using pbc_diff now in tetrahedral_order parameter calculation, since reference positions will not be periodic images in the default use case

Reviewed-on: #2

src/mdevaluate/checksum.py

@@ -73,7 +73,9 @@ def checksum(*args, csum=None):
         elif isinstance(arg, FunctionType):
             csum.update(strip_comments(inspect.getsource(arg)).encode())
             c = inspect.getclosurevars(arg)
-            for v in {**c.nonlocals, **c.globals}.values():
+            merged = {**c.nonlocals, **c.globals}
+            for key in sorted(merged):  # deterministic ordering
+                v = merged[key]
                 if v is not arg:
                     checksum(v, csum=csum)
         elif isinstance(arg, functools.partial):

src/mdevaluate/distribution.py

@@ -182,10 +182,10 @@ def tetrahedral_order(
     )
 
     # Connection vectors
-    neighbors_1 -= atoms
-    neighbors_2 -= atoms
-    neighbors_3 -= atoms
-    neighbors_4 -= atoms
+    neighbors_1 = pbc_diff(neighbors_1, atoms, box=atoms.box)
+    neighbors_2 = pbc_diff(neighbors_2, atoms, box=atoms.box)
+    neighbors_3 = pbc_diff(neighbors_3, atoms, box=atoms.box)
+    neighbors_4 = pbc_diff(neighbors_4, atoms, box=atoms.box)
 
     # Normed Connection vectors
     neighbors_1 /= np.linalg.norm(neighbors_1, axis=-1).reshape(-1, 1)