For the record, here’s what the 2nd place CooperateBot [Insub] did:
On the first turn, play 2.
On other turns:
If we added up to 5 on the last round, play the opponent’s last move
Otherwise, 50% of the time play max(my last move, opponents last move), and 50% of the time play 5 minus that
My goal for the bot was to find a simple strategy that gets into streaks of 2.5′s as quickly as possible with other cooperation-minded bots. Seems like it mostly worked.
Is something strange going on in the Round 21-40 plot vs the round 41-1208 plot? It looks like the line labeled MeasureBot in the Round 21-40 plot switches to be labeled CooperateBot [Insub] in the Round 41-1208 plot. I hope my simple little bot actually did get second place!