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//                        Kokkos v. 2.0
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#include <Kokkos_Core.hpp>
#include <cstdio>

// Using default execution space define a TeamPolicy and its member_type
// The member_type is what the operator of a functor or Lambda gets, for
// a simple RangePolicy the member_type is simply an integer
// For a TeamPolicy its a much richer object, since it provides all information
// to identify a thread uniquely and some team related function calls such as a
// barrier (which will be used in a subsequent example).
// A ThreadTeam consists of 1 to n threads where the maxmimum value of n is
// determined by the hardware. On a dual socket CPU machine with 8 cores per socket
// the maximum size of a team is 8. The number of teams (i.e. the league_size) is
// not limited by physical constraints. Its a pure logical number.

typedef Kokkos::TeamPolicy<>              team_policy ;
typedef team_policy::member_type team_member ;

// Define a functor which can be launched using the TeamPolicy
struct hello_world {
  typedef int value_type; //Specify value type for reduction target, sum

  // This is a reduction operator which now takes as first argument the
  // TeamPolicy member_type. Every member of the team contributes to the
  // total sum.
  // It is helpful to think of this operator as a parallel region for a team
  // (i.e. every team member is active and will execute the code).
  KOKKOS_INLINE_FUNCTION
  void operator() ( const team_member & thread, int& sum) const {
    sum+=1;
    // The TeamPolicy<>::member_type provides functions to query the multi
    // dimensional index of a thread as well as the number of thread-teams and the size
    // of each team.
    printf("Hello World: %i %i // %i %i\n",thread.league_rank(),thread.team_rank(),thread.league_size(),thread.team_size());
  }
};

int main(int narg, char* args[]) {
  Kokkos::initialize(narg,args);

  // Launch 12 teams of the maximum number of threads per team
  const int team_size_max = team_policy(1,1).team_size_max(hello_world(), Kokkos::ParallelReduceTag());
  const team_policy policy_a( 12 , team_size_max );

  int sum = 0;
  Kokkos::parallel_reduce( policy_a , hello_world() , sum );

  // The result will be 12*team_size_max
  printf("Result A: %i == %i\n",sum, team_size_max*12);

  // In practice it is often better to let Kokkos decide on the team_size
  const team_policy policy_b( 12 , Kokkos::AUTO );

  Kokkos::parallel_reduce( policy_b , hello_world() , sum );
  // The result will be 12*policy_b.team_size_recommended( hello_world(),  Kokkos::ParallelReduceTag())
  const int team_size_recommended = policy_b.team_size_recommended( hello_world(),  Kokkos::ParallelReduceTag());
  printf("Result B: %i %i\n",sum, team_size_recommended*12);

  Kokkos::finalize();
}

