Testing Melissa within Nix
Overview
The .nix/default.nix file provides a Nix shell or build environment for development. This is the quickest way to test Melissa Study locally.
Note: These Nix files do not provide any GPU support.
Installation and Development Setup
Nix installs Melissa using the current source directory, meaning the entry points for Melissa binaries such as melissa-launcher, melissa-server, etc., will point to the Melissa modules inside the /nix/store.
However, as developers, we prefer to have Melissa installed in an editable mode, similar to pip install -e .. This is not possible within /nix/store.
Workaround
To enable an editable installation, we update the PYTHONPATH to point to a desired source directory (EDITABLE_SRC), where we develop the Melissa module. This allows us to access the desired source directory directly.
Note: If you modify the api/ folder, which is not installed via pip install but rather through CMake, simply re-entering the shell will automatically update melissa_api.
Running Melissa
To enter a nix-shell with Melissa installed, run:
# from melissa/
nix-shell .nix/default.nix
That’s it! You are now in a nix-shell environment with Melissa installed.
Running the Heat-PDE Example
Step 1: Build the Executables
Run the following commands to build the executables:
cmake -S examples/heat-pde/executables -B examples/heat-pde/executables/build
make -C examples/heat-pde/executables/build
Step 2: Launch Melissa
Fix the paths in the config file, then run:
melissa-launcher --config examples/heat-pde-dl/config_mpi.json