Man page - lasd0(3)

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lasd0

NAME
SYNOPSIS
Functions
Detailed Description
Function Documentation
subroutine dlasd0 (integer n, integer sqre, double precision, dimension( *) d, double precision, dimension( * ) e, double precision, dimension(ldu, * ) u, integer ldu, double precision, dimension( ldvt, * ) vt,integer ldvt, integer smlsiz, integer, dimension( * ) iwork, doubleprecision, dimension( * ) work, integer info)
subroutine slasd0 (integer n, integer sqre, real, dimension( * ) d, real,dimension( * ) e, real, dimension( ldu, * ) u, integer ldu, real,dimension( ldvt, * ) vt, integer ldvt, integer smlsiz, integer,dimension( * ) iwork, real, dimension( * ) work, integer info)
Author

NAME

lasd0 - lasd0: D&C step: top level solver

SYNOPSIS

Functions

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.
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.

Detailed Description

Function Documentation

subroutine dlasd0 (integer n, integer sqre, double precision, dimension( *) d, double precision, dimension( * ) e, double precision, dimension(ldu, * ) u, integer ldu, double precision, dimension( ldvt, * ) vt,integer ldvt, integer smlsiz, integer, dimension( * ) iwork, doubleprecision, dimension( * ) work, integer 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.

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 (LDU, N)
On exit, U contains the left singular vectors,
if U passed in as (N, N) Identity.

LDU

LDU is INTEGER
On entry, leading dimension of U.

VT

VT is DOUBLE PRECISION array, dimension (LDVT, M)
On exit, VT**T contains the right singular vectors,
if VT passed in as (M, M) Identity.

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 DOUBLE PRECISION 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.

Contributors:

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

subroutine slasd0 (integer n, integer sqre, real, dimension( * ) d, real,dimension( * ) e, real, dimension( ldu, * ) u, integer ldu, real,dimension( ldvt, * ) vt, integer ldvt, integer smlsiz, integer,dimension( * ) iwork, real, dimension( * ) work, integer 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.

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 (LDU, N)
On exit, U contains the left singular vectors,
if U passed in as (N, N) Identity.

LDU

LDU is INTEGER
On entry, leading dimension of U.

VT

VT is REAL array, dimension (LDVT, M)
On exit, VT**T contains the right singular vectors,
if VT passed in as (M, M) Identity.

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.

Contributors:

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

Author

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