GrayScott.jl

ADIOS2-Examples GrayScott.jl

Julia version of the gray-scott C++ and Python example.

This is a 3D 7-point stencil code to simulate the following Gray-Scott reaction diffusion model:

u_t = Du * (u_xx + u_yy + u_zz) - u * v^2 + F * (1 - u) + noise * randn(-1,1)
v_t = Dv * (v_xx + v_yy + v_zz) + u * v^2 - (F + k) * v

This version contains:

• CPU threaded solver using Julia's [multithreading]](https://docs.julialang.org/en/v1/manual/multi-threading/)
• GPU solvers using CUDA.jl, AMDGPU.jl
• Parallel I/O using the ADIOS2.jl Julia bindings to ADIOS2
• Message passing interface (MPI) using MPI.jl Julia bindings to MPI
• Easily switch between float- (Float32) and double- (Float64) precision in the configuration file

How to run

Currently only the simulation part is ported from C++, the data analysis is work-in-progress.

Pre-requisities:

• A recent Julia version: v1.8.5 or v1.9.0-beta3 as of January 2023 from julialang.org/downloads

Run locally

1. Set up dependencies

From the GrayScott.jl directory instantiate and use MPI artifact jll (preferred method). To use a system provided MPI, see here

$ julia --project

Julia REPL

julia> ]  

(GrayScott.jl)> instantiate
...
(GrayScott.jl)> <-
julia> using MPIPreferences
julia> MPIPreferences.use_jll_binary()
julia> exit()

Julia manages its own packages using Pkg.jl, the above would create platform-specific LocalPreferences.toml and Manifest.toml files.

2. Set up the examples/settings-files.json configuration file

{
    "L": 64,
    "Du": 0.2,
    "Dv": 0.1,
    "F": 0.02,
    "k": 0.048,
    "dt": 1.0,
    "plotgap": 10,
    "steps": 10000,
    "noise": 0.1,
    "output": "gs-julia-1MPI-64L-F32.bp",
    "checkpoint": false,
    "checkpoint_freq": 700,
    "checkpoint_output": "ckpt.bp",
    "restart": false,
    "restart_input": "ckpt.bp",
    "adios_config": "adios2.xml",
    "adios_span": false,
    "adios_memory_selection": false,
    "mesh_type": "image",
    "precision": "Float32",
    "backend": "CPU"
}

The file is nearly identical to the C++ original example. Not all options are currently supported, but two Julia-only options are added:

- "precision": either Float32 or Float64 in the array simulation (including GPUs)
- "backend": "CPU", "CUDA" or "AMDGPU"

3. Running the simulation

• CPU threads: launch julia assigning a number of threads (e.g. -t 8):

  $ julia --project -t 8 gray-scott.jl examples/settings-files.json
  

• CUDA/AMDGPU: set the "backend" option in examples/settings-files.json to either "CUDA" or "AMDGPU"

  $ julia --project gray-scott.jl examples/settings-files.json
  

This would generate an adios2 file from the output entry in the configuration file (e.g. gs-julia-1MPI-64L-F32.bp) that can be visualized with ParaView with either the VTX or the FIDES readers. Important: the AMDGPU.jl implementation of randn is currently work in progress. See related issue here

4. Running on OLCF Summit and Crusher systems The code was tested on the Oak Ridge National Laboratory Leadership Computing Facilities (OLCF): Summit and Crusher. Both are used testing a recent version of Julia v1.9.0-beta3 and a JULIA_DEPOT_PATH is required to install packages and artifacts. DO NOT USE your home directory. We are providing configuration scripts in scripts/config_XXX.sh showing the plumming required for these systems. They need to be executed only once per session from the login nodes.

To reuse these file the first 3 entries must be modified and run on login-nodes and the PATH poiting at a downloaded Julia binary for the corresponding PowerPC (Summit) and x86-64 (Crusher) architectures. Only "CPU" and "CUDA" backends are supported on Summit, while "CPU" and "AMDGPU" backends are supported on Crusher.

```
# Replace these 3 entries
PROJ_DIR=/gpfs/alpine/proj-shared/csc383
export JULIA_DEPOT_PATH=$PROJ_DIR/etc/summit/julia_depot
GS_DIR=$PROJ_DIR/wgodoy/ADIOS2-Examples/source/julia/GrayScott.jl
...
# and the path 
export PATH=$PROJ_DIR/opt/summit/julia-1.9.0-beta3/bin:$PATH
```

To-do list

1. Add support including random number on device kernel code on AMDGPU.jl
2. Set the domain size L in the configuration file as a multiple of 6 for Summit, and a multiple of 4 on Crusher
3. Add data analysis: PDF for u and v and Julia 2D plotting capabilities: Plots.jl, Makie.jl
4. Add interactive computing with Pluto.jl notebooks

Acknowledgements

This research was supported by the Exascale Computing Project (17-SC-20-SC), a joint project of the U.S. Department of Energy’s Office of Science and National Nuclear Security Administration, responsible for delivering a capable exascale ecosystem, including software, applications, and hardware technology, to support the nation’s exascale computing imperative.

This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.

Thanks to the Exascale Computing Project PROTEAS-TUNE and ADIOS subprojects, and the ASCR Bluestone. Thanks to all the Julia community members, packages developers and maintainers for their great work.