Address comments by @smharper on openmc-dev#892.

openmc/mixin.py

@@ -25,6 +25,10 @@ def __ne__(self, other):
         return not self.__eq__(other)
 
 
+class IDWarning(UserWarning):
+    pass
+
+
 class IDManagerMixin(object):
     """A Class which automatically manages unique IDs.
 
@@ -52,8 +56,9 @@ def id(self, uid):
             cv.check_type('{} ID'.format(name), uid, Integral)
             cv.check_greater_than('{} ID'.format(name), uid, 0, equality=True)
             if uid in cls.used_ids:
-                warn('Another {} instance already exists with id={}.'.format(
-                    name, uid))
+                msg = 'Another {} instance already exists with id={}.'.format(
+                    name, uid)
+                warn(msg, IDWarning)
             else:
                 cls.used_ids.add(uid)
             self._id = uid
@@ -74,8 +79,8 @@ def reserve_ids(ids, cls=None):
     ids : iterable of int
         IDs to reserve
     cls : type or None
-        Class for which IDs should be reserved. If None, all classes that have
-        auto-generated IDs will be used.
+        Class for which IDs should be reserved (e.g., :class:`openmc.Cell`). If
+        None, all classes that have auto-generated IDs will be used.
 
     """
     if cls is None:

openmc/statepoint.py

@@ -358,7 +358,7 @@ def tallies(self):
 
             # Ignore warnings about duplicate IDs
             with warnings.catch_warnings():
-                warnings.simplefilter('ignore', UserWarning)
+                warnings.simplefilter('ignore', openmc.IDWarning)
 
                 # Iterate over all tallies
                 for tally_id in tally_ids:

openmc/summary.py

@@ -52,7 +52,7 @@ def __init__(self, filename):
 
         self._read_nuclides()
         with warnings.catch_warnings():
-            warnings.simplefilter("ignore", UserWarning)
+            warnings.simplefilter("ignore", openmc.IDWarning)
             self._read_geometry()
 
     @property

openmc/volume.py

@@ -223,7 +223,7 @@ def from_hdf5(cls, filename):
         # Instantiate some throw-away domains that are used by the constructor
         # to assign IDs
         with warnings.catch_warnings():
-            warnings.simplefilter('ignore', UserWarning)
+            warnings.simplefilter('ignore', openmc.IDWarning)
             if domain_type == 'cell':
                 domains = [openmc.Cell(uid) for uid in ids]
             elif domain_type == 'material':

src/physics.F90

@@ -818,7 +818,6 @@ subroutine sample_target_velocity(nuc, v_target, E, uvw, v_neut, wgt, xs_eff, kT
     real(8) :: xs_low  ! 0K xs at lowest practical relative energy
     real(8) :: xs_up   ! 0K xs at highest practical relative energy
     real(8) :: m       ! slope for interpolation
-    real(8) :: xi      ! pseudorandom number on [0,1)
     real(8) :: R       ! rejection criterion for DBRC / target speed
     real(8) :: cdf_low ! xs cdf at lowest practical relative energy
     real(8) :: cdf_up  ! xs cdf at highest practical relative energy