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slatrz.f(3)				      LAPACK				      slatrz.f(3)

NAME
       slatrz.f -

SYNOPSIS
   Functions/Subroutines
       subroutine slatrz (M, N, L, A, LDA, TAU, WORK)
	   SLATRZ factors an upper trapezoidal matrix by means of orthogonal transformations.

Function/Subroutine Documentation
   subroutine slatrz (integerM, integerN, integerL, real, dimension( lda, * )A, integerLDA, real,
       dimension( * )TAU, real, dimension( * )WORK)
       SLATRZ factors an upper trapezoidal matrix by means of orthogonal transformations.

       Purpose:

	    SLATRZ factors the M-by-(M+L) real upper trapezoidal matrix
	    [ A1 A2 ] = [ A(1:M,1:M) A(1:M,N-L+1:N) ] as ( R  0 ) * Z, by means
	    of orthogonal transformations.  Z is an (M+L)-by-(M+L) orthogonal
	    matrix and, R and A1 are M-by-M upper triangular matrices.

       Parameters:
	   M

		     M is INTEGER
		     The number of rows of the matrix A.  M >= 0.

	   N

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

	   L

		     L is INTEGER
		     The number of columns of the matrix A containing the
		     meaningful part of the Householder vectors. N-M >= L >= 0.

	   A

		     A is REAL array, dimension (LDA,N)
		     On entry, the leading M-by-N upper trapezoidal part of the
		     array A must contain the matrix to be factorized.
		     On exit, the leading M-by-M upper triangular part of A
		     contains the upper triangular matrix R, and elements N-L+1 to
		     N of the first M rows of A, with the array TAU, represent the
		     orthogonal matrix Z as a product of M elementary reflectors.

	   LDA

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

	   TAU

		     TAU is REAL array, dimension (M)
		     The scalar factors of the elementary reflectors.

	   WORK

		     WORK is REAL array, dimension (M)

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   September 2012

       Contributors:
	   A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA

       Further Details:

	     The factorization is obtained by Householder's method.  The kth
	     transformation matrix, Z( k ), which is used to introduce zeros into
	     the ( m - k + 1 )th row of A, is given in the form

		Z( k ) = ( I	 0   ),
			 ( 0  T( k ) )

	     where

		T( k ) = I - tau*u( k )*u( k )**T,   u( k ) = (   1    ),
							    (	0    )
							    ( z( k ) )

	     tau is a scalar and z( k ) is an l element vector. tau and z( k )
	     are chosen to annihilate the elements of the kth row of A2.

	     The scalar tau is returned in the kth element of TAU and the vector
	     u( k ) in the kth row of A2, such that the elements of z( k ) are
	     in  a( k, l + 1 ), ..., a( k, n ). The elements of R are returned in
	     the upper triangular part of A1.

	     Z is given by

		Z =  Z( 1 ) * Z( 2 ) * ... * Z( m ).

       Definition at line 141 of file slatrz.f.

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

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