\brief \b ESMF_DLASQ1 \htmlonly Download ESMF_DLASQ1 + dependencies [TGZ] [ZIP] [TXT] \endhtmlonly \par Purpose:
\verbatim
ESMF_DLASQ1 computes the singular values of a real N-by-N bidiagonal matrix with diagonal D and off-diagonal E. The singular values are computed to high relative accuracy, in the absence of denormalization, underflow and overflow. The algorithm was first presented in
“Accurate singular values and differential qd algorithms” by K. V. Fernando and B. N. Parlett, Numer. Math., Vol-67, No. 2, pp. 191-230, 1994,
and the present implementation is described in “An implementation of the dqds Algorithm (Positive Case)”, LAPACK Working Note. \endverbatim \param[in] N \verbatim N is INTEGER The number of rows and columns in the matrix. N >= 0. \endverbatim
\param[in,out] D \verbatim D is DOUBLE PRECISION array, dimension (N) On entry, D contains the diagonal elements of the bidiagonal matrix whose SVD is desired. On normal exit, D contains the singular values in decreasing order. \endverbatim
\param[in,out] E \verbatim E is DOUBLE PRECISION array, dimension (N) On entry, elements E(1:N-1) contain the off-diagonal elements of the bidiagonal matrix whose SVD is desired. On exit, E is overwritten. \endverbatim
\param[out] WORK \verbatim WORK is DOUBLE PRECISION array, dimension (4*N) \endverbatim
\param[out] INFO \verbatim INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: the algorithm failed = 1, a split was marked by a positive value in E = 2, current block of Z not diagonalized after 100*N iterations (in inner while loop) On exit D and E represent a matrix with the same singular values which the calling subroutine could use to finish the computation, or even feed back into ESMF_DLASQ1 = 3, termination criterion of outer while loop not met (program created more than N unreduced blocks) \endverbatim \author Univ. of Tennessee \author Univ. of California Berkeley \author Univ. of Colorado Denver \author NAG Ltd. \date November 2011 \ingroup auxOTHERcomputational
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| integer | :: | N | ||||
| double precision | :: | D(*) | ||||
| double precision | :: | E(*) | ||||
| double precision | :: | WORK(*) | ||||
| integer | :: | INFO |