  Cooperative artificial intelligence with human or superhuman proficiency in
collaborative tasks stands at the frontier of machine learning research. Prior
work has tended to evaluate cooperative AI performance under the restrictive
paradigms of self-play (teams composed of agents trained together) and
cross-play (teams of agents trained independently but using the same
algorithm). Recent work has indicated that AI optimized for these narrow
settings may make for undesirable collaborators in the real-world. We formalize
an alternative criteria for evaluating cooperative AI, referred to as
inter-algorithm cross-play, where agents are evaluated on teaming performance
with all other agents within an experiment pool with no assumption of
algorithmic similarities between agents. We show that existing state-of-the-art
cooperative AI algorithms, such as Other-Play and Off-Belief Learning,
under-perform in this paradigm. We propose the Any-Play learning augmentation
-- a multi-agent extension of diversity-based intrinsic rewards for zero-shot
coordination (ZSC) -- for generalizing self-play-based algorithms to the
inter-algorithm cross-play setting. We apply the Any-Play learning augmentation
to the Simplified Action Decoder (SAD) and demonstrate state-of-the-art
performance in the collaborative card game Hanabi.
