DLAQPS man page on IRIX

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DLAQPS(3S)							    DLAQPS(3S)

NAME
     DLAQPS - compute a step of QR factorization with column pivoting of a
     real M-by-N matrix A by using Blas-3

SYNOPSIS
     SUBROUTINE DLAQPS( M, N, OFFSET, NB, KB, A, LDA, JPVT, TAU, VN1, VN2,
			AUXV, F, LDF )

	 INTEGER	KB, LDA, LDF, M, N, NB, OFFSET

	 INTEGER	JPVT( * )

	 DOUBLE		PRECISION A( LDA, * ), AUXV( * ), F( LDF, * ), TAU( *
			), VN1( * ), VN2( * )

IMPLEMENTATION
     These routines are part of the SCSL Scientific Library and can be loaded
     using either the -lscs or the -lscs_mp option.  The -lscs_mp option
     directs the linker to use the multi-processor version of the library.

     When linking to SCSL with -lscs or -lscs_mp, the default integer size is
     4 bytes (32 bits). Another version of SCSL is available in which integers
     are 8 bytes (64 bits).  This version allows the user access to larger
     memory sizes and helps when porting legacy Cray codes.  It can be loaded
     by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
     only one of the two versions; 4-byte integer and 8-byte integer library
     calls cannot be mixed.

PURPOSE
     DLAQPS computes a step of QR factorization with column pivoting of a real
     M-by-N matrix A by using Blas-3. It tries to factorize NB columns from A
     starting from the row OFFSET+1, and updates all of the matrix with Blas-3
     xGEMM.

     In some cases, due to catastrophic cancellations, it cannot factorize NB
     columns.  Hence, the actual number of factorized columns is returned in
     KB.

     Block A(1:OFFSET,1:N) is accordingly pivoted, but not factorized.

ARGUMENTS
     M	     (input) INTEGER
	     The number of rows of the matrix A. M >= 0.

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

     OFFSET  (input) INTEGER
	     The number of rows of A that have been factorized in previous
	     steps.

									Page 1

DLAQPS(3S)							    DLAQPS(3S)

     NB	     (input) INTEGER
	     The number of columns to factorize.

     KB	     (output) INTEGER
	     The number of columns actually factorized.

     A	     (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	     On entry, the M-by-N matrix A.  On exit, block A(OFFSET+1:M,1:KB)
	     is the triangular
	     factor obtained and block A(1:OFFSET,1:N) has been accordingly
	     pivoted, but no factorized.  The rest of the matrix, block
	     A(OFFSET+1:M,KB+1:N) has been updated.

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

     JPVT    (input/output) INTEGER array, dimension (N)
	     JPVT(I) = K <==> Column K of the full matrix A has been permuted
	     into position I in AP.

     TAU     (output) DOUBLE PRECISION array, dimension (KB)
	     The scalar factors of the elementary reflectors.

     VN1     (input/output) DOUBLE PRECISION array, dimension (N)
	     The vector with the partial column norms.

     VN2     (input/output) DOUBLE PRECISION array, dimension (N)
	     The vector with the exact column norms.

     AUXV    (input/output) DOUBLE PRECISION array, dimension (NB)
	     Auxiliar vector.

     F	     (input/output) DOUBLE PRECISION array, dimension (LDF,NB)
	     Matrix F' = L*Y'*A.

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

FURTHER DETAILS
     Based on contributions by
       G. Quintana-Orti, Depto. de Informatica, Universidad Jaime I, Spain
       X. Sun, Computer Science Dept., Duke University, USA

SEE ALSO
     INTRO_LAPACK(3S), INTRO_SCSL(3S)

     This man page is available only online.

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