Prerequisites for the TRIQS Compilation on Mac OS X

Disclaimer

We here provide instructions on how to install the dependencies of TRIQS on Mac OS X in order to be able to compile TRIQS from source.

The installation of the scientific libraries that TRIQS depends upon (mpi, hdf5, boost, fftw, ipython, ….) is not as simple as in e.g. Debian/Ubuntu, where they are packaged with the distribution itself (i.e. “part of the system”).

This general problem of scientific computing on OS X is clearly illustrated by the large number of third-party attempts to provide “easy” installation of scientific libraries, such as brew, macports, fink, or the Enthought Python distribution.

In our experience, none of these solutions is perfect, nor complete or stable: they are still very far from the quality and stability of a Linux distribution like Debian/Ubuntu. It almost works, but at the end, there are some issues, sometimes severe, in the way scientific librairies are installed.

Moreover, because there is no notion of “distribution”, the versions of the libraries are always changing e.g. in brew. As a result, the installation instructions may work on one day, and suddenly stop to work the day after.

While this has a priori nothing to do with TRIQS and its applications, it clearly impacts its installation and usage. We are looking for a more robust solution to this OS X installation mess; help welcome !.

Installation of the dependencies

The following installation instructions are for Mac OS X 10.14.3 (Mojave) or later and should be executed on the terminal. They may work (possibly with some modifications) for earlier versions of OS X.

Install the XCode Command Line Tools:
```
xcode-select --install
```
and make sure the latest XCode SDK is set in your environment:
```
export SDKROOT=$(xcrun --show-sdk-path)
```
Install homebrew.

If you already had homebrew installed consider running brew doctor to resolve potential conflicts before continuing. It can further be useful to remove duplicate packages with the command brew cleanup.

Install the required dependencies using homebrew:

brew install cmake
brew install boost
brew install hdf5
brew install gmp
brew install fftw
brew install open-mpi
brew install openblas
brew install python

Create a Python virtual environment and make sure it is activated.

Install the required python packages into your virtual environment:

pip install --user --upgrade matplotlib
pip install --user --upgrade mako
pip install --user --upgrade numpy
pip install --user --upgrade scipy
pip install --user --upgrade mpi4py

We recommend using the clang compiler by default. The following command will install llvm together with the most recent clang compiler
```
brew install llvm
```

As a next step we make sure the llvm installation is available in your environment and we set clang as the default compiler

export PATH=$(brew --prefix)/opt/llvm/bin:$PATH
export LIBRARY_PATH=$(brew --prefix)/opt/llvm/lib:$LIBRARY_PATH
export CC=$(brew --prefix)/opt/llvm/bin/clang
export CXX=$(brew --prefix)/opt/llvm/bin/clang++

To make this choice permanent, add these lines to your $HOME/.zshrc.

You should now be set to compile TRIQS from source.