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// ************************************************************************************************
//
// BornAgain: simulate and fit reflection and scattering
//
//! @file Sample/Interface/TransientModels.cpp
//! @brief Implements TransientModel classes.
//!
//! @homepage http://www.bornagainproject.org
//! @license GNU General Public License v3 or higher (see COPYING)
//! @copyright Forschungszentrum Jülich GmbH 2018
//! @authors Scientific Computing Group at MLZ (see CITATION, AUTHORS)
//
// ************************************************************************************************
#include "Sample/Interface/TransientModels.h"
#include "Base/Math/Functions.h"
#include "Base/Util/Assert.h"
#include <cmath>
#include <numbers>
using std::numbers::pi;
namespace {
const double tanh_prefactor = pi / 2. / std::sqrt(3);
const double erf_prefactor = std::sqrt(1.0 / 2.0);
const double pi_2 = std::sqrt(pi);
} // namespace
ErfTransient::ErfTransient()
: TransientModel()
{
}
double ErfTransient::transient(double x, double sigma) const
{
ASSERT(sigma >= 0);
if (sigma == 0.0)
return Math::Heaviside(x);
return (1.0 + std::erf(erf_prefactor * x / sigma)) / 2.0;
}
double ErfTransient::distribution(double x, double sigma) const
{
ASSERT(sigma > 0);
return erf_prefactor / pi_2 / sigma * std::exp(-pow(erf_prefactor * x / sigma, 2));
}
double ErfTransient::sigmaRange() const
{
return 6.;
}
ErfTransient* ErfTransient::clone() const
{
return new ErfTransient;
}
//-------------------------------------------------------------------------------------------------
TanhTransient::TanhTransient()
: TransientModel()
{
}
double TanhTransient::transient(double x, double sigma) const
{
ASSERT(sigma >= 0);
if (sigma == 0.0)
return Math::Heaviside(x);
return (1.0 + std::tanh(tanh_prefactor * x / sigma)) / 2.0;
}
double TanhTransient::distribution(double x, double sigma) const
{
ASSERT(sigma > 0);
return tanh_prefactor / 2 / sigma / pow(std::cosh(tanh_prefactor * x / sigma), 2);
}
double TanhTransient::sigmaRange() const
{
return 11.;
}
TanhTransient* TanhTransient::clone() const
{
return new TanhTransient;
}
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