redhat man page for dlasd8

DLASD8(l)								 )								 DLASD8(l)

NAME
       DLASD8 - find the square roots of the roots of the secular equation,

SYNOPSIS
       SUBROUTINE DLASD8( ICOMPQ, K, D, Z, VF, VL, DIFL, DIFR, LDDIFR, DSIGMA, WORK, INFO )

	   INTEGER	  ICOMPQ, INFO, K, LDDIFR

	   DOUBLE	  PRECISION D( * ), DIFL( * ), DIFR( LDDIFR, * ), DSIGMA( * ), VF( * ), VL( * ), WORK( * ), Z( * )

PURPOSE
       DLASD8  finds  the  square  roots  of the roots of the secular equation, as defined by the values in DSIGMA and Z. It makes the appropriate
       calls to DLASD4, and stores, for each  element in D, the distance to its two nearest poles (elements in DSIGMA). It also updates the arrays
       VF and VL, the first and last components of all the right singular vectors of the original bidiagonal matrix.

       DLASD8 is called from DLASD6.

ARGUMENTS
       ICOMPQ  (input) INTEGER
	       Specifies whether singular vectors are to be computed in factored form in the calling routine:
	       = 0: Compute singular values only.
	       = 1: Compute singular vectors in factored form as well.

       K       (input) INTEGER
	       The number of terms in the rational function to be solved by DLASD4.  K >= 1.

       D       (output) DOUBLE PRECISION array, dimension ( K )
	       On output, D contains the updated singular values.

       Z       (input) DOUBLE PRECISION array, dimension ( K )
	       The first K elements of this array contain the components of the deflation-adjusted updating row vector.

       VF      (input/output) DOUBLE PRECISION array, dimension ( K )
	       On  entry,  VF contains	information passed through DBEDE8.  On exit, VF contains the first K components of the first components of
	       all right singular vectors of the bidiagonal matrix.

       VL      (input/output) DOUBLE PRECISION array, dimension ( K )
	       On entry, VL contains  information passed through DBEDE8.  On exit, VL contains the first K components of the  last  components	of
	       all right singular vectors of the bidiagonal matrix.

       DIFL    (output) DOUBLE PRECISION array, dimension ( K )
	       On exit, DIFL(I) = D(I) - DSIGMA(I).

       DIFR    (output) DOUBLE PRECISION array,
	       dimension ( LDDIFR, 2 ) if ICOMPQ = 1 and dimension ( K ) if ICOMPQ = 0.  On exit, DIFR(I,1) = D(I) - DSIGMA(I+1), DIFR(K,1) is not
	       defined and will not be referenced.

	       If ICOMPQ = 1, DIFR(1:K,2) is an array containing the normalizing factors for the right singular vector matrix.

       LDDIFR  (input) INTEGER
	       The leading dimension of DIFR, must be at least K.

       DSIGMA  (input) DOUBLE PRECISION array, dimension ( K )
	       The first K elements of this array contain the old roots of the deflated updating problem.  These are  the  poles  of  the  secular
	       equation.

       WORK    (workspace) DOUBLE PRECISION array, dimension at least 3 * K

       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

LAPACK version 3.0						   15 June 2000 							 DLASD8(l)