SLASD0(1) LAPACK auxiliary routine (version 3.2) SLASD0(1)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 com‐
putes orthogonal matrices U and VT such that B = U * S * VT. The singu‐
lar values S are overwritten on D. A related subroutine, SLASDA, com‐
putes 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 com‐
putation tree.
IWORK (workspace) INTEGER array, dimension (8*N)
WORK (workspace) REAL array, dimension (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 auxiliary routine (versioNovember 2008 SLASD0(1)