From 086568b5620094aebd4dc10dfd3c3e1cb6691537 Mon Sep 17 00:00:00 2001
From: davidjohnlong <david.long2@woodplc.com>
Date: Thu, 12 Mar 2020 12:10:55 +0000
Subject: [PATCH] Remove primary_source_ structure from particle class and
 sample directly from source distribution in Particle::write_restart()
 function for fixed source simulations. Eigenvalue simulations reverted back
 to indexing from primary source bank

---
 include/openmc/particle.h | 10 ----------
 src/particle.cpp          | 35 +++++++++++++++++++++++++----------
 2 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/include/openmc/particle.h b/include/openmc/particle.h
index bef2b1984..69a8eb6ba 100644
--- a/include/openmc/particle.h
+++ b/include/openmc/particle.h
@@ -181,15 +181,6 @@ public:
     int delayed_group; //!< particle delayed group
   };
 
-  //! Saved ("banked") state of primary source particle, for particle restart
-  struct RestartBank {
-    Position r;
-    Direction u;
-    double E;
-    double wgt;
-  };
-
-
   //==========================================================================
   // Constructors
 
@@ -371,7 +362,6 @@ public:
 
   int64_t n_progeny_ {0}; // Number of progeny produced by this particle
 
-  RestartBank primary_source_; // primary source particle data
 };
 
 } // namespace openmc
diff --git a/src/particle.cpp b/src/particle.cpp
index e278383cf..3465d6e6c 100644
--- a/src/particle.cpp
+++ b/src/particle.cpp
@@ -21,6 +21,7 @@
 #include "openmc/physics_mg.h"
 #include "openmc/random_lcg.h"
 #include "openmc/settings.h"
+#include "openmc/source.h"
 #include "openmc/surface.h"
 #include "openmc/simulation.h"
 #include "openmc/tallies/derivative.h"
@@ -128,12 +129,6 @@ Particle::from_source(const Bank* src)
     E_ = data::mg.energy_bin_avg_[g_];
   }
   E_last_ = E_;
-
-  // Saved copy of primary source attributes
-  primary_source_.r = src->r;
-  primary_source_.u = src->u;
-  primary_source_.E = E_last_;
-  primary_source_.wgt = wgt_;
 }
 
 void
@@ -687,10 +682,30 @@ Particle::write_restart() const
     write_dataset(file_id, "id", id_);
     write_dataset(file_id, "type", static_cast<int>(type_));
 
-    write_dataset(file_id, "weight", primary_source_.wgt);
-    write_dataset(file_id, "energy", primary_source_.E);
-    write_dataset(file_id, "xyz", primary_source_.r);
-    write_dataset(file_id, "uvw", primary_source_.u);
+    int64_t i = current_work_;
+    if (settings::run_mode == RunMode::EIGENVALUE) {
+      //take source data from primary bank for eigenvalue simulation
+      write_dataset(file_id, "weight", simulation::source_bank[i-1].wgt);
+      write_dataset(file_id, "energy", simulation::source_bank[i-1].E);
+      write_dataset(file_id, "xyz", simulation::source_bank[i-1].r);
+      write_dataset(file_id, "uvw", simulation::source_bank[i-1].u);
+    } else if (settings::run_mode == RunMode::FIXED_SOURCE) {
+      // re-sample using rng random number seed used to generate source particle
+      int64_t id = (simulation::total_gen + overall_generation() - 1)*settings::n_particles +
+        simulation::work_index[mpi::rank] + i;
+      uint64_t seed = init_seed(id, STREAM_SOURCE);
+      // re-sample source site
+      Particle::Bank site;
+      if (!settings::path_source_library.empty()) {
+        site = sample_custom_source_library(&seed);
+      } else {
+        site = sample_external_source(&seed);
+      }
+      write_dataset(file_id, "weight", site.wgt);
+      write_dataset(file_id, "energy", site.E);
+      write_dataset(file_id, "xyz", site.r);
+      write_dataset(file_id, "uvw", site.u);
+    }
 
     // Close file
     file_close(file_id);