slasd0.f man page

slasd0.f —

Synopsis

Functions/Subroutines

subroutine slasd0 (N, SQRE, D, E, U, LDU, VT, LDVT, SMLSIZ, IWORK, WORK, INFO)
SLASD0 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 slasd0 (integerN, integerSQRE, real, dimension( * )D, real, dimension( * )E, real, dimension( ldu, * )U, integerLDU, real, dimension( ldvt, * )VT, integerLDVT, integerSMLSIZ, integer, dimension( * )IWORK, real, dimension( * )WORK, integerINFO)

SLASD0 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, 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 singular values S are overwritten on D.

A related subroutine, SLASDA, 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 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

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

U

 U is REAL 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 REAL 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 array, dimension (8*N)

WORK

WORK is REAL array, dimension (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

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Contributors:

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

Definition at line 150 of file slasd0.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

slasd0(3) is an alias of slasd0.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK