#include "openmc/physics_common.h"

#include "openmc/random_lcg.h"

#include "openmc/settings.h"

namespace openmc {

//==============================================================================

// RUSSIAN_ROULETTE

//==============================================================================

void russian_roulette(Particle& p, double weight_survive)

{

if (weight_survive * prn(p.current_seed()) < p.wgt()) {

p.wgt() = weight_survive;

} else {

p.wgt() = 0.;

}

}

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