slasq3.f (3)

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.

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.

N0

          N0 is INTEGER
         Last index.

Z

          Z is REAL 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 REAL
         Minimum value of d.

SIGMA

          SIGMA is REAL
         Sum of shifts used in current segment.

DESIG

          DESIG is REAL
         Lower order part of SIGMA

QMAX

          QMAX is REAL
         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 SLASQ5).

TTYPE

          TTYPE is INTEGER
         Shift type.

DMIN1

          DMIN1 is REAL

DMIN2

          DMIN2 is REAL

DN

          DN is REAL

DN1

          DN1 is REAL

DN2

          DN2 is REAL

G

          G is REAL

TAU

          TAU 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.

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