sgsvj0.f(3)

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 pre-processor 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 pre-processor for the routine sgesvj.

Purpose:

     SGSVJ0 is called from SGESVJ as a pre-processor 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 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

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

    N

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

    A

              A is 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

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

    D

              D 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
              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

              SVA 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).

    MV

              MV is 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

              V is 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

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

    EPS

              EPS is REAL
              EPS = SLAMCH('Epsilon')

    SFMIN

              SFMIN is REAL
              SFMIN = SLAMCH('Safe Minimum')

    TOL

              TOL 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.

    NSWEEP

              NSWEEP is INTEGER
              NSWEEP is the number of sweeps of Jacobi rotations to be
              performed.

    WORK

              WORK is REAL array, dimension LWORK.

    LWORK

              LWORK is INTEGER
              LWORK is the dimension of WORK. LWORK .GE. M.

    INFO

              INFO is INTEGER
              = 0 : successful exit.
              < 0 : if INFO = -i, then the i-th 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@math.hr. Thank you.

Definition at line 218 of file sgsvj0.f.

Author

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