2. EL 7
  3. lapack
  4. DLASQ3(3)

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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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Tue Sep 25 2012 Version 3.4.2