Compiling ROOT

Compiling ROOT without nix on macOS

For of our repos have a nix flake with ROOT in it, but if you want to have ROOT installed in your mac with the HistFactory pacthes, you can follow the instructions below.

If you alread have a ROOT installation, you should delete it first as it often collides with new ones (rm -rf root_build root_install).

git clone --branch histfactory_patch https://github.com/umd-lhcb/root.git
mkdir root_build root_install && cd root_build
cmake -DCMAKE_INSTALL_PREFIX=../root_install/ -Dsqlite=OFF -Dmysql=OFF -Dx11=ON  -Droofit=ON -Dmt=ON -Dminuit2=ON -Dccache=ON -Dlibcxx=ON -Drpath=ON -DCMAKE_CXX_STANDARD=17 -Droot7=OFF ../root 
cmake --build . -- install -j6

Note: For -jN, N should be your number of CPU cores (or fewer).

Using pyroot in macOS

Starting in ROOT 6.22, the compilation is done for both python 2 and 3. Several of our scripts, which require python 3, rely on the python and pip commands, which in macOS are by default bound to python 2. This can be changed installing the python version that you want and adding the appropriate soft links. For instance,

brew install python
ln -s ../Cellar/python@3.9/3.9.6/bin/python3 /usr/local/bin/python
ln -s ../Cellar/python@3.9/3.9.6/bin/pip3 /usr/local/bin/pip