This is the repository for the brer Python module, a C++ extension that provides the GROMACS MD plugin for use with https://github.com/kassonlab/run_brer

To build and install the GROMACS MD plugin, first install GROMACS and gmxapi as described for run_brer.

NOTE: For several recent versions of GROMACS, the "legacy API" needs to be enabled when GROMACS is configured. The GMX_INSTALL_LEGACY_API GROMACS CMake variable is not documented. Example:

cmake /path/to/gromacs/sources -DGMX_INSTALL_LEGACY_API=ON -DGMX_THREAD_MPI=ON

You will also need a reasonably recent version of cmake. cmake is a command line tool that is often already available, but you can be sure of getting a recent version by activating your python environment and just doing pip install cmake.

This is a simple C++ extension module that can be attached to a GROMACS molecular dynamics (MD) simulator through the gmxapi Python interface. The module is necessary for research workflows based on the run_brer Python package. See https://github.com/kassonlab/run_brer for more information.

Once you have identified your compilers and Python installation (or virtual environment), use cmake to configure, build, and install. Refer to cmake documentation for usage and options. Note that GROMACS installs a CMake hints (or toolchain) file to help you specify the correct compiler toolchain to cmake. See GROMACS release notes.

See https://github.com/kassonlab/brer_plugin/releases for tagged releases. For development code, clone the repository and use the default branch.

This example assumes

• I have already activated a Python (virtual) environment in which gmxapi is installed, and
• A GROMACS installation is available on my $PATH (such as by "sourcing" the GMXRC or calling module load gromacs in an HPC environment)
• I am using GROMACS 2022, which provides a CMake "hints" file, which I will (optionally) provide when calling cmake.

To confirm:

• gmx --version (or gmx_mpi, gmx_d, etc. for other configurations) should ...
• which python should show a path to a python virtual environment for Python 3.7 or later.
• pip list should include gmxapi

To download, build, and install the brer Python module:

git clone https://github.com/kassonlab/brer_plugin.git
cd brer_plugin
mkdir build
cd build
cmake ..
make
make install

In the example above, the -C argument is usually optional. (See below.)

One of the most common installation problems is related to incompatible compiler toolchains between GROMACS, gmxapi, and the plugin module.

• CMake may warn "You are compiling with a different C++ compiler from the one that was used to compile GROMACS."
• When you import the brer module, you may get an error like the following. ImportError: dlopen(...): symbol not found in flat namespace '__ZN6gmxapi10MDWorkSpec9addModuleENSt3__110shared_ptrINS_8MDModuleEEE'

You can either set the CMAKE_CXX_COMPILER, explicitly, or you can use the GROMACS-installed CMake hints file.

You will have to rebuild and reinstall the brer module. First, remove the CMakeCache.txt file from the build directory.

For GROMACS 2022 and newer, you would invoke cmake with something like the following. (The exact path will depend on your installation.)

cmake .. -C /path/to/gromacs_installation/share/cmake/gromacs/gromacs-hints.cmake

For GROMACS 2021 and older,

cmake .. -DCMAKE_TOOLCHAIN_FILE=/path/to/gromacs_installation/share/cmake/gromacs/gromacs-toolchain.cmake

See GROMACS release notes.

Hays, J. M., Cafiso, D. S., & Kasson, P. M. Hybrid Refinement of Heterogeneous Conformational Ensembles using Spectroscopic Data. The Journal of Physical Chemistry Letters 2019. DOI: 10.1021/acs.jpclett.9b01407

Irrgang, M. E., Hays, J. M., & Kasson, P. M. gmxapi: a high-level interface for advanced control and extension of molecular dynamics simulations. Bioinformatics 2018. DOI: 10.1093/bioinformatics/bty484