Author: John Merlino
Date: 18:00:17 12/07/00
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On December 06, 2000 at 19:25:32, Uri Blass wrote: >On December 06, 2000 at 15:57:00, John Merlino wrote: > >>On December 04, 2000 at 23:27:21, William Penn wrote: >> >>>CM8000 - an analysis anomaly >>> >>>This is an analysis after 1.Nf3 Nf6 2.c4 c6 3.Nc3 d5 4.e3 e6 5.d4 Nbd7 6.Qc2 Bd6 >>>7.Be2 0-0 8.0-0 e5 9.cxd5 cxd5 10.Nb5 Bb8 11.dxe5 Nxe5 12.Bd2 Bg4. The position >>>after 12...Bg4 is as follows: >>> >>>BR BB -- BQ -- BR BK -- >>>BP BP -- -- -- BP BP BP >>>-- -- -- -- -- BN -- -- >>>-- WN -- BP BN -- -- -- >>>-- -- -- -- -- -- BB -- >>>-- -- -- -- WP WN -- -- >>>WP WP WQ WB WB WP WP WP >>>WR -- -- -- -- WR WK -- >>> >>>This is a known position with 17 example games found in the literature and >>>databases. 14 games played 13.Nbd4 which may be considered the book move, 2 >>>games played 13.Bb4, and 1 game played 13.Rfc1. Nobody tried 13.Nfd4. Using >>>CM8666 Deep (as described previously, analogous to Shep's CM6666 Deep for >>>CM6000), analysis yielded the following information in the Thinking Lines >>>window: >>> >>> after 12...Bg4 >>>Time Depth Score Positions Moves >>>0:28 9 0.37 1M * Bb4 (* rounded off to nearest 1000) >>>1:00 10 0.18 3M Bb4 >>>2:27 10 0.31 8M Nfd4 >>>5:58 11 0.23 19M Nfd4 >>>17:31 12 0.14 58M Nfd4 >>>23:07 12 0.28 78M Bb4 >>>41.43 13 0.12 142M Bb4 >>>2:11:00 14 0.13 448M Bb4 >>> >>>So my CM personality thinks 13.Bb4 is the best move in this position with a >>>+0.13 score at 14 ply. It didn't find the book move 13.Nbd4. Why? Well, maybe >>>the book move isn't as good. To test this theory, I made the book move. If >>>it's not as good, the resulting analysis should give poorer scores (smaller >>>positive values) than 13.Bb4. Here's what it shows: >>> >>> after 12...Bg4 13.Nbd4 >>>Time Depth Score Positions Moves >>>0.16 9 0.56 1M Nxf3+ >>>0.36 10 0.44 2M Nxf3+ >>>1:33 11 0.43 5M Nxf3+ >>>6:00 12 0.37 20M Nxf3+ >>>17:12 13 0.37 59M Nxf3+ >>>1:05:00 14 0.29 220M Nxf3+ >>> >>>Surprisingly 13.Nbd4 gives higher scores than 13.Bb4. I thought that might be >>>because the Selective Search was set too high in CM8666 Deep. So I searched >>>with smaller Selective Search settings (including a setting of zero, among >>>others) but it still couldn't find the book move, 13.Nbd4. >>> >>>Clearly 13.Nbd4 produces better scores, so why wasn't it found and selected as >>>the best move? This is an unexplained anomaly, and I don't know the answer. >>>Does anyone? >>>WP >> >>I forwarded your post on to Johan, and here is the gist of his reply: >> >>-- The GUI supports selective settings of 1 to 12 because those are the >>"reasonable" settings. The higher you go past 12, the less useful the data is. >>He basically stated the setting of 32 is pretty much a "garbage in/garbage out" >>scenario. >> >>-- The engine does NOT do any checking for "illegal" values in personalities >>(meaning values outside of the ranges available in the GUI). Therefore, your >>setting of 32 WAS used for CM8666 Deep. >> >>-- He also stated "This guy is still confused about the score being displayed >>for side to move. So the second line is just -0.37 for white, meaning the engine >>likes Nbd4 less than Bb4." >> >>-- Therefore, there is no bug, and this is completely acceptable behavior. >> >>jm > >Preprocessing can be also a reason for analysis anomality that the poster >described. > >I know that a lot of chess engines including some top programs do preprocessing >and it means that the score is based also on the root position. > >I know that Gandalf does not do preprocessing and I am interested to know if >Chessmaster8000 is supposed to have the same behaviour. > >Uri Here is Johan's response to the question of preprocessing: "The King changes the material and centrilzation tables gradually from opening to middle game to end game. These add only a small amount to the total evaluation, though the changes *are* visible after castling and queen (re)captures." jm
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