MeshLessAcousticSolver.cpp

#include <MeshLessAcousticSolver.hpp>
#include <rang.hpp>

#include <memory>

#include <BlockPerfectGas.hpp>

typedef const double my_double;

struct MeshLessAcousticSolver::ReduceMin {
private:
  const Kokkos::View<my_double*> x_;

public:
  typedef Kokkos::View<my_double*>::non_const_value_type value_type;

  ReduceMin(const Kokkos::View<my_double*>& x) : x_ (x) {}

  typedef Kokkos::View<my_double*>::size_type size_type;
    
  KOKKOS_INLINE_FUNCTION void
  operator() (const size_type i, value_type& update) const
  {
    if (x_(i) < update) {
      update = x_(i);
    }
  }

  KOKKOS_INLINE_FUNCTION void
  join (volatile value_type& dst,
	const volatile value_type& src) const
  {
    if (src < dst) {
      dst = src;
    }
  }

  KOKKOS_INLINE_FUNCTION void
  init (value_type& dst) const
  { // The identity under max is -Inf.
    dst= Kokkos::reduction_identity<value_type>::min();
  }
};
    

KOKKOS_INLINE_FUNCTION
double MeshLessAcousticSolver::
acoustic_dt(const Kokkos::View<const double*>& Vj,
	    const Kokkos::View<const double*>& cj) const
{
  const size_t nj = Vj.size();
  double dt = std::numeric_limits<double>::max();

  Kokkos::View<double*> Vj_cj("Vj_cj", nj);

  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
      Vj_cj[j] = Vj[j]/cj[j];
    });

  Kokkos::parallel_reduce(nj, ReduceMin(Vj_cj), dt);

  return dt;
}


KOKKOS_INLINE_FUNCTION
void MeshLessAcousticSolver::computeExplicitFluxes(const Kokkos::View<const double*>& xr,
					   const Kokkos::View<const double*>& xj,
					   const Kokkos::View<const double*>& rhoj,
					   const Kokkos::View<const double*>& uj,
					   const Kokkos::View<const double*>& pj,
					   const Kokkos::View<const double*>& cj,
					   const Kokkos::View<const double*>& Vj,
					   Kokkos::View<double*>& ur,
					   Kokkos::View<double*>& pr) const
{
  // calcul de ur
  ur[0]=0;
  const size_t nr = ur.size();
  const size_t nj = uj.size();

  Kokkos::parallel_for(nj-1, KOKKOS_LAMBDA(const int& j) {
    const int r = j+1;
    const int k = r;

    const double ujr = uj[j];
    const double ukr = uj[k];
    const double pjr = pj[j];
    const double pkr = pj[k];

    ur[r]=(rhoj[j]*cj[j]*ujr + rhoj[k]*cj[k]*ukr + pjr-pkr)/(rhoj[j]*cj[j]+rhoj[k]*cj[k]);
    });
  ur[nr-1]=0;

  // calcul de pr
  pr[0] = pj[0] + rhoj[0]*cj[0]*(ur[0] - uj[0]);
  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j) {
    const int r = j+1;

    const double ujr = uj[j];
    const double pjr = pj[j];

    pr[r]=pjr+rhoj[j]*cj[j]*(ujr-ur[r]);
    });
}


MeshLessAcousticSolver::MeshLessAcousticSolver(const long int& nj)
{
  Kokkos::View<double*> xj("xj", nj);
  Kokkos::View<double*> rhoj("rhoj", nj);

  Kokkos::View<double*> uj("uj", nj);

  Kokkos::View<double*> Ej("Ej", nj);
  Kokkos::View<double*> ej("ej", nj);
  Kokkos::View<double*> pj("pj", nj);
  Kokkos::View<double*> Vj("Vj", nj);
  Kokkos::View<double*> gammaj("gammaj", nj);
  Kokkos::View<double*> cj("cj", nj);
  Kokkos::View<double*> mj("mj", nj);
  Kokkos::View<double*> inv_mj("inv_mj", nj);

  const int nr=nj+1;

  Kokkos::View<double*>  xr("xr", nr);

  const double delta_x = 1./nj;

  Kokkos::parallel_for(nr, KOKKOS_LAMBDA(const int& r){
      xr[r] = r*delta_x;
    });


  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
      xj[j] = 0.5*(xr[j]+xr[j+1]);
    });

  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
      Vj[j] = xr[j+1]-xr[j];
    });

  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
    if (xj[j]<0.5) {
      rhoj[j]=1;
    } else {
      rhoj[j]=0.125;
    }
  });

  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
    if (xj[j]<0.5) {
      pj[j]=1;
    } else {
      pj[j]=0.1;
    }
  });

  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
      gammaj[j] = 1.4;
    });

  BlockPerfectGas block_eos(rhoj, ej, pj, gammaj, cj);

  block_eos.updateEandCFromRhoP();

  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
      Ej[j] = ej[j]+0.5*uj[j]*uj[j];
  });

  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
    mj[j] = rhoj[j] * Vj[j];
  });

  const double tmax=0.2;
  double t=0;

  int itermax=std::numeric_limits<int>::max();
  int iteration=0;

  while((t<tmax) and (iteration<itermax)) {
    double dt = 0.4*acoustic_dt(Vj, cj);
    if (t+dt<tmax) {
      t+=dt;
    } else {
      dt=tmax-t;
      t=tmax;
    }
    
    Kokkos::View<double*> ur("ur", nr);
    Kokkos::View<double*> pr("pr", nr);

    computeExplicitFluxes(xr, xj,
			  rhoj, uj, pj, cj, Vj,
			  ur, pr);

    Kokkos::View<double*> new_uj("new_uj", nj);
    Kokkos::View<double*> new_Ej("new_Ej", nj);
    
    Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
      int rm=j;
      int rp=j+1;

      new_uj[j] = uj[j] + dt/mj[j]*(pr[rm]-pr[rp]);
      new_Ej[j] = Ej[j] + dt/mj[j]*(pr[rm]*ur[rm]-pr[rp]*ur[rp]);
      });

    uj=new_uj;
    Ej=new_Ej;

    Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
	ej[j] = Ej[j] - 0.5 * uj[j]*uj[j];
      });

    Kokkos::View<double*> xr_new("new_xr", nr);

    Kokkos::parallel_for(nr, KOKKOS_LAMBDA(const int& r){
      xr_new[r] = xr[r] + dt*ur[r];
      });

    xr = xr_new;

    Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
      xj[j] = 0.5*(xr[j]+xr[j+1]);
      Vj[j] = xr[j+1]-xr[j];
      });

    Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
	rhoj[j] = mj[j]/Vj[j];
      });

    block_eos.updatePandCFromRhoE();    
    
    ++iteration;
  }

  std::cout << "* " << rang::style::underline << "Final time" << rang::style::reset
	    << ":  " << rang::fgB::green << t << rang::fg::reset << " (" << iteration << " iterations)\n";

}