dposv (l)  Linux Manuals
dposv: computes the solution to a real system of linear equations A * X = B,
NAME
DPOSV  computes the solution to a real system of linear equations A * X = B,SYNOPSIS
 SUBROUTINE DPOSV(
 UPLO, N, NRHS, A, LDA, B, LDB, INFO )
 CHARACTER UPLO
 INTEGER INFO, LDA, LDB, N, NRHS
 DOUBLE PRECISION A( LDA, * ), B( LDB, * )
PURPOSE
DPOSV computes the solution to a real system of linear equationsA
The Cholesky decomposition is used to factor A as
A
A
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) CHARACTER*1

= aqUaq: Upper triangle of A is stored;
= aqLaq: Lower triangle of A is stored.  N (input) INTEGER
 The number of linear equations, i.e., the order of the matrix A. N >= 0.
 NRHS (input) INTEGER
 The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
 A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
 On entry, the symmetric matrix A. If UPLO = aqUaq, the leading NbyN 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 = aqLaq, the leading NbyN 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) INTEGER
 The leading dimension of the array A. LDA >= max(1,N).
 B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
 On entry, the NbyNRHS right hand side matrix B. On exit, if INFO = 0, the NbyNRHS solution matrix X.
 LDB (input) INTEGER
 The leading dimension of the array B. LDB >= max(1,N).
 INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = i, the ith 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.