mirror of
https://github.com/openmc-dev/openmc.git
synced 2026-07-21 14:35:27 -04:00
69 lines
2.8 KiB
C++
69 lines
2.8 KiB
C++
#ifndef OPENMC_RANDOM_DIST_H
|
|
#define OPENMC_RANDOM_DIST_H
|
|
|
|
#include <cstdint> // for uint64_t
|
|
|
|
namespace openmc {
|
|
|
|
//==============================================================================
|
|
//! Sample a uniform distribution [a, b)
|
|
//
|
|
//! \param a Lower bound of uniform distribution
|
|
//! \param b Upper bound of uniform distribtion
|
|
//! \param seed A pointer to the pseudorandom seed
|
|
//! \return Sampled variate
|
|
//==============================================================================
|
|
|
|
double uniform_distribution(double a, double b, uint64_t* seed);
|
|
|
|
//==============================================================================
|
|
//! Samples an energy from the Maxwell fission distribution based on a direct
|
|
//! sampling scheme.
|
|
//!
|
|
//! The probability distribution function for a Maxwellian is given as
|
|
//! p(x) = 2/(T*sqrt(pi))*sqrt(x/T)*exp(-x/T). This PDF can be sampled using
|
|
//! rule C64 in the Monte Carlo Sampler LA-9721-MS.
|
|
//!
|
|
//! \param T The tabulated function of the incoming energy
|
|
//! \param seed A pointer to the pseudorandom seed
|
|
//! \return The sampled outgoing energy
|
|
//==============================================================================
|
|
|
|
extern "C" double maxwell_spectrum(double T, uint64_t* seed);
|
|
|
|
//==============================================================================
|
|
//! Samples an energy from a Watt energy-dependent fission distribution.
|
|
//!
|
|
//! Although fitted parameters exist for many nuclides, generally the
|
|
//! continuous tabular distributions (LAW 4) should be used in lieu of the Watt
|
|
//! spectrum. This direct sampling scheme is an unpublished scheme based on the
|
|
//! original Watt spectrum derivation (See F. Brown's MC lectures).
|
|
//!
|
|
//! \param a Watt parameter a
|
|
//! \param b Watt parameter b
|
|
//! \param seed A pointer to the pseudorandom seed
|
|
//! \return The sampled outgoing energy
|
|
//==============================================================================
|
|
|
|
extern "C" double watt_spectrum(double a, double b, uint64_t* seed);
|
|
|
|
//==============================================================================
|
|
//! Samples an energy from the Gaussian energy-dependent fission distribution.
|
|
//!
|
|
//! Samples from a Normal distribution with a given mean and standard deviation
|
|
//! The PDF is defined as s(x) = (1/2*sigma*sqrt(2) * e-((mu-x)/2*sigma)^2
|
|
//! Its sampled according to
|
|
//! http://www-pdg.lbl.gov/2009/reviews/rpp2009-rev-monte-carlo-techniques.pdf
|
|
//! section 33.4.4
|
|
//!
|
|
//! \param mean mean of the Gaussian distribution
|
|
//! \param std_dev standard deviation of the Gaussian distribution
|
|
//! \param seed A pointer to the pseudorandom seed
|
|
//! \result The sampled outgoing energy
|
|
//==============================================================================
|
|
|
|
extern "C" double normal_variate(double mean, double std_dev, uint64_t* seed);
|
|
|
|
} // namespace openmc
|
|
|
|
#endif // OPENMC_RANDOM_DIST_H
|