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Subject: Re: Q: null move

Author: Andrew Williams

Date: 07:41:55 08/02/99

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On August 01, 1999 at 21:02:54, Scott Gasch wrote:

>Ouch...
>
>I only can search to 4 ply in that position in 60 sec and my null move succeeds
>about 40% of the time.  I believe this bad performance has sometime to do with
>my qeval routine and the fact that it considers all captures/promotes.  I think
>I need to be more selective about captures in the qeval routine.  My program
>plays f2f3 after 1 minute of thought.  Here's the report (if anyone cares):
>
>  total nodes.....................................4588297
>  time (sec)......................................60.71
>  rate (nodes/sec)................................75579
>
Your program is nearly twice as fast as mine! But I think you're right
about selectivity in qsearch. This is a lot of nodes for 4 ply. You might
look carefully at your move ordering as well.


>  null move successes.............................73
>  null move failures..............................117
>  null move success rate..........................38.42%
>

Are these the actual figures? If so, I think there is a problem. Why do
you only try null move 190 times out of 4.5 million nodes? In my program
it tries null move so long two conditions are satisfied: (a) both sides
must have at least two Pieces and (b) the last move wasn't a null move.
In this case, it tries null move in about 70% of non-quiesce nodes. If
this figure (190) is correct, I think you could be using null move a lot
more.


>  pawn hash hits..................................4469147
>  pawn hash misses................................117413
>  pawn hash success rate..........................97.44%

There's clearly nothing wrong with your pawn hash table! :-) I get a 92%
hit rate here.

Regards,

Andrew



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