Parallel MODFLOW 6 Capabilities

[jdhughes-usgs]

Parallel capabilities are available in the current version of MODFLOW (6.4.2). Parallel functionality is part of the main code base and will be a core capability moving forward.

Although parallel functionality is part of the main code base it is considered alpha->beta functionality at this point. In the current develop branch on GitHub, GWF, GWT, and coupled GWF-GWT models can be run in parallel. As of 11/13/2023, parallelization of the MVR package is in progress.

Currently, the parallel version of MODFLOW is not included in the release distribution because we have not worked out the best way to distribute the parallel libraries (MPI and PETSc).

Instructions for compiling the parallel version of MODFLOW on MacOS and Linux is available at

https://github.com/MODFLOW-USGS/modflow6/blob/develop/PARALLEL.md

On Windows, the best solution we have so far is to use WSL. Instructions for compiling parallel MODFLOW on the Windows Subsystem for Linux (WSL) is available at

https://github.com/jdhughes-usgs/parallel-modflow6-class/blob/main/wsl_setup.md

Parallel capabilities are still new so not all options are fully supported. Some external users have been using the parallel version of MODFLOW, but we are only providing limited support currently because of the alpha->beta status of the functionality. However, we are interested in hearing about problems users run into with their models but don’t guarantee that we can fix an issue in the time frame users may need for actual production modeling.

We have also added model splitting functionality in FloPy to generate multiple models from a single model. The multi-model functionality in MODFLOW is how we are currently supporting parallel capabilities. An example of using the FloPy model splitter can be found at

https://flopy.readthedocs.io/en/latest/Notebooks/mf6_parallel_model_splitting_example.html

[wpbonelli]

Quick note: there is now a parallel nightly build for Windows. With flopy installed you can get it with get-modflow : --repo modflow6-nightly-build --ostag win64par. Non-system dlls are bundled, no dependency installations needed.

While we have tested the distribution in a few different Windows environments, there may still be rough edges. If you hit any troubles, please file an issue and tag it with the "parallel" and "nightly build" labels.