  In this paper the results of a simulation of a prisoner's dilemma robin-round
tournament are presented. In the tournament each participating strategy plays
an iterated prisoner's dilemma against each other strategy (round-robin) and as
a variant also against itself. The participants of a tournament are all
strategies that are deterministic and have the same size of memory with regard
to their own and their opponent's past actions: up to three most recent actions
of their opponent and up to two most recent actions of their own. A focus is
set on the investigation of the influence of the number of iterations, details
of the payoff matrix, and the influence of memory size. The main result is that
for the tournament as carried out here, different strategies emerge as winners
for different payoff matrices, even for different payoff matrices being similar
judged on if they fulfill relations T + S = P + R or 2R > T + S. As a
consequence of this result it is suggested that whenever the iterated
prisoner's dilemma is used to model a real system that does not explicitly fix
the payoff matrix, one should check if conclusions remain valid, when a
different payoff matrix is used.
