From c1d746164fa47849d7f4e89bfcd203a825e8556c Mon Sep 17 00:00:00 2001
From: Patrick Shriwise <pshriwise@gmail.com>
Date: Mon, 23 Sep 2019 12:00:24 -0500
Subject: [PATCH] Writing empty groups for nuclides/atoms in volume calc if no
 entries are found.

---
 openmc/volume.py    |  3 +--
 src/volume_calc.cpp | 26 ++++++++++++--------------
 2 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/openmc/volume.py b/openmc/volume.py
index 7ac4fdd0c..91ff829cb 100644
--- a/openmc/volume.py
+++ b/openmc/volume.py
@@ -212,13 +212,12 @@ class VolumeCalculation(object):
                     ids.append(domain_id)
                     group = f[obj_name]
                     volume = ufloat(*group['volume'][()])
+                    volumes[domain_id] = volume
                     nucnames = group['nuclides'][()]
                     atoms_ = group['atoms'][()]
-
                     atom_dict = OrderedDict()
                     for name_i, atoms_i in zip(nucnames, atoms_):
                         atom_dict[name_i.decode()] = ufloat(*atoms_i)
-                    volumes[domain_id] = volume
                     atoms[domain_id] = atom_dict
 
         # Instantiate some throw-away domains that are used by the constructor
diff --git a/src/volume_calc.cpp b/src/volume_calc.cpp
index 93b729bd6..6c1c48932 100644
--- a/src/volume_calc.cpp
+++ b/src/volume_calc.cpp
@@ -311,22 +311,20 @@ void VolumeCalculation::to_hdf5(const std::string& filename,
     // Create array of nuclide names from the vector
     auto n_nuc = result.nuclides.size();
 
-    if (!result.nuclides.empty()) {
-      std::vector<std::string> nucnames;
-      for (int i_nuc : result.nuclides) {
-        nucnames.push_back(data::nuclides[i_nuc]->name_);
-      }
-
-      // Create array of total # of atoms with uncertainty for each nuclide
-      xt::xtensor<double, 2> atom_data({n_nuc, 2});
-      xt::view(atom_data, xt::all(), 0) = xt::adapt(result.atoms);
-      xt::view(atom_data, xt::all(), 1) = xt::adapt(result.uncertainty);
-
-      // Write results
-      write_dataset(group_id, "nuclides", nucnames);
-      write_dataset(group_id, "atoms", atom_data);
+    std::vector<std::string> nucnames;
+    for (int i_nuc : result.nuclides) {
+      nucnames.push_back(data::nuclides[i_nuc]->name_);
     }
 
+    // Create array of total # of atoms with uncertainty for each nuclide
+    xt::xtensor<double, 2> atom_data({n_nuc, 2});
+    xt::view(atom_data, xt::all(), 0) = xt::adapt(result.atoms);
+    xt::view(atom_data, xt::all(), 1) = xt::adapt(result.uncertainty);
+
+    // Write results
+    write_dataset(group_id, "nuclides", nucnames);
+    write_dataset(group_id, "atoms", atom_data);
+
     close_group(group_id);
   }