Andreas_Giger

Prerequisites: Basic knowledge of the Prisoner's Dilemma and the Iterated Prisoner's Dilemma. I recently stumbled upon the selective IPD tournament results, and while I was very interested in the general concept I was also very disappointed by the strategies that were submitted, especially considering this is Less Wrong we are talking about. This post is designed to help people who are interested in IPD problems to come up with possibly successful strategies; hopefully the same effect another couple of tournaments would have, just in a shorter period of time. All of the following is written with the tournament rules in mind, with scores depicted as deviations of matches with full mutual cooperation since the actual number of turns per match is arbitrary anyway. Also, the hypothetical objective is not to have the highest population after a certain number of generations, but to achieve lasting superiority eventually while treating near-clones that behave exactly the same in the late game as one single strategy. The results of tournaments with a very limited number of generations depend way too much on the pool of submitted strategies to be of general interest, in my opinion. This post starts out with practical observations and some universal rules and gets increasingly theoretical. Here is a short glossary of terms I presume known: Feeding on a strategy: Scoring higher against that strategy in a match than against itself. Outperforming a strategy: Outscoring that strategy over the course of matches against all other strategies in the pool according to populations, including each other and themselves (i.e. improving the population ratio). Dominance: More than 50% of the total population. Dormant strategy: A strategy that will achieve dominance at some point but hasn't done so yet. Extinction: Asymptotical approach to 0% percent of the total population, or actual extinction in case of integer truncation. TFT-nD: A TFT strategy that defects from the nth last turn on,