Author: Omid David
Date: 13:03:35 09/10/02
Go up one level in this thread
On September 10, 2002 at 15:33:30, Vincent Diepeveen wrote: >On September 10, 2002 at 14:30:56, martin fierz wrote: > >>On September 10, 2002 at 09:26:14, Eli Liang wrote: >> >>>A couple of chess programming questions: >>hmm, i only wrote a checkers program, but here's my take: >> >>>(1) Are there any uses for ProbCut and/or Multi-ProbCut in chess positions where >>>the variance of leaf-nodes is low? >> >>i've tried multi-probcut and it works well in checkers. i never tuned it as much >>as my own pruning algorithm, and it doesn't perform quite as well - but it is BY >>FAR better than no pruning. i'll be trying to tune it in the near future. for >>games where the eval doesnt swing wildly, MPC is a fantastic algorithm. > >In my draughtsprogram, of course draughts is a more complicated game >than checkers and EGTBs play a smaller role there than they do in checkers. What's the difference between draughts and checkers?! I thought "draught" is merely the British equivalent for the word "checkers". Here are the definitions of "checkers" and "draughts" according to the Merriam-Webster Dictionary: checkers \che-kerz\ n : a game for two played on a checkerboard with each player having 12 pieces draughts \drafts\ n, Brit : checkers > >But in any endgame i search at a 10x10 board already like 40 ply fullwidth >easily. Middlegame like 20 ply fullwidth *easily*. > >At the very quick time controls i get 16 ply easily with Napoleon. > >In endgames i outsearch even good draughtsprograms by about 10-20 ply. > >Napoleon has saved many lost positions in the endgame, despite that i >feel its endgame code sucks ass. > >The whole game of draughts and checkers is only about zugzwang. > >How can MPC work *anyway* if doing nothing is a GREAT thing to do >in checkers? > >The first few versions of napoleon used to forward prune the >last few plies and it was great to solve the most difficult tricks >even faster (it already sees everything any world champion has >found in tactics within microseconds of course). I concluded then >that it worked, but i am of course a very stupid draughtsplayer. > >I am at the level of draughts like most chessprogrammers are in >chess. I know all the things, but if i play i blunder away so many >stones that i get sick of it. > >When i threw it out, it played much better. > >Can you explain why MPC works for you? > >Other question, not related to the above story, just general >interest: how many professional checker players are there >in the world now that tinsley is dead? > >Another question. What do you do in your qsearch for checkers? > >>>(3) Reading Aske Plaat's search & re-search paper, it really seems like mtd(f) >>>is something of a magic bullet. But I note it seems that more programs don't >>>use it than do (for example Crafty). What is wrong with mtd(f) which Plaat >>>doesn't say? >> >>i'm using MTD. i tried windowed search, PVS and MTD. in my tests, in long engine >>matches, MTD performed marginally (no statistical significance...) better than >>PVS. it typically searched a low 1-digit % less nodes for a given depth than >>PVS. >>i don't know how to get a PV out of MTD. in normal searches, a pv node is where >>the value is > alpha but < beta. in MTD, you never get this condition. >>retrieving a PV from the hashtable is possible, but in all probability, you will >>not get the full PV. which is real bad for debugging if you want to know what >>the program was thinking at the time... i once asked here how to get a pv from >>MTD but got no answer - and if you can't get the pv, then that is a major >>drawback. >> >>>(6) Has anyone found any real "practical" benefits to fractional-ply extensions? >> >>yes. i tried recapture extensions of different depth, and half a ply gave the >>best result. don't ask me why, it's just an observation. >> >>aloha >> martin
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