# cgsvj0.f man page

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 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 Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:

June 2016

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)

Please report all bugs and send interesting test examples and comments to drmac@math.hr. Thank you.

Definition at line 220 of file cgsvj0.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page cgsvj0(3) is an alias of cgsvj0.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK