Add pytools requirements to do single_valued

pyop2/types/set.py

@@ -1,8 +1,8 @@
 import ctypes
-import functools
 import numbers
 
 import numpy as np
+import pytools
 
 from pyop2 import (
     caching,
@@ -538,10 +538,7 @@ def __init__(self, sets):
             "All components of a MixedSet must have the same number of layers."
         # TODO: do all sets need the same communicator?
         self.comm = mpi.internal_comm(
-            functools.reduce(
-                lambda a, b: a or b,
-                map(lambda s: s if s is None else s.comm, sets)
-            ),
+            pytools.single_valued(s.comm for s in sets if s is not None),
             self
         )
         self._initialized = True

requirements-ext.txt

@@ -8,3 +8,4 @@ decorator<=4.4.2
 dataclasses
 cachetools
 packaging
+pytools

setup.py

@@ -89,6 +89,7 @@ def get_petsc_dir():
     'decorator',
     'mpi4py',
     'numpy>=1.6',
+    'pytools',
 ]
 
 version = sys.version_info[:2]