redhat man page for slasd9

SLASD9(l)								 )								 SLASD9(l)

NAME
       SLASD9 - find the square roots of the roots of the secular equation,

SYNOPSIS
       SUBROUTINE SLASD9( ICOMPQ, LDU, K, D, Z, VF, VL, DIFL, DIFR, DSIGMA, WORK, INFO )

	   INTEGER	  ICOMPQ, INFO, K, LDU

	   REAL 	  D( * ), DIFL( * ), DIFR( LDU, * ), DSIGMA( * ), VF( * ), VL( * ), WORK( * ), Z( * )

PURPOSE
       SLASD9 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  SLASD4,	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.

       SLASD9 is called from SLASD7.

ARGUMENTS
       ICOMPQ  (input) INTEGER
	       Specifies whether singular vectors are to be computed in factored form in the calling routine:

	       ICOMPQ = 0	      Compute singular values only.

	       ICOMPQ = 1	      Compute singular vector matrices in factored form also.  K       (input) INTEGER The number of terms in  the
	       rational function to be solved by SLASD4.  K >= 1.

       D       (output) REAL array, dimension(K)
	       D(I) contains the updated singular values.

       DSIGMA  (input) REAL 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.

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

       VF      (input/output) REAL array, dimension(K)
	       On entry, VF contains  information passed through SBEDE8.f On exit, VF contains the first K components of the first  components	of
	       all right singular vectors of the bidiagonal matrix.

       VL      (input/output) REAL array, dimension(K)
	       On  entry,  VL  contains  information passed through SBEDE8.f On exit, VL contains the first K components of the last components of
	       all right singular vectors of the bidiagonal matrix.

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

       DIFR    (output) REAL array,
	       dimension (LDU, 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.

       WORK    (workspace) REAL array,
	       dimension at least (3 * K) Workspace.

       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 							 SLASD9(l)