home.md

@@ -1701,6 +1701,54 @@ To make your R program to run parallel and more efficient, we have installed for
 Loading one of these libraires does **not** make your program to run parallel.
 For that, you have to adapt your R program.
 
+**Example**
+
+hello.R
+```
+library(Rmpi)
+
+id <- mpi.comm.rank(comm = 0)
+np <- mpi.comm.size(comm = 0)
+hostname <- mpi.get.processor.name()
+
+msg <- sprintf("Hello world from process %03d of %03d, on host %s\n", id, np, hostname)
+cat(msg)
+
+mpi.barrier(comm = 0)
+mpi.finalize()
+```
+
+run-rpmi.slurm
+```
+#!/bin/bash
+
+#SBATCH --job-name=hello_parallel       # Job name
+#SBATCH --output=slurm-rmpi.out         # Output file name
+#SBATCH --error=slurm-rmpi.err          # Error file name
+#SBATCH --partition=short               # Partition
+#SBATCH --time=00:05:00                 # Time limit
+#SBATCH --nodes=2                       # Number of nodes
+#SBATCH --ntasks-per-node=4             # MPI processes per node
+
+module purge
+module add statistical/R/4.0.0/gcc.8.3.1
+module add library/mpi/openmpi/4.0.3/gcc-8.3.1
+
+mpirun Rscript hello.R
+```
+
+```
+[username@res-hpc-lo01 R]$ cat slurm-rmpi.out 
+Hello world from process 000 of 008, on host res-hpc-gpu01
+Hello world from process 001 of 008, on host res-hpc-gpu01
+Hello world from process 002 of 008, on host res-hpc-gpu01
+Hello world from process 003 of 008, on host res-hpc-gpu01
+Hello world from process 004 of 008, on host res-hpc-gpu02
+Hello world from process 005 of 008, on host res-hpc-gpu02
+Hello world from process 006 of 008, on host res-hpc-gpu02
+Hello world from process 007 of 008, on host res-hpc-gpu02
+```
+
 We recommend to have a look at the following web pages:
 
 [High-Performance and Parallel Computing with R](https://cran.r-project.org/web/views/HighPerformanceComputing.html)