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Subject: Re: Hash and first Fail High

Author: Robert Hyatt

Date: 08:36:42 08/18/03

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On August 18, 2003 at 10:41:20, Gian-Carlo Pascutto wrote:

>On August 16, 2003 at 23:14:44, Robert Hyatt wrote:
>
>>If you don't try a hash table move first, then you will probably try captures
>>and captures have re-captures that work instantly.  Hence more cutoffs.  Just
>>try it...
>
>I did, and I already posted my results. So did Dieter, and so did the
>original poster after running a few more positions. None of those results
>suggested better 'move ordering' (FH%) with worse move ordering.

As I said, YMMV.  In my case, it _did_ show up as I explained.  I cleverly
wrecked the hash table move and didn't really notice it at first.  When I
fixed it, the 1fh% went _down_.  I investigated for a bit, and found that for
the tests I used, the captures were the key.


>
>>The hash move is often _not_ a capture.  But if you try a capture first,
>>then the corresponding re-capture will be an instant cutoff that is easier
>>to find than a reply to a non-capture.
>
>The reply to the noncapture will be an instant cutoff as well in most
>cases, since you have a hash move in that case


Most likely you won't.  IE I don't get but maybe 10-20% hash hits in
middlegame positions.  That leaves 80% misses.


>
>If it's a capture, and the correct reply is a noncapture, you're screwed
>without hash.

Not necessarily.  Killer moves.  Killer moves.  That's why they were
originally used.  :)



>
>--
>GCP



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