Author: Omid David
Date: 07:51:32 09/10/02
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On September 10, 2002 at 09:26:14, Eli Liang wrote: >A couple of chess programming questions: > >(1) Are there any uses for ProbCut and/or Multi-ProbCut in chess positions where >the variance of leaf-nodes is low? What about the use of Warren Smith's BPIP or >Russell&Wefald's meta-greedy algorithms in chess? Any wins? > >(2) Is it practical to use partial-order bounding as an improvement over >conventional static evaluation? > >(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? There has been a good discussion recently here, concerning Plaat's PhD thesis, and in particular his MTD(f) algorithm. The problem with all his research, is that he has conducted it merely on fixed-depth full-width trees, i.e. without considering any variable depth algorithm. Today there is no program which uses sheer brute-force, as researched by Plaat; and even in 1996 (thesis' publication) almost all of the programs used some kind of forward pruning (mostly null-move pruning R = 2). In fact, no brute-force searcher has won the World Computer Chess Championships since 1992. Another problem with Plaat's thesis, is that all chess test positions have been searched to a depth of 8 plies. To obtain a more realistic assessment, the depths 9, 10, 11 will yield better results. I agree with Dr. Hyatt's recent comment which said: "I think that for normal programs, they should be equivalent if they are both implemented with the same skill and development time". Anyway, a research regarding MTD(f)'s performance in variable depth environments is badly needed in my opinion. Omid. > >(4) What are the current thoughts concerning bitboards/rotated-bitboards versus >conventional 0x88 or other algorithms? Just looking at open source chess >programs, it doesn't seem that the chess programming community has come to a >consensus on relative performance... or have you? > >(5) What is currently thought to be the best algorithm for autofitting the >static evaluation function parameters? DT's least-squares approach seems >simplest, but it seems as if a dozen other things have been tried too. Is there >any best-of-breed approach here? > >(6) Has anyone found any real "practical" benefits to fractional-ply extensions? > >(7) Dennis Breuker has a paper comparing 5 different transposition table >replacement schemes. Has any else been able to validate his results that >replacement should be based on the number of nodes searched and not search >depth?
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