Add delay to activation of IFP tallies.

docs/source/usersguide/kinetics.rst

@@ -32,9 +32,7 @@ the ``ifp_n_generation`` settings in the Python API::
 
     settings.ifp_n_generation = 5
 
-``ifp_n_generation`` should be greater than 0, but should also be lower than
-or equal to the number of inactive batches declared for the calculation.
-The respect of these constraints is verified by OpenMC before any calculation.
+``ifp_n_generation`` should be greater than 0.
 
 OpenMC will automatically detect the type of data that needs to be stored based
 on the tally scores selected by the user. This guarantees that only information

include/openmc/tallies/tally.h

@@ -148,6 +148,9 @@ class Tally {
   //! Whether this tally is currently being updated
   bool active_ {false};
 
+  //! Offset batch to activate this tally after.
+  int offset_ {0};
+
   //! Number of realizations
   int n_realizations_ {0};
 

src/settings.cpp

@@ -552,14 +552,8 @@ void read_settings_xml(pugi::xml_node root)
     // Probability (IFP) method
     if (check_for_node(root, "ifp_n_generation")) {
       ifp_n_generation = std::stoi(get_node_value(root, "ifp_n_generation"));
-      if (ifp_n_generation <= 0) {
+      if (ifp_n_generation <= 0)
         fatal_error("'ifp_n_generation' must be greater than 0.");
-      }
-      // Avoid tallying 0 if IFP logs are not complete when active cycles start
-      if (ifp_n_generation > n_inactive) {
-        fatal_error("'ifp_n_generation' must be lower than or equal to the "
-                    "number of inactive cycles.");
-      }
     }
   }
 

src/simulation.cpp

@@ -391,7 +391,21 @@ void initialize_batch()
     simulation::time_inactive.stop();
     simulation::time_active.start();
     for (auto& t : model::tallies) {
-      t->active_ = true;
+      if (t->offset_ == 0)
+        t->active_ = true;
+    }
+  }
+
+  // Activate tallies which have activation offset.
+  for (auto& t : model::tallies) {
+    if (t->offset_ > 0) {
+      if (!settings::restart_run) {
+        if (simulation::current_batch == settings::n_inactive + 1 + t->offset_)
+          t->active_ = true;
+      } else if (simulation::current_batch == simulation::restart_batch + 1) {
+        if (simulation::restart_batch >= settings::n_inactive + t->offset_)
+          t->active_ = true;
+      }
     }
   }
 

src/tallies/tally.cpp

@@ -210,10 +210,6 @@ Tally::Tally(pugi::xml_node node)
             "changed using the 'ifp_n_generation' settings.",
             settings::ifp_n_generation));
         }
-        if (settings::ifp_n_generation > settings::n_inactive) {
-          fatal_error("'ifp_n_generation' must be lower than or equal to the "
-                      "number of inactive cycles.");
-        }
         settings::ifp_on = true;
       } else if (settings::run_mode == RunMode::FIXED_SOURCE) {
         fatal_error(
@@ -656,6 +652,7 @@ void Tally::set_scores(const vector<std::string>& scores)
     case SCORE_IFP_BETA_NUM:
     case SCORE_IFP_DENOM:
       estimator_ = TallyEstimator::COLLISION;
+      offset_ = settings::ifp_n_generation;
       break;
     }
 

src/tallies/tally_scoring.cpp

@@ -945,11 +945,9 @@ void score_general_ce_nonanalog(Particle& p, int i_tally, int start_index,
       if (settings::ifp_on) {
         if ((p.type() == Type::neutron) && (p.fission())) {
           if (is_generation_time_or_both()) {
-            const auto& lifetimes =
-              simulation::ifp_source_lifetime_bank[p.current_work() - 1];
-            if (lifetimes.size() == settings::ifp_n_generation) {
-              score = lifetimes[0] * p.wgt_last();
-            }
+            const auto& lifetime =
+              simulation::ifp_source_lifetime_bank[p.current_work() - 1][0];
+            score = lifetime * p.wgt_last();
           }
         }
       }
@@ -959,20 +957,19 @@ void score_general_ce_nonanalog(Particle& p, int i_tally, int start_index,
       if (settings::ifp_on) {
         if ((p.type() == Type::neutron) && (p.fission())) {
           if (is_beta_effective_or_both()) {
-            const auto& delayed_groups =
-              simulation::ifp_source_delayed_group_bank[p.current_work() - 1];
-            if (delayed_groups.size() == settings::ifp_n_generation) {
-              if (delayed_groups[0] > 0) {
-                score = p.wgt_last();
-                if (tally.delayedgroup_filter_ != C_NONE) {
-                  auto i_dg_filt = tally.filters()[tally.delayedgroup_filter_];
-                  const DelayedGroupFilter& filt {
-                    *dynamic_cast<DelayedGroupFilter*>(
-                      model::tally_filters[i_dg_filt].get())};
-                  score_fission_delayed_dg(i_tally, delayed_groups[0] - 1,
-                    score, score_index, p.filter_matches());
-                  continue;
-                }
+            const auto& delayed_group =
+              simulation::ifp_source_delayed_group_bank[p.current_work() - 1]
+                                                       [0];
+            if (delayed_group > 0) {
+              score = p.wgt_last();
+              if (tally.delayedgroup_filter_ != C_NONE) {
+                auto i_dg_filt = tally.filters()[tally.delayedgroup_filter_];
+                const DelayedGroupFilter& filt {
+                  *dynamic_cast<DelayedGroupFilter*>(
+                    model::tally_filters[i_dg_filt].get())};
+                score_fission_delayed_dg(i_tally, delayed_group - 1, score,
+                  score_index, p.filter_matches());
+                continue;
               }
             }
           }
@@ -982,21 +979,8 @@ void score_general_ce_nonanalog(Particle& p, int i_tally, int start_index,
 
     case SCORE_IFP_DENOM:
       if (settings::ifp_on) {
-        if ((p.type() == Type::neutron) && (p.fission())) {
-          int ifp_data_size;
-          if (is_beta_effective_or_both()) {
-            ifp_data_size = static_cast<int>(
-              simulation::ifp_source_delayed_group_bank[p.current_work() - 1]
-                .size());
-          } else {
-            ifp_data_size = static_cast<int>(
-              simulation::ifp_source_lifetime_bank[p.current_work() - 1]
-                .size());
-          }
-          if (ifp_data_size == settings::ifp_n_generation) {
-            score = p.wgt_last();
-          }
-        }
+        if ((p.type() == Type::neutron) && (p.fission()))
+          score = p.wgt_last();
       }
       break;
 
@@ -2644,7 +2628,7 @@ void score_surface_tally(Particle& p, const vector<int>& tallies)
       // for a further scoring function.
       double score = current * filter_weight;
       for (auto score_index = 0; score_index < tally.scores_.size();
-           ++score_index) {
+          ++score_index) {
 #pragma omp atomic
         tally.results_(filter_index, score_index, TallyResult::VALUE) += score;
       }
@@ -2719,7 +2703,7 @@ void score_pulse_height_tally(Particle& p, const vector<int>& tallies)
 
             // Loop over scores.
             for (auto score_index = 0; score_index < tally.scores_.size();
-                 ++score_index) {
+                ++score_index) {
 #pragma omp atomic
               tally.results_(filter_index, score_index, TallyResult::VALUE) +=
                 filter_weight;