slasd0.f - Man Page
SRC/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 (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
Definition at line 150 of file slasd0.f.
Author
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Referenced By
The man page slasd0(3) is an alias of slasd0.f(3).
Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK