nekRS

nekRS is an open-source Navier Stokes solver based on the spectral element method targeting modern processors and accelerators including multi/many-core CPU and GPU platforms . The code uses the CEED software products OCCA and libParanumal.

Capabilities:

Incompressible and low Mach-number Navier-Stokes + scalar transport
Conjugate fluid-solid heat transfer
CG-SEM using hexaheadral elements
2nd order semi-implicit time integration + OIFS
Dealiasing and high-pass filter relaxation term stabilization
MPI+X hybrid parallelism supporting serial (CPU), CUDA, OPENCL and HIP
Interface to Nek5000

Note, the code is an early prototype so it's very likely that you run into undiscovered issues. Moreover it's evolving quickly so things might change from one version to another without being backward compatible.

Build Instructions

Requirements:

POSIX compilant OS
GNU Fortran and C Compiler version 6.2 or later
MPI-3.1 or later
CMake version 3.1 or later
Login shell bash or zsh

Download the latest release tarball

wget https://github.com/Nek5000/nekRS/releases/download/v19.0/nekRS-v19.0.tar.gz 
tar -zxf nekRS-v19.0.tar.gz

or clone our GitHub repository:

git clone https://github.com/Nek5000/nekRS.git

To install the code just run:

cd nekRS
./makenrs

Please edit the make script to customize build settings.

Setting the Enviroment

Assuming you run bash and your install directory is $HOME/.local/nekrs, add the following line to your $HOME/.bash_profile:

export NEKRS_HOME=$HOME/.local/nekrs
PATH=${NEKRS_HOME}/bin:${PATH}

then type source $HOME/.bash_profile in the current terminal window.

Run Example

cd $NEKRS_HOME/examples/ethier
nrsmpi ethier 2 # run on two MPI ranks

Current Limitations

Kernels are optimized primarily for NVIDIA GPUs

Contributing

Our project is hosted on GitHub and everbody is welcome to become a part of it. If you are planning a large contribution, we encourage you to discuss the concept here on GitHub and interact with us frequently to ensure that your effort is well-directed.

Troubleshooting

If you run into problems compiling, installing, or running nekRS, please send a message to the User's Group mailing list. Please sign up to post your questions, concerns or suggestions.

Reporting Bugs

nekRS is hosted on GitHub and all bugs are reported and tracked through the Issues feature on GitHub. If you are having trouble installing the code or getting your model to run properly, you should first send a message to the User's Group mailing list.

License

nekRS is released under the BSD 3-clause license (see LICENSE file). All new contributions must be made under the BSD 3-clause license.

Acknowledgment

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.

LMNS3d/nekRS