dlasd0.f (3) Linux Manual Page

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

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 152 of file dlasd0.f.

Author

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