slasd8 (3)  Linux Manuals
NAME
slasd8.f 
SYNOPSIS
Functions/Subroutines
subroutine slasd8 (ICOMPQ, K, D, Z, VF, VL, DIFL, DIFR, LDDIFR, DSIGMA, WORK, INFO)
SLASD8 finds the square roots of the roots of the secular equation, and stores, for each element in D, the distance to its two nearest poles. Used by sbdsdc.
Function/Subroutine Documentation
subroutine slasd8 (integerICOMPQ, integerK, real, dimension( * )D, real, dimension( * )Z, real, dimension( * )VF, real, dimension( * )VL, real, dimension( * )DIFL, real, dimension( lddifr, * )DIFR, integerLDDIFR, real, dimension( * )DSIGMA, real, dimension( * )WORK, integerINFO)
SLASD8 finds the square roots of the roots of the secular equation, and stores, for each element in D, the distance to its two nearest poles. Used by sbdsdc.
Purpose:

SLASD8 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. SLASD8 is called from SLASD6.
Parameters:

ICOMPQ
ICOMPQ is 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.
KK is INTEGER The number of terms in the rational function to be solved by SLASD4. K >= 1.
DD is REAL array, dimension ( K ) On output, D contains the updated singular values.
ZZ is REAL array, dimension ( K ) On entry, the first K elements of this array contain the components of the deflationadjusted updating row vector. On exit, Z is updated.
VFVF is REAL 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.
VLVL is REAL 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.
DIFLDIFL is REAL array, dimension ( K ) On exit, DIFL(I) = D(I)  DSIGMA(I).
DIFRDIFR is REAL 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.
LDDIFRLDDIFR is INTEGER The leading dimension of DIFR, must be at least K.
DSIGMADSIGMA is REAL array, dimension ( K ) On entry, the first K elements of this array contain the old roots of the deflated updating problem. These are the poles of the secular equation. On exit, the elements of DSIGMA may be very slightly altered in value.
WORKWORK is REAL array, dimension at least 3 * K
INFOINFO is INTEGER = 0: successful exit. < 0: if INFO = i, the ith 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 166 of file slasd8.f.
Author
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