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Subject: Re: Hash and first Fail High

Author: Ralf Elvsén

Date: 18:43:42 08/14/03

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On August 14, 2003 at 15:27:06, Peter Fendrich wrote:

>1FH = The ratio where the first generated move in the node is a Fail High.
>
>I experimented with removing the the hash table and became a bit surprised.
>Normally I have about 1FH = 95-96%. When I removed the hash table that figure
>raised to more like 1FH = 96-97% while the search depth, as expected, was
>decreased.
>
>Increased 1FH when removing the hash table. Is this normal?
>
>/Peter

Hello

I haven't done any chess programming in over a year now (cured :). As you say
yourself below, this could be a statistical fluctuation. But I'm with Uri here:
I remember implementing a special improvement in move ordering in my program.
It worked fine, the time to search to a certain depth decreased. However, the
measure you call 1FH got worse. I made the same interpretation as Uri, namely if
you produce crappy moves at one ply you can will get a lot of FHs at the next
and your statistics looks fine :) I actually had a more refined statistic then
you:
I had 1FH for each ply, it probably was opposite effects for the last ply and
the ply before that (can't remember for sure though) but there are more nodes
closer to the leafs and they dominate the statistics. Hope I made myself clear,
it's late at night...

After that I didn't care much about this number anymore.

Ralf





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