sgsvj0.f (3)  Linux Manuals
NAME
sgsvj0.f 
SYNOPSIS
Functions/Subroutines
subroutine sgsvj0 (JOBV, M, N, A, LDA, D, SVA, MV, V, LDV, EPS, SFMIN, TOL, NSWEEP, WORK, LWORK, INFO)
SGSVJ0 preprocessor for the routine sgesvj.
Function/Subroutine Documentation
subroutine sgsvj0 (character*1JOBV, integerM, integerN, real, dimension( lda, * )A, integerLDA, real, dimension( n )D, real, dimension( n )SVA, integerMV, real, dimension( ldv, * )V, integerLDV, realEPS, realSFMIN, realTOL, integerNSWEEP, real, dimension( lwork )WORK, integerLWORK, integerINFO)
SGSVJ0 preprocessor for the routine sgesvj.
Purpose:

SGSVJ0 is called from SGESVJ as a preprocessor and that is its main purpose. It applies Jacobi rotations in the same way as SGESVJ does, but it does not check convergence (stopping criterion). Few tuning parameters (marked by [TP]) are available for the implementer.
Parameters:

JOBV
JOBV is 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 NbyN array V. (See the description of V.) = 'A': the product of the Jacobi rotations is accumulated by postmulyiplying the MVbyN array V. (See the descriptions of MV and V.) = 'N': the Jacobi rotations are not accumulated.
MM is INTEGER The number of rows of the input matrix A. M >= 0.
NN is INTEGER The number of columns of the input matrix A. M >= N >= 0.
AA is REAL array, dimension (LDA,N) On entry, MbyN matrix A, such that A*diag(D) represents the input matrix. On exit, A_onexit * D_onexit represents the input matrix A*diag(D) postmultiplied 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.)
LDALDA is INTEGER The leading dimension of the array A. LDA >= max(1,M).
DD is 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 postmultiplied 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.)
SVASVA is 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).
MVMV is INTEGER If JOBV .EQ. 'A', then MV rows of V are postmultipled by a sequence of Jacobi rotations. If JOBV = 'N', then MV is not referenced.
VV is REAL array, dimension (LDV,N) If JOBV .EQ. 'V' then N rows of V are postmultipled by a sequence of Jacobi rotations. If JOBV .EQ. 'A' then MV rows of V are postmultipled by a sequence of Jacobi rotations. If JOBV = 'N', then V is not referenced.
LDVLDV is INTEGER The leading dimension of the array V, LDV >= 1. If JOBV = 'V', LDV .GE. N. If JOBV = 'A', LDV .GE. MV.
EPSEPS is REAL EPS = SLAMCH('Epsilon')
SFMINSFMIN is REAL SFMIN = SLAMCH('Safe Minimum')
TOLTOL is 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 ABS(COS(angle(A(:,p),A(:,q)))) .GT. TOL.
NSWEEPNSWEEP is INTEGER NSWEEP is the number of sweeps of Jacobi rotations to be performed.
WORKWORK is REAL array, dimension LWORK.
LWORKLWORK is INTEGER LWORK is the dimension of WORK. LWORK .GE. M.
INFOINFO is INTEGER = 0 : successful exit. < 0 : if INFO = i, then the ith argument had an illegal value
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Further Details:
 SGSVJ0 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 [at] math.hr. Thank you.
Definition at line 218 of file sgsvj0.f.
Author
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