Rev Language Reference

getNumProcesses - Get the number of MPI processes

Returns the number of processes used by the current RevBayes session.

Usage

getNumProcesses()

Arguments

Return Type

Natural

Details

In an MPI-enabled build (i.e., `rb-mpi`, launched as `mpirun -np N ./rb-mpi`), the function returns `N` (i.e., the size of the `MPI_COMM_WORLD` communicator). In a non-MPI build, it always returns 1. The value is the number of MPI ranks, not necessarily the number of hardware CPU cores.

Example

# For `mpirun -np 16 ./rb-mpi`, this prints 16:
getNumProcesses()

# Record the process count for reproducibility bookkeeping
print("Running on " + getNumProcesses() + " process(es).")

# Guard-check the launch configuration
if (getNumProcesses() != 32) {
    stop("Expected 32 processes, got " + getNumProcesses() + ".")
}

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