Provided by: liblapack-doc_3.12.0-3build1_all 
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, double precision, 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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