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Subject: Re: Hash codes (test results)

Author: Miguel A. Ballicora

Date: 13:20:48 11/14/01

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On November 14, 2001 at 11:00:29, Gian-Carlo Pascutto wrote:

>On November 14, 2001 at 07:10:35, Dan Newman wrote:
>
>>I decided to try an experiment to see if I got different results on a
>>test suite using just 32 bits.  Part way into the test, Shrike crashed.
>>So it looks like I've probably got a bug in my hash table move validity
>>checker.  Looks like 64 bits spares my program from such failures--so
>>it has at least some utility :).
>
>On the contrary, I would say. Thanks to 32 bits hashing you have now
>discovered a dangerous bug that was luring around in your programand surely
>would have triggered at a critical time in a tournament :)

I think it is a very good idea to relax the number of bits used once in while.
I did this (using a ridiculously low number like 16 or 24, I do not remember)
and helped me to catch a couple of bugs right after being coded. This is in
agreement with "make unlikely things happen more often" to detect bugs before
the bugs catch _you_ :-).
One of the debug versions of my programs contain this switch.

Anyway, this is like killing cocroaches, you can kill as many as you want, but
never the last one :-)

Regards,
Miguel


>
>I did a run of 90 positions, at 1 minute on my Athlon 1000, with
>32 and 64 bit hashing:
>
>             32 bit          64 bit          Ratio
>-----------------------------------------------------
>Nodes:    574508449       564330729          98.23%
>Time:        186910          193491         103.52%
>Depth:           10.40           10.36       -0.03
>Solved:          58              58
>
>
>The fluctuations are entirely within the range that I would
>expect from just choosing another random seed for the hash
>number generator. So, I do not think it makes a difference.
>--
>GCP



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