Contents
sgesv - compute the solution to a real system of linear
equations A * X = B,
SUBROUTINE SGESV(N, NRHS, A, LDA, IPIVOT, B, LDB, INFO)
INTEGER N, NRHS, LDA, LDB, INFO
INTEGER IPIVOT(*)
REAL A(LDA,*), B(LDB,*)
SUBROUTINE SGESV_64(N, NRHS, A, LDA, IPIVOT, B, LDB, INFO)
INTEGER*8 N, NRHS, LDA, LDB, INFO
INTEGER*8 IPIVOT(*)
REAL 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, 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, DIMENSION(:,:) :: A, B
C INTERFACE
#include <sunperf.h>
void sgesv(int n, int nrhs, float *a, int lda, int *ipivot,
float *b, int ldb, int *info);
void sgesv_64(long n, long nrhs, float *a, long lda, long
*ipivot, float *b, long ldb, long *info);
sgesv computes the solution to a real system of linear equa-
tions
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.
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 factors L and U from the factorization A
= P*L*U; the unit diagonal 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 ille-
gal 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.