GitLab

* updated requirement list
* added optional package list
* reworked manual installation
* warning not to call 'make install' #16
* notes on parallel setup requirements #24

(cherry picked from commit efc64606)

[ci skip] Never use easy_install if you can avoid it. The correct way to install pip is with the official script.

Small tweaks to Dockerfile

Updated documentation build instructions (Sphinx and Breathe are installed by CMake during configure and probably not found during the first build)

  * use dunecontrol for all commands instead of fiddling with CMake in the build directory
  * some third-party version requirements seemed too strict
  * removed optional packages (METIS, parMETIS, Breathe, Sphinx)
  * removed Python VTK as suggested package. This is nearly impossible to build from source. People can use our VTK readers for post-processing (coming soon).
  * added section on cleaning build (delete build-cmake folder)
  * stressed that dunecontrol make install is optional (may not be desired by the user due to permissions / personal preference)

Added setup.py file for doc folder, so Sphinx and Breathe are installed at configure time now

Removed third-party Python packages from install_requires in setup.py files

Compiler flags are handled by CMake now. Default build type is Release, which automatically adds optimization flags, and equivalently for the Debug build type (cf. e.g. CMAKE_CXX_FLAGS_RELEASE).