Optimize submesh_init for periodic systems
Description
Minor changes to submesh_init for the periodic case which give some performance improvements. This provides roughly 20% improvement in time for a reasonable test case.
The initialization of the submesh is now done using over OpenMP. This shows a speedup of roughly a factor of 3 for 8 OpenMP task.
A unit test is added to ease the testing of this.
Checklist
-
I have checked that my code follows the Octopus coding standards -
I have added tests for all the new features added in this request.
Edited by Nicolas Tancogne-Dejean