Author: Jon Dart
Date: 17:08:24 01/20/02
CCT-4 notes Here are some notes re Arasan's participation in CCT4. I had a worry a couple of weeks ago when my wireless network quit working. I have a couple of Linux boxes and a network hub in the basement. But the fast machine, the Athlon, is upstairs on a wireless link. It broke, and it would be a pain to move the Athlon downstairs onto the wired net, so I was afraid I'd have to use a Pentium III/733 for the tournament. But I was able to get a replacement wireless card in time and all was well, hardware-wise, anyway. I am still tuning Arasan. In the last year or so I have made king safety changes, extension changes, bug fixes, and built a new opening book. Oh yeah, and ported it to Linux. None of this is publically released yet. Soon, I hope. Arasan was paired against Ferret (!) in the first round. Bruce reminded me that Arasan has played several games against Ferret on ICC under the handle "Mink", but Mink was on a lot slower hardware. Ferret had a dual Athlon setup for the tournament. Arasan played a somewhat passive English Opening setup. Not bad, but not very active. Ferret crushed it. Next round I had PolarChess. Arasan got an early advantage and won easily. Round 3 Arasan was matched with monsoon. Arasan has played monsoon on ICC. It is a strong engine. I am impressed, in fact, with how many good amateur engines there are. Chester, Insomniac, monsoon, amyan, tao, to name just a few. monsoon played the Benoni, which I think is just bad for Black. But Arasan chose the Four Pawns defense (A68), which is far from the best system. 7. Nf3 is better than f4. I think White can also play g3. Arasan played into the f4 line because there were some draws and wins with it from the White side in its book database. But I think 15 .. Nb6 may bust this line. After that, Arasan played one move out of book (16. Qb3) and the next move was failing low. It doubled the search time but still had a bad position, and it never really recovered. Which is not to deny that monsoon played well. But I took the f4 line out of the book since this game. Round 5 today Arasan was matched with Tao. Arasan had the White side of a Tarrasch defense. At least that's what I think it was. Tao gave up a Rook for Bishop plus two pawns at move 25. A short time later it had posted a rook on the 7th and advanced its passed pawn, with a decisive advantage. Round 6, Arasan played Avernox. Arasan has a reasonable record against Averno on ICC. But here it hit another opening problem, playing the Pirc defense. After 1. e4 d6 2. d4 Nf6 3. f3 d5 4. e5, Arasan was out of book and soon had a miserable position. The pawn on e5 continued to cramp it through much of the game. It was able to exchange down and escape immediate danger but wound up down material in the endgame and succumbed. This showed up a problem in Arasan's book selection code. Normally it scores each possible book move and uses a combination of move frequency, win/loss percentage, and book learning to score each move. But move selection is then random. It will prefer moves with high scores, but as long as the score is not zero, the move has some probability of being selected. So .. d6 after e4 is a possibility, although not likely. I now plan to implement some selectivity. I think Crafty has a similar feature: if I set the selectivity to 70, for example, it shouldn't play moves whose score is less than 70% of the highest move's score. This will narrow the opening book selection but also steer it into more main lines. I almost have this coded and it should be in place by next week. I think randomness is good against human players but against computers you probably want a higher selectivity value. Round 7, Arasan played Armageddon, which is a Polish engine I've never heard of before. Arasan dropped a pawn early in the opening and had to play most of the game with a minus score, which was not fun to watch. However, in the end it wound up in an endgame in which the extra pawn was ineffective. Arasan had only 4-man tablebases and its opponent had the full 5-man set, so it was lucky to draw here: it was depending on search while Armageddon was getting steady tablebase hits (according to the operator's comments during the game). Well, it was fun, and I learned some things. So I'm looking forward to next week.
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