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.
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 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 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 .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 COMPLEX 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 COMPLEX 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 California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
Further Details:
Contributor:
Bugs, Examples and Comments:
Definition at line 220 of file cgsvj0.f.
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