Author: Vincent Diepeveen
Date: 15:06:57 08/09/01
Go up one level in this thread
On August 09, 2001 at 10:39:00, Robert Hyatt wrote:
>On August 09, 2001 at 09:31:02, Alvaro Jose Povoa Cardoso wrote:
>
>>Since you are undertaking the Gerbil educational project, I would like to ask
>>you if you could implement Enhanced Transposition Cuttofs (ETC) in Gerbil with a
>>switch so that it can be turned on/off.
>>I know ETC doesn't give much in chess but I would like to experiment in
>>checkers.
>>My inplementation is working but it is not elegant at all.
>>Since we are dealing with the other player I avoided some complications
>>by creating a special version of Hashprobe() wich returns a score and by use of
>>an additonal flag informs me if there was a cutoff at the next ply.
>>So, and using 'crafty language' I do the following:
>>
>>for every move at this ply:
>>
>>Makemove
>>
>>Score =
>>-ETC_HashProbe(tree,ply+1,depth-INCPLY,ChangeSide(wtm),-beta,-alpha,&cutoff)
>>
>>Unmakemove
>>
>>if (cutoff) {
>> if (Score >= beta) {
>> return (Score);
>> }
>>}
>>
>>
>>Best regards,
>>Alvaro Cardoso
>
>
>
>That is not the right way to do it. I did it like that for testing, but it was
>actually a loss for me, because MakeMove() does a lot of work in Crafty. I
You must be kidding here. Isn't a lookup from hundreds of clocks
for each hashtable probe the real problem?
>first wanted to see if the tree would shrink by any significant amount. If it
>did, I would then write a special hash probe function that would only do the
>hash signature update extracted from MakeMove() which would be much more
>efficient. However, I found no appreciable tree size reduction and therefore
>gave up without going that far.
>
>In things like this, the first goal is to shrink the tree. If you can do that
>then you work trying to make the new code as fast as possible. If the new stuff
>doesn't shrink the tree, then making it faster is worthless...
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