Communicate with other ranks and swap beta

Given a current log-likelihood, temperature and step-size, this decides whether to send or receive the same variables from a neighboring process and swap temperatures with them.

Usage

pbdMPI_swap_temperatures(i, B, LL, H, r, comm, cs)

Arguments

i

MCMC iteration

B

inverse temperature (parallel tempering)

LL

log-likelihood value of current point

H

algorithm's step size (often called epsilon in literature)

r

MPI rank

comm

MPI communicator

cs

MPI comm size

Details

Only one of the two communicating ranks is allowed to make the decision to swap, because a random variable is used to make this decision. Which rank will make this swap decision needs to be determined somehow. Currently we alternate this reposibility based on the current iteration i.