Author: Vasik Rajlich
Date: 01:42:14 02/04/06
Go up one level in this thread
On February 04, 2006 at 04:18:58, Bernd Nürnberger wrote: >On February 04, 2006 at 03:56:09, Vasik Rajlich wrote: > >>On February 04, 2006 at 03:21:12, Bernd Nürnberger wrote: >> >>>Hello, >>> >>>I have a question concerning the rate of beta cuts. My program prunes the tree >>>by doing a beta cut at about 5-10% of all nodes. This seems rather low to me. >>>Thus most moves that were generated are actually made. Nethertheless I am >>>getting rather low node counts and a mediocre first cut rate: for WAC (pos >>>1-300) at depth 8, my program searches about 69 M nodes with a first cut rate of >>>88%. >>> >>>Now to the question: is a cut rate of 5..10% common?? I often heard that most >>>moves generated are nether done because of beta cuts. That's not the case in my >>>program. >>>For WAC (depth 8) 88 M nodes are generated and 69 M nodes are done ! >>> >>>Configuration: >>>- Hash Table (1 M entries, deep/new two-level replacement) >>>- Razoring/(Extended) Futility Pruning >>>- Null Move (rather aggressive) >>>- Move Ordering: >>> x hash move (IID) >>> x winning + equals caps (by SEE, only x-rays capturer) >>> x killer 1 / killer 2 >>> x non-caps (history heuristics) >>> x losing caps >>>- PVS / aspiration search >>>- QS (prunes rather aggresively using SEE) >>>- plain vanilla eval (mat + pc-sq + boni/penality for castlings) >>> >>>Any comments appreciated :-) >>> >>>Bernd >> >>In a classical search without razoring-type stuff you'll fail high at well over >>90% of nodes, and will need much fewer than 69M nodes to do 8 iterations. >> >>It's possible you have the alpha-beta logic mixed up. You might want to step >>through a sample variation move by move. For this the "Chant" tool (advertised >>here from the search engine page) is quite handy, it's what I use. >> >>Vas > >Hello Vas, > >I don't think that 69 M nodes for 300 positions to depth 8 is way too much. >After disabling null move and razoring/futility pruning, I am getting >98% average first cuts at WAC positions 1-10 (depth 8) while getting >24% beta cuts on average. With null move the it's 91% / 4% and with >null move and razoring/fut. it's 90% / 7%. > >So the first cut rate is good with null moves disabled, but the total beta cut >rate is somewhat low. Did you mean, that the total beta cut rate should be >over 90% or just the first cuts?? > >Bernd Aha, now I understand what you mean. 69M for all 300 positions sounds ok. Your first cut rates sound right. They will drop further if you are more selective at the leaves (ie. more razoring). Re. what you call beta cut rate, I have never measured this. Offhand, I'd guess that it should be way over 90%. The vast majority of program nodes where any moves are generated are depth == 1 fail-high nodes where the first move causes a cut. Vas
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