Listed below are common problems found when installing CLASS-PT and their resolutions.
We have found that the OpenBLAS library conflicts with the library Intel MKL which is used in numpy version 1.16 and higher on some machines. This incompatibility makes classy crash with “segmentation fault” even though the code can be executed with a .ini file without any errors. If this is the case on the user’s computer, an easy fix is to use a numpy version below 1.16. We plan to resolve this issue in future releases.
When using some newer versions of Python, segmentation faults can occur when interfacing CLASS-PT with MontePython, even though there are no issues when classy is run on its own. This is related to the above problem, a sourced by an internal conflict of classy and the latest scipy modules. This can be straightforwardly fixed by ensuring that classy is imported before scipy in MontePython. Practically, the line from classy import Class should be inserted at the top of the montepython/Montepython.py script.