p?potrf

Computes the Cholesky factorization of a symmetric (Hermitian) positive-definite distributed matrix.

Syntax

call pspotrf(uplo, n, a, ia, ja, desca, info)

call pdpotrf(uplo, n, a, ia, ja, desca, info)

call pcpotrf(uplo, n, a, ia, ja, desca, info)

call pzpotrf(uplo, n, a, ia, ja, desca, info)

Include Files

C: mkl_scalapack.h

Description

The p?potrf routine computes the Cholesky factorization of a real symmetric or complex Hermitian positive-definite distributed n-by-n matrix A(ia:ia+n-1, ja:ja+n-1), denoted below as sub(A).

The factorization has the form

sub(A) = U^H*U if uplo='U', or

sub(A) = L*L^H if uplo='L'

where L is a lower triangular matrix and U is upper triangular.

Input Parameters

uplo

(global) CHARACTER*1.

Indicates whether the upper or lower triangular part of sub(A) is stored. Must be 'U' or 'L'.

If uplo = 'U', the array a stores the upper triangular part of the matrix sub(A) that is factored as U^H*U.

If uplo = 'L', the array a stores the lower triangular part of the matrix sub(A) that is factored as L*L^H.

n

(global) INTEGER. The order of the distributed submatrix sub(A) (n≥0).

a

(local)

REAL for pspotrf

DOUBLE PRECISON for pdpotrf

COMPLEX for pcpotrf

DOUBLE COMPLEX for pzpotrf.

Pointer into the local memory to an array of dimension (lld_a, LOCc(ja+n-1)).

On entry, this array contains the local pieces of the n-by-n symmetric/Hermitian distributed matrix sub(A) to be factored.

Depending on uplo, the array a contains either the upper or the lower triangular part of the matrix sub(A) (see uplo).

ia, ja

(global) INTEGER. The row and column indices in the global array A indicating the first row and the first column of the submatrix sub(A), respectively.

desca

(global and local) INTEGER array, dimension (dlen_). The array descriptor for the distributed matrix A.

Output Parameters

a

The upper or lower triangular part of a is overwritten by the Cholesky factor U or L, as specified by uplo.

info

(global) INTEGER.

If info=0, the execution is successful;

info < 0: if the i-th argument is an array, and the j-th entry had an illegal value, then info = -(i*100+j); if the i-th argument is a scalar and had an illegal value, then info = -i.

If info = k >0, the leading minor of order k, A(ia:ia+k-1, ja:ja+k-1), is not positive-definite, and the factorization could not be completed.