dgesv(3P) Sun Performance Library dgesv(3P)NAMEdgesv - compute the solution to a real system of linear equations A *
X = B,
SYNOPSIS
SUBROUTINE DGESV(N, NRHS, A, LDA, IPIVOT, B, LDB, INFO)
INTEGER N, NRHS, LDA, LDB, INFO
INTEGER IPIVOT(*)
DOUBLE PRECISION A(LDA,*), B(LDB,*)
SUBROUTINE DGESV_64(N, NRHS, A, LDA, IPIVOT, B, LDB, INFO)
INTEGER*8 N, NRHS, LDA, LDB, INFO
INTEGER*8 IPIVOT(*)
DOUBLE PRECISION A(LDA,*), B(LDB,*)
F95 INTERFACE
SUBROUTINE GESV([N], [NRHS], A, [LDA], IPIVOT, B, [LDB], [INFO])
INTEGER :: N, NRHS, LDA, LDB, INFO
INTEGER, DIMENSION(:) :: IPIVOT
REAL(8), DIMENSION(:,:) :: A, B
SUBROUTINE GESV_64([N], [NRHS], A, [LDA], IPIVOT, B, [LDB], [INFO])
INTEGER(8) :: N, NRHS, LDA, LDB, INFO
INTEGER(8), DIMENSION(:) :: IPIVOT
REAL(8), DIMENSION(:,:) :: A, B
C INTERFACE
#include <sunperf.h>
void dgesv(int n, int nrhs, double *a, int lda, int *ipivot, double *b,
int ldb, int *info);
void dgesv_64(long n, long nrhs, double *a, long lda, long *ipivot,
double *b, long ldb, long *info);
PURPOSEdgesv 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.
ARGUMENTS
N (input) The number of linear equations, i.e., the order of the matrix
A. N >= 0.
NRHS (input)
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 0.
A (input/output)
On entry, the N-by-N coefficient matrix A. On exit, the fac‐
tors L and U from the factorization A = P*L*U; the unit diag‐
onal elements of L are not stored.
LDA (input)
The leading dimension of the array A. LDA >= max(1,N).
IPIVOT (output)
The pivot indices that define the permutation matrix P; row i
of the matrix was interchanged with row IPIVOT(i).
B (input/output)
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.
LDB (input)
The leading dimension of the array B. LDB >= max(1,N).
INFO (output)
= 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.
6 Mar 2009 dgesv(3P)
