Compiling CREST on macOS with M-series Chips

CREST (Conformer-Rotamer Ensemble Sampling Tool) is a program for exploring molecular conformations. Developed by the Grimme group at the University of Bonn, it automates the search for low-energy conformers and rotamers, which is particularly useful for flexible molecules that can adopt many configurations.^{1 2}

The official CREST documentation provides clear installation instructions, but following them on a Mac with an M-series chip leads to problems. By default, cmake links against Apple’s Accelerate framework. On Arm-based Macs (M1, M2, etc.), this either fails or produces binaries that segfault at runtime. The solution is to compile against openblas and lapack instead of Accelerate.

# Building against openblas and lapack

Let’s start by getting the source code. Download the latest release of CREST following the instructions on the official documentation . Be sure to clone the repository and update the necessary submodules. This can be done by running git submodule update --init after git clone, as explained here (credit to Jingdan Chen for pointing this out).

Now we need to get the right libraries: cmake, gcc, openblas and lapack. Doing this with Homebrew is straightforward:

1brew install gcc cmake openblas lapack

Next, we need to tell cmake where to find these libraries. This is where the official docs don’t work when applied on a Mac. CREST’s documentation suggests doing this with:

1export FC=gfortran CC=gcc

On a Mac with an Arm chip, this resolves to macOS’s default compilers, which will link against Accelerate. Point to the Homebrew-installed compilers instead:

1export FC=gfortran-14 CC=gcc-14

Now tell cmake where to find the lapack and openblas libraries you installed with Homebrew. Without this, cmake falls back to the macOS system libraries. Look for the path where Homebrew installed them, and run:

1cmake -DCMAKE_PREFIX_PATH="/opt/homebrew/opt/lapack;/opt/homebrew/opt/openblas" -B _build

With everything configured correctly, you can finish the compilation:

1make -C _build

This builds CREST in the _build directory, linked against openblas and lapack.

# Troubleshooting

If the build fails, check these first:

• Verify which version of gcc you have installed. Typing gfortran-14 when you have version 13 will produce confusing errors. Run brew info gcc to confirm.
• Confirm the paths to lapack and openblas match your Homebrew configuration. They may differ depending on how Homebrew is set up on your system.
• If you see errors about missing dependencies, make sure all submodules are initialized (git submodule update --init).

The entire problem comes down to which math libraries cmake links against. The error messages do not make this obvious, and I spent a couple of hours on it before finding the fix. Hopefully this saves you the same trouble.