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dlasq3.f(3) LAPACK dlasq3.f(3)

NAME

dlasq3.f -

SYNOPSIS

Functions/Subroutines


subroutine dlasq3 (I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL, ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1, DN2, G, TAU)
 
DLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

Function/Subroutine Documentation

subroutine dlasq3 (integerI0, integerN0, double precision, dimension( * )Z, integerPP, double precisionDMIN, double precisionSIGMA, double precisionDESIG, double precisionQMAX, integerNFAIL, integerITER, integerNDIV, logicalIEEE, integerTTYPE, double precisionDMIN1, double precisionDMIN2, double precisionDN, double precisionDN1, double precisionDN2, double precisionG, double precisionTAU)

DLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.
Purpose: 
 DLASQ3 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.
N0 
          N0 is INTEGER
         Last index.
Z 
          Z is DOUBLE PRECISION array, dimension ( 4*N )
         Z holds the qd array.
PP 
          PP 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.
DMIN 
          DMIN is DOUBLE PRECISION
         Minimum value of d.
SIGMA 
          SIGMA is DOUBLE PRECISION
         Sum of shifts used in current segment.
DESIG 
          DESIG is DOUBLE PRECISION
         Lower order part of SIGMA
QMAX 
          QMAX is DOUBLE PRECISION
         Maximum value of q.
NFAIL 
          NFAIL is INTEGER
         Number of times shift was too big.
ITER 
          ITER is INTEGER
         Number of iterations.
NDIV 
          NDIV is INTEGER
         Number of divisions.
IEEE 
          IEEE is LOGICAL
         Flag for IEEE or non IEEE arithmetic (passed to DLASQ5).
TTYPE 
          TTYPE is INTEGER
         Shift type.
DMIN1 
          DMIN1 is DOUBLE PRECISION
DMIN2 
          DMIN2 is DOUBLE PRECISION
DN 
          DN is DOUBLE PRECISION
DN1 
          DN1 is DOUBLE PRECISION
DN2 
          DN2 is DOUBLE PRECISION
G 
          G is DOUBLE PRECISION
TAU 
          TAU is DOUBLE PRECISION


         These are passed as arguments in order to save their values
         between calls to DLASQ3.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Definition at line 181 of file dlasq3.f.

Author

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