Maple maq_query returns empty set on some instances

[hnisonoff]

Subject of the issue

For some MRF instances MPLP returns the empty set. The best_assignment is also empty.

Your environment

• pgmpy version 0.1.24 (also tried 0.1.22, 0.1.19)
• Python version 3.10.12
• Operating System Linux

Steps to reproduce

Tell us how to reproduce this issue. Please provide a minimal reproducible code of
the issue you are facing if possible.
Not sure if this is expected behavior or not. If not, I can try to find a minimal example?

Expected behaviour

Tell us what should happen

Actual behaviour

Tell us what happens instead

[hnisonoff]

Update I was able to fix this by adding a tiny constant (1e-6) to all of the discrete factors. Not sure why this is necessary though.