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        Arimaa >> Game Analysis >> Game 157067 722caasi vs. bot_Opfor2009Fast
        
(Message started by: 722caasi on Oct 12^th, 2010, 11:08pm)

Title: Game 157067 722caasi vs. bot_Opfor2009Fast
Post by 722caasi on Oct 12^th, 2010, 11:08pm

http://arimaa.com/arimaa/games/jsShowGame.cgi?gid=157067&s=w

I'd like some analysis, particularly on the endgame. Also, why do many bots fall apart when the endgame appears, which seems to be the phase requiring the most calculation?

Title: Re: Game 157067 722caasi vs. bot_Opfor2009Fast
Post by Fritzlein on Oct 17^th, 2010, 11:07pm

on 10/12/10 at 23:08:12, 722caasi wrote:

To answer your general question first, I think that when bots fall apart in the endgame it is generally because they are too materialistic and not sufficiently attuned to goal attack/defense. Bots are great at calculating forced goals when they are present within the search horizon, but terrible at evaluating how strong (or weak) a rabbit will be if there is no forced goal. An idea such as "try to get rabbits rolling when the board thins out" is not calculation, which bots are good at; it is strategy, which bots are not good at.

Specific to your endgame, I think 32s is a strategic mistake as well as a tactical one. Cats are generally most useful for home defense, and generally dead meat when sitting between the two opposing traps. A strategic distaste for advancing the cat would lead one to tactically consider 32s EvHE<R5v. The gold horse can't escape in two steps, and if it tries to escape in three or four, the silver elephant will be within range of defending c3.

Your 36g was strong, taking the b6-square and creating a long-term threat in the west. While OpFor calculated well enough to know that it was in danger, I am sure it didn't understand how painful losing the corner would be. On 36s is it futile to place the dog on b7 where it has no hope of retaking b6. If OpFor can't get the silver horse across to regain control of b6, then the western gold rabbits are strong instead of being weak.

A silver horse crossing seems to me more important than saving the g4-rabbit, if one must choose on move 36s or 37s. However, on move 40s, OpFor could have played H^<<R6>, switching wings without immediately losing the rabbit.

41s was short-sightedly materialistic. The silver horse could have pushed into c5 instead, regaining control of the c6-trap. Trading away a monster goal threat for only a cat on 43s is outright insanity. 44s again should have moved the horse to c5 to regain control of c6; when the horse finally threatens b6 on move 45s it is too late.

45g, 46g, and 47g are very nice attacking moves to seal the victory for Gold. Congratulations on fighting to the death and pulling out a victory from a poor position!

Title: Re: Game 157067 722caasi vs. bot_Opfor2009Fast
Post by 722caasi on Oct 18^th, 2010, 5:26pm

Thank you for the advice and the complements.