From fb8b1c9b7829bdb68caf7468d14d2e7c49b17a74 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Mon, 2 Dec 2019 10:36:53 -0600
Subject: [PATCH] Add constructor for CellInstanceFilter. Call
 prepare_distribcells at simulation initialization, not program initialization

---
 include/openmc/tallies/filter_cell_instance.h | 4 ++--
 src/geometry_aux.cpp                          | 4 +++-
 src/initialize.cpp                            | 3 ---
 src/simulation.cpp                            | 4 ++++
 src/tallies/filter_cell_instance.cpp          | 5 +++++
 5 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/openmc/tallies/filter_cell_instance.h b/include/openmc/tallies/filter_cell_instance.h
index d9e3785dc..0895cc1ef 100644
--- a/include/openmc/tallies/filter_cell_instance.h
+++ b/include/openmc/tallies/filter_cell_instance.h
@@ -51,8 +51,8 @@ public:
   //----------------------------------------------------------------------------
   // Constructors, destructors
 
-  //CellInstanceFilter() = default;
-  //CellInstanceFilter(gsl::span<CellInstance> instances);
+  CellInstanceFilter() = default;
+  CellInstanceFilter(gsl::span<CellInstance> instances);
   ~CellInstanceFilter() = default;
 
   //----------------------------------------------------------------------------
diff --git a/src/geometry_aux.cpp b/src/geometry_aux.cpp
index 965a58aea..8a3394743 100644
--- a/src/geometry_aux.cpp
+++ b/src/geometry_aux.cpp
@@ -320,6 +320,8 @@ find_root_universe()
 void
 prepare_distribcell()
 {
+  write_message("Preparing distributed cell instances...", 5);
+
   // Find all cells listed in a DistribcellFilter or CellInstanceFilter
   std::unordered_set<int32_t> distribcells;
   for (auto& filt : model::tally_filters) {
@@ -395,7 +397,7 @@ prepare_distribcell()
   for (int map = 0; map < target_univ_ids.size(); map++) {
     auto target_univ_id = target_univ_ids[map];
     for (const auto& univ : model::universes) {
-      int32_t offset {0};  // TODO: is this a bug?  It matches F90 implementation.
+      int32_t offset = 0;
       for (int32_t cell_indx : univ->cells_) {
         Cell& c = *model::cells[cell_indx];
 
diff --git a/src/initialize.cpp b/src/initialize.cpp
index 460db2436..387fd9f11 100644
--- a/src/initialize.cpp
+++ b/src/initialize.cpp
@@ -269,9 +269,6 @@ void read_input_xml()
 
   read_tallies_xml();
 
-  // Initialize distribcell_filters
-  prepare_distribcell();
-
   if (settings::run_mode == RUN_MODE_PLOTTING) {
     // Read plots.xml if it exists
     read_plots_xml();
diff --git a/src/simulation.cpp b/src/simulation.cpp
index 2f3230c6e..ec588a9ad 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -5,6 +5,7 @@
 #include "openmc/container_util.h"
 #include "openmc/eigenvalue.h"
 #include "openmc/error.h"
+#include "openmc/geometry_aux.h"
 #include "openmc/material.h"
 #include "openmc/message_passing.h"
 #include "openmc/nuclide.h"
@@ -57,6 +58,9 @@ int openmc_simulation_init()
   // Skip if simulation has already been initialized
   if (simulation::initialized) return 0;
 
+  // Initialize distribcell_filters
+  prepare_distribcell();
+
   // Determine how much work each process should do
   calculate_work();
 
diff --git a/src/tallies/filter_cell_instance.cpp b/src/tallies/filter_cell_instance.cpp
index 21573c8da..8149f746f 100644
--- a/src/tallies/filter_cell_instance.cpp
+++ b/src/tallies/filter_cell_instance.cpp
@@ -9,6 +9,11 @@
 
 namespace openmc {
 
+CellInstanceFilter::CellInstanceFilter(gsl::span<CellInstance> instances)
+{
+  this->set_cell_instances(instances);
+}
+
 void
 CellInstanceFilter::from_xml(pugi::xml_node node)
 {