another check

docs/changelog.md

@@ -19,7 +19,7 @@
 -->
 
 
-## v0.3.0 / 2024-07-19
+## v0.3.0 / 2024-07-21
 
 #### Breaking Changes
 

qcmanybody/core.py

@@ -103,6 +103,14 @@ def __init__(
         assert self.mc_levels == set(self.nbodies_per_mc_level.keys())  # remove after some downstream testing
         self.mc_levels = self.nbodies_per_mc_level.keys()
 
+        for mc, nbs in self.nbodies_per_mc_level.items():
+            if nbs and ((nbs[-1] - nbs[0]) != len(nbs) - 1):
+                raise ValueError(
+                    f"QCManyBody: N-Body levels must be contiguous within a model chemistry spec ({mc}: {nbs}). Use an alternate spec name to accomplish this input."
+                )
+                # TODO - test and reenable if appropriate. my guess is that noncontig nb is fine on the core computing side,
+                #   but trouble for computer and nbodies_per_mc_level inverting and indexing. Safer to deflect for now since input tweak allows the calc.
+
         # Supersystem is always at the end
         if "supersystem" in levels:
             ss_mc = levels["supersystem"]

qcmanybody/tests/test_core_auxiliary.py

@@ -31,6 +31,13 @@ def test_noncontiguous_fragments_evaded():
     assert "QCManyBody: non-contiguous fragments could be implemented but aren't at present" in str(e.value)
 
 
+def test_noncontiguous_nbody_levels_same_mc(he_tetramer):
+    with pytest.raises(ValueError) as e:
+        ManyBodyCalculator(he_tetramer, ["cp"], {2: "mp2", 1: "mp2", 4: "mp2", 3: "ccsd"}, True, False, None)
+
+    assert "QCManyBody: N-Body levels must be contiguous within a model chemistry spec" in str(e.value)
+
+
 @pytest.mark.parametrize("mbe_keywords,ref_count,ref_text", [
     pytest.param(
         {"bsse_type": ["nocp", "cp", "vmfc"]},