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Diffstat (limited to '2.3-1/src/fortran/lapack/dlasq5.f')
| -rw-r--r-- | 2.3-1/src/fortran/lapack/dlasq5.f | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/lapack/dlasq5.f b/2.3-1/src/fortran/lapack/dlasq5.f new file mode 100644 index 00000000..a006c99e --- /dev/null +++ b/2.3-1/src/fortran/lapack/dlasq5.f @@ -0,0 +1,195 @@ + SUBROUTINE DLASQ5( 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 + DOUBLE PRECISION DMIN, DMIN1, DMIN2, DN, DNM1, DNM2, TAU +* .. +* .. Array Arguments .. + DOUBLE PRECISION Z( * ) +* .. +* +* Purpose +* ======= +* +* DLASQ5 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) 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. +* +* TAU (input) DOUBLE PRECISION +* This is the shift. +* +* 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). +* +* IEEE (input) LOGICAL +* Flag for IEEE or non IEEE arithmetic. +* +* ===================================================================== +* +* .. Parameter .. + DOUBLE PRECISION ZERO + PARAMETER ( ZERO = 0.0D0 ) +* .. +* .. Local Scalars .. + INTEGER J4, J4P2 + DOUBLE PRECISION 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 DLASQ5 +* + END |