# dgsvj0.f man page

dgsvj0.f —

## Synopsis

### Functions/Subroutines

subroutinedgsvj0(JOBV, M, N, A, LDA, D, SVA, MV, V, LDV, EPS, SFMIN, TOL, NSWEEP, WORK, LWORK, INFO)DGSVJ0pre-processor for the routine sgesvj.

## Function/Subroutine Documentation

### subroutine dgsvj0 (character*1JOBV, integerM, integerN, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( n )D, double precision, dimension( n )SVA, integerMV, double precision, dimension( ldv, * )V, integerLDV, double precisionEPS, double precisionSFMIN, double precisionTOL, integerNSWEEP, double precision, dimension( lwork )WORK, integerLWORK, integerINFO)

**DGSVJ0** pre-processor for the routine sgesvj.

**Purpose:**

```
DGSVJ0 is called from DGESVJ as a pre-processor and that is its main
purpose. It applies Jacobi rotations in the same way as DGESVJ 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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 DOUBLE PRECISION
EPS = DLAMCH('Epsilon')
```

*SFMIN*

```
SFMIN is DOUBLE PRECISION
SFMIN = DLAMCH('Safe Minimum')
```

*TOL*

```
TOL is DOUBLE PRECISION
TOL is the threshold for Jacobi rotations. For a pair
A(:,p), A(:,q) of pivot columns, the Jacobi rotation is
applied only if DABS(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 DOUBLE PRECISION 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:**

DGSVJ0 is used just to enable DGESVJ 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 dgsvj0.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dgsvj0(3) is an alias of dgsvj0.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK