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dlasyf.f(3)				      LAPACK				      dlasyf.f(3)

NAME
       dlasyf.f -

SYNOPSIS
   Functions/Subroutines
       subroutine dlasyf (UPLO, N, NB, KB, A, LDA, IPIV, W, LDW, INFO)
	   DLASYF computes a partial factorization of a real symmetric matrix, using the diagonal
	   pivoting method.

Function/Subroutine Documentation
   subroutine dlasyf (characterUPLO, integerN, integerNB, integerKB, double precision, dimension(
       lda, * )A, integerLDA, integer, dimension( * )IPIV, double precision, dimension( ldw, *
       )W, integerLDW, integerINFO)
       DLASYF computes a partial factorization of a real symmetric matrix, using the diagonal
       pivoting method.

       Purpose:

	    DLASYF computes a partial factorization of a real symmetric matrix A
	    using the Bunch-Kaufman diagonal pivoting method. The partial
	    factorization has the form:

	    A  =  ( I  U12 ) ( A11  0  ) (  I	    0	 )  if UPLO = 'U', or:
		  ( 0  U22 ) (	0   D  ) ( U12**T U22**T )

	    A  =  ( L11  0 ) (	D   0  ) ( L11**T L21**T )  if UPLO = 'L'
		  ( L21  I ) (	0  A22 ) (  0	    I	 )

	    where the order of D is at most NB. The actual order is returned in
	    the argument KB, and is either NB or NB-1, or N if N <= NB.

	    DLASYF is an auxiliary routine called by DSYTRF. It uses blocked code
	    (calling Level 3 BLAS) to update the submatrix A11 (if UPLO = 'U') or
	    A22 (if UPLO = 'L').

       Parameters:
	   UPLO

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

	   N

		     N is INTEGER
		     The order of the matrix A.  N >= 0.

	   NB

		     NB is INTEGER
		     The maximum number of columns of the matrix A that should be
		     factored.	NB should be at least 2 to allow for 2-by-2 pivot
		     blocks.

	   KB

		     KB is INTEGER
		     The number of columns of A that were actually factored.
		     KB is either NB-1 or NB, or N if N <= NB.

	   A

		     A is 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 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, A contains details of the partial factorization.

	   LDA

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

	   IPIV

		     IPIV is INTEGER array, dimension (N)
		     Details of the interchanges and the block structure of D.
		     If UPLO = 'U', only the last KB elements of IPIV are set;
		     if UPLO = 'L', only the first KB elements are set.

		     If IPIV(k) > 0, then rows and columns k and IPIV(k) were
		     interchanged and D(k,k) is a 1-by-1 diagonal block.
		     If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and
		     columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k)
		     is a 2-by-2 diagonal block.  If UPLO = 'L' and IPIV(k) =
		     IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were
		     interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block.

	   W

		     W is DOUBLE PRECISION array, dimension (LDW,NB)

	   LDW

		     LDW is INTEGER
		     The leading dimension of the array W.  LDW >= max(1,N).

	   INFO

		     INFO is INTEGER
		     = 0: successful exit
		     > 0: if INFO = k, D(k,k) is exactly zero.	The factorization
			  has been completed, but the block diagonal matrix D is
			  exactly singular.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   September 2012

       Definition at line 157 of file dlasyf.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      dlasyf.f(3)
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