pspbtrf(3) [debian man page]

PSPBTRF(l)						   LAPACK routine (version 1.5) 						PSPBTRF(l)

NAME

       PSPBTRF - compute a Cholesky factorization of an N-by-N real banded symmetric positive definite distributed matrix with bandwidth BW

SYNOPSIS

       SUBROUTINE PSPBTRF( UPLO, N, BW, A, JA, DESCA, AF, LAF, WORK, LWORK, INFO )

	   CHARACTER	   UPLO

	   INTEGER	   BW, INFO, JA, LAF, LWORK, N

	   INTEGER	   DESCA( * )

	   REAL 	   A( * ), AF( * ), WORK( * )

PURPOSE

       PSPBTRF computes a Cholesky factorization of an N-by-N real banded symmetric positive definite distributed matrix with bandwidth BW: A(1:N,
       JA:JA+N-1).  Reordering is used to increase parallelism in the factorization.  This reordering results in factors that are  DIFFERENT  from
       those produced by equivalent sequential codes. These factors cannot be used directly by users; however, they can be used in
       subsequent calls to PSPBTRS to solve linear systems.

       The factorization has the form

	       P A(1:N, JA:JA+N-1) P^T = U' U ,  if UPLO = 'U', or

	       P A(1:N, JA:JA+N-1) P^T = L L', if UPLO = 'L'

       where U is a banded upper triangular matrix and L is banded lower triangular, and P is a permutation matrix.

LAPACK version 1.5						    12 May 1997 							PSPBTRF(l)

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)