I think that kind of deviation was probably a large part of the motivation for those who submitted random-playing bots, since the contest rules specified one round.

I haven't looked too closely at K, nor ran any tests, but I have a slight suspicion it sometimes cooperated in simulation, despite always defecting on its turn.

As for the cooperatebots, there were multiple reasons I didn't write N to exploit them, but not source complexity--they don't even do anything besides cooperate; the middle term is just the function's argument list.

I checked the behavior of all the bots that cooperated with K, and all but two (T and Q) would have always cooperated with a defectBot. Specifically the defect bot:

(lambda (opp) 'D)

Sometimes they cooperated for different reasons. For example, U cooperates with K because it has "quine" in the code, while it cooperates with defectBot because it doesn't have "quine", "eval", or "thread" in it.

Q, of course, acts randomly. T is the only one that doesn't cooperate with defectBot but was tricked by K into cooperating. Tho... (read more)

1[anonymous]7yTrue. I'm not saying that the random people did a poor job of selecting strategies, but Error was depressed that random behavior dominated. My and Luke_A_Somers's points appears to be that the amount randomness dominates by, if it is dominant, would be easier to determine with more rounds.

Prisoner's dilemma tournament results

by AlexMennen 1 min read9th Jul 2013124 comments


The prisoner's dilemma tournament is over. There were a total of 21 entries. The winner is Margaret Sy, with a total of 39 points. 2nd and 3rd place go to rpglover64 and THE BLACK KNIGHT, with scores of 38 and 36 points respectively. There were some fairly intricate strategies in the tournament, but all three of these top scorers submitted programs that completely ignored the source code of the other player and acted randomly, with the winner having a bias towards defecting.

You can download a chart describing the outcomes here, and the source codes for the entries can be downloaded here.

I represented each submission with a single letter while running the tournament. Here is a directory of the entries, along with their scores: (some people gave me a term to refer to the player by, while others gave me a term to refer to the program. I went with whatever they gave me, and if they gave me both, I put the player first and then the program)

A: rpglover64 (38)
B: Watson Ladd (27)
D: skepsci (24)
E: Devin Bayer (30)
F: Billy, Mimic-- (27)
G: itaibn (34)
H: CooperateBot (24)
I: Sean Nolan (28)
J: oaz (26)
K: selbram (34)
L: Alexei (25)
M: LEmma (25)
N: BloodyShrimp (34)
O: caa (32)
P: nshepperd (25)
Q: Margaret Sy (39)
R: So8res, NateBot (33)
S: Quinn (33)
T: HonoreDB (23)
U: SlappedTogetherAtTheLastMinuteBot (20)