slasq3.f (3)  Linux Manuals
NAME
slasq3.f 
SYNOPSIS
Functions/Subroutines
subroutine slasq3 (I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL, ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1, DN2, G, TAU)
SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.
Function/Subroutine Documentation
subroutine slasq3 (integerI0, integerN0, real, dimension( * )Z, integerPP, realDMIN, realSIGMA, realDESIG, realQMAX, integerNFAIL, integerITER, integerNDIV, logicalIEEE, integerTTYPE, realDMIN1, realDMIN2, realDN, realDN1, realDN2, realG, realTAU)
SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.
Purpose:

SLASQ3 checks for deflation, computes a shift (TAU) and calls dqds. In case of failure it changes shifts, and tries again until output is positive.
Parameters:

I0
I0 is INTEGER First index.
N0N0 is INTEGER Last index.
ZZ is REAL array, dimension ( 4*N ) Z holds the qd array.
PPPP is INTEGER PP=0 for ping, PP=1 for pong. PP=2 indicates that flipping was applied to the Z array and that the initial tests for deflation should not be performed.
DMINDMIN is REAL Minimum value of d.
SIGMASIGMA is REAL Sum of shifts used in current segment.
DESIGDESIG is REAL Lower order part of SIGMA
QMAXQMAX is REAL Maximum value of q.
NFAILNFAIL is INTEGER Number of times shift was too big.
ITERITER is INTEGER Number of iterations.
NDIVNDIV is INTEGER Number of divisions.
IEEEIEEE is LOGICAL Flag for IEEE or non IEEE arithmetic (passed to SLASQ5).
TTYPETTYPE is INTEGER Shift type.
DMIN1DMIN1 is REAL
DMIN2DMIN2 is REAL
DNDN is REAL
DN1DN1 is REAL
DN2DN2 is REAL
GG is REAL
TAUTAU is REAL These are passed as arguments in order to save their values between calls to SLASQ3.
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Definition at line 181 of file slasq3.f.
Author
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