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Subject: Re: CCT4 notes - Arasan

Author: James Swafford

Date: 17:42:36 01/20/02

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On January 20, 2002 at 20:08:24, Jon Dart wrote:

I always love reading the programmer's post-analysis.  Thanks
for taking the time Jon.

--
James


>
>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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