Author: Robert Hyatt
Date: 06:25:58 09/28/99
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On September 28, 1999 at 08:13:47, Bas Hamstra wrote: >Hello, > >A while ago it was posted here that movesorting near the root was much more >important than near the leafs. > >- Is that true? >- If so, how much more important? Think about this for a minute. If you get the wrong move first near the leaves, how much work does it take to search the wrong move and then get the right one to get that cutoff? Compare this to positions near the root. So yes, it is _exponentially_ more important to get the move ordering right nearer to the root than nearer to the leaves. > >For instance Crafty has a FH FirstMove/FH rate of 94%. Now most nodes are near >the leafs, on average 94%, so near the root it is probably a good bit better. >Say 98%. Many moves come from hash, there. > >Now what if it went from 98% to 99%? What would be the impact on total nodes? >Any ideas? again, that 1% is an exponential improvement in the search, not linear... That last (missing) 6% would make the tree 2x smaller if I could get it... > >If sorting near the root is more important, isn't it an idea to try to improve >sorting for the first couple of plies (say 3) by Enhanced Transp Cutoffs? > >Some reported rootsorting by failsoftvalue gave good results. Why not the first >3 plies try something similar? > this doesn't work. for positions where you have to search _all_ moves, ordering is totally unimportant. And even with failsoft, you do _not_ discover the best move. Alpha/beta simply won't do it. ETC is certainly worth a try. When I tried it it made the tree smaller, but it was no faster due to the extra overhead it entails. Trying it near the root is something I didn't try, so you ought to give that a test.. > >Regards, >Bas Hamstra.
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