```      SUBROUTINE SLASQ5( I0, N0, Z, PP, TAU, DMIN, DMIN1, DMIN2, DN,
\$                   DNM1, DNM2, IEEE )
*
*  -- LAPACK auxiliary routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
LOGICAL            IEEE
INTEGER            I0, N0, PP
REAL               DMIN, DMIN1, DMIN2, DN, DNM1, DNM2, TAU
*     ..
*     .. Array Arguments ..
REAL               Z( * )
*     ..
*
*  Purpose
*  =======
*
*  SLASQ5 computes one dqds transform in ping-pong form, one
*  version for IEEE machines another for non IEEE machines.
*
*  Arguments
*  =========
*
*  I0    (input) INTEGER
*        First index.
*
*  N0    (input) INTEGER
*        Last index.
*
*  Z     (input) REAL 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.
*
*  TAU   (input) REAL
*        This is the shift.
*
*  DMIN  (output) REAL
*        Minimum value of d.
*
*  DMIN1 (output) REAL
*        Minimum value of d, excluding D( N0 ).
*
*  DMIN2 (output) REAL
*        Minimum value of d, excluding D( N0 ) and D( N0-1 ).
*
*  DN    (output) REAL
*        d(N0), the last value of d.
*
*  DNM1  (output) REAL
*        d(N0-1).
*
*  DNM2  (output) REAL
*        d(N0-2).
*
*  IEEE  (input) LOGICAL
*        Flag for IEEE or non IEEE arithmetic.
*
*  =====================================================================
*
*     .. Parameter ..
REAL               ZERO
PARAMETER          ( ZERO = 0.0E0 )
*     ..
*     .. Local Scalars ..
INTEGER            J4, J4P2
REAL               D, EMIN, TEMP
*     ..
*     .. Intrinsic Functions ..
INTRINSIC          MIN
*     ..
*     .. Executable Statements ..
*
IF( ( N0-I0-1 ).LE.0 )
\$   RETURN
*
J4 = 4*I0 + PP - 3
EMIN = Z( J4+4 )
D = Z( J4 ) - TAU
DMIN = D
DMIN1 = -Z( J4 )
*
IF( IEEE ) THEN
*
*        Code for IEEE arithmetic.
*
IF( PP.EQ.0 ) THEN
DO 10 J4 = 4*I0, 4*( N0-3 ), 4
Z( J4-2 ) = D + Z( J4-1 )
TEMP = Z( J4+1 ) / Z( J4-2 )
D = D*TEMP - TAU
DMIN = MIN( DMIN, D )
Z( J4 ) = Z( J4-1 )*TEMP
EMIN = MIN( Z( J4 ), EMIN )
10       CONTINUE
ELSE
DO 20 J4 = 4*I0, 4*( N0-3 ), 4
Z( J4-3 ) = D + Z( J4 )
TEMP = Z( J4+2 ) / Z( J4-3 )
D = D*TEMP - TAU
DMIN = MIN( DMIN, D )
Z( J4-1 ) = Z( J4 )*TEMP
EMIN = MIN( Z( J4-1 ), EMIN )
20       CONTINUE
END IF
*
*        Unroll last two steps.
*
DNM2 = D
DMIN2 = DMIN
J4 = 4*( N0-2 ) - PP
J4P2 = J4 + 2*PP - 1
Z( J4-2 ) = DNM2 + Z( J4P2 )
Z( J4 ) = Z( J4P2+2 )*( Z( J4P2 ) / Z( J4-2 ) )
DNM1 = Z( J4P2+2 )*( DNM2 / Z( J4-2 ) ) - TAU
DMIN = MIN( DMIN, DNM1 )
*
DMIN1 = DMIN
J4 = J4 + 4
J4P2 = J4 + 2*PP - 1
Z( J4-2 ) = DNM1 + Z( J4P2 )
Z( J4 ) = Z( J4P2+2 )*( Z( J4P2 ) / Z( J4-2 ) )
DN = Z( J4P2+2 )*( DNM1 / Z( J4-2 ) ) - TAU
DMIN = MIN( DMIN, DN )
*
ELSE
*
*        Code for non IEEE arithmetic.
*
IF( PP.EQ.0 ) THEN
DO 30 J4 = 4*I0, 4*( N0-3 ), 4
Z( J4-2 ) = D + Z( J4-1 )
IF( D.LT.ZERO ) THEN
RETURN
ELSE
Z( J4 ) = Z( J4+1 )*( Z( J4-1 ) / Z( J4-2 ) )
D = Z( J4+1 )*( D / Z( J4-2 ) ) - TAU
END IF
DMIN = MIN( DMIN, D )
EMIN = MIN( EMIN, Z( J4 ) )
30       CONTINUE
ELSE
DO 40 J4 = 4*I0, 4*( N0-3 ), 4
Z( J4-3 ) = D + Z( J4 )
IF( D.LT.ZERO ) THEN
RETURN
ELSE
Z( J4-1 ) = Z( J4+2 )*( Z( J4 ) / Z( J4-3 ) )
D = Z( J4+2 )*( D / Z( J4-3 ) ) - TAU
END IF
DMIN = MIN( DMIN, D )
EMIN = MIN( EMIN, Z( J4-1 ) )
40       CONTINUE
END IF
*
*        Unroll last two steps.
*
DNM2 = D
DMIN2 = DMIN
J4 = 4*( N0-2 ) - PP
J4P2 = J4 + 2*PP - 1
Z( J4-2 ) = DNM2 + Z( J4P2 )
IF( DNM2.LT.ZERO ) THEN
RETURN
ELSE
Z( J4 ) = Z( J4P2+2 )*( Z( J4P2 ) / Z( J4-2 ) )
DNM1 = Z( J4P2+2 )*( DNM2 / Z( J4-2 ) ) - TAU
END IF
DMIN = MIN( DMIN, DNM1 )
*
DMIN1 = DMIN
J4 = J4 + 4
J4P2 = J4 + 2*PP - 1
Z( J4-2 ) = DNM1 + Z( J4P2 )
IF( DNM1.LT.ZERO ) THEN
RETURN
ELSE
Z( J4 ) = Z( J4P2+2 )*( Z( J4P2 ) / Z( J4-2 ) )
DN = Z( J4P2+2 )*( DNM1 / Z( J4-2 ) ) - TAU
END IF
DMIN = MIN( DMIN, DN )
*
END IF
*
Z( J4+2 ) = DN
Z( 4*N0-PP ) = EMIN
RETURN
*
*     End of SLASQ5
*
END

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