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Move distributions into random_dist.h/cpp

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Paul Romano 2021-04-26 10:00:21 -05:00
parent 516745ce87
commit f0aaac4601
9 changed files with 131 additions and 114 deletions
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1
CMakeLists.txt
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@ -303,6 +303,7 @@ list(APPEND libopenmc_SOURCES
src/plot.cpp
src/position.cpp
src/progress_bar.cpp
src/random_dist.cpp
src/random_lcg.cpp
src/reaction.cpp
src/reaction_product.cpp

67
include/openmc/math_functions.h
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@ -8,9 +8,7 @@
#include <complex>
#include <cstdlib>
#include "openmc/constants.h"
#include "openmc/position.h"
#include "openmc/random_lcg.h"
namespace openmc {
@ -138,71 +136,6 @@ extern "C" void rotate_angle_c(double uvw[3], double mu, const double* phi,
Direction rotate_angle(Direction u, double mu, const double* phi,
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 This direct sampling scheme is an unpublished scheme based on the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);
//==============================================================================
//! Samples an energy from the Muir (Gaussian) energy-dependent distribution.
//!
//! This is another form of the Gaussian distribution but with more easily
//! modifiable parameters
//! https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-05411-MS
//!
//! @param e0 peak neutron energy [eV]
//! @param m_rat ratio of the fusion reactants to AMU
//! @param kt the ion temperature of the reactants [eV]
//! @param seed A pointer to the pseudorandom seed
//! @result The sampled outgoing energy
//==============================================================================
extern "C" double muir_spectrum(double e0, double m_rat, double kt,
uint64_t* seed);
//==============================================================================
//! Constructs a natural cubic spline.
//!

74
include/openmc/random_dist.h Normal file
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@ -0,0 +1,74 @@
#ifndef OPENMC_RANDOM_DIST_H
#define OPENMC_RANDOM_DIST_H
#include <cstdint> // for uint64_t
namespace openmc {
//==============================================================================
//! 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);
//==============================================================================
//! Samples an energy from the Muir (Gaussian) energy-dependent distribution.
//!
//! This is another form of the Gaussian distribution but with more easily
//! modifiable parameters
//! https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-05411-MS
//!
//! \param e0 peak neutron energy [eV]
//! \param m_rat ratio of the fusion reactants to AMU
//! \param kt the ion temperature of the reactants [eV]
//! \param seed A pointer to the pseudorandom seed
//! \result The sampled outgoing energy
//==============================================================================
extern "C" double muir_spectrum(double e0, double m_rat, double kt, uint64_t* seed);
} // namespace openmc
#endif // OPENMC_RANDOM_DIST_H

1
src/distribution.cpp
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@ -9,6 +9,7 @@
#include "openmc/error.h"
#include "openmc/math_functions.h"
#include "openmc/random_dist.h"
#include "openmc/random_lcg.h"
#include "openmc/xml_interface.h"

1
src/distribution_energy.cpp
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@ -9,6 +9,7 @@
#include "openmc/endf.h"
#include "openmc/hdf5_interface.h"
#include "openmc/math_functions.h"
#include "openmc/random_dist.h"
#include "openmc/random_lcg.h"
#include "openmc/search.h"

46
src/math_functions.cpp
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@ -2,6 +2,9 @@
#include "Faddeeva.hh"
#include "openmc/constants.h"
#include "openmc/random_lcg.h"
namespace openmc {
//==============================================================================
@ -669,49 +672,6 @@ Direction rotate_angle(Direction u, double mu, const double* phi, uint64_t* seed
}
double maxwell_spectrum(double T, uint64_t* seed) {
// Set the random numbers
double r1 = prn(seed);
double r2 = prn(seed);
double r3 = prn(seed);
// determine cosine of pi/2*r
double c = std::cos(PI / 2. * r3);
// Determine outgoing energy
double E_out = -T * (std::log(r1) + std::log(r2) * c * c);
return E_out;
}
double normal_variate(double mean, double standard_deviation, uint64_t* seed) {
// Sample a normal variate using Marsaglia's polar method
double x, y, r2;
do {
x = 2 * prn(seed) - 1.;
y = 2 * prn(seed) - 1.;
r2 = x*x + y*y;
} while (r2 > 1 || r2 == 0);
double z = std::sqrt(-2.0 * std::log(r2)/r2);
return mean + standard_deviation*z*x;
}
double muir_spectrum(double e0, double m_rat, double kt, uint64_t* seed) {
// https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-05411-MS
double sigma = std::sqrt(4.*e0*kt/m_rat);
return normal_variate(e0, sigma, seed);
}
double watt_spectrum(double a, double b, uint64_t* seed) {
double w = maxwell_spectrum(a, seed);
double E_out = w + 0.25 * a * a * b + (2. * prn(seed) - 1.) * std::sqrt(a * a * b * w);
return E_out;
}
void spline(int n, const double x[], const double y[], double z[])
{
std::vector<double> c_new(n-1);

48
src/random_dist.cpp Normal file
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@ -0,0 +1,48 @@
#include "openmc/random_dist.h"
#include <cmath>
#include "openmc/constants.h"
#include "openmc/random_lcg.h"
namespace openmc {
double maxwell_spectrum(double T, uint64_t* seed) {
// Set the random numbers
double r1 = prn(seed);
double r2 = prn(seed);
double r3 = prn(seed);
// determine cosine of pi/2*r
double c = std::cos(PI / 2. * r3);
// Determine outgoing energy
return -T * (std::log(r1) + std::log(r2) * c * c);
}
double watt_spectrum(double a, double b, uint64_t* seed) {
double w = maxwell_spectrum(a, seed);
return w + 0.25 * a * a * b + (2. * prn(seed) - 1.) * std::sqrt(a * a * b * w);
}
double normal_variate(double mean, double standard_deviation, uint64_t* seed) {
// Sample a normal variate using Marsaglia's polar method
double x, y, r2;
do {
x = 2 * prn(seed) - 1.;
y = 2 * prn(seed) - 1.;
r2 = x*x + y*y;
} while (r2 > 1 || r2 == 0);
double z = std::sqrt(-2.0 * std::log(r2)/r2);
return mean + standard_deviation*z*x;
}
double muir_spectrum(double e0, double m_rat, double kt, uint64_t* seed) {
// https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-05411-MS
double sigma = std::sqrt(4.*e0*kt/m_rat);
return normal_variate(e0, sigma, seed);
}
} // namespace openmc

6
src/random_lcg.cpp
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@ -39,9 +39,7 @@ double prn(uint64_t* seed)
uint64_t result = (word >> 43u) ^ word;
// Convert output from unsigned integer to double
double result_d = ldexp(result, -64);
return result_d;
return ldexp(result, -64);
}
//==============================================================================
@ -51,7 +49,7 @@ double prn(uint64_t* seed)
double future_prn(int64_t n, uint64_t seed)
{
uint64_t fseed = future_seed(static_cast<uint64_t>(n), seed);
return prn( &fseed );
return prn(&fseed);
}
//==============================================================================

1
src/secondary_nbody.cpp
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@ -5,6 +5,7 @@
#include "openmc/constants.h"
#include "openmc/hdf5_interface.h"
#include "openmc/math_functions.h"
#include "openmc/random_dist.h"
#include "openmc/random_lcg.h"
namespace openmc {