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slasd0.f(3) LAPACK slasd0.f(3)

NAME

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 (integerN, integerSQRE, real, dimension( * )D, real, dimension( * )E, real, dimension( ldu, * )U, integerLDU, real, dimension( ldvt, * )VT, integerLDVT, integerSMLSIZ, integer, dimension( * )IWORK, real, dimension( * )WORK, integerINFO)

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 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 REAL 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 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.
Date:
September 2012
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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