Author: Sune Fischer
Date: 18:55:53 08/14/03
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On August 14, 2003 at 21:43:42, Ralf Elvsén wrote: >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 think it is a different effect, because if you do have a bad move ordering, it is expected to be consistently bad so you won't quickly get a FH at the next ply. It is true however that having a bad ordering could possibly produce a much larger tree, and this subtree might contain a lot of easy FHs. E.g. at a node you have 1 FH move and 30 FL moves, now you search these 30 FL moves first (assuming worst possible move ordering), so that gives you the chance to get 30 FHs at the next ply at the expence of 1 missed FH at the top ply. This is what you mean I guess, but note the inherent contradiction of assumptions. -S. >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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