# dlasd0.f(3) [centos man page]

```dlasd0.f(3)							      LAPACK							       dlasd0.f(3)

NAME
dlasd0.f -

SYNOPSIS
Functions/Subroutines
subroutine dlasd0 (N, SQRE, D, E, U, LDU, VT, LDVT, SMLSIZ, IWORK, WORK, INFO)
DLASD0 computes the singular values of a real upper bidiagonal n-by-m matrix B with diagonal d and off-diagonal e. Used by sbdsdc.

Function/Subroutine Documentation
subroutine dlasd0 (integerN, integerSQRE, double precision, dimension( * )D, double precision, dimension( * )E, double precision, dimension(
ldu, * )U, integerLDU, double precision, dimension( ldvt, * )VT, integerLDVT, integerSMLSIZ, integer, dimension( * )IWORK, double
precision, dimension( * )WORK, integerINFO)
DLASD0 computes the singular values of a real upper bidiagonal n-by-m matrix B with diagonal d and off-diagonal e. Used by sbdsdc.

Purpose:

Using a divide and conquer approach, DLASD0 computes the singular
value decomposition (SVD) of a real upper bidiagonal N-by-M
matrix B with diagonal D and offdiagonal E, where M = N + SQRE.
The algorithm computes orthogonal matrices U and VT such that
B = U * S * VT. The singular values S are overwritten on D.

A related subroutine, DLASDA, computes only the singular values,
and optionally, the singular vectors in compact form.

Parameters:
N

N is INTEGER
On entry, the row dimension of the upper bidiagonal matrix.
This is also the dimension of the main diagonal array D.

SQRE

SQRE is INTEGER
Specifies the column dimension of the bidiagonal matrix.
= 0: The bidiagonal matrix has column dimension M = N;
= 1: The bidiagonal matrix has column dimension M = N+1;

D

D is DOUBLE PRECISION array, dimension (N)
On entry D contains the main diagonal of the bidiagonal
matrix.
On exit D, if INFO = 0, contains its singular values.

E

E is DOUBLE PRECISION array, dimension (M-1)
Contains the subdiagonal entries of the bidiagonal matrix.
On exit, E has been destroyed.

U

U is DOUBLE PRECISION array, dimension at least (LDQ, N)
On exit, U contains the left singular vectors.

LDU

LDU is INTEGER
On entry, leading dimension of U.

VT

VT is DOUBLE PRECISION array, dimension at least (LDVT, M)
On exit, VT**T contains the right singular vectors.

LDVT

LDVT is INTEGER
On entry, leading dimension of VT.

SMLSIZ

SMLSIZ is INTEGER
On entry, maximum size of the subproblems at the
bottom of the computation tree.

IWORK

IWORK is INTEGER work array.
Dimension must be at least (8 * N)

WORK

WORK is DOUBLE PRECISION work array.
Dimension must be at least (3 * M**2 + 2 * M)

INFO

INFO is INTEGER
= 0:  successful exit.
< 0:  if INFO = -i, the i-th argument had an illegal value.
> 0:  if INFO = 1, a singular value did not converge

Author:
Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:
September 2012

Contributors:
Ming Gu and Huan Ren, Computer Science Division, University of California at Berkeley, USA

Definition at line 152 of file dlasd0.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2							  Tue Sep 25 2012						       dlasd0.f(3)```

## Check Out this Related Man Page

```SLASD0(l)								 )								 SLASD0(l)

NAME
SLASD0  -  a divide and conquer approach, SLASD0 computes the singular value decomposition (SVD) of a real upper bidiagonal N-by-M matrix B
with diagonal D and offdiagonal E, where M = N + SQRE

SYNOPSIS
SUBROUTINE SLASD0( N, SQRE, D, E, U, LDU, VT, LDVT, SMLSIZ, IWORK, WORK, INFO )

INTEGER	  INFO, LDU, LDVT, N, SMLSIZ, SQRE

INTEGER	  IWORK( * )

REAL 	  D( * ), E( * ), U( LDU, * ), VT( LDVT, * ), WORK( * )

PURPOSE
Using a divide and conquer approach, SLASD0 computes the singular value decomposition (SVD) of a real upper bidiagonal N-by-M matrix B with
diagonal  D and offdiagonal E, where M = N + SQRE. The algorithm computes orthogonal matrices U and VT such that B = U * S * VT. The singu-
lar values S are overwritten on D.

A related subroutine, SLASDA, computes only the singular values, and optionally, the singular vectors in compact form.

ARGUMENTS
N      (input) INTEGER
On entry, the row dimension of the upper bidiagonal matrix.  This is also the dimension of the main diagonal array D.

SQRE   (input) INTEGER
Specifies the column dimension of the bidiagonal matrix.	= 0: The bidiagonal matrix has column dimension M = N;
= 1: The bidiagonal matrix has column dimension M = N+1;

D      (input/output) REAL array, dimension (N)
On entry D contains the main diagonal of the bidiagonal matrix.  On exit D, if INFO = 0, contains its singular values.

E      (input) REAL array, dimension (M-1)
Contains the subdiagonal entries of the bidiagonal matrix.  On exit, E has been destroyed.

U      (output) REAL array, dimension at least (LDQ, N)
On exit, U contains the left singular vectors.

LDU    (input) INTEGER
On entry, leading dimension of U.

VT     (output) REAL array, dimension at least (LDVT, M)
On exit, VT' contains the right singular vectors.

LDVT   (input) INTEGER
On entry, leading dimension of VT.

SMLSIZ (input) INTEGER On entry, maximum size of the subproblems at the bottom of the computation tree.

IWORK  INTEGER work array.
Dimension must be at least (8 * N)

WORK   REAL work array.
Dimension must be at least (3 * M**2 + 2 * M)

INFO   (output) INTEGER
= 0:  successful exit.
< 0:  if INFO = -i, the i-th argument had an illegal value.
> 0:  if INFO = 1, an singular value did not converge

FURTHER DETAILS
Based on contributions by
Ming Gu and Huan Ren, Computer Science Division, University of
California at Berkeley, USA

LAPACK version 3.0						   15 June 2000 							 SLASD0(l)```
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