dlasd8.f (3)  Linux Man Pages
NAME
dlasd8.f 
SYNOPSIS
Functions/Subroutines
subroutine dlasd8 (ICOMPQ, K, D, Z, VF, VL, DIFL, DIFR, LDDIFR, DSIGMA, WORK, INFO)
DLASD8 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 dlasd8 (integerICOMPQ, integerK, double precision, dimension( * )D, double precision, dimension( * )Z, double precision, dimension( * )VF, double precision, dimension( * )VL, double precision, dimension( * )DIFL, double precision, dimension( lddifr, * )DIFR, integerLDDIFR, double precision, dimension( * )DSIGMA, double precision, dimension( * )WORK, integerINFO)
DLASD8 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:

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.
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 DLASD4. K >= 1.
DD is DOUBLE PRECISION array, dimension ( K ) On output, D contains the updated singular values.
ZZ is DOUBLE PRECISION 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 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.
VLVL is 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.
DIFLDIFL is DOUBLE PRECISION array, dimension ( K ) On exit, DIFL(I) = D(I)  DSIGMA(I).
DIFRDIFR is 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.
LDDIFRLDDIFR is INTEGER The leading dimension of DIFR, must be at least K.
DSIGMADSIGMA is DOUBLE PRECISION 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 DOUBLE PRECISION 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 dlasd8.f.
Author
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