mark analysis.atomicdistances.AtomicDistances as not parallelizable

package/CHANGELOG

@@ -14,13 +14,14 @@ The rules for this file:
 
 
 -------------------------------------------------------------------------------
-??/??/?? IAlibay
+??/??/?? IAlibay, talagayev
 
  * 2.9.0
 
 Fixes
 
 Enhancements
+ * marked `analysis.atomicdistances.AtomicDistances` as not parallelizable (Issue #4662)
 
 Changes
 

package/MDAnalysis/analysis/atomicdistances.py

@@ -146,6 +146,7 @@ class AtomicDistances(AnalysisBase):
 
     .. versionadded:: 2.5.0
     """
+    _analysis_algorithm_is_parallelizable = False
 
     def __init__(self, ag1, ag2, pbc=True, **kwargs):
         # check ag1 and ag2 have the same number of atoms

testsuite/MDAnalysisTests/analysis/test_atomicdistances.py

@@ -134,3 +134,23 @@ def test_ad_pairwise_dist_pbc(self, ad_ag1, ad_ag2,
 
         # compare with expected values from dist()
         assert_allclose(actual, expected_pbc_dist)
+
+
+@pytest.mark.parametrize(
+    "classname,is_parallelizable",
+    [
+        (ad.AtomicDistances, False),
+    ]
+)
+def test_class_is_parallelizable(classname, is_parallelizable):
+    assert classname._analysis_algorithm_is_parallelizable == is_parallelizable
+
+
+@pytest.mark.parametrize(
+    "classname,backends",
+    [
+        (ad.AtomicDistances,  ('serial',)),
+    ]
+)
+def test_supported_backends(classname, backends):
+    assert classname.get_supported_backends() == backends