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Resolve conflict with weight windows and global russian roulette (#3751)

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Co-authored-by: Patrick Shriwise <pshriwise@gmail.com>
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GuySten 2026-02-25 22:01:33 +02:00 • committed by GitHub
parent 5a85bd92f2
commit c0427dd40a
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13 changed files with 748 additions and 154 deletions
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4
include/openmc/physics_common.h
View file

@ -13,5 +13,9 @@ namespace openmc {
//! \param[in] weight_survive Weight assigned to particles that survive
void russian_roulette(Particle& p, double weight_survive);
//! \brief Performs the global russian roulette operation on a particle
//! \param[in,out] p Particle object
void apply_russian_roulette(Particle& p);
} // namespace openmc
#endif // OPENMC_PHYSICS_COMMON_H

33
include/openmc/weight_windows.h
View file

@ -25,17 +25,6 @@ enum class WeightWindowUpdateMethod { MAGIC, FW_CADIS };
constexpr double DEFAULT_WEIGHT_CUTOFF {1.0e-38}; // default low weight cutoff
//==============================================================================
// 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
//==============================================================================
@ -137,7 +126,7 @@ public:
//! Retrieve the weight window for a particle
//! \param[in] p Particle to get weight window for
WeightWindow get_weight_window(const Particle& p) const;
std::pair<bool, WeightWindow> get_weight_window(const Particle& p) const;
std::array<int, 2> bounds_size() const;
@ -236,6 +225,26 @@ public:
double ratio_ {5.0}; //<! ratio of lower to upper weight window bounds
};
//==============================================================================
// Non-member functions
//==============================================================================
//! Apply weight windows to a particle
//! \param[in] p Particle to apply weight windows to
void apply_weight_windows(Particle& p);
//! Apply weight window to a particle
//! \param[in] p Particle to apply weight window to
//! \param[in] weight_window WeightWindow to apply
void apply_weight_window(Particle& p, WeightWindow weight_window);
//! Free memory associated with weight windows
void free_memory_weight_windows();
//! Search weight window that apply to a particle
//! \param[in] p Particle to search weight window for
std::pair<bool, WeightWindow> search_weight_window(const Particle& p);
//! Finalize variance reduction objects after all inputs have been read
void finalize_variance_reduction();

28
src/physics.cpp
View file

@ -64,8 +64,17 @@ void collision(Particle& p)
fatal_error("Unsupported particle PDG for collision sampling.");
}
if (settings::weight_window_checkpoint_collision)
apply_weight_windows(p);
if (settings::weight_windows_on) {
auto [ww_found, ww] = search_weight_window(p);
if (!ww_found && p.type() == ParticleType::neutron()) {
// if the weight window is not valid, apply russian roulette for neutrons
// (regardless of weight window collision checkpoint setting)
apply_russian_roulette(p);
} else if (settings::weight_window_checkpoint_collision) {
// if collision checkpointing is on, apply weight window
apply_weight_window(p, ww);
}
}
// Kill particle if energy falls below cutoff
int type = p.type().transport_index();
@ -156,18 +165,9 @@ void sample_neutron_reaction(Particle& p)
advance_prn_seed(data::nuclides.size(), &p.seeds(STREAM_URR_PTABLE));
}
// Play russian roulette if survival biasing is turned on
if (settings::survival_biasing) {
// if survival normalization is on, use normalized weight cutoff and
// normalized weight survive
if (settings::survival_normalization) {
if (p.wgt() < settings::weight_cutoff * p.wgt_born()) {
russian_roulette(p, settings::weight_survive * p.wgt_born());
}
} else if (p.wgt() < settings::weight_cutoff) {
russian_roulette(p, settings::weight_survive);
}
}
// Play russian roulette if there are no weight windows
if (!settings::weight_windows_on)
apply_russian_roulette(p);
}
void create_fission_sites(Particle& p, int i_nuclide, const Reaction& rx)

16
src/physics_common.cpp
View file

@ -18,4 +18,20 @@ void russian_roulette(Particle& p, double weight_survive)
}
}
void apply_russian_roulette(Particle& p)
{
// Exit if survival biasing is turned off
if (!settings::survival_biasing)
return;
// if survival normalization is on, use normalized weight cutoff and
// normalized weight survive
if (settings::survival_normalization) {
if (p.wgt() < settings::weight_cutoff * p.wgt_born()) {
russian_roulette(p, settings::weight_survive * p.wgt_born());
}
} else if (p.wgt() < settings::weight_cutoff) {
russian_roulette(p, settings::weight_survive);
}
}
} // namespace openmc

28
src/physics_mg.cpp
View file

@ -32,8 +32,17 @@ void collision_mg(Particle& p)
// Sample the reaction type
sample_reaction(p);
if (settings::weight_window_checkpoint_collision)
apply_weight_windows(p);
if (settings::weight_windows_on) {
auto [ww_found, ww] = search_weight_window(p);
if (!ww_found && p.type() == ParticleType::neutron()) {
// if the weight window is not valid, apply russian roulette
// (regardless of weight window collision checkpoint setting)
apply_russian_roulette(p);
} else if (settings::weight_window_checkpoint_collision) {
// if collision checkpointing is on, apply weight window
apply_weight_window(p, ww);
}
}
// Display information about collision
if ((settings::verbosity >= 10) || p.trace()) {
@ -67,18 +76,9 @@ void sample_reaction(Particle& p)
// Sample a scattering event to determine the energy of the exiting neutron
scatter(p);
// Play Russian roulette if survival biasing is turned on
if (settings::survival_biasing) {
// if survival normalization is applicable, use normalized weight cutoff and
// normalized weight survive
if (settings::survival_normalization) {
if (p.wgt() < settings::weight_cutoff * p.wgt_born()) {
russian_roulette(p, settings::weight_survive * p.wgt_born());
}
} else if (p.wgt() < settings::weight_cutoff) {
russian_roulette(p, settings::weight_survive);
}
}
// Play russian roulette if there are no weight windows
if (!settings::weight_windows_on)
apply_russian_roulette(p);
}
void scatter(Particle& p)

2
src/random_ray/flat_source_domain.cpp
View file

@ -843,7 +843,7 @@ void FlatSourceDomain::output_to_vtk() const
voxel_positions[z * Ny * Nx + y * Nx + x] = sample;
if (variance_reduction::weight_windows.size() == 1) {
WeightWindow ww =
auto [ww_found, ww] =
variance_reduction::weight_windows[0]->get_weight_window(p);
float weight = ww.lower_weight;
weight_windows[z * Ny * Nx + y * Nx + x] = weight;

7
src/settings.cpp
View file

@ -1266,6 +1266,13 @@ void read_settings_xml(pugi::xml_node root)
}
}
if (weight_windows_on) {
if (!weight_window_checkpoint_surface &&
!weight_window_checkpoint_collision)
fatal_error(
"Weight Windows are enabled but there are no valid checkpoints.");
}
if (check_for_node(root, "use_decay_photons")) {
settings::use_decay_photons =
get_node_value_bool(root, "use_decay_photons");

234
src/weight_windows.cpp
View file

@ -44,108 +44,6 @@ openmc::vector<unique_ptr<WeightWindowsGenerator>> weight_windows_generators;
} // namespace variance_reduction
//==============================================================================
// Non-member functions
//==============================================================================
void apply_weight_windows(Particle& p)
{
if (!settings::weight_windows_on)
return;
// WW on photon and neutron only
if (!p.type().is_neutron() && !p.type().is_photon())
return;
// skip dead or no energy
if (p.E() <= 0 || !p.alive())
return;
bool in_domain = false;
// TODO: this is a linear search - should do something more clever
WeightWindow weight_window;
for (const auto& ww : variance_reduction::weight_windows) {
weight_window = ww->get_weight_window(p);
if (weight_window.is_valid())
break;
}
// If particle has not yet had its birth weight window value set, set it to
// the current weight window (or 1.0 if not born in a weight window).
if (p.wgt_ww_born() == -1.0) {
if (weight_window.is_valid()) {
p.wgt_ww_born() =
(weight_window.lower_weight + weight_window.upper_weight) / 2;
} else {
p.wgt_ww_born() = 1.0;
}
}
// particle is not in any of the ww domains, do nothing
if (!weight_window.is_valid())
return;
// Normalize weight windows based on particle's starting weight
// and the value of the weight window the particle was born in.
weight_window.scale(p.wgt_born() / p.wgt_ww_born());
// get the paramters
double weight = p.wgt();
// first check to see if particle should be killed for weight cutoff
if (p.wgt() < weight_window.weight_cutoff) {
p.wgt() = 0.0;
return;
}
// check if particle is far above current weight window
// only do this if the factor is not already set on the particle and a
// maximum lower bound ratio is specified
if (p.ww_factor() == 0.0 && weight_window.max_lb_ratio > 1.0 &&
p.wgt() > weight_window.lower_weight * weight_window.max_lb_ratio) {
p.ww_factor() =
p.wgt() / (weight_window.lower_weight * weight_window.max_lb_ratio);
}
// move weight window closer to the particle weight if needed
if (p.ww_factor() > 1.0)
weight_window.scale(p.ww_factor());
// if particle's weight is above the weight window split until they are within
// the window
if (weight > weight_window.upper_weight) {
// do not further split the particle if above the limit
if (p.n_split() >= settings::max_history_splits)
return;
double n_split = std::ceil(weight / weight_window.upper_weight);
double max_split = weight_window.max_split;
n_split = std::min(n_split, max_split);
p.n_split() += n_split;
// Create secondaries and divide weight among all particles
int i_split = std::round(n_split);
for (int l = 0; l < i_split - 1; l++) {
p.split(weight / n_split);
}
// remaining weight is applied to current particle
p.wgt() = weight / n_split;
} else if (weight <= weight_window.lower_weight) {
// if the particle weight is below the window, play Russian roulette
double weight_survive =
std::min(weight * weight_window.max_split, weight_window.survival_weight);
russian_roulette(p, weight_survive);
} // else particle is in the window, continue as normal
}
void free_memory_weight_windows()
{
variance_reduction::ww_map.clear();
variance_reduction::weight_windows.clear();
}
//==============================================================================
// WeightWindowSettings implementation
//==============================================================================
@ -375,27 +273,28 @@ void WeightWindows::set_mesh(const Mesh* mesh)
set_mesh(model::mesh_map[mesh->id_]);
}
WeightWindow WeightWindows::get_weight_window(const Particle& p) const
std::pair<bool, WeightWindow> WeightWindows::get_weight_window(
const Particle& p) const
{
// check for particle type
if (particle_type_ != p.type()) {
return {};
return {false, {}};
}
// particle energy
double E = p.E();
// check to make sure energy is in range, expects sorted energy values
if (E < energy_bounds_.front() || E > energy_bounds_.back())
return {false, {}};
// Get mesh index for particle's position
const auto& mesh = this->mesh();
int mesh_bin = mesh->get_bin(p.r());
// particle is outside the weight window mesh
if (mesh_bin < 0)
return {};
// particle energy
double E = p.E();
// check to make sure energy is in range, expects sorted energy values
if (E < energy_bounds_.front() || E > energy_bounds_.back())
return {};
return {false, {}};
// get the mesh bin in energy group
int energy_bin =
@ -410,7 +309,7 @@ WeightWindow WeightWindows::get_weight_window(const Particle& p) const
ww.max_lb_ratio = max_lb_ratio_;
ww.max_split = max_split_;
ww.weight_cutoff = weight_cutoff_;
return ww;
return {true, ww};
}
std::array<int, 2> WeightWindows::bounds_size() const
@ -1023,6 +922,115 @@ void WeightWindowsGenerator::update() const
// Non-member functions
//==============================================================================
std::pair<bool, WeightWindow> search_weight_window(const Particle& p)
{
// TODO: this is a linear search - should do something more clever
for (const auto& ww : variance_reduction::weight_windows) {
auto [ww_found, weight_window] = ww->get_weight_window(p);
if (ww_found)
return {true, weight_window};
}
return {false, {}};
}
void apply_weight_windows(Particle& p)
{
if (!settings::weight_windows_on)
return;
// WW on photon and neutron only
if (!p.type().is_neutron() && !p.type().is_photon())
return;
// skip dead or no energy
if (p.E() <= 0 || !p.alive())
return;
auto [ww_found, ww] = search_weight_window(p);
if (ww_found && ww.is_valid()) {
apply_weight_window(p, ww);
} else {
if (p.wgt_ww_born() == -1.0)
p.wgt_ww_born() = 1.0;
}
}
void apply_weight_window(Particle& p, WeightWindow weight_window)
{
if (!weight_window.is_valid())
return;
// skip dead or no energy
if (p.E() <= 0 || !p.alive())
return;
// If particle has not yet had its birth weight window value set, set it to
// the current weight window.
if (p.wgt_ww_born() == -1.0)
p.wgt_ww_born() =
(weight_window.lower_weight + weight_window.upper_weight) / 2;
// Normalize weight windows based on particle's starting weight
// and the value of the weight window the particle was born in.
weight_window.scale(p.wgt_born() / p.wgt_ww_born());
// get the paramters
double weight = p.wgt();
// first check to see if particle should be killed for weight cutoff
if (p.wgt() < weight_window.weight_cutoff) {
p.wgt() = 0.0;
return;
}
// check if particle is far above current weight window
// only do this if the factor is not already set on the particle and a
// maximum lower bound ratio is specified
if (p.ww_factor() == 0.0 && weight_window.max_lb_ratio > 1.0 &&
p.wgt() > weight_window.lower_weight * weight_window.max_lb_ratio) {
p.ww_factor() =
p.wgt() / (weight_window.lower_weight * weight_window.max_lb_ratio);
}
// move weight window closer to the particle weight if needed
if (p.ww_factor() > 1.0)
weight_window.scale(p.ww_factor());
// if particle's weight is above the weight window split until they are within
// the window
if (weight > weight_window.upper_weight) {
// do not further split the particle if above the limit
if (p.n_split() >= settings::max_history_splits)
return;
double n_split = std::ceil(weight / weight_window.upper_weight);
double max_split = weight_window.max_split;
n_split = std::min(n_split, max_split);
p.n_split() += n_split;
// Create secondaries and divide weight among all particles
int i_split = std::round(n_split);
for (int l = 0; l < i_split - 1; l++) {
p.split(weight / n_split);
}
// remaining weight is applied to current particle
p.wgt() = weight / n_split;
} else if (weight <= weight_window.lower_weight) {
// if the particle weight is below the window, play Russian roulette
double weight_survive =
std::min(weight * weight_window.max_split, weight_window.survival_weight);
russian_roulette(p, weight_survive);
} // else particle is in the window, continue as normal
}
void free_memory_weight_windows()
{
variance_reduction::ww_map.clear();
variance_reduction::weight_windows.clear();
}
void finalize_variance_reduction()
{
for (const auto& wwg : variance_reduction::weight_windows_generators) {

0
tests/regression_tests/weightwindows/survival_biasing/__init__.py Normal file
View file

68
tests/regression_tests/weightwindows/survival_biasing/inputs_true.dat Normal file
View file

@ -0,0 +1,68 @@
<?xml version='1.0' encoding='utf-8'?>
<model>
<materials>
<material id="1" name="Tungsten">
<density value="19.25" units="g/cm3"/>
<nuclide name="W180" ao="0.0012"/>
<nuclide name="W182" ao="0.265"/>
<nuclide name="W183" ao="0.1431"/>
<nuclide name="W184" ao="0.3064"/>
<nuclide name="W186" ao="0.2843"/>
</material>
</materials>
<geometry>
<cell id="1" material="1" region="1 -2 3 -4 5 -6" universe="1"/>
<surface id="1" type="x-plane" boundary="reflective" coeffs="0.0"/>
<surface id="2" type="x-plane" boundary="vacuum" coeffs="160.0"/>
<surface id="3" type="y-plane" boundary="reflective" coeffs="0.0"/>
<surface id="4" type="y-plane" boundary="reflective" coeffs="160.0"/>
<surface id="5" type="z-plane" boundary="reflective" coeffs="0.0"/>
<surface id="6" type="z-plane" boundary="reflective" coeffs="160.0"/>
</geometry>
<settings>
<run_mode>fixed source</run_mode>
<particles>50</particles>
<batches>5</batches>
<source type="independent" strength="1.0" particle="neutron">
<space type="cartesian">
<x type="discrete">
<parameters>0.01 1.0</parameters>
</x>
<y type="uniform" parameters="0.0 160.0"/>
<z type="uniform" parameters="0.0 160.0"/>
</space>
<angle type="monodirectional" reference_uvw="1.0 0.0 0.0"/>
<energy type="discrete">
<parameters>14100000.0 1.0</parameters>
</energy>
</source>
<survival_biasing>true</survival_biasing>
<weight_windows id="1">
<mesh>1</mesh>
<particle_type>neutron</particle_type>
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<upper_ww_bounds>2.306798078447855 1.4372426951013015 0.6628006975247303 0.2638260480490365 0.10479220416342819 0.03158625017874938 0.013135185878412529 0.0015016171796218643 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.3055892466950807 1.4312431280421012 0.6999935311310568 0.2754239704479878 0.09140620979127496 0.027788882436180776 0.007632716113146698 0.0012149386176318483 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.314747895653166 1.4288671837730256 0.6682811595168472 0.25173710831135515 0.08762925906456634 0.025483627259255386 0.013148820475765701 0.0016866212196013073 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.288629937523628 1.407474607357475 0.6802198981381123 0.2739644073614768 0.09901188449377762 0.036675872789564246 0.01033696473033213 0.00047647370429630714 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.369881491745159 1.4209530768523382 0.6378754950753944 0.2584601465098665 0.09595839373936176 0.03796517982353924 0.008744088157053638 0.00048391339548409945 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.3780099549279137 1.3864194573478497 0.6380401286267812 0.26259829058567763 0.11249480322475816 0.053168622966257545 0.021210355274573163 0.0022801556101332593 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.382959973596735 1.4443333472126108 0.6293187866990806 0.29094311879778284 0.10238156860372381 0.035715966220091315 0.011182041511257637 0.001976561890704237 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.3467436848034113 1.3590431069745064 0.6416727785211741 0.2757337177996917 0.10333701764735166 0.03945754361568573 0.00821775852703679 0.0032507083906766388 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.2693624655116684 1.412245710542148 0.637670853175783 0.27513750570946854 0.11525573202540434 0.04299651579303599 0.012541305597080901 0.00259265155615848 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.262922237661006 1.3419551233242126 0.6495816959398542 0.2721131854973884 0.09847947611735743 0.02676602480943759 0.007537349146920078 0.000799340449090029 0.0004436023940405703 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.2412339929914022 1.4066382350916795 0.6724930395384323 0.28051639095266717 0.1313716016709848 0.03442035954214652 0.016549695369367727 0.0026687271988374613 0.0006931901997327875 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.4378744750697434 1.4542933526581239 0.7106030329196139 0.3034054004818636 0.09733985234394739 0.03185512139731995 0.014255212633095843 0.006092210889057744 0.0014702270783573093 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.5 1.4260507756489118 0.6811153586160822 0.2915125994216997 0.11562367457576313 0.03700763919819398 0.012638178263719959 0.004254806157581241 0.0009106667287277384 3.9079889923977307e-05 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.385319884449209 1.4156718429747983 0.6585312372110987 0.2627267563832745 0.10555876579159552 0.03372585697780482 0.016021352698590185 0.005154053621131596 0.001379605072397102 0.000686390268269366 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.432099432964226 1.4080866157356209 0.657709250305995 0.2739660012416398 0.08258850845578287 0.03378795890928128 0.012712675375454322 0.0031916390429197216 0.0001139710820532113 0.0017987162361121855 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.1538775796226863 1.3263568920404245 0.6376928978767826 0.27351984264407886 0.10249086547102815 0.028327987062367603 0.0036069233827325737 0.0003424012295655504 -5.0 0.0004304654407462007 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.181566201247801 1.3195389127652835 0.6684368981371207 0.2606765801860381 0.10314430234871916 0.041341924223393264 0.014299610506967188 0.0006529878564991358 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.29631436191095 1.317912074441944 0.6552140498399739 0.27689906093020955 0.09627521280970537 0.03626047845123436 0.009013296744070498 0.0016079182292712106 4.574200880001655e-05 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.287189499200302 1.435748558996386 0.6817539555256685 0.25051579773271737 0.08981639494785537 0.029499088148985803 0.010696567833083998 0.0007838787516541741 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 2.410721391489406 1.3852066116541752 0.7074537017831153 0.2773021407917024 0.08400324691134999 0.020484023015271167 0.009580554199289014 0.0026448001265776534 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0 -5.0</upper_ww_bounds>
<survival_ratio>3.0</survival_ratio>
<max_split>10</max_split>
<weight_cutoff>1e-38</weight_cutoff>
</weight_windows>
<mesh id="1">
<dimension>20 20 1</dimension>
<lower_left>0.0 0.0 0.0</lower_left>
<upper_right>160.0 160.0 160.0</upper_right>
</mesh>
<weight_window_checkpoints>
<collision>true</collision>
<surface>true</surface>
</weight_window_checkpoints>
</settings>
<tallies>
<filter id="1" type="mesh">
<bins>1</bins>
</filter>
<tally id="1" name="flux">
<filters>1</filters>
<scores>flux</scores>
</tally>
</tallies>
</model>

1
tests/regression_tests/weightwindows/survival_biasing/results_true.dat Normal file
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@ -0,0 +1 @@
386e507008ed3c72c6e1a101aafc01cfaaff2c0b10555558d1eab6332441f7b17264b55002d721151bac2f3e7c1a8aac4c5ed243f5270533d171850f985206ed

81
tests/regression_tests/weightwindows/survival_biasing/test.py Normal file
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@ -0,0 +1,81 @@
import pytest
import numpy as np
import openmc
from openmc.stats import Discrete, Point
from tests.testing_harness import HashedPyAPITestHarness
@pytest.fixture
def model():
# Material
w = openmc.Material(name='Tungsten')
w.add_element('W', 1.0)
w.set_density('g/cm3', 19.25)
materials = openmc.Materials([w])
# Geometry surfaces
x0 = openmc.XPlane(x0=0.0, boundary_type='reflective')
x1 = openmc.XPlane(x0=160.0, boundary_type='vacuum')
y0 = openmc.YPlane(y0=0.0, boundary_type='reflective')
y1 = openmc.YPlane(y0=160.0, boundary_type='reflective')
z0 = openmc.ZPlane(z0=0.0, boundary_type='reflective')
z1 = openmc.ZPlane(z0=160.0, boundary_type='reflective')
region = +x0 & -x1 & +y0 & -y1 & +z0 & -z1
cell = openmc.Cell(region=region, fill=w)
root = openmc.Universe(cells=[cell])
geometry = openmc.Geometry(root)
# Source: planar on x=0, mono-directional along +x, 14.1 MeV neutrons
space = openmc.stats.CartesianIndependent(
openmc.stats.Discrete([0.01], [1.0]),
openmc.stats.Uniform(0.0, 160.0),
openmc.stats.Uniform(0.0, 160.0),
)
angle = openmc.stats.Monodirectional((1.0, 0.0, 0.0))
energy = openmc.stats.Discrete([14.1e6], [1.0])
source = openmc.Source(space=space, angle=angle, energy=energy)
settings = openmc.Settings()
settings.run_mode = 'fixed source'
settings.batches = 5
settings.particles = 50
settings.source = source
model = openmc.Model(geometry=geometry, materials=materials, settings=settings)
# Mesh tally: 1 cm voxels, flux only
mesh = openmc.RegularMesh()
mesh.dimension = (20, 20, 1)
mesh.lower_left = (0.0, 0.0, 0.0)
mesh.upper_right = (160.0, 160.0, 160.0)
mesh_filter = openmc.MeshFilter(mesh)
flux_tally = openmc.Tally(name='flux')
flux_tally.filters = [mesh_filter]
flux_tally.scores = ['flux']
tallies = openmc.Tallies([flux_tally])
model.tallies = tallies
lower_ww_bounds = np.loadtxt('ww_n.txt')
weight_windows = openmc.WeightWindows(mesh,
lower_ww_bounds,
upper_bound_ratio=5.0,
particle_type='neutron')
model.settings.weight_windows = weight_windows
model.settings.weight_window_checkpoints = {'surface': True,
'collision': True}
model.settings.survival_biasing = True
return model
def test_weight_windows_with_survival_biasing(model):
harness = HashedPyAPITestHarness('statepoint.5.h5', model)
harness.main()

400
tests/regression_tests/weightwindows/survival_biasing/ww_n.txt Normal file
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@ -0,0 +1,400 @@
4.613596156895709566e-01
4.611178493390161726e-01
4.629495791306331709e-01
4.577259875047255400e-01
4.739762983490318216e-01
4.756019909855827565e-01
4.765919947193469342e-01
4.693487369606823001e-01
4.538724931023336850e-01
4.525844475322012284e-01
4.482467985982804271e-01
4.875748950139486837e-01
5.000000000000000000e-01
4.770639768898417565e-01
4.864198865928451299e-01
4.307755159245372223e-01
4.363132402495602524e-01
4.592628723821899905e-01
4.574378998400603913e-01
4.821442782978812014e-01
2.874485390202602964e-01
2.862486256084202374e-01
2.857734367546050924e-01
2.814949214714950187e-01
2.841906153704676363e-01
2.772838914695699430e-01
2.888666694425221504e-01
2.718086213949012508e-01
2.824491421084295850e-01
2.683910246648425479e-01
2.813276470183359024e-01
2.908586705316247856e-01
2.852101551297823723e-01
2.831343685949596622e-01
2.816173231471241767e-01
2.652713784080849013e-01
2.639077825530566912e-01
2.635824148883887941e-01
2.871497117992772297e-01
2.770413223308350603e-01
1.325601395049460507e-01
1.399987062262113557e-01
1.336562319033694490e-01
1.360439796276224633e-01
1.275750990150788799e-01
1.276080257253562333e-01
1.258637573398161125e-01
1.283345557042348262e-01
1.275341706351565962e-01
1.299163391879708251e-01
1.344986079076864738e-01
1.421206065839227817e-01
1.362230717232164323e-01
1.317062474422197593e-01
1.315418500611990060e-01
1.275385795753565255e-01
1.336873796274241355e-01
1.310428099679947778e-01
1.363507911051337063e-01
1.414907403566230681e-01
5.276520960980729535e-02
5.508479408959755796e-02
5.034742166227103299e-02
5.479288147229536415e-02
5.169202930197330098e-02
5.251965811713552035e-02
5.818862375955657223e-02
5.514674355993834376e-02
5.502750114189370462e-02
5.442263709947767203e-02
5.610327819053343573e-02
6.068108009637272066e-02
5.830251988433994559e-02
5.254535127665489747e-02
5.479320024832795566e-02
5.470396852881576760e-02
5.213531603720762686e-02
5.537981218604190459e-02
5.010315954654347148e-02
5.546042815834047873e-02
2.095844083268563751e-02
1.828124195825499287e-02
1.752585181291326649e-02
1.980237689875552487e-02
1.919167874787235106e-02
2.249896064495163217e-02
2.047631372074476194e-02
2.066740352947033302e-02
2.305114640508086968e-02
1.969589522347148583e-02
2.627432033419696208e-02
1.946797046878947710e-02
2.312473491515262478e-02
2.111175315831910482e-02
1.651770169115657563e-02
2.049817309420563088e-02
2.062886046974383297e-02
1.925504256194107353e-02
1.796327898957107358e-02
1.680064938226999774e-02
6.317250035749876098e-03
5.557776487236155451e-03
5.096725451851077254e-03
7.335174557912849461e-03
7.593035964707848043e-03
1.063372459325150933e-02
7.143193244018263000e-03
7.891508723137145853e-03
8.599303158607197670e-03
5.353204961887517849e-03
6.884071908429303423e-03
6.371024279463989581e-03
7.401527839638795750e-03
6.745171395560964518e-03
6.757591781856257113e-03
5.665597412473520264e-03
8.268384844678653561e-03
7.252095690246871881e-03
5.899817629797160512e-03
4.096804603054233183e-03
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