dlasq5 (3)

Functions/Subroutines

subroutine dlasq5 (I0, N0, Z, PP, TAU, SIGMA, DMIN, DMIN1, DMIN2, DN, DNM1, DNM2, IEEE, EPS)

DLASQ5 computes one dqds transform in ping-pong form. Used by sbdsqr and sstegr.

subroutine dlasq5 (integerI0, integerN0, double precision, dimension( * )Z, integerPP, double precisionTAU, double precisionSIGMA, double precisionDMIN, double precisionDMIN1, double precisionDMIN2, double precisionDN, double precisionDNM1, double precisionDNM2, logicalIEEE, double precisionEPS)

DLASQ5 computes one dqds transform in ping-pong form. Used by sbdsqr and sstegr.

Purpose:

 DLASQ5 computes one dqds transform in ping-pong form, one
 version for IEEE machines another for non IEEE machines.

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. EMIN is stored in Z(4*N0) to avoid
        an extra argument.

PP

          PP is INTEGER
        PP=0 for ping, PP=1 for pong.

TAU

          TAU is DOUBLE PRECISION
        This is the shift.

SIGMA

          SIGMA is DOUBLE PRECISION
        This is the accumulated shift up to this step.

DMIN

          DMIN is DOUBLE PRECISION
        Minimum value of d.

DMIN1

          DMIN1 is DOUBLE PRECISION
        Minimum value of d, excluding D( N0 ).

DMIN2

          DMIN2 is DOUBLE PRECISION
        Minimum value of d, excluding D( N0 ) and D( N0-1 ).

DN

          DN is DOUBLE PRECISION
        d(N0), the last value of d.

DNM1

          DNM1 is DOUBLE PRECISION
        d(N0-1).

DNM2

          DNM2 is DOUBLE PRECISION
        d(N0-2).

IEEE

          IEEE is LOGICAL
        Flag for IEEE or non IEEE arithmetic.

EPS

          EPS is DOUBLE PRECISION
        This is the value of epsilon used.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 144 of file dlasq5.f.

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