dgsvj0 man page on Scientific

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DGSVJ0(1LAPACK routine (version 3.2)				     DGSVJ0(1)

NAME
       DGSVJ0  - is called from DGESVJ as a pre-processor and that is its main
       purpose

SYNOPSIS
       SUBROUTINE DGSVJ0( JOBV, M, N, A, LDA, D, SVA, MV, V, LDV, EPS,

	   +		  SFMIN, TOL, NSWEEP, WORK, LWORK, INFO )

	   IMPLICIT	  NONE

	   INTEGER	  INFO, LDA, LDV, LWORK, M, MV, N, NSWEEP

	   DOUBLE	  PRECISION EPS, SFMIN, TOL

	   CHARACTER*1	  JOBV

	   DOUBLE	  PRECISION A( LDA, * ), SVA( N ), D( N ), V(  LDV,  *
			  ),

	   +		  WORK( LWORK )

PURPOSE
       DGSVJ0  is  called  from DGESVJ as a pre-processor and that is its main
       purpose. It applies Jacobi rotations in the same way  as	 DGESVJ	 does,
       but  it	does  not  check  convergence (stopping criterion). Few tuning
       parameters (marked by [TP]) are available for the implementer.  Further
       Details
       DGSVJ0  is  used	 just to enable SGESVJ to call a simplified version of
       itself to work on a submatrix of the original matrix.
       Contributors
       ~~~~~~~~~~~~
       Zlatko Drmac (Zagreb, Croatia) and Kresimir  Veselic  (Hagen,  Germany)
       Bugs, Examples and Comments
       ~~~~~~~~~~~~~~~~~~~~~~~~~~~
       Please  report all bugs and send interesting test examples and comments
       to drmac@math.hr. Thank you.

ARGUMENTS
       JOBV    (input) CHARACTER*1
	       Specifies whether the output from this  procedure  is  used  to
	       compute the matrix V:
	       =  'V':	the  product of the Jacobi rotations is accumulated by
	       postmulyiplying the N-by-N array V.  (See  the  description  of
	       V.)   = 'A': the product of the Jacobi rotations is accumulated
	       by postmulyiplying the MV-by-N array V.	(See the  descriptions
	       of MV and V.)  = 'N': the Jacobi rotations are not accumulated.

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

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

       A       (input/output) REAL array, dimension (LDA,N)
	       On  entry,  M-by-N matrix A, such that A*diag(D) represents the
	       input matrix.  On exit,	A_onexit  *  D_onexit  represents  the
	       input  matrix A*diag(D) post-multiplied by a sequence of Jacobi
	       rotations, where the rotation threshold and the total number of
	       sweeps  are  given  in  TOL and NSWEEP, respectively.  (See the
	       descriptions of D, TOL and NSWEEP.)

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

       D       (input/workspace/output) REAL array, dimension (N)
	       The array D accumulates	the  scaling  factors  from  the  fast
	       scaled  Jacobi  rotations.   On entry, A*diag(D) represents the
	       input matrix.  On exit, A_onexit*diag(D_onexit) represents  the
	       input matrix post-multiplied by a sequence of Jacobi rotations,
	       where the rotation threshold and the total number of sweeps are
	       given  in  TOL and NSWEEP, respectively.	 (See the descriptions
	       of A, TOL and NSWEEP.)

       SVA     (input/workspace/output) REAL array, dimension (N)
	       On entry, SVA contains the Euclidean norms of  the  columns  of
	       the  matrix  A*diag(D).	 On  exit,  SVA contains the Euclidean
	       norms of the columns of the matrix onexit*diag(D_onexit).

       MV      (input) INTEGER
	       If JOBV .EQ. 'A', then MV rows of V  are	 post-multipled	 by  a
	       sequence	 of Jacobi rotations.  If JOBV = 'N',	then MV is not
	       referenced.

       V       (input/output) REAL array, dimension (LDV,N)
	       If JOBV .EQ. 'V' then N rows  of	 V  are	 post-multipled	 by  a
	       sequence of Jacobi rotations.  If JOBV .EQ. 'A' then MV rows of
	       V are post-multipled by a sequence  of  Jacobi  rotations.   If
	       JOBV = 'N',   then V is not referenced.

       LDV     (input) INTEGER
	       The  leading  dimension	of  the array V,  LDV >= 1.  If JOBV =
	       'V', LDV .GE. N.	 If JOBV = 'A', LDV .GE. MV.

       EPS     (input) INTEGER
	       EPS = SLAMCH('Epsilon')

       SFMIN   (input) INTEGER
	       SFMIN = SLAMCH('Safe Minimum')

       TOL     (input) REAL
	       TOL is the threshold for Jacobi rotations. For a	 pair  A(:,p),
	       A(:,q) of pivot columns, the Jacobi rotation is
	       applied only if DABS(COS(angle(A(:,p),A(:,q)))) .GT. TOL.

       NSWEEP  (input) INTEGER
	       NSWEEP  is  the number of sweeps of Jacobi rotations to be per‐
	       formed.

       WORK    (workspace) REAL array, dimension LWORK.

       LWORK   (input) INTEGER
	       LWORK is the dimension of WORK. LWORK .GE. M.

       INFO    (output) INTEGER
	       = 0 : successful exit.
	       < 0 : if INFO = -i, then the i-th argument had an illegal value

 LAPACK routine (version 3.2)	 November 2008			     DGSVJ0(1)
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