CPOSV(3f)

NAME
CPOSV - the solution to a complex system of linear equations A * X = B,

SYNOPSIS

SUBROUTINE CPOSV(
    UPLO, N, NRHS, A, LDA, B, LDB, INFO )

CHARACTER
    UPLO

INTEGER
    INFO, LDA, LDB, N, NRHS

COMPLEX
    A( LDA, * ), B( LDB, * )

PURPOSE
CPOSV computes the solution to a complex system of linear equations
   A * X = B, where A is an N-by-N Hermitian positive definite matrix and X and B are N-by-NRHS matrices.
The Cholesky decomposition is used to factor A as
   A = U**H* U, if UPLO = 'U', or
   A = L * L**H, 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) CHARACTER*1
    = 'U': Upper triangle of A is stored;
    = 'L': 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) COMPLEX array, dimension (LDA,N)
    On entry, the Hermitian matrix A. If UPLO = 'U', the leading N-by-N 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 = '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**H*U or A = L*L**H.

LDA     (input) INTEGER
    The leading dimension of the array A. LDA >= max(1,N).

B       (input/output) COMPLEX array, dimension (LDB,NRHS)
    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) INTEGER
    The leading dimension of the array B. LDB >= max(1,N).

INFO    (output) INTEGER
    = 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 completed, and the solution has not been computed.