Merge pull request #1947 from pshriwise/ww-final-tests

Weight windows final push

include/openmc/constants.h

@@ -358,6 +358,10 @@ constexpr int CMFD_NOACCEL {-1};
 
 enum class GeometryType { CSG, DAG };
 
+//==============================================================================
+// Variance Reduction constants
+constexpr double DEFAULT_WEIGHT_CUTOFF {1.0e-38}; // default low weight cutoff
+
 } // namespace openmc
 
 #endif // OPENMC_CONSTANTS_H

include/openmc/particle_data.h

@@ -305,6 +305,9 @@ private:
 
   int n_event_ {0}; // number of events executed in this particle's history
 
+  // Weight window information
+  int n_split_ {0}; // Number of splits this particle has undergone
+
 // DagMC state variables
 #ifdef DAGMC
   moab::DagMC::RayHistory history_;
@@ -426,6 +429,9 @@ public:
   double& collision_distance() { return collision_distance_; }
   int& n_event() { return n_event_; }
 
+  int n_split() const { return n_split_; }
+  int& n_split() { return n_split_; }
+
 #ifdef DAGMC
   moab::DagMC::RayHistory& history() { return history_; }
   Direction& last_dir() { return last_dir_; }

include/openmc/physics.h

@@ -89,6 +89,11 @@ void inelastic_scatter(const Nuclide& nuc, const Reaction& rx, Particle& p);
 
 void sample_secondary_photons(Particle& p, int i_nuclide);
 
+//！Split or Roulette particles based their weight and the lower weight window
+// bound.
+//! \param[in] p, particle to be split or rouletted with the weight window.
+void split_particle(Particle& p);
+
 } // namespace openmc
 
 #endif // OPENMC_PHYSICS_H

include/openmc/settings.h

@@ -55,6 +55,7 @@ extern "C" bool trigger_on;        //!< tally triggers enabled?
 extern bool trigger_predict;       //!< predict batches for triggers?
 extern bool ufs_on;                //!< uniform fission site method on?
 extern bool urr_ptables_on;        //!< use unresolved resonance prob. tables?
+extern bool weight_windows_on;     //!< are weight windows are enabled?
 extern bool write_all_tracks;      //!< write track files for every particle?
 extern bool write_initial_source;  //!< write out initial source file?
 
@@ -99,6 +100,7 @@ extern std::unordered_set<int>
   statepoint_batch; //!< Batches when state should be written
 extern std::unordered_set<int>
   source_write_surf_id; //!< Surface ids where sources will be written
+extern int max_splits; //!< maximum number of particle splits for weight windows
 extern int64_t max_surface_particles; //!< maximum number of particles to be
                                       //!< banked on surfaces per process
 extern TemperatureMethod

include/openmc/weight_windows.h

@@ -0,0 +1,99 @@
+#ifndef OPENMC_WEIGHT_WINDOWS_H
+#define OPENMC_WEIGHT_WINDOWS_H
+
+#include <cstdint>
+#include <unordered_map>
+
+#include <hdf5.h>
+#include <pugixml.hpp>
+
+#include "openmc/constants.h"
+#include "openmc/memory.h"
+#include "openmc/mesh.h"
+#include "openmc/particle.h"
+#include "openmc/vector.h"
+
+namespace openmc {
+
+//==============================================================================
+// Non-member functions
+//==============================================================================
+
+//! Apply weight windows to a particle
+//! \param[in] p  Particle to apply weight windows to
+void apply_weight_windows(Particle& p);
+
+//! Free memory associated with weight windows
+void free_memory_weight_windows();
+
+//==============================================================================
+// Global variables
+//==============================================================================
+
+class WeightWindows;
+
+namespace variance_reduction {
+
+extern std::unordered_map<int32_t, int32_t> ww_map;
+extern vector<unique_ptr<WeightWindows>> weight_windows;
+
+} // namespace variance_reduction
+
+//==============================================================================
+//! Individual weight window information
+//==============================================================================
+
+struct WeightWindow {
+  double lower_weight {-1}; // -1 indicates invalid state
+  double upper_weight {1};
+  double survival_weight {0.5};
+  double weight_cutoff {DEFAULT_WEIGHT_CUTOFF};
+  int max_split {1};
+
+  //! Whether the weight window is in a valid state
+  bool is_valid() const { return lower_weight >= 0.0; }
+};
+
+//==============================================================================
+//! Weight window settings
+//==============================================================================
+
+class WeightWindows {
+public:
+  // Constructors
+  WeightWindows();
+  WeightWindows(pugi::xml_node node);
+
+  // Methods
+
+  //! Set the weight window ID
+  void set_id(int32_t id = -1);
+
+  // NOTE: This is unused for now but may be used in the future
+  //! Write weight window settings to an HDF5 file
+  //! \param[in] group  HDF5 group to write to
+  void to_hdf5(hid_t group) const;
+
+  //! Retrieve the weight window for a particle
+  //! \param[in] p  Particle to get weight window for
+  WeightWindow get_weight_window(const Particle& p) const;
+
+  // Accessors
+  int32_t id() const { return id_; }
+  const Mesh& mesh() const { return *model::meshes[mesh_idx_]; }
+
+private:
+  // Data members
+  int32_t id_;                     //!< Unique ID
+  ParticleType particle_type_;     //!< Particle type to apply weight windows to
+  vector<double> energy_bins_;     //!< Energy bins [eV]
+  vector<double> lower_ww_;        //!< Lower weight window bounds
+  vector<double> upper_ww_;        //!< Upper weight window bounds
+  double survival_ratio_ {3.0};    //!< Survival weight ratio
+  double weight_cutoff_ {DEFAULT_WEIGHT_CUTOFF}; //!< Weight cutoff
+  int max_split_ {10};             //!< Maximum value for particle splitting
+  int32_t mesh_idx_;               //!< index in meshes vector
+};
+
+} // namespace openmc
+#endif // OPENMC_WEIGHT_WINDOWS_H