Anti-Omega: the weakest failure detector for set agreement
In the set agreement problem, n processes have to decide on at most n - 1 of the proposed values. This paper considers asynchronous shared-memory systems equipped with an anti-Omega failure detector. Each query to the anti-Omega returns a process id; the specification ensures that there is a correct process whose id is returned only finitely many times. The main result is that anti-Omega is both necessary and sufficient to solve set agreement in the asynchronous shared memory model.
failure detectors set agreement wait-free impossibilities weakest failure detector ever