Use global maximum similarity distance in local adaptivity (#197)

* Use global maximum similarity distance in local adaptivity

* Add changelog entry

Author: IshaanDesai

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## latest
 
+- Use global maximum similarity distance in local adaptivity [#197](https://github.com/precice/micro-manager/pull/197)
 - Log adaptivity metrics at t=0 [#194](https://github.com/precice/micro-manager/pull/194)
 - Use `|` delimiter in CSV files of adaptivity metrics data [#193](https://github.com/precice/micro-manager/pull/193)
 - Add profiling sections for solving the micro simulations [commit](https://github.com/precice/micro-manager/commit/fa81f6a7e8f494a3e441fee7f70de5271ae8d83b)

micro_manager/adaptivity/local_adaptivity.py

@@ -5,6 +5,7 @@
 """
 import numpy as np
 from copy import deepcopy
+from mpi4py import MPI
 
 from .adaptivity import AdaptivityCalculator
 from ..micro_simulation import create_simulation_class
@@ -76,7 +77,12 @@ def compute_adaptivity(
 
         self._update_similarity_dists(dt, data_for_adaptivity)
 
-        self._max_similarity_dist = np.amax(self._similarity_dists)
+        self._local_max_similarity_dist = np.amax(self._similarity_dists)
+
+        # Gather maximum similarity distance from every rank, and use the global maximum distance
+        self._max_similarity_dist = self._comm_world.allreduce(
+            self._local_max_similarity_dist, op=MPI.MAX
+        )
 
         self._update_active_sims()