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# dpotf2

NAME
DPOTF2 - compute the Cholesky factorization of a real sym-
metric positive definite matrix A

SYNOPSIS
SUBROUTINE DPOTF2( UPLO, N, A, LDA, INFO )

CHARACTER      UPLO

INTEGER        INFO, LDA, N

DOUBLE         PRECISION A( LDA, * )

PURPOSE
DPOTF2 computes the Cholesky factorization of a real sym-
metric 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 tri-
angular.

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 symmetric matrix A is stored.  = 'U':  Upper
triangular
= 'L':  Lower triangular

N       (input) INTEGER
The order of the matrix A.  N >= 0.

A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the symmetric matrix A.  If UPLO = 'U',
the leading n by n upper triangular part of A con-
tains 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 tri-
angular 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.