Summary: Faster randomized consensus with an oblivious adversary
February 15, 2012
Two new algorithms are given for randomized consensus in a shared-memory model with an
oblivious adversary. Each is based on a new construction of a conciliator, an object that guar-
antees termination and validity, but that only guarantees agreement with constant probability.
The first conciliator assumes unit-cost snapshots and achieves agreement among n processes
with probability 1 - in O(log
n + log(1/ )) steps for each process. The second uses ordinary
multi-writer registers, and achieves agreement with probability 1 - in O(log log n + log(1/ ))
steps. Combining these constructions with known results gives randomized consensus for ar-
bitrarily many possible input values using unit-cost snapshots in O(log
n) expected steps and
randomized consensus for up to O(log n log log n) possible input values using ordinary registers
in O(log log n) expected steps. The possibility of further improvement is considered.
Department of Computer Science, Yale University. Email: firstname.lastname@example.org. Supported in part by NSF