Author: Uri Blass
Date: 17:26:12 09/19/03
Go up one level in this thread
On September 19, 2003 at 20:06:02, Sune Fischer wrote: >On September 19, 2003 at 19:46:38, Uri Blass wrote: > >>On September 19, 2003 at 17:42:47, Sune Fischer wrote: >> >>>On September 18, 2003 at 10:02:33, Edward Seid wrote: >>> >>>>I'm learning how to program by reading Deitel's Visual Basic.NET How to Program. >>>> I'm eager to try out my new skills on a chess-related project. >>>> >>>>The Pawn Game - as presented by GM Lev Alburt in Comprehensive Chess Course, Vol >>>>1 >>>> >>>>[D]8/pppppppp/8/8/8/8/PPPPPPPP/8 w - - 0 0 >>>> >>>>The game is won by: >>>>1- capturing all of the opponent's pawns >>>>2- reaching the last rank first >>>>3- 'stalemating' the opponent, while still having at least one move for yourself >>> >>>I tried a simple unoptimzed search, just returning matescore for reaching 7th >>>rank. It's not going as deep as I expected, of course you would not expect to >>>get the same kind of hitrate as with pawn tables (no color or depth or bounds >>>dependency in pawn tables): >>> >>>1 -3 5 1 1.a3 >>>1 0 10 9 1.a4 >>>2 0 10 33 1.a4 h5 >>>3 0 12 121 1.a4 g5 2.g4 >>>4 0 13 1056 1.a4 g5 2.g4 a5 >>>5 0 15 2529 1.a4 g5 2.e4 g4 3.h4 >>>6 0 22 14205 1.a4 f5 2.f4 a5 3.d4 h5 >>>7 0 26 33039 1.a4 f5 2.h4 a5 3.c4 c5 4.f4 >>>8 0 51 135649 1.a4 f5 2.f4 d5 3.d4 a5 4.h4 h5 >>>9 0 107 360649 1.a4 f5 2.f4 c5 3.h3 a5 4.h4 h5 5.c4 >>>10 0 339 1303780 1.a4 f5 2.d4 a5 3.c4 g5 4.e3 e6 5.c5 g4 >>>11 0 689 2716466 1.a4 f5 2.c4 g5 3.d4 f4 4.e4 g4 5.b4 h6 6.h4 >>>12 0 2241 8928849 1.a4 d5 2.d4 h5 3.h4 a5 4.f4 f5 5.b3 b6 6.c4 c5 >>>13 0 6084 23078374 1.a4 a5 2.c4 h5 3.f4 f5 4.h4 c5 5.d3 e6 6.e3 d5 7.d4 >>>14 0 16715 64599238 1.a4 f5 2.d4 a5 3.h4 c6 4.e3 b5 5.b3 h5 6.c4 bxa4 >>>15 0 37273 146539781 1.a4 f5 2.e3 g5 3.f4 h6 4.b4 c6 5.d4 b5 6.axb5 cxb5 >>> >>>This is without nullmove or specially tuned eval or move ordering of any kind. >>>Optimizing for it will of course give a few more plies, but double depth seems >>>out of reach. >>> >>>-S. >> >>I do not think that you are right. >>The branching factor is going to get smaller when you search deeper > >Why should that be the case? because the number of moves get smaller when pawns are blocked. >I would not expect such a thing to happen until you start hitting the solving of >the game limit. > >You mostly get many transposition in blocked pawn type positions, in this >position there are no blocked pawns at all, so it's going to take a while for >the transpositions to really fire. No tranposition. after a4 a5 pawns are blocked and you have less moves. less moves mean smaller branching factor. > >There is also another effect, the TTable gets overfilled at some point and >efficiency starts to drop, even with a good scheme you get more and more >outdated entries. I am talking about solving it without hash tables. > >>and >>evaluating passed pawns as winning if they are more advanced than the opponent >>pawns may significantly help. > >Yes, if you do it right you might even be able to cut branches directly at that >point (not sure, but there must be some obvious cases which would be theoreticly >sound). The question is if this represents a significant amount of the nodes. >Perhaps trying to solve an even simpler game: "win by creating a passed pawn" >could answer this question. I think that game would be pretty hard too. > >>I also guess that you should generate pushing moves 2 steps forward first and >>moves that lose a pawn only last. > >The move ordering is the standard move ordering I use for normal search, so it's >not that far from optimal (I hope not!:). > >Again I don't care much about fiddling to get 3-5 more plies, to go from 15 to >80 plies I need something revolutionary. You do not need 80 plies. I believe that there are even no logical games of 50 plies. I suspect that even your existing version may solve the game if you give it a lot of time. I already see a tendency for smaller branching factor in the last plies based on your data. I guess that you may get even effective branching factor smaller than 2 if you continue to run it for many hours if you have no bugs. Uri
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