slasq3.f(3)

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.

    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.

Author

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