Re: [Chicken-users] Big Randoms

[Kon Lovett]

On Mar 10, 2011, at 7:26 PM, David N Murray wrote:

> $ csi
>
> CHICKEN
> (c)2008-2010 The Chicken Team
> (c)2000-2007 Felix L. Winkelmann
> Version 4.6.0
> macosx-unix-gnu-x86-64 [ 64bit manyargs dload ptables ]
> compiled 2010-12-08 on sauron.local (Darwin)
>
> #;1> (use srfi-27)
> [snip loadings]
> ; loading /usr/local/lib/chicken/5/numbers.import.so ...
> ; loading /usr/local/lib/chicken/5/regex.import.so ...
> ; loading /usr/local/lib/chicken/5/srfi-27-numbers.import.so ...
> ; loading /usr/local/lib/chicken/5/srfi-27.so ...
> [snip more loads]
> ; loading /usr/local/lib/chicken/5/numbers.so ...
> ; loading /usr/local/lib/chicken/5/srfi-27-numbers.so ...
> [snip more loads]
> #;2> (random-integer (expt 2 32))
> Floating point exception
> $
>
> I'm working on a genetic algorithm framework and ran into this while
> testing.  Is there something I'm missing, or should I be trying to
> implement the dna handling in chunks of 31 bits? (random-integer  
> (expt 2
> 31)) works fine.

Hi David,

I get the folllowing:

$ csi -n

CHICKEN
(c)2008-2011 The Chicken Team
(c)2000-2007 Felix L. Winkelmann
Version 4.6.5
macosx-unix-gnu-ppc [ manyargs dload ptables ]
compiled 2011-02-03 on Nikko.local (Darwin)

#;1> (use srfi-27)
; loading /usr/local/chicken/5/lib/chicken/6/srfi-27.import.so ...
; loading /usr/local/chicken/5/lib/chicken/6/scheme.import.so ...
<snip>
; loading /usr/local/chicken/5/lib/chicken/6/srfi-4-checks.so ...
; loading /usr/local/chicken/5/lib/chicken/6/srfi-4-errors.so ...
#;2> (expt 2 32)
4294967296.0
#;3> (random-integer (expt 2 32))
3682515858.0

but notice that this is Chicken 4.6.5 & I do not have 4.6.0 installed  
so I cannot try it.

In reference to your question about "... chunks of 31 bits" 'random- 
integer ' accepts any exact integer in the full numeric tower as a  
bound.

What happens w/ 4.6.0 when you import 'numbers' into the toplevel? i.e.

(use numbers srfi-27)
(expt 2 32) ;=> ???
(random-integer (expt 2 32)) ;=> ???

Best Wishes,
Kon

> TIA,
> Dave
>
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