Configuration
There are multiple MPI implementations
- OpenMPI
- MPICH
- Intel MPI
- Microsoft MPI
- IBM Spectrum MPI
- MVAPICH
- Cray MPICH
- Fujitsu MPI
- HPE MPT/HMPT
julia> using MPI
julia> MPI.versioninfo()
MPIPreferences:
binary: MPICH_jll
abi: MPICH
Package versions
MPI.jl: 0.20.22
MPIPreferences.jl: 0.1.11
MPICH_jll: 4.3.0+1
Library information:
libmpi: /home/vchuravy/.julia/artifacts/05d8c79b270470018e9de8dd24ddb6d7954aff9d/lib/libmpi.so
libmpi dlpath: /home/vchuravy/.julia/artifacts/05d8c79b270470018e9de8dd24ddb6d7954aff9d/lib/libmpi.so
MPI version: 4.1.0
Library version:
MPICH Version: 4.3.0
MPICH Release date: Mon Feb 3 09:09:47 AM CST 2025
MPICH ABI: 17:0:5
MPICH Device: ch3:nemesis
MPICH configure: –build=x86_64-linux-musl –disable-dependency-tracking –disable-doc –enable-fast=ndebug,O3 –enable-static=no –host=x86_64-linux-gnu –prefix=/workspace/destdir –with-device=ch3 –with-hwloc=/workspace/destdir
MPICH CC: cc -DNDEBUG -DNVALGRIND -O3
MPICH CXX: c++ -DNDEBUG -DNVALGRIND -O3
MPICH F77: gfortran -O3
MPICH FC: gfortran -O3
MPICH features:
On Unix, MPI.jl will install and use MPICH through the MPICH_jll package.
MPIPreferences
To switch which MPI implementation MPI.jl uses you can use the package MPIPreferences.jl.
For more information see: https://juliaparallel.org/MPI.jl/stable/configuration/
When executing on a cluster you will likely need to configure MPI.jl to use the system provided MPI.
Installing mpiexecjl
julia> using MPI
julia> MPI.install_mpiexecjl()
By default, it will install to ~/.julia/bin, but you can also choose to install it somewhere else
As an example to install it in the current working directory.
julia> using MPI
julia> MPI.install_mpiexecjl(destdir=".")
After installing it, you can use it to start Julia.
mpiexecjl --project=/path/to/project -n 4 julia script.jl
# or
./mpiexecjl --project=/path/to/project -n 4 julia script.jl
Exercises
MPI.jl has a series of examples:
Diffusion
In exercise 2 we looked at a diffusion kernel. Instead of implementing this on the GPU you can also implement it with MPI.
Note
The “hard” part is the handling of the boundary-conditions and ghost cells. So focus on that in the beginning. How are you going to split the computational domain? Who needs to talk to whom?
