Author: José Carlos
Date: 10:11:44 10/30/03
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On October 30, 2003 at 12:45:47, Christophe Theron wrote: >On October 30, 2003 at 12:43:04, José Carlos wrote: > >>On October 30, 2003 at 12:27:16, Tord Romstad wrote: >> >>>On October 30, 2003 at 11:05:41, Uri Blass wrote: >>> >>>>On October 30, 2003 at 10:46:09, Vladimir Medvedev wrote: >>>> >>>>>>>In order to find out how good my move ordering is, I determined to check >>>>>>>which percentage of the cutoffs occured on the first move searched. >>>>> >>>>>Is branching factor more or less accurate parameter to evaluate quality of >>>>>sorting moves? >>> >>>Perhaps, but how do you measure the branching factor? I have asked this >>>question here before, but never recieved any answer. >> >> >> After every iteration I print in my log file something like: >> >> Branching factor: >> - This iteration = Total Nodes / Nodes Last Iteration >> - Acumulated: pow(Total Nodes,1.0 / Depth) >> >> With this measure, I'm finding that my program has huges BF's (per iterartion) >>in the first nodes, that go down to <= 3 after 5 iterations or so. But the >>acumulated has a slow reducing behaviour, going to <= 3 after at least 12 plies. >> I'm still working on understanding it :) >> >> José C. > > > >The QSearch is maybe a part of the reason. > >The percentage of QSearch nodes in the first iterations is higher than in the >deeper iterations. > >At least that is my experience. > > > > Christophe Yes, and I also do some checks and other strong threats before capture only part of qsearch. Those checks need a big % in some positions (30-40% of total nodes). What I still don't understand (I haven't had too much time to think about it) is that those nodes seem to affect too much to later iterations. Kind of counter intuitive when you consider the exponential growing of the tree. José C. > >> >> >> >>>>You can improve your branching factor by pruning or reduce it by extensions. >>> >>>Everybody always seem to claim that extensions increase the branching factor >>>(I suppose that is what you meant, although you wrote "reduce"), but it is >>>not at all obvious to me why this should be so. On the few occasions I have >>>experimented with this myself, removing all extensions has not resulted in >>>a noticably better branching factor. Of course the program needs fewer >>>nodes to complete a given search depth without extensions, but the difference >>>does not seem to be exponential. Perhaps more detailed and careful >>>experiments would have given a different result. >>> >>>Tord
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