Author: Ed Schröder
Date: 12:24:04 12/28/99
Go up one level in this thread
>Posted by John Warfield on December 28, 1999 at 07:02:31: > >>Thanks for the compliment in the first place. Your observations are very >>interesting for me. What in your opinion was it that made Rebel9 so much >>better than version 8? Same question for Rebel10 -> Century. I know these >>questions are hard to answer because the subjective nature. Keep in mind >>you maybe got a faster PC during Rebel9 and Century? >> > > > Well as you said my impression is mostly subjective. But after playing hundres >of games with 6, , 8, 9, 10, and now century , one gets to get used to the >playing styles. A subtle differnece I noticed between version 9 and 10, is that >Rebel 10 tended to play more aggressive. Also I felt more pressure on my game >out of the opening. Don't get me wrong I thought rebel 9 was extremely strong, >infact I have to say, I believe the difference between rebel 10 and century is >larger than the differences in rebel 9 and 10. It just seems to me that rebel >10 possessed just a little more finesse than version 9. Another notable >diffence in Rebel 10 from nine, was that version 10 seemed to be alot less >materialistic, Positional considerations seemed to play a larger role in it's >evaluation. It would not hungrily snatch a pawn as 9 would occasionally do. > I think the main improvemnt of century over Rebel 10, is that Century now has >much more tactical vision then 10, not that I was able to play tactically with >version 10, but in my observations in computer vs computer play, i noticed >century doesn't get tactically outplayed by the likes of chessmaster and fritz >as was the case with rebel 10. Also Century seems to be even more agressive >than 10, it has a very nice human feel to it, my games are never boring. it makes >beautiful quiet moves that are often seen in grandmaster play. (good example >is the Kg6!! in the rebel russek game!) After a game with Century I get a feeling >of chess art and apprecatation. I am not claiming any of these observations are >facts, i can only say they are crystal clear and evident to me personally. >Although Many may not be able to articulate these differences precisely, I am >sure that anyone who is a relatively strong chess player, will immediately >notice the differences in strength and playing style. Hundreds of games, wow. One plausible reason seems to be the improvements made to selective search. Every release (year) at least one month (sometimes 3 months) are spend to work on selective search. Failures in selective search can hurt a chess program a lot. Here is a (tactical) example: 1nr1b1k1/r4p2/1p1q2p1/pPppN3/3P4/2RBP3/P1Q2PP1/2R3K1 w - - bm dxc5; 00:00:06 8.00 0.16 1.Nc6 Nxc6 2.dxc5 bxc5 3.Rxc5 Rac7 4.bxc6 Rxc6 5.Rxc6 Rxc6 6.Qb2 Rxc1+ 7.Qxc1 (6) 00:00:14 8.33 0.18 1.dxc5 Qxe5 2.cxb6 Rxc3 3.Qxc3 Qxc3 4.Rxc3 Rb7 (13) 00:00:15 9.00 1.42 1.dxc5 Qxe5 2.cxb6 Rxc3 3.bxa7 Rxc2 4.Bxc2 Qb2 5.axb8=Q (15) 00:00:22 10.00 1.51 1.dxc5 Qxe5 2.cxb6 Rxc3 3.bxa7 Rxc2 4.Bxc2 Qb2 5.axb8=Q (20) Try this with previous Rebel's and 1.dxc5! isn't found at all because of a pruning failure. A positional example: 1k6/3K4/1P3p1p/3B2pP/3b2P1/8/8/8 w - - bm b7; 00:00:00 9.00 1.07 1.Kc6 Kc8 2.Bc4 Be5 3.Be6 Kb8 4.Bd5 00:00:00 9.01 1.07 1.b7 00:00:01 9.01 1.59 1.b7 Bc5 2.Ke6 f5 3.gxf5 g4 4.f6 Ka7 5.Kf7 Bd4 (0) 00:00:01 10.00 1.72 1.b7 Be5 2.Ke6 Kc7 3.Kf5 Kb6 4.Kg6 Kc5 5.Bf3 f5 6.gxf5 (1) 00:00:02 11.00 1.79 1.b7 Be5 2.Ke6 Kc7 00:00:04 12.00 2.03 1.b7 Be5 2.Be4 00:00:07 13.00 2.07 1.b7 Be5 2.Be4 Bc3+ Key move found op ply 9. Rebel10 needs 13 plies. Last example: 3rrb2/1pq2ppk/p1p1p2p/4P3/3P4/2P3QR/PP4PP/2B2R1K w - - bm Rf6 or Bxh6; 00:00:02 7.00 1.32 1.Qg4 Qe7 2.Bg5 f6 3.exf6 Qf7 4.Qe4+ Kg8 (2) 00:00:04 7.10 1.32 1.Bxh6 00:00:05 7.10 3.36 1.Bxh6 Kg8 2.Bg5 Be7 3.Qh4 f5 4.exf6 00:00:07 8.00 3.19 1.Bxh6 gxh6 2.Rf6 Qe7 3.Qg5 Qxf6 4.Qxf6 Rd7 5.Rg3 Red8 (6) Rebel10 needs 11 plies to see 1.Rf6! These so called "selective search failures" hurt chess programs a lot especially in the positional area as I had to learn the hard way as these mistakes in the selective search are "invisible". Your program plays an inferior move (no blunder) and after hours of debugging its reason is not the present chess knowledge but selective search. Tactical failures of selective search are easy to recognize as your program misses a pre-defined key-move and these are (luckily) not so many. But these positional errors in selective search are real killers for a program's positional play and often a lot of chess knowledge present in the program is simply killed because of that resulting in minor positional mistakes (no big blunders). Since version 9 I have made it an important topic for Rebel. Especially Rebel10 and Century have many improvements here. There is quite a loss in ply-depth (factor 2 between version 9 and Century compensated by new speed-up ideas) but the quality in the positional area improved a lot not because of the added new chess knowledge only but most of the time by not pruning "good moves" any more as now Rebel's chess knowledge is not killed any more by selective search failures. Errors in selective search can make an intelligent chess program sometimes look very dumb while actually there is no reason for that. The program has the knowledge to play the right move but during the search the knowledge is killed (lost). I consider these selective search improvements as the main reason Rebel plays better chess. Other reasons are of course new added chess knowledge but I do think the selective search improvements are dominant. Also Century's new king safety has done some good too to Rebel's tactical and positional understanding. It was (is) definitely needed to survive against GM's. Ed
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