First real calculation

- acoustic Godunov solver running with Kokkos.
- quite rough implementation, needs many coding tests and arrangements

main.cpp

@@ -5,6 +5,113 @@
 
 #include <CLI/CLI.hpp>
 
+inline double e(double rho, double p, double gamma)
+{
+  return p/(rho*(gamma-1));
+}
+
+inline double p(double rho, double e, double gamma)
+{
+  return (gamma-1)*rho*e;
+}
+
+struct ReduceMin {
+private:
+  Kokkos::View<double*> x_;
+
+public:
+  typedef Kokkos::View<double*>::value_type value_type;
+
+  ReduceMin(const Kokkos::View<double*>& x) : x_ (x) {}
+
+  typedef Kokkos::View<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();
+  }
+};
+    
+
+double acoustic_dt(const Kokkos::View<double*>& Vj,
+		   const Kokkos::View<double*>& cj)
+{
+  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);
+
+  // Kokkos::parallel_reduce(n, KOKKOS_LAMBDA(const long i, long& lcount) {
+  //   lcount += (i % 2) == 0;
+  // }, count);
+  return dt;
+}
+
+
+void computeExplicitFluxes(const Kokkos::View<double*>& xr,
+			   const Kokkos::View<double*>& xj,
+			   const Kokkos::View<double*>& rhoj,
+			   const Kokkos::View<double*>& uj,
+			   const Kokkos::View<double*>& pj,
+			   const Kokkos::View<double*>& cj,
+			   const Kokkos::View<double*>& Vj,
+			   Kokkos::View<double*>& ur,
+			   Kokkos::View<double*>& pr)
+{
+  // 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]);
+    });
+}
+
+
 int main(int argc, char *argv[])
 {
   CLI::App app{"Pastis help"};
@@ -40,39 +147,7 @@ int main(int argc, char *argv[])
   Kokkos::initialize(argc, argv);
   Kokkos::DefaultExecutionSpace::print_configuration(std::cout);
 
-  // if (argc < 2) {
-  //   fprintf(stderr, "Usage: %s [<kokkos_options>] <size>\n", argv[0]);
-  //   Kokkos::finalize();
-  //   exit(1);
-  // }
-
-  const long& n = number;
-  std::cout << "Number of even integers from 0 to " << n - 1 << '\n';
-
-  Kokkos::Timer timer;
-  timer.reset();
-
-  // Compute the number of even integers from 0 to n-1, in parallel.
-  long count = 0;
-  Kokkos::parallel_reduce(n, KOKKOS_LAMBDA(const long i, long& lcount) {
-    lcount += (i % 2) == 0;
-  }, count);
-
-  double count_time = timer.seconds();
-  std::cout << "  Parallel: " << count << " " << rang::style::bold << count_time << rang::style::reset << '\n';
-
-  timer.reset();
-
-  // Compare to a sequential loop.
-  long seq_count = 0;
-  for (long i = 0; i < n; ++i) {
-    seq_count += (i % 2) == 0;
-  }
-
-  count_time = timer.seconds();
-  std::cout << "Sequential: " << seq_count << ' ' << rang::style::bold << count_time << rang::style::reset << '\n';
-
-  const int nj=n; 
+  const long& nj=number; 
 
   Kokkos::View<double*> xj("xj", nj);
   Kokkos::View<double*> rhoj("rhoj", nj);
@@ -86,26 +161,133 @@ int main(int argc, char *argv[])
   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::Timer timer;
   timer.reset();
 
   Kokkos::parallel_for(nr, KOKKOS_LAMBDA(const int& r){
       xr[r] = r*delta_x;
     });
 
-  count_time = timer.seconds();
-  std::cout << "  Parallel: " << count << " " << rang::style::bold << count_time << rang::style::reset << '\n';
 
-  for (int r=0; r<nr; ++r) {
-    std::cout << xr[r] << '\n';
+  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;
+    });
+
+  Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
+    ej[j] = e(rhoj[j],pj[j],gammaj[j]);
+  });
+
+  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){
+    cj[j] = std::sqrt(gammaj[j]*pj[j]/rhoj[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;
+    }
+
+    if (iteration%100 == 0) {
+      std::cout << "dt=" << dt << "t=" << t << " i=" << iteration << '\n';
+    }
+    
+    Kokkos::View<double*> ur("ur", nr);
+    Kokkos::View<double*> pr("pr", nr);
+
+    computeExplicitFluxes(xr, xj,
+			  rhoj, uj, pj, cj, Vj,
+			  ur, pr);
+    
+    Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
+      int rm=j;
+      int rp=j+1;
+
+      uj[j] += dt/mj[j]*(pr[rm]-pr[rp]);
+      Ej[j] += dt/mj[j]*(pr[rm]*ur[rm]-pr[rp]*ur[rp]);
+      });
+
+    Kokkos::parallel_for(nj, KOKKOS_LAMBDA(const int& j){
+	ej[j] = Ej[j] - 0.5 * uj[j]*uj[j];
+      });
+
+    Kokkos::parallel_for(nr, KOKKOS_LAMBDA(const int& r){
+      xr[r] += dt*ur[r];
+      });
+
+    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];
+	pj[j] = p(rhoj[j], ej[j], gammaj[j]);
+	cj[j] = std::sqrt(gammaj[j]*pj[j]/rhoj[j]); // inv_mj*vj
+      });
+    
+    ++iteration;
   }
 
+  std::cout << "* " << rang::style::underline << "Final time" << rang::style::reset
+	    << ":  " << rang::fgB::green << t << rang::fg::reset << " (" << iteration << " iterations)\n";
+  double count_time = timer.seconds();
+  std::cout << "* Execution time: " << rang::style::bold << count_time << rang::style::reset << '\n';
+
+  {
+    std::ofstream fout("rho");
+  
+    for (int j=0; j<nj; ++j) {
+      fout << xj[j] << ' ' << rhoj[j] << '\n';
+    }
+  }
   Kokkos::finalize();
 
   return 0;