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dlasd0 examples
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Man Page Details
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NAME
       DLASD0  -  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

SYNOPSIS
       SUBROUTINE DLASD0( N,  SQRE,  D,  E,  U,  LDU, VT, LDVT, SMLSIZ, IWORK,
                          WORK, INFO )

           INTEGER        INFO, LDU, LDVT, N, SMLSIZ, SQRE

           INTEGER        IWORK( * )

           DOUBLE         PRECISION D( * ), E( * ), U( LDU, * ), VT(  LDVT,  *
                          ), WORK( * )

 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.

  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) 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      (input) DOUBLE PRECISION array, dimension (M-1)
         Contains the subdiagonal entries of the bidiagonal matrix.
         On exit, E has been destroyed.

  U      (output) DOUBLE PRECISION 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) DOUBLE PRECISION 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 computation tree.

  IWORK  INTEGER work array.
         Dimension must be at least (8 * N)

  WORK   DOUBLE PRECISION work array.
         Dimension must be at least (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

