integrators.hpp

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#ifndef SRC_INTEGRATOR_INTEGRATORS_HPP_
#define SRC_INTEGRATOR_INTEGRATORS_HPP_
 
// athena
#include <athena/athena.hpp>
 
struct IntegratorWeight {
  // 2S or 3S* low-storage RK coefficients, Ketchenson (2010)
  Real delta;  
  Real gamma_1, gamma_2,
      gamma_3;  // low-storage coeff for weighted ave of registers
  Real beta;  // coeff. from bidiagonal Shu-Osher form Beta matrix, -1 diagonal
              // terms
  Real sbeta, ebeta;  // time coeff describing start/end time of each stage
  bool main_stage,
      orbital_stage;  // flag for whether the main calculation is done
};
 
class MultiStageIntegrator {
 public:
  virtual ~MultiStageIntegrator() {}
  virtual void TimeIntegrate(Real time, Real dt) = 0;
  virtual void WeightedAverage(Real ave_wghts[]) = 0;
 
  IntegratorWeight const& GetStageWeights(int stage) const {
    return stage_wghts_[stage];
  }
 
  void SetIntegrator(std::string name);
  int GetNumStages() const { return nstages_; }
 
 protected:
  IntegratorWeight stage_wghts_[MAX_NSTAGE];
  int nstages_;
};
 
#endif  // SRC_INTEGRATOR_INTEGRATOR_HPP_