dposv(3P) Sun Performance Library dposv(3P)NAMEdposv - compute the solution to a real system of linear equations A *
X = B,
SYNOPSIS
SUBROUTINE DPOSV(UPLO, N, NRHS, A, LDA, B, LDB, INFO)
CHARACTER * 1 UPLO
INTEGER N, NRHS, LDA, LDB, INFO
DOUBLE PRECISION A(LDA,*), B(LDB,*)
SUBROUTINE DPOSV_64(UPLO, N, NRHS, A, LDA, B, LDB, INFO)
CHARACTER * 1 UPLO
INTEGER*8 N, NRHS, LDA, LDB, INFO
DOUBLE PRECISION A(LDA,*), B(LDB,*)
F95 INTERFACE
SUBROUTINE POSV(UPLO, [N], [NRHS], A, [LDA], B, [LDB], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER :: N, NRHS, LDA, LDB, INFO
REAL(8), DIMENSION(:,:) :: A, B
SUBROUTINE POSV_64(UPLO, [N], [NRHS], A, [LDA], B, [LDB], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER(8) :: N, NRHS, LDA, LDB, INFO
REAL(8), DIMENSION(:,:) :: A, B
C INTERFACE
#include <sunperf.h>
void dposv(char uplo, int n, int nrhs, double *a, int lda, double *b,
int ldb, int *info);
void dposv_64(char uplo, long n, long nrhs, double *a, long lda, double
*b, long ldb, long *info);
PURPOSEdposv 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.
ARGUMENTS
UPLO (input)
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
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 symmetric matrix A. If UPLO = 'U', the leading
N-by-N upper triangular part of A contains the upper triangu‐
lar 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.
LDA (input)
The leading dimension of the array A. LDA >= max(1,N).
B (input/output)
On entry, the N-by-NRHS 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, the leading minor of order i of A is not
positive definite, so the factorization could not be com‐
pleted, and the solution has not been computed.
6 Mar 2009 dposv(3P)
