Author: Juergen Wolf
Date: 11:37:50 12/17/03
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On December 17, 2003 at 05:38:52, Tord Romstad wrote: >On December 16, 2003 at 21:22:56, Anthony Cozzie wrote: > >>Recently I experimented with adding MTD(F) into Zappa. It has been an >>interesting experiment, but I am going back to PVS(). >> >>I thought that since Zappa has a [UL,LL] paired transposition table and an >>evaluation granularity of only 1/100 of a pawn, > >I use 1/64 of a pawn in Gothmog. In the new engine I am writing, the >granularity will be configurable by the user, with possible values between >1/8 and 1/512 of a pawn. > >>MTD(f) would work quite well, >>but that does not seem to be the case. The MTD(f) version of Zappa does >>slightly better on test suites (113/183 @ecmgcp v 106 @ 10s/move) but in the >>positional test suites it averaged about 3/4 of a ply less than the PVS() >>version. My guess is that because MTD(F) tries all moves, some of the >>"ridiculously losing captures" ordered near the end by PVS() are tried earlier, >>which accounts for the increased test suite performance. > >I don't understand this, I'm afraid. What does MTD(f) vs PVS have to do >with move ordering? > >>If anyone has any suggestions, I'm keeping the MTD(F) code in Zappa (just turned >>off) and I'm willing to try anything. >> > >Some suggestions: > >1. As Dan Andersson has pointed out, enhanced transposition cutoffs are very > effective when combined with MTD(f). If you don't use them already, give > them a try. > >2. Do you hash the qsearch? You'll probably find that it helps you reduce > the tree size quite a lot, even if it doesn't give you much in PVS. > >3. Do you use the plain MTD(f) algorithm (as described in Plaat's paper), > or do you use some kind of convergence accelerator? Plain MTD(f) never > worked well for me. I now increase the step size when the search fails > in the same direction more than once. > >Tord My engine supports both modes (MTD and PVS). Stepsize of MTD and Granularity of Evaluationfunction. So far i see minor improvements by using MTD only (Granularity 1/50 and Stepsize 1/25 gave best results in tournament). Didn;t give ETC and convergence accelarator so far a try , as game losses are more due to missing knowledge than anything else. Do you have a link/more information wrt "convergence accelerator" and to be expected gain by addding ETC to MTD ? thanks in advance kind regards juergen
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