/*
//@HEADER
// ************************************************************************
// 
//                        Kokkos v. 2.0
//              Copyright (2014) Sandia Corporation
// 
// Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
// the U.S. Government retains certain rights in this software.
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// 1. Redistributions of source code must retain the above copyright
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// documentation and/or other materials provided with the distribution.
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// this software without specific prior written permission.
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*/

#include <Kokkos_Core.hpp>
#include <Kokkos_DualView.hpp>
#include <impl/Kokkos_Timer.hpp>
#include <cstdio>
#include <cstdlib>

typedef Kokkos::DefaultExecutionSpace       Device ;
typedef Kokkos::HostSpace::execution_space  Host ;

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

static const int TEAM_SIZE = 16 ;

struct find_2_tuples {
  int chunk_size;
  Kokkos::View<const int*> data;
  Kokkos::View<int**> histogram;

  find_2_tuples(int chunk_size_, Kokkos::DualView<int*> data_,
                Kokkos::DualView<int**> histogram_):chunk_size(chunk_size_),
                data(data_.d_view),histogram(histogram_.d_view) {
      data_.sync<Device>();
      histogram_.sync<Device>();
      histogram_.modify<Device>();
  }

  KOKKOS_INLINE_FUNCTION
  void operator() ( const team_member & dev) const {
    Kokkos::View<int**,Kokkos::MemoryUnmanaged> l_histogram(dev.team_shmem(),TEAM_SIZE,TEAM_SIZE);
    Kokkos::View<int*,Kokkos::MemoryUnmanaged> l_data(dev.team_shmem(),chunk_size+1);

    const int i = dev.league_rank() * chunk_size;
    for(int j = dev.team_rank(); j<chunk_size+1; j+=dev.team_size())
      l_data(j) = data(i+j);

    for(int k = dev.team_rank(); k < TEAM_SIZE; k+=dev.team_size())
      for(int l = 0; l < TEAM_SIZE; l++)
        l_histogram(k,l) = 0;
    dev.team_barrier();

    for(int j = 0; j<chunk_size; j++) {
      for(int k = dev.team_rank(); k < TEAM_SIZE; k+=dev.team_size())
        for(int l = 0; l < TEAM_SIZE; l++) {
          if((l_data(j) == k) && (l_data(j+1)==l))
            l_histogram(k,l)++;
        }
    }

    for(int k = dev.team_rank(); k < TEAM_SIZE; k+=dev.team_size())
      for(int l = 0; l < TEAM_SIZE; l++) {
        Kokkos::atomic_fetch_add(&histogram(k,l),l_histogram(k,l));
      }
    dev.team_barrier();
  }
  size_t team_shmem_size( int team_size ) const { 
    return Kokkos::View<int**,Kokkos::MemoryUnmanaged>::shmem_size(TEAM_SIZE,TEAM_SIZE) +
           Kokkos::View<int*,Kokkos::MemoryUnmanaged>::shmem_size(chunk_size+1);
  }
};

int main(int narg, char* args[]) {
  Kokkos::initialize(narg,args);
  
  int chunk_size = 1024;
  int nchunks = 100000; //1024*1024;
  Kokkos::DualView<int*> data("data",nchunks*chunk_size+1);

  srand(1231093);

  for(int i = 0; i < (int) data.dimension_0(); i++) {
    data.h_view(i) = rand()%TEAM_SIZE;
  }
  data.modify<Host>();
  data.sync<Device>();

  Kokkos::DualView<int**> histogram("histogram",TEAM_SIZE,TEAM_SIZE);


  Kokkos::Timer timer;
  // threads/team is automatically limited to maximum supported by the device.
  Kokkos::parallel_for( team_policy( nchunks , TEAM_SIZE )
                      , find_2_tuples(chunk_size,data,histogram) );
  Kokkos::fence();
  double time = timer.seconds();

  histogram.sync<Host>();

  printf("Time: %f \n\n",time);
  int sum = 0;
  for(int k=0; k<TEAM_SIZE; k++) {
    for(int l=0; l<TEAM_SIZE; l++) {
      printf("%i ",histogram.h_view(k,l));
      sum += histogram.h_view(k,l);
    }
    printf("\n");
  }
  printf("Result: %i %i\n",sum,chunk_size*nchunks);
  Kokkos::finalize();
}

