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Is there a reasonable number of pawn hash entries?
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Lucas Braesch



Joined: 31 May 2010
Posts: 1824
PostPost subject: Re: Is there a reasonable number of pawn hash entries?    Posted: Fri Jul 13, 2012 4:08 am Reply to topic Reply with quote
bob wrote:
Kempelen wrote:
Hello,

I don't know if someone has made any kind of statistical study to see how many different pawn formation is on average, or the max number seen, based on depth. I ask this because this would be a nice data in order to correctly allocate the pawn hash table size.

Fermin


Simplest is to test. I did this in Crafty, basically by running several positions for a fixed amount of time, with a constant (and way too big) pawn hash. Hit rate is typically 99%+. Run same test with 1/2 as much memory. Keep repeating until the hit rate drops enough to show you are beginning to lose useful entries. You now know the right size for that time control. Try a couple of other time limits, and you should be able to create a simple function such that f(time) -> optimal phash size...

I also did a similar experiment, in order to estimate the pawn hash size. And I eventually used 0x10000 hash entries. My hit rate however, was more around 90%, but I use the kings positions into the pawn hash key (as I do some basic pawn shelter stuff and passed pawn eval depends on relative king position).
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Subject Author Date/Time
Is there a reasonable number of pawn hash entries? Fermin Serrano Tue Jul 10, 2012 9:24 pm
      Re: Is there a reasonable number of pawn hash entries? Robert Hyatt Tue Jul 10, 2012 11:20 pm
            Re: Is there a reasonable number of pawn hash entries? Lucas Braesch Fri Jul 13, 2012 4:08 am
                  Re: Is there a reasonable number of pawn hash entries? Vincent Diepeveen Sat Jul 14, 2012 9:54 am
      Re: Is there a reasonable number of pawn hash entries? Vincent Diepeveen Tue Jul 10, 2012 11:49 pm
      Re: Is there a reasonable number of pawn hash entries? Daniel Shawul Thu Jul 12, 2012 2:41 am
            Re: Is there a reasonable number of pawn hash entries? Fermin Serrano Mon Jul 16, 2012 12:03 pm
                  Re: Is there a reasonable number of pawn hash entries? Lucas Braesch Mon Jul 16, 2012 1:06 pm
                        Re: Is there a reasonable number of pawn hash entries? Fermin Serrano Mon Jul 16, 2012 1:47 pm
                  Re: Is there a reasonable number of pawn hash entries? Daniel Shawul Tue Jul 17, 2012 11:18 am
      Re: Is there a reasonable number of pawn hash entries? Marcel van Kervinck Sat Jul 14, 2012 10:46 am
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