A simple asynchronous replica-exchange implementation

We discuss the possibility of implementing asynchronous replica-exchange (or parallel tempering) molecular dynamics. In our scheme, the exchange attempts are driven by asynchronous messages sent by one of the computing nodes, so that different replicas are allowed to perform a different number of time-steps between subsequent attempts. The implementation is simple and based on the message-passing interface (MPI). We illustrate the advantages of our scheme with respect to the standard synchronous algorithm and we benchmark it for a model Lennard-Jones liquid on an IBM-LS21 blade center cluster.