SPOTRF(l)								 )								 SPOTRF(l)

NAME

       SPOTRF - compute the Cholesky factorization of a real symmetric positive definite matrix A

SYNOPSIS

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

	   CHARACTER	  UPLO

	   INTEGER	  INFO, LDA, N

	   REAL 	  A( LDA, * )

PURPOSE

       SPOTRF computes the Cholesky factorization of a real symmetric positive definite matrix A.  The factorization has the form
	  A = U**T * U,  if UPLO = 'U', or
	  A = L  * L**T,  if UPLO = 'L',
       where U is an upper triangular matrix and L is lower triangular.

       This is the block version of the algorithm, calling Level 3 BLAS.

ARGUMENTS

       UPLO    (input) CHARACTER*1
	       = 'U':  Upper triangle of A is stored;
	       = 'L':  Lower triangle of A is stored.

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

       A       (input/output) REAL array, dimension (LDA,N)
	       On  entry, the symmetric 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**T*U or A = L*L**T.

       LDA     (input) INTEGER
	       The leading dimension of the array A.  LDA >= 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 is not positive definite, and the factorization could not be completed.

LAPACK version 3.0						   15 June 2000 							 SPOTRF(l)