CPOTF2 (3lapack)

compute the Cholesky factorization of a complex Hermitian positive definite matrix A

SYNOPSIS

  SUBROUTINE CPOTF2( UPLO, N, A, LDA, INFO )

      CHARACTER      UPLO

      INTEGER        INFO, LDA, N

      COMPLEX        A( LDA, * )

PURPOSE

  CPOTF2 computes the Cholesky factorization of a complex Hermitian positive
  definite matrix A.

  The factorization has the form
     A = U' * U ,  if UPLO = 'U', or
     A = L  * L',  if UPLO = 'L',
  where U is an upper triangular matrix and L is lower triangular.

  This is the unblocked version of the algorithm, calling Level 2 BLAS.

ARGUMENTS

  UPLO    (input) CHARACTER*1
          Specifies whether the upper or lower triangular part of the
          Hermitian matrix A is stored.  = 'U':  Upper triangular
          = 'L':  Lower triangular

  N       (input) INTEGER
          The order of the matrix A.  N >= 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'*U  or A = L*L'.

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

  INFO    (output) INTEGER
          = 0: successful exit
          < 0: if INFO = -k, the k-th argument had an illegal value
          > 0: if INFO = k, the leading minor of order k is not positive
          definite, and the factorization could not be completed.