DLASQ6 - compute one dqd (shift equal to zero) transform
in ping-pong form, with protection against underflow and
overflow
SYNOPSIS
SUBROUTINE DLASQ6( I0, N0, Z, PP, DMIN, DMIN1, DMIN2, DN,
DNM1, DNM2 )
INTEGER I0, N0, PP
DOUBLE PRECISION DMIN, DMIN1, DMIN2, DN, DNM1,
DNM2
DOUBLE PRECISION Z( * )
PURPOSE
DLASQ6 computes one dqd (shift equal to zero) transform in
ping-pong form, with protection against underflow and
overflow.
ARGUMENTS
I0 (input) INTEGER
First index.
N0 (input) INTEGER
Last index.
Z (input) DOUBLE PRECISION array, dimension ( 4*N )
Z holds the qd array. EMIN is stored in Z(4*N0) to
avoid an extra argument.
PP (input) INTEGER
PP=0 for ping, PP=1 for pong.
DMIN (output) DOUBLE PRECISION
Minimum value of d.
DMIN1 (output) DOUBLE PRECISION Minimum value of d,
excluding D( N0 ).
DMIN2 (output) DOUBLE PRECISION Minimum value of d,
excluding D( N0 ) and D( N0-1 ).
DN (output) DOUBLE PRECISION
d(N0), the last value of d.
DNM1 (output) DOUBLE PRECISION
d(N0-1).
DNM2 (output) DOUBLE PRECISION
d(N0-2).
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