Author: Robert Hyatt
Date: 10:05:23 09/09/99
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On September 09, 1999 at 12:17:56, Steve Maughan wrote: >Bob > >A couple of questions. Firstly, I've seen in a couple of posts you have give a >measure of Move Order Quality as the percentage of cutoffs that are as a result >of the first move played. Surely this is really a measure of Hash Table >Strategy since it is the hash table move that is played first (Crafty's hashing >strategy being sophisticated and including internal iterative deepening). Is it >not the case that if you swapped Killer and History moves, the statistic would >not change? Am I missing something? Yes.. You are assuming that nearly _every_ position is a hash hit. This is wrong. IE only about 10% or so of typical middlegame positions result in hash hits. Which means that 90% of the time I am relying on _other_ move ordering to pick the best move. Most of the time this is a winning capture, but killers and history do help. > >Secondly, when talking about Killers, is this the last (two) moves that created >a cutoff at this level or do you store refutational killers ie a killer based >upon the last move? I store the last two moves that either failed high or backed up a true score. Note that this doesn't gain much over history moves, if anything, unless you do as I do and try the killer moves without generating any moves first. Suddenly when a killer causes a cutoff you avoided generating the non- captures totally, a time saver... > >Thanks > >Steve Maughan > >>I do it like this: >> >>1. transposition move >>2. positive captures sorted by SEE score (best capture first) >>3. killer 1 >>4. killer 2 >>5. history moves (4) >>6. rest of moves, which just happens to do remaining captures first >> since they were generated first. >>
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