SRC/cgsvj0.f(3) | Library Functions Manual | SRC/cgsvj0.f(3) |
NAME
SRC/cgsvj0.f
SYNOPSIS
Functions/Subroutines
subroutine cgsvj0 (jobv, m, n, a, lda, d, sva, mv, v, ldv,
eps, sfmin, tol, nsweep, work, lwork, info)
CGSVJ0 pre-processor for the routine cgesvj.
Function/Subroutine Documentation
subroutine cgsvj0 (character*1 jobv, integer m, integer n, complex, dimension( lda, * ) a, integer lda, complex, dimension( n ) d, real, dimension( n ) sva, integer mv, complex, dimension( ldv, * ) v, integer ldv, real eps, real sfmin, real tol, integer nsweep, complex, dimension( lwork ) work, integer lwork, integer info)
CGSVJ0 pre-processor for the routine cgesvj.
Purpose:
CGSVJ0 is called from CGESVJ as a pre-processor and that is its main purpose. It applies Jacobi rotations in the same way as CGESVJ 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 postmultiplying the N-by-N array V. (See the description of V.) = 'A': the product of the Jacobi rotations is accumulated by postmultiplying 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 COMPLEX array, dimension (LDA,N) On entry, M-by-N matrix A, such that A*diag(D) represents the input matrix. On exit, A_onexit * diag(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 COMPLEX array, dimension (N) The array D accumulates the scaling factors from the complex 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 A_onexit*diag(D_onexit).
MV
MV is INTEGER If JOBV = 'A', then MV rows of V are post-multiplied by a sequence of Jacobi rotations. If JOBV = 'N', then MV is not referenced.
V
V is COMPLEX array, dimension (LDV,N) If JOBV = 'V' then N rows of V are post-multiplied by a sequence of Jacobi rotations. If JOBV = 'A' then MV rows of V are post-multiplied 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 >= N. If JOBV = 'A', LDV >= 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)))) > TOL.
NSWEEP
NSWEEP is INTEGER NSWEEP is the number of sweeps of Jacobi rotations to be performed.
WORK
WORK is COMPLEX array, dimension (LWORK)
LWORK
LWORK is INTEGER LWORK is the dimension of WORK. LWORK >= 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.
Further Details:
CGSVJ0 is used just to enable CGESVJ to call a simplified
version of itself to work on a submatrix of the original matrix.
Contributor:
Zlatko Drmac (Zagreb, Croatia)
Bugs, Examples and Comments:
Please report all bugs and send interesting test examples
and comments to drmac@math.hr. Thank you.
Definition at line 216 of file cgsvj0.f.
Author
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