < max(1,*n))
{
*info = -5;
}
else if (*ldb < max(1,*n))
{
*info = -7;
}
if (*info != 0)
{
i__1 = -(*info);
xerbla_("SPOSV ", &i__1);
return 0;
}
/* Compute the Cholesky factorization A = U**T*U or A = L*L**T. */
spotrf_(uplo, n, &a[a_offset], lda, info);
if (*info == 0)
{
/* Solve the system A*X = B, overwriting B with X. */
spotrs_(uplo, n, nrhs, &a[a_offset], lda, &b[b_offset], ldb, info);
}
return 0;
/* End of SPOSV */
}
/* sposv_ */
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