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*/
#include "f2c.h"
/* > \brief <b> DGESV computes the solution to system of linear equations A * X = B for GE matrices</b>
=========== DOCUMENTATION ===========
Online html documentation available at
http://www.netlib.org/lapack/explore-html/
> \htmlonly
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">
> [TGZ]</a>
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> [ZIP]</a>
> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dgesv.f
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> [TXT]</a>
> \endhtmlonly
Definition:
===========
SUBROUTINE DGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO )
INTEGER INFO, LDA, LDB, N, NRHS
INTEGER IPIV( * )
DOUBLE PRECISION A( LDA, * ), B( LDB, * )
> \par Purpose:
=============
>
> \verbatim
>
> DGESV computes the solution to a real system of linear equations
> A * X = B,
> where A is an N-by-N matrix and X and B are N-by-NRHS matrices.
>
> The LU decomposition with partial pivoting and row interchanges is
> used to factor A as
> A = P * L * U,
> where P is a permutation matrix, L is unit lower triangular, and U is
> upper triangular. The factored form of A is then used to solve the
> system of equations A * X = B.
> \endverbatim
Arguments:
==========
> \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 DOUBLE PRECISION array, dimension (LDA,N)
> On entry, the N-by-N coefficient matrix A.
> On exit, the factors L and U from the factorization
> A = P*L*U; the unit diagonal elements of L are not stored.
> \endverbatim
>
> \param[in] LDA
> \verbatim
> LDA is INTEGER
> The leading dimension of the array A. LDA >= max(1,N).
> \endverbatim
>
> \param[out] IPIV
> \verbatim
> IPIV is INTEGER array, dimension (N)
> The pivot indices that define the permutation matrix P;
> row i of the matrix was interchanged with row IPIV(i).
> \endverbatim
>
> \param[in,out] B
> \verbatim
> B is DOUBLE PRECISION array, dimension (LDB,NRHS)
> On entry, the N-by-NRHS matrix of 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, U(i,i) is exactly zero. The factorization
> has been completed, but the factor U is exactly
> singular, so the solution could not be computed.
> \endverbatim
Authors:
========
> \author Univ. of Tennessee
> \author Univ. of California Berkeley
> \author Univ. of Colorado Denver
> \author NAG Ltd.
> \date November 2011
> \ingroup doubleGEsolve
=====================================================================
Subroutine */ int igraphdgesv_(integer *n, integer *nrhs, doublereal *a, integer
*lda, integer *ipiv, doublereal *b, integer *ldb, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, b_dim1, b_offset, i__1;
/* Local variables */
extern /* Subroutine */ int igraphdgetrf_(integer *, integer *, doublereal *,
integer *, integer *, integer *), igraphxerbla_(char *, integer *,
ftnlen), igraphdgetrs_(char *, integer *, integer *, doublereal *,
integer *, integer *, doublereal *, 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
=====================================================================
Test the input parameters.
Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--ipiv;
b_dim1 = *ldb;
b_offset = 1 + b_dim1;
b -= b_offset;
/* Function Body */
*info = 0;
if (*n < 0) {
*info = -1;
} else if (*nrhs < 0) {
*info = -2;
} else if (*lda < max(1,*n)) {
*info = -4;
} else if (*ldb < max(1,*n)) {
*info = -7;
}
if (*info != 0) {
i__1 = -(*info);
igraphxerbla_("DGESV ", &i__1, (ftnlen)6);
return 0;
}
/* Compute the LU factorization of A. */
igraphdgetrf_(n, n, &a[a_offset], lda, &ipiv[1], info);
if (*info == 0) {
/* Solve the system A*X = B, overwriting B with X. */
igraphdgetrs_("No transpose", n, nrhs, &a[a_offset], lda, &ipiv[1], &b[
b_offset], ldb, info);
}
return 0;
/* End of DGESV */
} /* igraphdgesv_ */