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lackofcheese comments on 2014 iterated prisoner's dilemma tournament results - LessWrong
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Comments (57)
Your win frequency graph is wrong; it should say 963 for VOFB, not 968.
Anyways, I did some more detailed statistics with the power of
ls | xargs perl -sn0e 'while (/next round:.(\N*)/sg) {print "$1->"}; print "$ARGV\n"' | sort -V
and here's the results I came up with:
963 matches went like this:
ALL->[Cheese,DMRB,SimHatingTFT,Switch,TwoFacedTit,VOFB]->[Cheese,DMRB,VOFB]
32 matches went like this:
ALL->[Cheese,DMRB,SimHatingTFT,Switch,TatForTit,TwoFacedTit]->[Cheese,DMRB,TatForTit]->[DMRB,TatForTit]->[TatForTit]
(13, 19, 30, 31, 33, 40, 42, 54, 74, 119, 137, 203, 236, 272, 301, 303,
321, 326, 343, 400, 438, 476, 516, 526, 539, 608, 626, 815, 823, 827, 941, 977)
3 matches went like this:
ALL->[Cheese,DMRB,SimHatingTFT,Switch,TatForTit,TwoFacedTit,VOFB]->[Cheese,DMRB,SimHatingTFT,TwoFacedTit]->[Cheese,DMRB]
(64, 553, 979)
Match #11 went like this:
ALL->[Cheese,DMRB,SimHatingTFT,Switch,TatForTit,VOFB]->[Cheese,DMRB,SimHatingTFT]->[Cheese,DMRB]
Match #12 went like this:
ALL->[Cheese,DMRB,SimHatingTFT,Switch,TwoFacedTit,VOFB]->[Cheese,DMRB,SimHatingTFT]->[Cheese,DMRB]
OK, so here's what I can gather from those numbers, plus some extra time spent looking at the individual files.
Cheese, DMRB, SHTFT and Switch did well enough in Round 1 every time to guarantee that they would get through; this left two spots that were potentially up for grabs due to variance (although TwoFacedTit got one of those spots 999 times out of 1000 because its score was generally pretty solid).
964/1000 times VOFB got through Round 1.
963/964 of those times it ended up being a 3-way tie between VOFB, DMRB, and CheeseBot.
1/964 of those times (Match #12) VOFB had a spasm and defected against TwoFacedTit on Turn #43; TwoFacedTit punished it by defecting and so they defected for the rest of the game, which caused SimHatingTFT to get through to Round 3 instead of VOFB. The result was a tie between CheeseBot and DMRB.
32/1000 times TatForTit got through Round 1.
In those cases, TatForTit proceeded to win because VOFB wasn't there to stop it---Cheese, DMRB and TatForTit would always make it to Round 3, and the matches turned out the same way every time:
TatForTit would defect against CheeseBot on Turn #98, followed by mutual defection on the last two turns, resulting in a score of 298-293
TatForTit would defect agiainst DMRB on Turn #99, followed by mutual defection on the last turn, for a score of 300-295
CheeseBot and DMRB would cooperate for 300-300.
with totals of 598 for TatForTit, 595 for DMRB, and 593 for CheeseBot.
As such, CheeseBot would be knocked out, leading to DMRB vs TatForTit in Round 4, in which TatForTit would (obviously) win 300-295.
3/1000 times VOFB and TatForTit both made it through Round 1 because their scores were tied (i.e. TwoFacedTit still made it through, and 7 bots got through R1 instead of the usual 6)
1/1000 times (Match #11) TwoFacedTit failed to get through Round 1, which meant that both VOFB and TatForTit went through instead.
In that round, TwoFacedTit defected against VOFB in Turn #50, triggering a string of defections for the rest of the time, and meanwhile VOFB got really lucky and managed to cooperate with Pip for 97 turns.
In those 4 matches where VOFB and TatForTit both made it to Round 2 they knocked each other out; apparently VOFB and TatForTit really hate each other. The final result of all 4 of those matches was a tie between CheeseBot and DMRB.
Thanks for the analysis. Assuming that Pip uses a random strategy, it seems that the only surprising behavior of VOFB occurred with TwoFacedTit. Maybe this is due to timing issues.
It seems like VOFB and TwoFacedTit had some weird chemistry, since each inexplicably defected against the other exactly once. I assume it's a coincidence, since TwoFacedTit is entirely deterministic and could only have been screwed up by anomalous processing times or something.
Thanks; fixed. And thanks for this analysis! I've added it to the OP.