From cef713b91e633f5f37bf165cba51145e7befba0e Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Wed, 5 Dec 2018 08:35:08 -0600
Subject: [PATCH] Make sure fission neutron energy is resampled if > max energy

Also fix two other bugs, one where openmc.capi.find_material crashes if a
material is void, and one where OpenMC doesn't compile if omp.h is missing (can
happen on macOS).
---
 openmc/capi/core.py | 2 +-
 src/physics.cpp     | 6 ++++--
 src/settings.cpp    | 2 ++
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/openmc/capi/core.py b/openmc/capi/core.py
index bedde6e162..88c2b45a38 100644
--- a/openmc/capi/core.py
+++ b/openmc/capi/core.py
@@ -121,7 +121,7 @@ def find_material(xyz):
     _dll.openmc_find_cell((c_double*3)(*xyz), index, instance)
 
     mats = openmc.capi.Cell(index=index.value).fill
-    if isinstance(mats, openmc.capi.Material):
+    if isinstance(mats, (openmc.capi.Material, type(None))):
         return mats
     else:
         return mats[instance.value]
diff --git a/src/physics.cpp b/src/physics.cpp
index 43fc2871b4..4d8c01cf35 100644
--- a/src/physics.cpp
+++ b/src/physics.cpp
@@ -1057,7 +1057,8 @@ void sample_fission_neutron(int i_nuclide, const Reaction* rx, double E_in, Bank
       rx->products_[group].sample(E_in, site->E, mu);
 
       // resample if energy is greater than maximum neutron energy
-      constexpr int neutron = static_cast<int>(ParticleType::neutron);
+      // TODO: off-by-one
+      constexpr int neutron = static_cast<int>(ParticleType::neutron) - 1;
       if (site->E < data::energy_max[neutron]) break;
 
       // check for large number of resamples
@@ -1082,7 +1083,8 @@ void sample_fission_neutron(int i_nuclide, const Reaction* rx, double E_in, Bank
       rx->products_[0].sample(E_in, site->E, mu);
 
       // resample if energy is greater than maximum neutron energy
-      constexpr int neutron = static_cast<int>(ParticleType::neutron);
+      // TODO: off-by-one
+      constexpr int neutron = static_cast<int>(ParticleType::neutron) - 1;
       if (site->E < data::energy_max[neutron]) break;
 
       // check for large number of resamples
diff --git a/src/settings.cpp b/src/settings.cpp
index 303a35ddd9..261536813c 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -5,7 +5,9 @@
 #include <sstream>
 #include <string>
 
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 #include "openmc/capi.h"
 #include "openmc/constants.h"