I wrote an 8-part series with 11,277 words and 24 graphs.

I think a lot of us are still curious what happened! Maybe concatenate the whole thing into a non-Frontpageable post with an explanatory disclaimer at the top?

I just remembered something I forgot to post in an earlier thread:

CloneBot's cooperateWithClone method uses parity checking on its and the opponent's payloads to determine the first move, but after that it always plays whatever move the opponent played last. I.e. pure naive tit-for-tat.

This suggests a possible strategy for a MimicBot: against a clone, play 0, 5, 0, 5, 0, 5... Assuming the opposing clone started with 3, this results in plays (0, 3), (5, 0), (0, 5), (5, 0)...

If the number of turns per game is even, you end up with one 5 per two turns, for the same 2.5 points per turn as if you had cooperated. Because the clone played a 2 or 3 on the first turn instead of a 5, it loses 2 or 3 points compared to perfect cooperation. This could be a big advantage over the 90 rounds before the CloneBot showdown.

Unfortunately, if the number of turns is odd, the clone gets just as many 5s as you plus its initial 2 or 3, so you're the one who gets outscored. I haven't been able to think of any strategy that would get you 2.5 points per turn, get the clone fewer points, and work whether the number of turns was odd or even. 

Using a defecting strategy would be a coinflip between a big advantage and a crippling disadvantage, so my actual submission played it safe and just cooperates with clones. The actual number of turns wound up being even, but I had no reasonable way of expecting that was more likely than not (IIRC, in Zvi's original game the number of turns was odd).

If you're willing to score fewer than 2.5 points per turn if the clone does much worse than you, there are a series of dastardly strategies that I'm thinking of as "Lucy pulling away the football", where you ruin the opponent's big play while setting up your next big play.

0, 5, 1, 4, 2, 3 repeated gives (0, 3), (5, 0), (1, 5), (4, 1), (2, 4), (3, 2) repeated. You get (5 + 4 + 3) / 6 = 2 per turn, while the opponent gets (3 + 1 + 2) /6 = 1 per turn.

0, 5, 1, 4, 2 repeated gives (0, 2), (5, 0), (1, 5), (4, 1), (2, 4) repeated. You get (5 + 4) / 5 = 1.8 per turn, opponent gets (2 + 1) / 5 = 0.6 per turn.

0, 5, 1 repeated gives (0, 1) (5, 0) (1, 5) repeated. You get 5/3 per turn, opponent gets 1/3 per turn.

Sacrificing some points to outscore the clones by a full five times might be worth it if there were four or fewer clones, but with one MimicBot against eight clones I don't think the penalty to my score is worth the damage I can inflict on them. (Also, I only thought of the dastardly strategies today; before submission I only considered the "minor edge" strategy described earlier.)

This analysis also applies generally to any bot known to be a naive tit-for-tat bot.

Oops! I look forward to getting some more accurate beliefs...

So I notice that I'm still confused as to how CliqueZviBot outperformed the other clique bots so consistently in the previous game (and still is! At least for this one round). I assume that the 300-200 goes in the favour of whoever won the starting tiebreaker [LW(p) · GW(p)]. No bot should be able to consistentely win this?

In the mutant game where you always think that your opponent's last move was the same as your last move, I think EarlyBirdMimicBot behaves as follows in the first 10 rounds:

Against clones, gets full clone cooperation of either all 3-2 or all 2-3. I put in a check to stop cooperating with clone if the clone ever starts exploiting me, but the check doesn't notice that turns so far seem to have been all 2-2 or all 3-3.

Against simulatable bots, gets one turn of simulation, then next turn sees that the opponent's apparent move was not the same as what was predicted. Reverts to the fallback plan.

Against everything else, thinks that every turn so far has been a match, so continues its early match-breaking strategy of playing 2 with probability 2/3 and 3 with probability 1/3. I think that's close to a Nash equilibrium in the blind game.

Against outsiders, Clonebot will always play 3 if it played 2 last turn, and in an apparent 3-3 match it transitions between 50% chance to play 2 initially and 0% by turn 50.