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author | julie <julielangou@users.noreply.github.com> | 2010-07-02 23:39:07 +0000 |
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committer | julie <julielangou@users.noreply.github.com> | 2010-07-02 23:39:07 +0000 |
commit | 075253023292256e67adc407ddafcc9e75ef4222 (patch) | |
tree | 0b6b7bd0b0d5d0e20afbc6afd2d05fdb45842d3d /INSTALL | |
parent | 393209c09fac29367b9ee330005be09caca74d83 (diff) | |
download | lapack-075253023292256e67adc407ddafcc9e75ef4222.tar.gz lapack-075253023292256e67adc407ddafcc9e75ef4222.tar.bz2 lapack-075253023292256e67adc407ddafcc9e75ef4222.zip |
Time has come to have the fortran90 slamch and dlamch in the lapack package.
Jason (Riedy) wrote our ( ... his? :) ) ideas about it three years ago:
http://www.netlib.org/lapack-dev/lapack-coding/program-style.html#id2537289
Piotr (Luszczek) has written two subroutines, tested them on few platforms, collected the result on his webpage, and sent emails to the lapackers a few times. See:
http://www.cs.utk.edu/~luszczek/lapack/lamch.html
Theses slamch.f and dlamch.f subroutines were taken from PLASMA-2.1.0.
Change to the LAPACK library:
* move the current LAPACK subroutine slamch.f (resp dlamch.f) as
slamchf77.f (resp. dlamchf77.f),
* take the new slamch.f subroutines (resp. dlamch.f), remove the PLASMA
header, have a LAPACK header, and insert the new routines in the
library.
Minor:
* I would leave these routines compiled with the NOOPT flag.
Problem:
* CLAPACK: no idea how CLAPACK's going to handle this. CLAPACK can rely on
IEEE arithmetic, can relay on float.h, or can rely on the previous
xlamch.f
Diffstat (limited to 'INSTALL')
-rw-r--r-- | INSTALL/dlamch.f | 768 | ||||
-rw-r--r-- | INSTALL/dlamchf77.f | 852 | ||||
-rw-r--r-- | INSTALL/slamch.f | 769 | ||||
-rw-r--r-- | INSTALL/slamchf77.f | 853 |
4 files changed, 1777 insertions, 1465 deletions
diff --git a/INSTALL/dlamch.f b/INSTALL/dlamch.f index 8f830e87..aa90112b 100644 --- a/INSTALL/dlamch.f +++ b/INSTALL/dlamch.f @@ -1,8 +1,12 @@ DOUBLE PRECISION FUNCTION DLAMCH( CMACH ) * -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 +* -- LAPACK auxiliary routine (version 3.2.2) -- +* -- LAPACK is a software package provided by Univ. of Tennessee, -- +* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- +* Based on LAPACK DLAMCH but with Fortran 95 query functions +* See: http://www.cs.utk.edu/~luszczek/lapack/lamch.html +* and http://www.netlib.org/lapack-dev/lapack-coding/program-style.html#id2537289 +* July 2010 * * .. Scalar Arguments .. CHARACTER CMACH @@ -49,526 +53,68 @@ PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) * .. * .. Local Scalars .. - LOGICAL FIRST, LRND - INTEGER BETA, IMAX, IMIN, IT - DOUBLE PRECISION BASE, EMAX, EMIN, EPS, PREC, RMACH, RMAX, RMIN, - $ RND, SFMIN, SMALL, T + DOUBLE PRECISION RND, EPS, SFMIN, SMALL, RMACH * .. * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. -* .. External Subroutines .. - EXTERNAL DLAMC2 -* .. -* .. Save statement .. - SAVE FIRST, EPS, SFMIN, BASE, T, RND, EMIN, RMIN, - $ EMAX, RMAX, PREC -* .. -* .. Data statements .. - DATA FIRST / .TRUE. / +* .. Intrinsic Functions .. + INTRINSIC DIGITS, EPSILON, HUGE, MAXEXPONENT, + $ MINEXPONENT, RADIX, TINY * .. * .. Executable Statements .. * - IF( FIRST ) THEN - CALL DLAMC2( BETA, IT, LRND, EPS, IMIN, RMIN, IMAX, RMAX ) - BASE = BETA - T = IT - IF( LRND ) THEN - RND = ONE - EPS = ( BASE**( 1-IT ) ) / 2 - ELSE - RND = ZERO - EPS = BASE**( 1-IT ) - END IF - PREC = EPS*BASE - EMIN = IMIN - EMAX = IMAX - SFMIN = RMIN - SMALL = ONE / RMAX - IF( SMALL.GE.SFMIN ) THEN * -* Use SMALL plus a bit, to avoid the possibility of rounding -* causing overflow when computing 1/sfmin. +* Assume rounding, not chopping. Always. * - SFMIN = SMALL*( ONE+EPS ) - END IF + RND = ONE +* + IF( ONE.EQ.RND ) THEN + EPS = EPSILON(ZERO) * 0.5 + ELSE + EPS = EPSILON(ZERO) END IF * IF( LSAME( CMACH, 'E' ) ) THEN RMACH = EPS ELSE IF( LSAME( CMACH, 'S' ) ) THEN + SFMIN = TINY(ZERO) + SMALL = ONE / HUGE(ZERO) + IF( SMALL.GE.SFMIN ) THEN +* +* Use SMALL plus a bit, to avoid the possibility of rounding +* causing overflow when computing 1/sfmin. +* + SFMIN = SMALL*( ONE+EPS ) + END IF RMACH = SFMIN ELSE IF( LSAME( CMACH, 'B' ) ) THEN - RMACH = BASE + RMACH = RADIX(ZERO) ELSE IF( LSAME( CMACH, 'P' ) ) THEN - RMACH = PREC + RMACH = EPS * RADIX(ZERO) ELSE IF( LSAME( CMACH, 'N' ) ) THEN - RMACH = T + RMACH = DIGITS(ZERO) ELSE IF( LSAME( CMACH, 'R' ) ) THEN RMACH = RND ELSE IF( LSAME( CMACH, 'M' ) ) THEN - RMACH = EMIN + RMACH = MINEXPONENT(ZERO) ELSE IF( LSAME( CMACH, 'U' ) ) THEN - RMACH = RMIN + RMACH = tiny(zero) ELSE IF( LSAME( CMACH, 'L' ) ) THEN - RMACH = EMAX + RMACH = MAXEXPONENT(ZERO) ELSE IF( LSAME( CMACH, 'O' ) ) THEN - RMACH = RMAX + RMACH = HUGE(ZERO) + ELSE + RMACH = ZERO END IF * DLAMCH = RMACH - FIRST = .FALSE. RETURN * * End of DLAMCH * END -* -************************************************************************ -* - SUBROUTINE DLAMC1( BETA, T, RND, IEEE1 ) -* -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 -* -* .. 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 - 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 - FIRST = .FALSE. - RETURN -* -* End of DLAMC1 -* - END -* -************************************************************************ -* - SUBROUTINE DLAMC2( BETA, T, RND, EPS, EMIN, RMIN, EMAX, RMAX ) -* -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 -* -* .. 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 - 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 - FIRST = .FALSE. -*** -* 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 ) @@ -608,245 +154,3 @@ END * ************************************************************************ -* - SUBROUTINE DLAMC4( EMIN, START, BASE ) -* -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 -* -* .. Scalar Arguments .. - INTEGER BASE, EMIN - DOUBLE PRECISION START -* .. -* -* Purpose -* ======= -* -* DLAMC4 is a service routine for DLAMC2. -* -* Arguments -* ========= -* -* EMIN (output) INTEGER -* 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 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 -* -* .. 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 diff --git a/INSTALL/dlamchf77.f b/INSTALL/dlamchf77.f new file mode 100644 index 00000000..8f830e87 --- /dev/null +++ b/INSTALL/dlamchf77.f @@ -0,0 +1,852 @@ + DOUBLE PRECISION FUNCTION DLAMCH( CMACH ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER CMACH +* .. +* +* Purpose +* ======= +* +* DLAMCH determines double precision machine parameters. +* +* Arguments +* ========= +* +* CMACH (input) CHARACTER*1 +* Specifies the value to be returned by DLAMCH: +* = 'E' or 'e', DLAMCH := eps +* = 'S' or 's , DLAMCH := sfmin +* = 'B' or 'b', DLAMCH := base +* = 'P' or 'p', DLAMCH := eps*base +* = 'N' or 'n', DLAMCH := t +* = 'R' or 'r', DLAMCH := rnd +* = 'M' or 'm', DLAMCH := emin +* = 'U' or 'u', DLAMCH := rmin +* = 'L' or 'l', DLAMCH := emax +* = 'O' or 'o', DLAMCH := rmax +* +* where +* +* eps = relative machine precision +* sfmin = safe minimum, such that 1/sfmin does not overflow +* base = base of the machine +* prec = eps*base +* t = number of (base) digits in the mantissa +* rnd = 1.0 when rounding occurs in addition, 0.0 otherwise +* emin = minimum exponent before (gradual) underflow +* rmin = underflow threshold - base**(emin-1) +* emax = largest exponent before overflow +* rmax = overflow threshold - (base**emax)*(1-eps) +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ONE, ZERO + PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) +* .. +* .. Local Scalars .. + LOGICAL FIRST, LRND + INTEGER BETA, IMAX, IMIN, IT + DOUBLE PRECISION BASE, EMAX, EMIN, EPS, PREC, RMACH, RMAX, RMIN, + $ RND, SFMIN, SMALL, T +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL DLAMC2 +* .. +* .. Save statement .. + SAVE FIRST, EPS, SFMIN, BASE, T, RND, EMIN, RMIN, + $ EMAX, RMAX, PREC +* .. +* .. Data statements .. + DATA FIRST / .TRUE. / +* .. +* .. Executable Statements .. +* + IF( FIRST ) THEN + CALL DLAMC2( BETA, IT, LRND, EPS, IMIN, RMIN, IMAX, RMAX ) + BASE = BETA + T = IT + IF( LRND ) THEN + RND = ONE + EPS = ( BASE**( 1-IT ) ) / 2 + ELSE + RND = ZERO + EPS = BASE**( 1-IT ) + END IF + PREC = EPS*BASE + EMIN = IMIN + EMAX = IMAX + SFMIN = RMIN + SMALL = ONE / RMAX + IF( SMALL.GE.SFMIN ) THEN +* +* Use SMALL plus a bit, to avoid the possibility of rounding +* causing overflow when computing 1/sfmin. +* + SFMIN = SMALL*( ONE+EPS ) + END IF + END IF +* + IF( LSAME( CMACH, 'E' ) ) THEN + RMACH = EPS + ELSE IF( LSAME( CMACH, 'S' ) ) THEN + RMACH = SFMIN + ELSE IF( LSAME( CMACH, 'B' ) ) THEN + RMACH = BASE + ELSE IF( LSAME( CMACH, 'P' ) ) THEN + RMACH = PREC + ELSE IF( LSAME( CMACH, 'N' ) ) THEN + RMACH = T + ELSE IF( LSAME( CMACH, 'R' ) ) THEN + RMACH = RND + ELSE IF( LSAME( CMACH, 'M' ) ) THEN + RMACH = EMIN + ELSE IF( LSAME( CMACH, 'U' ) ) THEN + RMACH = RMIN + ELSE IF( LSAME( CMACH, 'L' ) ) THEN + RMACH = EMAX + ELSE IF( LSAME( CMACH, 'O' ) ) THEN + RMACH = RMAX + END IF +* + DLAMCH = RMACH + FIRST = .FALSE. + RETURN +* +* End of DLAMCH +* + END +* +************************************************************************ +* + SUBROUTINE DLAMC1( BETA, T, RND, IEEE1 ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. 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 + 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 + FIRST = .FALSE. + RETURN +* +* End of DLAMC1 +* + END +* +************************************************************************ +* + SUBROUTINE DLAMC2( BETA, T, RND, EPS, EMIN, RMIN, EMAX, RMAX ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. 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 + 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 + FIRST = .FALSE. +*** +* 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 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. 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 (input) DOUBLE PRECISION +* 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 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + INTEGER BASE, EMIN + DOUBLE PRECISION START +* .. +* +* Purpose +* ======= +* +* DLAMC4 is a service routine for DLAMC2. +* +* Arguments +* ========= +* +* EMIN (output) INTEGER +* 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 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. 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 diff --git a/INSTALL/slamch.f b/INSTALL/slamch.f index 5bb2c7be..902f3220 100644 --- a/INSTALL/slamch.f +++ b/INSTALL/slamch.f @@ -1,8 +1,12 @@ REAL FUNCTION SLAMCH( CMACH ) * -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 +* -- LAPACK auxiliary routine (version 3.2.2) -- +* -- LAPACK is a software package provided by Univ. of Tennessee, -- +* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- +* Based on LAPACK DLAMCH but with Fortran 95 query functions +* See: http://www.cs.utk.edu/~luszczek/lapack/lamch.html +* and http://www.netlib.org/lapack-dev/lapack-coding/program-style.html#id2537289 +* July 2010 * * .. Scalar Arguments .. CHARACTER CMACH @@ -49,526 +53,68 @@ PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 ) * .. * .. Local Scalars .. - LOGICAL FIRST, LRND - INTEGER BETA, IMAX, IMIN, IT - REAL BASE, EMAX, EMIN, EPS, PREC, RMACH, RMAX, RMIN, - $ RND, SFMIN, SMALL, T + REAL RND, EPS, SFMIN, SMALL, RMACH * .. * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. -* .. External Subroutines .. - EXTERNAL SLAMC2 -* .. -* .. Save statement .. - SAVE FIRST, EPS, SFMIN, BASE, T, RND, EMIN, RMIN, - $ EMAX, RMAX, PREC -* .. -* .. Data statements .. - DATA FIRST / .TRUE. / +* .. Intrinsic Functions .. + INTRINSIC DIGITS, EPSILON, HUGE, MAXEXPONENT, + $ MINEXPONENT, RADIX, TINY * .. * .. Executable Statements .. * - IF( FIRST ) THEN - CALL SLAMC2( BETA, IT, LRND, EPS, IMIN, RMIN, IMAX, RMAX ) - BASE = BETA - T = IT - IF( LRND ) THEN - RND = ONE - EPS = ( BASE**( 1-IT ) ) / 2 - ELSE - RND = ZERO - EPS = BASE**( 1-IT ) - END IF - PREC = EPS*BASE - EMIN = IMIN - EMAX = IMAX - SFMIN = RMIN - SMALL = ONE / RMAX - IF( SMALL.GE.SFMIN ) THEN * -* Use SMALL plus a bit, to avoid the possibility of rounding -* causing overflow when computing 1/sfmin. +* Assume rounding, not chopping. Always. * - SFMIN = SMALL*( ONE+EPS ) - END IF + RND = ONE +* + IF( ONE.EQ.RND ) THEN + EPS = EPSILON(ZERO) * 0.5 + ELSE + EPS = EPSILON(ZERO) END IF * IF( LSAME( CMACH, 'E' ) ) THEN RMACH = EPS ELSE IF( LSAME( CMACH, 'S' ) ) THEN + SFMIN = TINY(ZERO) + SMALL = ONE / HUGE(ZERO) + IF( SMALL.GE.SFMIN ) THEN +* +* Use SMALL plus a bit, to avoid the possibility of rounding +* causing overflow when computing 1/sfmin. +* + SFMIN = SMALL*( ONE+EPS ) + END IF RMACH = SFMIN ELSE IF( LSAME( CMACH, 'B' ) ) THEN - RMACH = BASE + RMACH = RADIX(ZERO) ELSE IF( LSAME( CMACH, 'P' ) ) THEN - RMACH = PREC + RMACH = EPS * RADIX(ZERO) ELSE IF( LSAME( CMACH, 'N' ) ) THEN - RMACH = T + RMACH = DIGITS(ZERO) ELSE IF( LSAME( CMACH, 'R' ) ) THEN RMACH = RND ELSE IF( LSAME( CMACH, 'M' ) ) THEN - RMACH = EMIN + RMACH = MINEXPONENT(ZERO) ELSE IF( LSAME( CMACH, 'U' ) ) THEN - RMACH = RMIN + RMACH = tiny(zero) ELSE IF( LSAME( CMACH, 'L' ) ) THEN - RMACH = EMAX + RMACH = MAXEXPONENT(ZERO) ELSE IF( LSAME( CMACH, 'O' ) ) THEN - RMACH = RMAX + RMACH = HUGE(ZERO) + ELSE + RMACH = ZERO END IF * SLAMCH = RMACH - FIRST = .FALSE. RETURN * * End of SLAMCH * END -* -************************************************************************ -* - SUBROUTINE SLAMC1( BETA, T, RND, IEEE1 ) -* -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 -* -* .. Scalar Arguments .. - LOGICAL IEEE1, RND - INTEGER BETA, T -* .. -* -* Purpose -* ======= -* -* SLAMC1 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 - REAL A, B, C, F, ONE, QTR, SAVEC, T1, T2 -* .. -* .. External Functions .. - REAL SLAMC3 - EXTERNAL SLAMC3 -* .. -* .. Save statement .. - SAVE FIRST, LIEEE1, LBETA, LRND, LT -* .. -* .. Data statements .. - DATA FIRST / .TRUE. / -* .. -* .. Executable Statements .. -* - IF( FIRST ) THEN - ONE = 1 -* -* LBETA, LIEEE1, LT and LRND are the local values of BETA, -* IEEE1, T and RND. -* -* Throughout this routine we use the function SLAMC3 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 = SLAMC3( A, ONE ) - C = SLAMC3( 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 = SLAMC3( A, B ) -* -*+ WHILE( C.EQ.A )LOOP - 20 CONTINUE - IF( C.EQ.A ) THEN - B = 2*B - C = SLAMC3( 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 = SLAMC3( 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 = SLAMC3( B / 2, -B / 100 ) - C = SLAMC3( F, A ) - IF( C.EQ.A ) THEN - LRND = .TRUE. - ELSE - LRND = .FALSE. - END IF - F = SLAMC3( B / 2, B / 100 ) - C = SLAMC3( 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 = SLAMC3( B / 2, A ) - T2 = SLAMC3( 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 = SLAMC3( A, ONE ) - C = SLAMC3( C, -A ) - GO TO 30 - END IF -*+ END WHILE -* - END IF -* - BETA = LBETA - T = LT - RND = LRND - IEEE1 = LIEEE1 - FIRST = .FALSE. - RETURN -* -* End of SLAMC1 -* - END -* -************************************************************************ -* - SUBROUTINE SLAMC2( BETA, T, RND, EPS, EMIN, RMIN, EMAX, RMAX ) -* -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 -* -* .. Scalar Arguments .. - LOGICAL RND - INTEGER BETA, EMAX, EMIN, T - REAL EPS, RMAX, RMIN -* .. -* -* Purpose -* ======= -* -* SLAMC2 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) REAL -* 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) REAL -* 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) REAL -* 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 - REAL A, B, C, HALF, LEPS, LRMAX, LRMIN, ONE, RBASE, - $ SIXTH, SMALL, THIRD, TWO, ZERO -* .. -* .. External Functions .. - REAL SLAMC3 - EXTERNAL SLAMC3 -* .. -* .. External Subroutines .. - EXTERNAL SLAMC1, SLAMC4, SLAMC5 -* .. -* .. 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 - 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 SLAMC3 to ensure -* that relevant values are stored and not held in registers, or -* are not affected by optimizers. -* -* SLAMC1 returns the parameters LBETA, LT, LRND and LIEEE1. -* - CALL SLAMC1( 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 = SLAMC3( B, -HALF ) - THIRD = SLAMC3( SIXTH, SIXTH ) - B = SLAMC3( THIRD, -HALF ) - B = SLAMC3( 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 = SLAMC3( HALF*LEPS, ( TWO**5 )*( LEPS**2 ) ) - C = SLAMC3( HALF, -C ) - B = SLAMC3( HALF, C ) - C = SLAMC3( HALF, -B ) - B = SLAMC3( 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 = SLAMC3( SMALL*RBASE, ZERO ) - 20 CONTINUE - A = SLAMC3( ONE, SMALL ) - CALL SLAMC4( NGPMIN, ONE, LBETA ) - CALL SLAMC4( NGNMIN, -ONE, LBETA ) - CALL SLAMC4( GPMIN, A, LBETA ) - CALL SLAMC4( 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 - FIRST = .FALSE. -*** -* 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 SLAMC1. 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 = SLAMC3( LRMIN*RBASE, ZERO ) - 30 CONTINUE -* -* Finally, call SLAMC5 to compute EMAX and RMAX. -* - CALL SLAMC5( 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', - $ ' SLAMC2,', / ' otherwise supply EMIN explicitly.', / ) -* -* End of SLAMC2 -* - END -* ************************************************************************ * REAL FUNCTION SLAMC3( A, B ) @@ -608,246 +154,3 @@ END * ************************************************************************ -* - SUBROUTINE SLAMC4( EMIN, START, BASE ) -* -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 -* -* .. Scalar Arguments .. - INTEGER BASE - INTEGER EMIN - REAL START -* .. -* -* Purpose -* ======= -* -* SLAMC4 is a service routine for SLAMC2. -* -* Arguments -* ========= -* -* EMIN (output) INTEGER -* 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) REAL -* The starting point for determining EMIN. -* -* BASE (input) INTEGER -* The base of the machine. -* -* ===================================================================== -* -* .. Local Scalars .. - INTEGER I - REAL A, B1, B2, C1, C2, D1, D2, ONE, RBASE, ZERO -* .. -* .. External Functions .. - REAL SLAMC3 - EXTERNAL SLAMC3 -* .. -* .. Executable Statements .. -* - A = START - ONE = 1 - RBASE = ONE / BASE - ZERO = 0 - EMIN = 1 - B1 = SLAMC3( 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 = SLAMC3( A / BASE, ZERO ) - C1 = SLAMC3( B1*BASE, ZERO ) - D1 = ZERO - DO 20 I = 1, BASE - D1 = D1 + B1 - 20 CONTINUE - B2 = SLAMC3( A*RBASE, ZERO ) - C2 = SLAMC3( 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 SLAMC4 -* - END -* -************************************************************************ -* - SUBROUTINE SLAMC5( BETA, P, EMIN, IEEE, EMAX, RMAX ) -* -* -- LAPACK auxiliary routine (version 3.2) -- -* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. -* November 2006 -* -* .. Scalar Arguments .. - LOGICAL IEEE - INTEGER BETA, EMAX, EMIN, P - REAL RMAX -* .. -* -* Purpose -* ======= -* -* SLAMC5 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) REAL -* The largest machine floating-point number. -* -* ===================================================================== -* -* .. Parameters .. - REAL ZERO, ONE - PARAMETER ( ZERO = 0.0E0, ONE = 1.0E0 ) -* .. -* .. Local Scalars .. - INTEGER EXBITS, EXPSUM, I, LEXP, NBITS, TRY, UEXP - REAL OLDY, RECBAS, Y, Z -* .. -* .. External Functions .. - REAL SLAMC3 - EXTERNAL SLAMC3 -* .. -* .. 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 = SLAMC3( Y, Z ) - 20 CONTINUE - IF( Y.GE.ONE ) - $ Y = OLDY -* -* Now multiply by BETA**EMAX to get RMAX. -* - DO 30 I = 1, EMAX - Y = SLAMC3( Y*BETA, ZERO ) - 30 CONTINUE -* - RMAX = Y - RETURN -* -* End of SLAMC5 -* - END diff --git a/INSTALL/slamchf77.f b/INSTALL/slamchf77.f new file mode 100644 index 00000000..5bb2c7be --- /dev/null +++ b/INSTALL/slamchf77.f @@ -0,0 +1,853 @@ + REAL FUNCTION SLAMCH( CMACH ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER CMACH +* .. +* +* Purpose +* ======= +* +* SLAMCH determines single precision machine parameters. +* +* Arguments +* ========= +* +* CMACH (input) CHARACTER*1 +* Specifies the value to be returned by SLAMCH: +* = 'E' or 'e', SLAMCH := eps +* = 'S' or 's , SLAMCH := sfmin +* = 'B' or 'b', SLAMCH := base +* = 'P' or 'p', SLAMCH := eps*base +* = 'N' or 'n', SLAMCH := t +* = 'R' or 'r', SLAMCH := rnd +* = 'M' or 'm', SLAMCH := emin +* = 'U' or 'u', SLAMCH := rmin +* = 'L' or 'l', SLAMCH := emax +* = 'O' or 'o', SLAMCH := rmax +* +* where +* +* eps = relative machine precision +* sfmin = safe minimum, such that 1/sfmin does not overflow +* base = base of the machine +* prec = eps*base +* t = number of (base) digits in the mantissa +* rnd = 1.0 when rounding occurs in addition, 0.0 otherwise +* emin = minimum exponent before (gradual) underflow +* rmin = underflow threshold - base**(emin-1) +* emax = largest exponent before overflow +* rmax = overflow threshold - (base**emax)*(1-eps) +* +* ===================================================================== +* +* .. Parameters .. + REAL ONE, ZERO + PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 ) +* .. +* .. Local Scalars .. + LOGICAL FIRST, LRND + INTEGER BETA, IMAX, IMIN, IT + REAL BASE, EMAX, EMIN, EPS, PREC, RMACH, RMAX, RMIN, + $ RND, SFMIN, SMALL, T +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL SLAMC2 +* .. +* .. Save statement .. + SAVE FIRST, EPS, SFMIN, BASE, T, RND, EMIN, RMIN, + $ EMAX, RMAX, PREC +* .. +* .. Data statements .. + DATA FIRST / .TRUE. / +* .. +* .. Executable Statements .. +* + IF( FIRST ) THEN + CALL SLAMC2( BETA, IT, LRND, EPS, IMIN, RMIN, IMAX, RMAX ) + BASE = BETA + T = IT + IF( LRND ) THEN + RND = ONE + EPS = ( BASE**( 1-IT ) ) / 2 + ELSE + RND = ZERO + EPS = BASE**( 1-IT ) + END IF + PREC = EPS*BASE + EMIN = IMIN + EMAX = IMAX + SFMIN = RMIN + SMALL = ONE / RMAX + IF( SMALL.GE.SFMIN ) THEN +* +* Use SMALL plus a bit, to avoid the possibility of rounding +* causing overflow when computing 1/sfmin. +* + SFMIN = SMALL*( ONE+EPS ) + END IF + END IF +* + IF( LSAME( CMACH, 'E' ) ) THEN + RMACH = EPS + ELSE IF( LSAME( CMACH, 'S' ) ) THEN + RMACH = SFMIN + ELSE IF( LSAME( CMACH, 'B' ) ) THEN + RMACH = BASE + ELSE IF( LSAME( CMACH, 'P' ) ) THEN + RMACH = PREC + ELSE IF( LSAME( CMACH, 'N' ) ) THEN + RMACH = T + ELSE IF( LSAME( CMACH, 'R' ) ) THEN + RMACH = RND + ELSE IF( LSAME( CMACH, 'M' ) ) THEN + RMACH = EMIN + ELSE IF( LSAME( CMACH, 'U' ) ) THEN + RMACH = RMIN + ELSE IF( LSAME( CMACH, 'L' ) ) THEN + RMACH = EMAX + ELSE IF( LSAME( CMACH, 'O' ) ) THEN + RMACH = RMAX + END IF +* + SLAMCH = RMACH + FIRST = .FALSE. + RETURN +* +* End of SLAMCH +* + END +* +************************************************************************ +* + SUBROUTINE SLAMC1( BETA, T, RND, IEEE1 ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + LOGICAL IEEE1, RND + INTEGER BETA, T +* .. +* +* Purpose +* ======= +* +* SLAMC1 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 + REAL A, B, C, F, ONE, QTR, SAVEC, T1, T2 +* .. +* .. External Functions .. + REAL SLAMC3 + EXTERNAL SLAMC3 +* .. +* .. Save statement .. + SAVE FIRST, LIEEE1, LBETA, LRND, LT +* .. +* .. Data statements .. + DATA FIRST / .TRUE. / +* .. +* .. Executable Statements .. +* + IF( FIRST ) THEN + ONE = 1 +* +* LBETA, LIEEE1, LT and LRND are the local values of BETA, +* IEEE1, T and RND. +* +* Throughout this routine we use the function SLAMC3 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 = SLAMC3( A, ONE ) + C = SLAMC3( 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 = SLAMC3( A, B ) +* +*+ WHILE( C.EQ.A )LOOP + 20 CONTINUE + IF( C.EQ.A ) THEN + B = 2*B + C = SLAMC3( 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 = SLAMC3( 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 = SLAMC3( B / 2, -B / 100 ) + C = SLAMC3( F, A ) + IF( C.EQ.A ) THEN + LRND = .TRUE. + ELSE + LRND = .FALSE. + END IF + F = SLAMC3( B / 2, B / 100 ) + C = SLAMC3( 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 = SLAMC3( B / 2, A ) + T2 = SLAMC3( 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 = SLAMC3( A, ONE ) + C = SLAMC3( C, -A ) + GO TO 30 + END IF +*+ END WHILE +* + END IF +* + BETA = LBETA + T = LT + RND = LRND + IEEE1 = LIEEE1 + FIRST = .FALSE. + RETURN +* +* End of SLAMC1 +* + END +* +************************************************************************ +* + SUBROUTINE SLAMC2( BETA, T, RND, EPS, EMIN, RMIN, EMAX, RMAX ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + LOGICAL RND + INTEGER BETA, EMAX, EMIN, T + REAL EPS, RMAX, RMIN +* .. +* +* Purpose +* ======= +* +* SLAMC2 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) REAL +* 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) REAL +* 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) REAL +* 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 + REAL A, B, C, HALF, LEPS, LRMAX, LRMIN, ONE, RBASE, + $ SIXTH, SMALL, THIRD, TWO, ZERO +* .. +* .. External Functions .. + REAL SLAMC3 + EXTERNAL SLAMC3 +* .. +* .. External Subroutines .. + EXTERNAL SLAMC1, SLAMC4, SLAMC5 +* .. +* .. 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 + 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 SLAMC3 to ensure +* that relevant values are stored and not held in registers, or +* are not affected by optimizers. +* +* SLAMC1 returns the parameters LBETA, LT, LRND and LIEEE1. +* + CALL SLAMC1( 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 = SLAMC3( B, -HALF ) + THIRD = SLAMC3( SIXTH, SIXTH ) + B = SLAMC3( THIRD, -HALF ) + B = SLAMC3( 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 = SLAMC3( HALF*LEPS, ( TWO**5 )*( LEPS**2 ) ) + C = SLAMC3( HALF, -C ) + B = SLAMC3( HALF, C ) + C = SLAMC3( HALF, -B ) + B = SLAMC3( 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 = SLAMC3( SMALL*RBASE, ZERO ) + 20 CONTINUE + A = SLAMC3( ONE, SMALL ) + CALL SLAMC4( NGPMIN, ONE, LBETA ) + CALL SLAMC4( NGNMIN, -ONE, LBETA ) + CALL SLAMC4( GPMIN, A, LBETA ) + CALL SLAMC4( 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 + FIRST = .FALSE. +*** +* 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 SLAMC1. 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 = SLAMC3( LRMIN*RBASE, ZERO ) + 30 CONTINUE +* +* Finally, call SLAMC5 to compute EMAX and RMAX. +* + CALL SLAMC5( 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', + $ ' SLAMC2,', / ' otherwise supply EMIN explicitly.', / ) +* +* End of SLAMC2 +* + END +* +************************************************************************ +* + REAL FUNCTION SLAMC3( A, B ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + REAL A, B +* .. +* +* Purpose +* ======= +* +* SLAMC3 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 (input) REAL +* B (input) REAL +* The values A and B. +* +* ===================================================================== +* +* .. Executable Statements .. +* + SLAMC3 = A + B +* + RETURN +* +* End of SLAMC3 +* + END +* +************************************************************************ +* + SUBROUTINE SLAMC4( EMIN, START, BASE ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + INTEGER BASE + INTEGER EMIN + REAL START +* .. +* +* Purpose +* ======= +* +* SLAMC4 is a service routine for SLAMC2. +* +* Arguments +* ========= +* +* EMIN (output) INTEGER +* 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) REAL +* The starting point for determining EMIN. +* +* BASE (input) INTEGER +* The base of the machine. +* +* ===================================================================== +* +* .. Local Scalars .. + INTEGER I + REAL A, B1, B2, C1, C2, D1, D2, ONE, RBASE, ZERO +* .. +* .. External Functions .. + REAL SLAMC3 + EXTERNAL SLAMC3 +* .. +* .. Executable Statements .. +* + A = START + ONE = 1 + RBASE = ONE / BASE + ZERO = 0 + EMIN = 1 + B1 = SLAMC3( 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 = SLAMC3( A / BASE, ZERO ) + C1 = SLAMC3( B1*BASE, ZERO ) + D1 = ZERO + DO 20 I = 1, BASE + D1 = D1 + B1 + 20 CONTINUE + B2 = SLAMC3( A*RBASE, ZERO ) + C2 = SLAMC3( 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 SLAMC4 +* + END +* +************************************************************************ +* + SUBROUTINE SLAMC5( BETA, P, EMIN, IEEE, EMAX, RMAX ) +* +* -- LAPACK auxiliary routine (version 3.2) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + LOGICAL IEEE + INTEGER BETA, EMAX, EMIN, P + REAL RMAX +* .. +* +* Purpose +* ======= +* +* SLAMC5 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) REAL +* The largest machine floating-point number. +* +* ===================================================================== +* +* .. Parameters .. + REAL ZERO, ONE + PARAMETER ( ZERO = 0.0E0, ONE = 1.0E0 ) +* .. +* .. Local Scalars .. + INTEGER EXBITS, EXPSUM, I, LEXP, NBITS, TRY, UEXP + REAL OLDY, RECBAS, Y, Z +* .. +* .. External Functions .. + REAL SLAMC3 + EXTERNAL SLAMC3 +* .. +* .. 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 = SLAMC3( Y, Z ) + 20 CONTINUE + IF( Y.GE.ONE ) + $ Y = OLDY +* +* Now multiply by BETA**EMAX to get RMAX. +* + DO 30 I = 1, EMAX + Y = SLAMC3( Y*BETA, ZERO ) + 30 CONTINUE +* + RMAX = Y + RETURN +* +* End of SLAMC5 +* + END |