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

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

Pre-requisities:

• A recent Julia version: v1.9.0 as of May 2023 from julialang.org/downloads

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.

To use a system provided ADIOS2 library, see here. It just sets the environment variable JULIA_ADIOS2_PATH and build ADIOS2.jl in Julia.

Note: GrayScott.jl requires the main development version.

```
$ julia
julia> ]
GrayScott.jl> add ADIOS2#main  
```

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": 1000,
    "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
```

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

Please cite the following paper associated with the code, if you find it useful:

@inproceedings{10.1145/3624062.3624278,
author = {Godoy, William F. and Valero-Lara, Pedro and Anderson, Caira and Lee, Katrina W. and Gainaru, Ana and Ferreira Da Silva, Rafael and Vetter, Jeffrey S.},
title = {Julia as a Unifying End-to-End Workflow Language on the Frontier Exascale System},
year = {2023},
isbn = {9798400707858},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/3624062.3624278},
doi = {10.1145/3624062.3624278},
booktitle = {Proceedings of the SC '23 Workshops of The International Conference on High Performance Computing, Network, Storage, and Analysis},
pages = {1989–1999},
numpages = {11},
keywords = {data analysis, exascale, Frontier supercomputer, Jupyter notebooks, end-to-end workflows, High-Performance Computing, Julia, HPC},
location = {Denver, CO, USA},
series = {SC-W '23}
}

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 work is funded, in part, by Bluestone, a X-Stack project in the DOE Advanced Scientific Computing Office with program manager Hal Finkel.

This research used resources of the Oak Ridge Leadership Computing Facility and the Experimental Computing Laboratory (ExCL) 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 all the Julia community members, packages developers and maintainers for their great work.