Re: [Chicken-users] Possible numbers bug
What was the final word on this? Is it a real issue on some platforms? Anyhow, I found this whole exercise pretty interesting and played with it a bit more and observed a couple curious things: 1. Performance (see below) of guile was better than the compiled chicken-4.6.5 for my code. It looked like it might be due to string operations based on profile (I wasn't exactly trying to be efficient). 2. Taking the inverse exponent (i.e. result^(1/n) ) runs into trouble at n=144. Anyone care to explain why that is and is there a numerical methods trick to work around it? 3. Why do guile, scm and STk put out +inf.0 and chicken puts out +inf (gauche gives #i1/0)? My hazy understanding is that +inf.0 is not the same as +inf. The code I used is below. == Chicken 3.4: csi (load test.scm) ; loading test.scm ... 1000368...(2987 hidden digits)...0846700 Inverse of 144th expt is +inf == Chicken 4.6.5: Note: re-importing already imported identifier: magnitude ; loading /nfs/ch/disks/ch_umg_disk0003/mrwellan/tools/4/lib/chicken/6/numbers.so ... ; loading /nfs/ch/disks/ch_umg_disk0003/mrwellan/tools/4/lib/chicken/6/regex.so ... 1000368...(2987 hidden digits)...0846700 Inverse of 144th expt is +inf == STk (load test.scm) 1000368...(2987 hidden digits)...0846700 Inverse of 144th expt is inf.0 == guile -s test.scm ~ 1000368...(2987 hidden digits)...0846700 Inverse of 144th expt is +inf.0 == scm -f test.scm ~ 1000368...(2987 hidden digits)...0846700 Inverse of 144th expt is +inf.0 == gosh -b -q test.scm ~ 1000368...(2987 hidden digits)...0846700 Inverse of 144th expt is #i1/0 == Speed (on Atom n550) Chicken 4.6.5, compiled: 0.46s Chicken 3.4, compiled: 37s stk -f test.scm 2.9s guile -s test.scm: 0.16s scm -f test.scm: 1.49s gosh -b -q test.scm: 0.46s == ;(use numbers) (define vals #f) (define (print . strs) (map display strs) (display \n)) (define (sum-of-exponents n lim) (if ( n lim) 0 (+ (expt n n) (sum-of-exponents (+ n 1) lim (define (pp-bignum num) (let* ((str (number-string num)) (len (string-length str))) (if ( len 45) (string-append (substring str 0 7) ...( (number-string (- len 14)) hidden digits)... (substring str (- len 7) len)) str))) (define (cmpit lim) (set! vals (make-vector (+ 2 lim))) (let loop ((n 1) (sum 0)) (vector-set! vals n (expt n n)) (if ( n lim) (print (pp-bignum sum)) (loop (+ n 1)(+ sum (vector-ref vals n) (let loop ((n 1)) (let ((invexpt (expt (vector-ref vals n)(/ 1.0 n (if ( (abs (- invexpt n)) 0.0001) (print Inverse of n th expt is (pp-bignum invexpt)) (if ( n lim) (print Done) (loop (+ n 1))) ;; (print (message-digest-string (md5-primitive) (number-string (sum-of-exponents 1 1000' (cmpit 1000) (exit) On Fri, May 27, 2011 at 2:00 PM, David N Murray dmur...@jsbsystems.com wrote: On May 27, Kon Lovett scribed: Chicken x86: 520cbadfbf1e95567b1b49bd543fa8ab sauron:chicken-4.7.0 dnm$ csi -v CHICKEN (c)2008-2011 The Chicken Team (c)2000-2007 Felix L. Winkelmann Version 4.7.0 macosx-unix-gnu-x86-64 [ 64bit manyargs dload ptables ] compiled 2011-05-26 on sauron.local (Darwin) sauron:chicken-4.7.0 dnm$ csi -b -n -q -e '(use md5 message-digest numbers) (define (sum-of-exponents n lim) (if ( n lim) 0 (+ (expt n n) (sum-of-exponents (+ n 1) lim (print (message-digest-string (md5-primitive) (number-string (sum-of-exponents 1 1000' 89f880d1887706b3d1a2263b177f3352 Yup, that doesn't match. I have a debug build of x64-64 (macosx) available if someone wants to give me an idea on where to look. Dave ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
Re: [Chicken-users] Possible numbers bug
On Sat, May 28, 2011 at 11:03:41AM -0700, Matt Welland wrote: What was the final word on this? Is it a real issue on some platforms? Probably. I will look into it when time allows. Anyhow, I found this whole exercise pretty interesting and played with it a bit more and observed a couple curious things: 2. Taking the inverse exponent (i.e. result^(1/n) ) runs into trouble at n=144. Anyone care to explain why that is and is there a numerical methods trick to work around it? You divide the inexact 1.0 by the number. Try doing an exact division like (/ 1 n) or just (/ n). This will produce a rational number which is exact and not limited in any way. 3. Why do guile, scm and STk put out +inf.0 and chicken puts out +inf (gauche gives #i1/0)? My hazy understanding is that +inf.0 is not the same as +inf. I think it's the same. Only flonums can be +inf and hence the .0 is superfluous. Cheers, Peter -- http://sjamaan.ath.cx -- The process of preparing programs for a digital computer is especially attractive, not only because it can be economically and scientifically rewarding, but also because it can be an aesthetic experience much like composing poetry or music. -- Donald Knuth ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
Re: [Chicken-users] Possible numbers bug
On Sat, May 28, 2011 at 11:11 AM, Peter Bex peter@xs4all.nl wrote: On Sat, May 28, 2011 at 11:03:41AM -0700, Matt Welland wrote: 2. Taking the inverse exponent (i.e. result^(1/n) ) runs into trouble at n=144. Anyone care to explain why that is and is there a numerical methods trick to work around it? You divide the inexact 1.0 by the number. Try doing an exact division like (/ 1 n) or just (/ n). This will produce a rational number which is exact and not limited in any way. Ah, yeah, I forgot to mention that I tried both 1.0 and 1 and got the same result. Matt -=- Cheers, Peter -- http://sjamaan.ath.cx -- The process of preparing programs for a digital computer is especially attractive, not only because it can be economically and scientifically rewarding, but also because it can be an aesthetic experience much like composing poetry or music. -- Donald Knuth ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
Re: [Chicken-users] Non-finite number I/O (was: Possible numbers bug)
Peter Bex scripsit:
I think it's the same. Only flonums can be +inf and hence the .0 is
superfluous.
Superfluous, maybe, but now standard. R6RS prescribes it (for systems
supporting IEEE floats) and so will R7RS-small, despite being much more
like R5RS in most ways.
Existing implementations use either +inf.0 or something specific to
that implementation. Specifically: Racket, Gauche, Guile, Kawa, Chibi,
SCM, Ikarus, Larceny, IronScheme, Ypsilon, Mosh, and STklos all use
+inf.0. Bigloo uses +Infinity. Scheme48/scsh uses #{Inf}. SISC uses
infinity.0, which is not even rereadable. MIT Scheme and Scheme 9 do
not have non-finite values; they always report floating overflow or
divide by zero errors. (Scheme 9 is non-IEEE; it handles flonums up to
10^10^10 - 1.)
What is more, Chicken is not even consistent: on Linux it prints +inf,
but on Cygwin, which uses Newlib instead of GNU libc, it prints +inf.0.
My recommendations:
Use wrapper logic in number-string to print +inf.0, -inf.0, and +nan.0
in the appropriate circumstances, and make sure that string-number
always accepts them.
Remove the divide-by-zero exception when dividing by inexact 0, which
does not represent a mathematical 0, but any number between the smallest
positive flonum and the largest negative flonum.
--
We do, doodley do, doodley do, doodley do,John Cowan co...@ccil.org
What we must, muddily must, muddily must, muddily must;
Muddily do, muddily do, muddily do, muddily do,http://www.ccil.org/~cowan
Until we bust, bodily bust, bodily bust, bodily bust. --Bokonon
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