Author: Uri Blass
Date: 16:25:32 12/06/00
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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
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