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   Author  Topic: Arimaa rating deflation  (Read 22458 times)
99of9
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Re: Arimaa rating deflation
« Reply #30 on: Dec 1st, 2003, 4:10pm »
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on Dec 1st, 2003, 1:21pm, MrBrain wrote:
How about using the inherent scoring function in the game itself?  This takes into account material and rabbit position.  The score of a function could be s1-s2 where s1 is the score of our position and s2 is the score of the opponent's position.  (This approach is simply utilizing something that's in the rules of the game already.  There is no abitrary decision that has to be made about any kind of evaluation function.)

 
Yes, I think that's a good idea.
 
Personally I think this scoring function overvalues rabbits heaps, but hey, if it's in the game already, we might as well use it.
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MrBrain
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Re: Arimaa rating deflation
« Reply #31 on: Dec 2nd, 2003, 8:22am »
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Actually, thinking about it some more, it's really not that important to me what kind of evaluation function we use for intermediate bots.  The only really important thing is that we have a very firm definition for a bot of rating 0, and I think we've done that.  "Chooses randomly from all possible new positions with equal probability, including the setup move."  As long as that is satisfied, intermediate bots can do whatever they want, really.
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omar
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Re: Arimaa rating deflation
« Reply #32 on: Dec 2nd, 2003, 1:44pm »
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Can someone send me a random bot written in C or C++. I'd like to run some initial experiments by playing it against shallowBlue offline. Thanks.
 
Omar
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99of9
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Re: Arimaa rating deflation
« Reply #33 on: Dec 2nd, 2003, 3:58pm »
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I can when I get back, but that's a couple of weeks.
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MrBrain
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Re: Arimaa rating deflation
« Reply #34 on: Dec 2nd, 2003, 4:27pm »
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Make sure it has a random initial setup to start.  Perhaps then the very next intermediate bot could be one with a predetermined setup.  Although, I would predict that there would be very little discernable difference in strength between the two bots.  Aesthetically, though, the totally random setup makes the most sense for a rating of 0.
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99of9
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Re: Arimaa rating deflation
« Reply #35 on: Dec 2nd, 2003, 5:31pm »
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Yes, good point... random's not in at the moment.
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clauchau
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Re: Arimaa rating deflation
« Reply #36 on: Dec 5th, 2003, 11:44pm »
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Here is yet another way to weaken and randomize a bot: add a weighted random value to every board value. For example have
value := 0.95*value + 0.05*rand(1)*(max_value - min_value);
 
 
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clauchau
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Re: Arimaa rating deflation
« Reply #37 on: Dec 14th, 2003, 7:43am »
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Here are the outcomes of a million games I ran between bots playing elementary strategies.
 
The most elementary strategy consists in randomly picking up a valid step among the immediately available steps, making the selected step on the board, and repeating this four times for every move.
 
random stepper / random stepper
 
Gold won 50.3%,  Silver won 49.7%
 
The winner reached the goal 62.5%
The loser moved an opposing rabbit to the goal 26.0%
The loser was unable to move 11.5%
Loss by 3-times repetition: 0 (no such loss).
 
Shortest game: 11 half-moves
Mean length: 76.9 half-moves (standard deviation = 21.7)
Longest game: 194 half-moves
 
(figures based on 100,000 games run in 4 minutes)
 
Ok, I need time to sum it all and provide Omar with bots. See you later.
« Last Edit: Dec 16th, 2003, 7:29am by clauchau » IP Logged
clauchau
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Re: Arimaa rating deflation
« Reply #38 on: Dec 14th, 2003, 11:50am »
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As we know, a more elaborate player is able to look ahead at his next steps and consider his move as a whole. Unfortunately it takes about 600 times more time to make a move, so multiple experiments and acurate data are harder to get.
 
random mover / random mover
 
Gold won 46%, Silver won 54%
 
The winner reached the goal 79%
The loser moved an opposing rabbit to the goal 19%
The loser was unable to move 2%
Loss by 3-times repetition: 0 (no such loss)
 
shortest game: 33 half-moves
mean length: 71.5 half-moves (standard deviation = 18.9)
longest game: 131 half-moves
 
mean number of different reachable positions = 16380 (st. dev. = 10950)
max number of different reachable positions = 90023
 
figures based on 500 games (12 minutes).
 
random mover / random stepper
 
the mover won 54%, the stepper won 46% (no connection with the previous 46% 56% figures)
 
figures based on 1500 games (19 minutes)
« Last Edit: Dec 16th, 2003, 7:35am by clauchau » IP Logged
MrBrain
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Re: Arimaa rating deflation
« Reply #39 on: Dec 15th, 2003, 9:05am »
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Very interesting!  As I predicted, the random mover is stronger than the random stepper.  Again, I believe this is due to the fact that random moves more often accomplish something meaningful than moves composed of random steps; e.g. a rabbit moving 4 steps forward is more likely with the random mover than with the random stepper.
« Last Edit: Dec 15th, 2003, 9:07am by MrBrain » IP Logged
99of9
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Re: Arimaa rating deflation
« Reply #40 on: Dec 15th, 2003, 10:08am »
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Can I just check... are these for initial random positions?
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MrBrain
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Re: Arimaa rating deflation
« Reply #41 on: Dec 15th, 2003, 10:53am »
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I hope so.  If not, I would recommend that these same cases be re-run for random start positions.
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MrBrain
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Re: Arimaa rating deflation
« Reply #42 on: Dec 15th, 2003, 10:56am »
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Claude, how do you handle the case in the random stepper if the fourth step leads to the same position as before the move started?  Do you wipe out this move and do four new random steps?  Or do you just force the fourth step to be something different?
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clauchau
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Re: Arimaa rating deflation
« Reply #43 on: Dec 16th, 2003, 7:19am »
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Yes the initial position is uniformly random in those games. We agree this seems the right thing to do, both for the Stepper and the Mover. It amounts to the same either we see it as randomly setting one piece after the other or picking up a position among the 64,864,800 legal initial Gold or Silver positions.
 
To me the first move is much like other moves. So for the bots that like having a rabbit as far as possible, I force the initial position to have at least one rabbit on the second row. For the bots that like having as many rabbits as far as possible, I force the eight rabbits to fill in the second row while setting the other pieces randomly on the first row.
 
Aha, Brian, you are my kind, seeing any single possible flaw. I considered any fourth step that gets us back to the position before the move started as illegal and I excluded such a step. It cannot be picked up when the bot looks for a fourth step. If no other fourth step was available, the move is made of three or fewer steps.
 
Now, in moves consisting of less than 4 steps - which I allow the Stepper to make only when no further legal step is available - I considered any move that gets us back to the position before the move started as a loss (for not being able to move) instead of asking for other steps. I slightly like it better like that but it deserves a distinct figure to know how often that happens and I'll get that right.
« Last Edit: Dec 16th, 2003, 7:25am by clauchau » IP Logged
MrBrain
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Re: Arimaa rating deflation
« Reply #44 on: Dec 16th, 2003, 8:46am »
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That all sounds very good.  Any chance you could get the random mover, possibly called "bot_random", on line and start playing against other bots?  (I suppose Omar would first have to implement a change to the rating system so that bot_random's rating stays at 0 no matter what, but the opponent's rating moves accordingly.)
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