betafunction.cpp

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// ====================================================================
// This file is part of FlexibleSUSY.
//
// FlexibleSUSY is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// FlexibleSUSY is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with FlexibleSUSY.  If not, see
// <http://www.gnu.org/licenses/>.
// ====================================================================
 
#include "betafunction.hpp"
#include "basic_rk_integrator.hpp"
#include "error.hpp"
 
#include <cmath>
 
namespace flexiblesusy {
 
namespace {
 
const auto integrator = runge_kutta::Basic_rk_integrator<Eigen::ArrayXd>();
 
} // anonymous namespace
 
void Beta_function::reset()
{
   num_pars = 0;
   loops = 0;
   thresholds = 0;
   scale = 0.0;
   tolerance = 1.e-4;
   min_tolerance = 1.0e-11;
   zero_threshold = 1.e-11;
}
 
void Beta_function::run_to(double x2, double eps)
{
   const double tol = get_tolerance(eps);
   run(scale, x2, tol);
}
 
void Beta_function::run(double x1, double x2, double eps)
{
   if (get_loops() > 0) {
      const double tol = get_tolerance(eps);
 
      if (std::fabs(x1) < tol)
         throw NonPerturbativeRunningError(x1);
      if (std::fabs(x2) < tol)
         throw NonPerturbativeRunningError(x2);
 
      if (fabs(x1 - x2) >= min_tolerance) {
         Eigen::ArrayXd y(get());
         const double start = std::log(fabs(x1));
         const double end = std::log(fabs(x2));
 
         integrator(start, end, y,
                    [this](double x, const Eigen::ArrayXd& y) { return derivatives(x, y); },
                    tol);
 
         set_scale(x2);
         set(y);
      }
   }
 
   set_scale(x2);
}
 
Eigen::ArrayXd Beta_function::derivatives(double x, const Eigen::ArrayXd& y)
{
   set_scale(exp(x));
   set(y);
   return beta();
}
 
double Beta_function::get_tolerance(double eps) const
{
   double tol = 0;
   if (eps < 0.0)
      tol = tolerance;
   else if (eps < min_tolerance)
      tol = min_tolerance;
   else
      tol = eps;
 
   return tol;
}
 
} // namespace flexiblesusy