Mercurial > hg > octave-max
changeset 3339:f8b4692eb51c
[project @ 1999-11-04 16:24:30 by jwe]
| author | jwe |
|---|---|
| date | Thu, 04 Nov 1999 16:24:31 +0000 |
| parents | bb5023dbee3d |
| children | 585a8809fd9b |
| files | libcruft/lapack/dlamc1.f libcruft/lapack/dlamc2.f libcruft/lapack/dlamc3.f libcruft/lapack/dlamc4.f libcruft/lapack/dlamc5.f libcruft/lapack/dlamch.f |
| diffstat | 6 files changed, 5 insertions(+), 750 deletions(-) [+] |
line wrap: on
line diff
--- a/libcruft/lapack/dlamc1.f +++ b/libcruft/lapack/dlamc1.f @@ -1,9 +1,6 @@ -* -************************************************************************ -* SUBROUTINE DLAMC1( BETA, T, RND, IEEE1 ) * -* -- LAPACK auxiliary routine (version 2.0) -- +* -- LAPACK auxiliary routine (version 3.0) -- * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., * Courant Institute, Argonne National Lab, and Rice University * October 31, 1992
--- a/libcruft/lapack/dlamc2.f +++ b/libcruft/lapack/dlamc2.f @@ -1,9 +1,6 @@ -* -************************************************************************ -* SUBROUTINE DLAMC2( BETA, T, RND, EPS, EMIN, RMIN, EMAX, RMAX ) * -* -- LAPACK auxiliary routine (version 2.0) -- +* -- LAPACK auxiliary routine (version 3.0) -- * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., * Courant Institute, Argonne National Lab, and Rice University * October 31, 1992
--- a/libcruft/lapack/dlamc3.f +++ b/libcruft/lapack/dlamc3.f @@ -1,9 +1,6 @@ -* -************************************************************************ -* DOUBLE PRECISION FUNCTION DLAMC3( A, B ) * -* -- LAPACK auxiliary routine (version 2.0) -- +* -- LAPACK auxiliary routine (version 3.0) -- * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., * Courant Institute, Argonne National Lab, and Rice University * October 31, 1992
--- a/libcruft/lapack/dlamc4.f +++ b/libcruft/lapack/dlamc4.f @@ -1,9 +1,6 @@ -* -************************************************************************ -* SUBROUTINE DLAMC4( EMIN, START, BASE ) * -* -- LAPACK auxiliary routine (version 2.0) -- +* -- LAPACK auxiliary routine (version 3.0) -- * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., * Courant Institute, Argonne National Lab, and Rice University * October 31, 1992
--- a/libcruft/lapack/dlamc5.f +++ b/libcruft/lapack/dlamc5.f @@ -1,9 +1,6 @@ -* -************************************************************************ -* SUBROUTINE DLAMC5( BETA, P, EMIN, IEEE, EMAX, RMAX ) * -* -- LAPACK auxiliary routine (version 2.0) -- +* -- LAPACK auxiliary routine (version 3.0) -- * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., * Courant Institute, Argonne National Lab, and Rice University * October 31, 1992
--- a/libcruft/lapack/dlamch.f +++ b/libcruft/lapack/dlamch.f @@ -125,733 +125,3 @@ * End of DLAMCH * END -* -************************************************************************ -* - SUBROUTINE DLAMC1( BETA, T, RND, IEEE1 ) -* -* -- LAPACK auxiliary routine (version 3.0) -- -* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., -* Courant Institute, Argonne National Lab, and Rice University -* October 31, 1992 -* -* .. Scalar Arguments .. - LOGICAL IEEE1, RND - INTEGER BETA, T -* .. -* -* Purpose -* ======= -* -* DLAMC1 determines the machine parameters given by BETA, T, RND, and -* IEEE1. -* -* Arguments -* ========= -* -* BETA (output) INTEGER -* The base of the machine. -* -* T (output) INTEGER -* The number of ( BETA ) digits in the mantissa. -* -* RND (output) LOGICAL -* Specifies whether proper rounding ( RND = .TRUE. ) or -* chopping ( RND = .FALSE. ) occurs in addition. This may not -* be a reliable guide to the way in which the machine performs -* its arithmetic. -* -* IEEE1 (output) LOGICAL -* Specifies whether rounding appears to be done in the IEEE -* 'round to nearest' style. -* -* Further Details -* =============== -* -* The routine is based on the routine ENVRON by Malcolm and -* incorporates suggestions by Gentleman and Marovich. See -* -* Malcolm M. A. (1972) Algorithms to reveal properties of -* floating-point arithmetic. Comms. of the ACM, 15, 949-951. -* -* Gentleman W. M. and Marovich S. B. (1974) More on algorithms -* that reveal properties of floating point arithmetic units. -* Comms. of the ACM, 17, 276-277. -* -* ===================================================================== -* -* .. Local Scalars .. - LOGICAL FIRST, LIEEE1, LRND - INTEGER LBETA, LT - DOUBLE PRECISION A, B, C, F, ONE, QTR, SAVEC, T1, T2 -* .. -* .. External Functions .. - DOUBLE PRECISION DLAMC3 - EXTERNAL DLAMC3 -* .. -* .. Save statement .. - SAVE FIRST, LIEEE1, LBETA, LRND, LT -* .. -* .. Data statements .. - DATA FIRST / .TRUE. / -* .. -* .. Executable Statements .. -* - IF( FIRST ) THEN - FIRST = .FALSE. - ONE = 1 -* -* LBETA, LIEEE1, LT and LRND are the local values of BETA, -* IEEE1, T and RND. -* -* Throughout this routine we use the function DLAMC3 to ensure -* that relevant values are stored and not held in registers, or -* are not affected by optimizers. -* -* Compute a = 2.0**m with the smallest positive integer m such -* that -* -* fl( a + 1.0 ) = a. -* - A = 1 - C = 1 -* -*+ WHILE( C.EQ.ONE )LOOP - 10 CONTINUE - IF( C.EQ.ONE ) THEN - A = 2*A - C = DLAMC3( A, ONE ) - C = DLAMC3( C, -A ) - GO TO 10 - END IF -*+ END WHILE -* -* Now compute b = 2.0**m with the smallest positive integer m -* such that -* -* fl( a + b ) .gt. a. -* - B = 1 - C = DLAMC3( A, B ) -* -*+ WHILE( C.EQ.A )LOOP - 20 CONTINUE - IF( C.EQ.A ) THEN - B = 2*B - C = DLAMC3( A, B ) - GO TO 20 - END IF -*+ END WHILE -* -* Now compute the base. a and c are neighbouring floating point -* numbers in the interval ( beta**t, beta**( t + 1 ) ) and so -* their difference is beta. Adding 0.25 to c is to ensure that it -* is truncated to beta and not ( beta - 1 ). -* - QTR = ONE / 4 - SAVEC = C - C = DLAMC3( C, -A ) - LBETA = C + QTR -* -* Now determine whether rounding or chopping occurs, by adding a -* bit less than beta/2 and a bit more than beta/2 to a. -* - B = LBETA - F = DLAMC3( B / 2, -B / 100 ) - C = DLAMC3( F, A ) - IF( C.EQ.A ) THEN - LRND = .TRUE. - ELSE - LRND = .FALSE. - END IF - F = DLAMC3( B / 2, B / 100 ) - C = DLAMC3( F, A ) - IF( ( LRND ) .AND. ( C.EQ.A ) ) - $ LRND = .FALSE. -* -* Try and decide whether rounding is done in the IEEE 'round to -* nearest' style. B/2 is half a unit in the last place of the two -* numbers A and SAVEC. Furthermore, A is even, i.e. has last bit -* zero, and SAVEC is odd. Thus adding B/2 to A should not change -* A, but adding B/2 to SAVEC should change SAVEC. -* - T1 = DLAMC3( B / 2, A ) - T2 = DLAMC3( B / 2, SAVEC ) - LIEEE1 = ( T1.EQ.A ) .AND. ( T2.GT.SAVEC ) .AND. LRND -* -* Now find the mantissa, t. It should be the integer part of -* log to the base beta of a, however it is safer to determine t -* by powering. So we find t as the smallest positive integer for -* which -* -* fl( beta**t + 1.0 ) = 1.0. -* - LT = 0 - A = 1 - C = 1 -* -*+ WHILE( C.EQ.ONE )LOOP - 30 CONTINUE - IF( C.EQ.ONE ) THEN - LT = LT + 1 - A = A*LBETA - C = DLAMC3( A, ONE ) - C = DLAMC3( C, -A ) - GO TO 30 - END IF -*+ END WHILE -* - END IF -* - BETA = LBETA - T = LT - RND = LRND - IEEE1 = LIEEE1 - RETURN -* -* End of DLAMC1 -* - END -* -************************************************************************ -* - SUBROUTINE DLAMC2( BETA, T, RND, EPS, EMIN, RMIN, EMAX, RMAX ) -* -* -- LAPACK auxiliary routine (version 3.0) -- -* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., -* Courant Institute, Argonne National Lab, and Rice University -* October 31, 1992 -* -* .. Scalar Arguments .. - LOGICAL RND - INTEGER BETA, EMAX, EMIN, T - DOUBLE PRECISION EPS, RMAX, RMIN -* .. -* -* Purpose -* ======= -* -* DLAMC2 determines the machine parameters specified in its argument -* list. -* -* Arguments -* ========= -* -* BETA (output) INTEGER -* The base of the machine. -* -* T (output) INTEGER -* The number of ( BETA ) digits in the mantissa. -* -* RND (output) LOGICAL -* Specifies whether proper rounding ( RND = .TRUE. ) or -* chopping ( RND = .FALSE. ) occurs in addition. This may not -* be a reliable guide to the way in which the machine performs -* its arithmetic. -* -* EPS (output) DOUBLE PRECISION -* The smallest positive number such that -* -* fl( 1.0 - EPS ) .LT. 1.0, -* -* where fl denotes the computed value. -* -* EMIN (output) INTEGER -* The minimum exponent before (gradual) underflow occurs. -* -* RMIN (output) DOUBLE PRECISION -* The smallest normalized number for the machine, given by -* BASE**( EMIN - 1 ), where BASE is the floating point value -* of BETA. -* -* EMAX (output) INTEGER -* The maximum exponent before overflow occurs. -* -* RMAX (output) DOUBLE PRECISION -* The largest positive number for the machine, given by -* BASE**EMAX * ( 1 - EPS ), where BASE is the floating point -* value of BETA. -* -* Further Details -* =============== -* -* The computation of EPS is based on a routine PARANOIA by -* W. Kahan of the University of California at Berkeley. -* -* ===================================================================== -* -* .. Local Scalars .. - LOGICAL FIRST, IEEE, IWARN, LIEEE1, LRND - INTEGER GNMIN, GPMIN, I, LBETA, LEMAX, LEMIN, LT, - $ NGNMIN, NGPMIN - DOUBLE PRECISION A, B, C, HALF, LEPS, LRMAX, LRMIN, ONE, RBASE, - $ SIXTH, SMALL, THIRD, TWO, ZERO -* .. -* .. External Functions .. - DOUBLE PRECISION DLAMC3 - EXTERNAL DLAMC3 -* .. -* .. External Subroutines .. - EXTERNAL DLAMC1, DLAMC4, DLAMC5 -* .. -* .. Intrinsic Functions .. - INTRINSIC ABS, MAX, MIN -* .. -* .. Save statement .. - SAVE FIRST, IWARN, LBETA, LEMAX, LEMIN, LEPS, LRMAX, - $ LRMIN, LT -* .. -* .. Data statements .. - DATA FIRST / .TRUE. / , IWARN / .FALSE. / -* .. -* .. Executable Statements .. -* - IF( FIRST ) THEN - FIRST = .FALSE. - ZERO = 0 - ONE = 1 - TWO = 2 -* -* LBETA, LT, LRND, LEPS, LEMIN and LRMIN are the local values of -* BETA, T, RND, EPS, EMIN and RMIN. -* -* Throughout this routine we use the function DLAMC3 to ensure -* that relevant values are stored and not held in registers, or -* are not affected by optimizers. -* -* DLAMC1 returns the parameters LBETA, LT, LRND and LIEEE1. -* - CALL DLAMC1( LBETA, LT, LRND, LIEEE1 ) -* -* Start to find EPS. -* - B = LBETA - A = B**( -LT ) - LEPS = A -* -* Try some tricks to see whether or not this is the correct EPS. -* - B = TWO / 3 - HALF = ONE / 2 - SIXTH = DLAMC3( B, -HALF ) - THIRD = DLAMC3( SIXTH, SIXTH ) - B = DLAMC3( THIRD, -HALF ) - B = DLAMC3( B, SIXTH ) - B = ABS( B ) - IF( B.LT.LEPS ) - $ B = LEPS -* - LEPS = 1 -* -*+ WHILE( ( LEPS.GT.B ).AND.( B.GT.ZERO ) )LOOP - 10 CONTINUE - IF( ( LEPS.GT.B ) .AND. ( B.GT.ZERO ) ) THEN - LEPS = B - C = DLAMC3( HALF*LEPS, ( TWO**5 )*( LEPS**2 ) ) - C = DLAMC3( HALF, -C ) - B = DLAMC3( HALF, C ) - C = DLAMC3( HALF, -B ) - B = DLAMC3( HALF, C ) - GO TO 10 - END IF -*+ END WHILE -* - IF( A.LT.LEPS ) - $ LEPS = A -* -* Computation of EPS complete. -* -* Now find EMIN. Let A = + or - 1, and + or - (1 + BASE**(-3)). -* Keep dividing A by BETA until (gradual) underflow occurs. This -* is detected when we cannot recover the previous A. -* - RBASE = ONE / LBETA - SMALL = ONE - DO 20 I = 1, 3 - SMALL = DLAMC3( SMALL*RBASE, ZERO ) - 20 CONTINUE - A = DLAMC3( ONE, SMALL ) - CALL DLAMC4( NGPMIN, ONE, LBETA ) - CALL DLAMC4( NGNMIN, -ONE, LBETA ) - CALL DLAMC4( GPMIN, A, LBETA ) - CALL DLAMC4( GNMIN, -A, LBETA ) - IEEE = .FALSE. -* - IF( ( NGPMIN.EQ.NGNMIN ) .AND. ( GPMIN.EQ.GNMIN ) ) THEN - IF( NGPMIN.EQ.GPMIN ) THEN - LEMIN = NGPMIN -* ( Non twos-complement machines, no gradual underflow; -* e.g., VAX ) - ELSE IF( ( GPMIN-NGPMIN ).EQ.3 ) THEN - LEMIN = NGPMIN - 1 + LT - IEEE = .TRUE. -* ( Non twos-complement machines, with gradual underflow; -* e.g., IEEE standard followers ) - ELSE - LEMIN = MIN( NGPMIN, GPMIN ) -* ( A guess; no known machine ) - IWARN = .TRUE. - END IF -* - ELSE IF( ( NGPMIN.EQ.GPMIN ) .AND. ( NGNMIN.EQ.GNMIN ) ) THEN - IF( ABS( NGPMIN-NGNMIN ).EQ.1 ) THEN - LEMIN = MAX( NGPMIN, NGNMIN ) -* ( Twos-complement machines, no gradual underflow; -* e.g., CYBER 205 ) - ELSE - LEMIN = MIN( NGPMIN, NGNMIN ) -* ( A guess; no known machine ) - IWARN = .TRUE. - END IF -* - ELSE IF( ( ABS( NGPMIN-NGNMIN ).EQ.1 ) .AND. - $ ( GPMIN.EQ.GNMIN ) ) THEN - IF( ( GPMIN-MIN( NGPMIN, NGNMIN ) ).EQ.3 ) THEN - LEMIN = MAX( NGPMIN, NGNMIN ) - 1 + LT -* ( Twos-complement machines with gradual underflow; -* no known machine ) - ELSE - LEMIN = MIN( NGPMIN, NGNMIN ) -* ( A guess; no known machine ) - IWARN = .TRUE. - END IF -* - ELSE - LEMIN = MIN( NGPMIN, NGNMIN, GPMIN, GNMIN ) -* ( A guess; no known machine ) - IWARN = .TRUE. - END IF -*** -* Comment out this if block if EMIN is ok - IF( IWARN ) THEN - FIRST = .TRUE. - WRITE( 6, FMT = 9999 )LEMIN - END IF -*** -* -* Assume IEEE arithmetic if we found denormalised numbers above, -* or if arithmetic seems to round in the IEEE style, determined -* in routine DLAMC1. A true IEEE machine should have both things -* true; however, faulty machines may have one or the other. -* - IEEE = IEEE .OR. LIEEE1 -* -* Compute RMIN by successive division by BETA. We could compute -* RMIN as BASE**( EMIN - 1 ), but some machines underflow during -* this computation. -* - LRMIN = 1 - DO 30 I = 1, 1 - LEMIN - LRMIN = DLAMC3( LRMIN*RBASE, ZERO ) - 30 CONTINUE -* -* Finally, call DLAMC5 to compute EMAX and RMAX. -* - CALL DLAMC5( LBETA, LT, LEMIN, IEEE, LEMAX, LRMAX ) - END IF -* - BETA = LBETA - T = LT - RND = LRND - EPS = LEPS - EMIN = LEMIN - RMIN = LRMIN - EMAX = LEMAX - RMAX = LRMAX -* - RETURN -* - 9999 FORMAT( / / ' WARNING. The value EMIN may be incorrect:-', - $ ' EMIN = ', I8, / - $ ' If, after inspection, the value EMIN looks', - $ ' acceptable please comment out ', - $ / ' the IF block as marked within the code of routine', - $ ' DLAMC2,', / ' otherwise supply EMIN explicitly.', / ) -* -* End of DLAMC2 -* - END -* -************************************************************************ -* - DOUBLE PRECISION FUNCTION DLAMC3( A, B ) -* -* -- LAPACK auxiliary routine (version 3.0) -- -* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., -* Courant Institute, Argonne National Lab, and Rice University -* October 31, 1992 -* -* .. Scalar Arguments .. - DOUBLE PRECISION A, B -* .. -* -* Purpose -* ======= -* -* DLAMC3 is intended to force A and B to be stored prior to doing -* the addition of A and B , for use in situations where optimizers -* might hold one of these in a register. -* -* Arguments -* ========= -* -* A, B (input) DOUBLE PRECISION -* The values A and B. -* -* ===================================================================== -* -* .. Executable Statements .. -* - DLAMC3 = A + B -* - RETURN -* -* End of DLAMC3 -* - END -* -************************************************************************ -* - SUBROUTINE DLAMC4( EMIN, START, BASE ) -* -* -- LAPACK auxiliary routine (version 3.0) -- -* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., -* Courant Institute, Argonne National Lab, and Rice University -* October 31, 1992 -* -* .. Scalar Arguments .. - INTEGER BASE, EMIN - DOUBLE PRECISION START -* .. -* -* Purpose -* ======= -* -* DLAMC4 is a service routine for DLAMC2. -* -* Arguments -* ========= -* -* EMIN (output) EMIN -* The minimum exponent before (gradual) underflow, computed by -* setting A = START and dividing by BASE until the previous A -* can not be recovered. -* -* START (input) DOUBLE PRECISION -* The starting point for determining EMIN. -* -* BASE (input) INTEGER -* The base of the machine. -* -* ===================================================================== -* -* .. Local Scalars .. - INTEGER I - DOUBLE PRECISION A, B1, B2, C1, C2, D1, D2, ONE, RBASE, ZERO -* .. -* .. External Functions .. - DOUBLE PRECISION DLAMC3 - EXTERNAL DLAMC3 -* .. -* .. Executable Statements .. -* - A = START - ONE = 1 - RBASE = ONE / BASE - ZERO = 0 - EMIN = 1 - B1 = DLAMC3( A*RBASE, ZERO ) - C1 = A - C2 = A - D1 = A - D2 = A -*+ WHILE( ( C1.EQ.A ).AND.( C2.EQ.A ).AND. -* $ ( D1.EQ.A ).AND.( D2.EQ.A ) )LOOP - 10 CONTINUE - IF( ( C1.EQ.A ) .AND. ( C2.EQ.A ) .AND. ( D1.EQ.A ) .AND. - $ ( D2.EQ.A ) ) THEN - EMIN = EMIN - 1 - A = B1 - B1 = DLAMC3( A / BASE, ZERO ) - C1 = DLAMC3( B1*BASE, ZERO ) - D1 = ZERO - DO 20 I = 1, BASE - D1 = D1 + B1 - 20 CONTINUE - B2 = DLAMC3( A*RBASE, ZERO ) - C2 = DLAMC3( B2 / RBASE, ZERO ) - D2 = ZERO - DO 30 I = 1, BASE - D2 = D2 + B2 - 30 CONTINUE - GO TO 10 - END IF -*+ END WHILE -* - RETURN -* -* End of DLAMC4 -* - END -* -************************************************************************ -* - SUBROUTINE DLAMC5( BETA, P, EMIN, IEEE, EMAX, RMAX ) -* -* -- LAPACK auxiliary routine (version 3.0) -- -* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., -* Courant Institute, Argonne National Lab, and Rice University -* October 31, 1992 -* -* .. Scalar Arguments .. - LOGICAL IEEE - INTEGER BETA, EMAX, EMIN, P - DOUBLE PRECISION RMAX -* .. -* -* Purpose -* ======= -* -* DLAMC5 attempts to compute RMAX, the largest machine floating-point -* number, without overflow. It assumes that EMAX + abs(EMIN) sum -* approximately to a power of 2. It will fail on machines where this -* assumption does not hold, for example, the Cyber 205 (EMIN = -28625, -* EMAX = 28718). It will also fail if the value supplied for EMIN is -* too large (i.e. too close to zero), probably with overflow. -* -* Arguments -* ========= -* -* BETA (input) INTEGER -* The base of floating-point arithmetic. -* -* P (input) INTEGER -* The number of base BETA digits in the mantissa of a -* floating-point value. -* -* EMIN (input) INTEGER -* The minimum exponent before (gradual) underflow. -* -* IEEE (input) LOGICAL -* A logical flag specifying whether or not the arithmetic -* system is thought to comply with the IEEE standard. -* -* EMAX (output) INTEGER -* The largest exponent before overflow -* -* RMAX (output) DOUBLE PRECISION -* The largest machine floating-point number. -* -* ===================================================================== -* -* .. Parameters .. - DOUBLE PRECISION ZERO, ONE - PARAMETER ( ZERO = 0.0D0, ONE = 1.0D0 ) -* .. -* .. Local Scalars .. - INTEGER EXBITS, EXPSUM, I, LEXP, NBITS, TRY, UEXP - DOUBLE PRECISION OLDY, RECBAS, Y, Z -* .. -* .. External Functions .. - DOUBLE PRECISION DLAMC3 - EXTERNAL DLAMC3 -* .. -* .. Intrinsic Functions .. - INTRINSIC MOD -* .. -* .. Executable Statements .. -* -* First compute LEXP and UEXP, two powers of 2 that bound -* abs(EMIN). We then assume that EMAX + abs(EMIN) will sum -* approximately to the bound that is closest to abs(EMIN). -* (EMAX is the exponent of the required number RMAX). -* - LEXP = 1 - EXBITS = 1 - 10 CONTINUE - TRY = LEXP*2 - IF( TRY.LE.( -EMIN ) ) THEN - LEXP = TRY - EXBITS = EXBITS + 1 - GO TO 10 - END IF - IF( LEXP.EQ.-EMIN ) THEN - UEXP = LEXP - ELSE - UEXP = TRY - EXBITS = EXBITS + 1 - END IF -* -* Now -LEXP is less than or equal to EMIN, and -UEXP is greater -* than or equal to EMIN. EXBITS is the number of bits needed to -* store the exponent. -* - IF( ( UEXP+EMIN ).GT.( -LEXP-EMIN ) ) THEN - EXPSUM = 2*LEXP - ELSE - EXPSUM = 2*UEXP - END IF -* -* EXPSUM is the exponent range, approximately equal to -* EMAX - EMIN + 1 . -* - EMAX = EXPSUM + EMIN - 1 - NBITS = 1 + EXBITS + P -* -* NBITS is the total number of bits needed to store a -* floating-point number. -* - IF( ( MOD( NBITS, 2 ).EQ.1 ) .AND. ( BETA.EQ.2 ) ) THEN -* -* Either there are an odd number of bits used to store a -* floating-point number, which is unlikely, or some bits are -* not used in the representation of numbers, which is possible, -* (e.g. Cray machines) or the mantissa has an implicit bit, -* (e.g. IEEE machines, Dec Vax machines), which is perhaps the -* most likely. We have to assume the last alternative. -* If this is true, then we need to reduce EMAX by one because -* there must be some way of representing zero in an implicit-bit -* system. On machines like Cray, we are reducing EMAX by one -* unnecessarily. -* - EMAX = EMAX - 1 - END IF -* - IF( IEEE ) THEN -* -* Assume we are on an IEEE machine which reserves one exponent -* for infinity and NaN. -* - EMAX = EMAX - 1 - END IF -* -* Now create RMAX, the largest machine number, which should -* be equal to (1.0 - BETA**(-P)) * BETA**EMAX . -* -* First compute 1.0 - BETA**(-P), being careful that the -* result is less than 1.0 . -* - RECBAS = ONE / BETA - Z = BETA - ONE - Y = ZERO - DO 20 I = 1, P - Z = Z*RECBAS - IF( Y.LT.ONE ) - $ OLDY = Y - Y = DLAMC3( Y, Z ) - 20 CONTINUE - IF( Y.GE.ONE ) - $ Y = OLDY -* -* Now multiply by BETA**EMAX to get RMAX. -* - DO 30 I = 1, EMAX - Y = DLAMC3( Y*BETA, ZERO ) - 30 CONTINUE -* - RMAX = Y - RETURN -* -* End of DLAMC5 -* - END