Use strings in representation of particle filter

openmc/filter.py

@@ -32,7 +32,8 @@ _CURRENT_NAMES = (
     'z-min out', 'z-min in', 'z-max out', 'z-max in'
 )
 
-_PARTICLE_IDS = {'neutron': 1, 'photon': 2, 'electron': 3, 'positron': 4}
+_PARTICLES = {'neutron', 'photon', 'electron', 'positron'}
+
 
 class FilterMeta(ABCMeta):
     def __new__(cls, name, bases, namespace, **kwargs):
@@ -547,10 +548,9 @@ class ParticleFilter(Filter):
 
     Parameters
     ----------
-    bins : str, int, or iterable of Integral
-        The Particles to tally. Either str with particle type or their
-        ID numbers can be used ('neutron' = 1, 'photon' = 2, 'electron' = 3,
-        'positron' = 4).
+    bins : str, or iterable of str
+        The particles to tally represented as strings ('neutron', 'photon',
+        'electron', 'positron').
     filter_id : int
         Unique identifier for the filter
 
@@ -571,16 +571,26 @@ class ParticleFilter(Filter):
     @bins.setter
     def bins(self, bins):
         bins = np.atleast_1d(bins)
-        cv.check_iterable_type('filter bins', bins, (Integral, str))
+        cv.check_iterable_type('filter bins', bins, str)
         for edge in bins:
-            if isinstance(edge, Integral):
-                cv.check_value('filter bin', edge, _PARTICLE_IDS.values())
-            else:
-                cv.check_value('filter bin', edge, _PARTICLE_IDS.keys())
-        bins = np.atleast_1d([b if isinstance(b, Integral) else _PARTICLE_IDS[b]
-                              for b in bins])
+            cv.check_value('filter bin', edge, _PARTICLES)
         self._bins = bins
 
+    @classmethod
+    def from_hdf5(cls, group, **kwargs):
+        if group['type'][()].decode() != cls.short_name.lower():
+            raise ValueError("Expected HDF5 data for filter type '"
+                             + cls.short_name.lower() + "' but got '"
+                             + group['type'][()].decode() + " instead")
+
+        if 'meshes' not in kwargs:
+            raise ValueError(cls.__name__ + " requires a 'meshes' keyword "
+                             "argument.")
+
+        particles = [b.decode() for b in group['bins'][()]]
+        filter_id = int(group.name.split('/')[-1].lstrip('filter '))
+        return cls(particles, filter_id=filter_id)
+
 
 class MeshFilter(Filter):
     """Bins tally event locations onto a regular, rectangular mesh.

src/tallies/filter_particle.cpp

@@ -7,12 +7,20 @@ namespace openmc {
 void
 ParticleFilter::from_xml(pugi::xml_node node)
 {
-  auto particles = get_node_array<int>(node, "bins");
+  auto particles = get_node_array<std::string>(node, "bins");
 
   // Convert to vector of Particle::Type
   std::vector<Particle::Type> types;
   for (auto& p : particles) {
-    types.push_back(static_cast<Particle::Type>(p - 1));
+    if (p == "neutron") {
+      types.push_back(Particle::Type::neutron);
+    } else if (p == "photon") {
+      types.push_back(Particle::Type::photon);
+    } else if (p == "electron") {
+      types.push_back(Particle::Type::electron);
+    } else if (p == "positron") {
+      types.push_back(Particle::Type::positron);
+    }
   }
   this->set_particles(types);
 }
@@ -47,9 +55,22 @@ void
 ParticleFilter::to_statepoint(hid_t filter_group) const
 {
   Filter::to_statepoint(filter_group);
-  std::vector<int> particles;
+  std::vector<std::string> particles;
   for (auto p : particles_) {
-    particles.push_back(static_cast<int>(p) + 1);
+    switch (p) {
+    case Particle::Type::neutron:
+      particles.push_back("neutron");
+      break;
+    case Particle::Type::photon:
+      particles.push_back("photon");
+      break;
+    case Particle::Type::electron:
+      particles.push_back("electron");
+      break;
+    case Particle::Type::positron:
+      particles.push_back("positron");
+      break;
+    }
   }
   write_dataset(filter_group, "bins", particles);
 }

tests/regression_tests/photon_production/inputs_true.dat

@@ -41,7 +41,7 @@
     <bins>9</bins>
   </filter>
   <filter id="2" type="particle">
-    <bins>2</bins>
+    <bins>photon</bins>
   </filter>
   <tally id="1">
     <filters>1 2</filters>

tests/regression_tests/photon_source/inputs_true.dat

@@ -36,7 +36,7 @@
 <?xml version='1.0' encoding='utf-8'?>
 <tallies>
   <filter id="1" type="particle">
-    <bins>2</bins>
+    <bins>photon</bins>
   </filter>
   <tally id="1">
     <filters>1</filters>