/*
//@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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// notice, this list of conditions and the following disclaimer in the
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// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Questions? Contact  H. Carter Edwards (hcedwar@sandia.gov)
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*/

#ifndef KOKKOS_CUDA_INTERNAL_HPP
#define KOKKOS_CUDA_INTERNAL_HPP
#include<iostream>
#include <Kokkos_Macros.hpp>

/* only compile this file if CUDA is enabled for Kokkos */
#ifdef KOKKOS_HAVE_CUDA

#include <Cuda/Kokkos_Cuda_Error.hpp>

namespace Kokkos { namespace Impl {

template<class DriverType, bool Large>
struct CudaGetMaxBlockSize;

template<class DriverType, bool Large = (CudaTraits::ConstantMemoryUseThreshold < sizeof(DriverType))>
int cuda_get_max_block_size(const typename DriverType::functor_type & f, const size_t vector_length,
                            const size_t shmem_extra_block, const size_t shmem_extra_thread) {
  return CudaGetMaxBlockSize<DriverType,Large>::get_block_size(f,vector_length, shmem_extra_block,shmem_extra_thread);
}


template<class DriverType>
struct CudaGetMaxBlockSize<DriverType,true> {
  static int get_block_size(const typename DriverType::functor_type & f, const size_t vector_length,
                            const size_t shmem_extra_block, const size_t shmem_extra_thread) {
    int numBlocks;
    int blockSize=32;
    int sharedmem = shmem_extra_block + shmem_extra_thread*(blockSize/vector_length) +
                    FunctorTeamShmemSize< typename DriverType::functor_type  >::value( f , blockSize/vector_length );
    cudaOccupancyMaxActiveBlocksPerMultiprocessor(
        &numBlocks,
        cuda_parallel_launch_constant_memory<DriverType>,
        blockSize,
        sharedmem);

    while (blockSize<1024 && numBlocks>0) {
      blockSize*=2;
      sharedmem = shmem_extra_block + shmem_extra_thread*(blockSize/vector_length) +
                  FunctorTeamShmemSize< typename DriverType::functor_type  >::value( f , blockSize/vector_length );

      cudaOccupancyMaxActiveBlocksPerMultiprocessor(
          &numBlocks,
          cuda_parallel_launch_constant_memory<DriverType>,
          blockSize,
          sharedmem);
    }
    if(numBlocks>0) return blockSize;
    else return blockSize/2;
  }
};

template<class DriverType>
struct CudaGetMaxBlockSize<DriverType,false> {
  static int get_block_size(const typename DriverType::functor_type & f, const size_t vector_length,
                            const size_t shmem_extra_block, const size_t shmem_extra_thread) {
    int numBlocks;

    int blockSize=32;
    int sharedmem = shmem_extra_block + shmem_extra_thread*(blockSize/vector_length) +
                    FunctorTeamShmemSize< typename DriverType::functor_type  >::value( f , blockSize/vector_length );
    cudaOccupancyMaxActiveBlocksPerMultiprocessor(
        &numBlocks,
        cuda_parallel_launch_local_memory<DriverType>,
        blockSize,
        sharedmem);

    while (blockSize<1024 && numBlocks>0) {
      blockSize*=2;
      sharedmem = shmem_extra_block + shmem_extra_thread*(blockSize/vector_length) +
                  FunctorTeamShmemSize< typename DriverType::functor_type  >::value( f , blockSize/vector_length );

      cudaOccupancyMaxActiveBlocksPerMultiprocessor(
          &numBlocks,
          cuda_parallel_launch_local_memory<DriverType>,
          blockSize,
          sharedmem);
    }
    if(numBlocks>0) return blockSize;
    else return blockSize/2;
  }
};



template<class DriverType, bool Large>
struct CudaGetOptBlockSize;

template<class DriverType, bool Large = (CudaTraits::ConstantMemoryUseThreshold < sizeof(DriverType))>
int cuda_get_opt_block_size(const typename DriverType::functor_type & f, const size_t vector_length,
                            const size_t shmem_extra_block, const size_t shmem_extra_thread) {
  return CudaGetOptBlockSize<DriverType,Large>::get_block_size(f,vector_length,shmem_extra_block,shmem_extra_thread);
}

template<class DriverType>
struct CudaGetOptBlockSize<DriverType,true> {
  static int get_block_size(const typename DriverType::functor_type & f, const size_t vector_length,
                            const size_t shmem_extra_block, const size_t shmem_extra_thread) {
    int blockSize=16;
    int numBlocks;
    int sharedmem;
    int maxOccupancy=0;
    int bestBlockSize=0;

    while(blockSize<1024) {
      blockSize*=2;

      //calculate the occupancy with that optBlockSize and check whether its larger than the largest one found so far
      sharedmem = shmem_extra_block + shmem_extra_thread*(blockSize/vector_length) +
                  FunctorTeamShmemSize< typename DriverType::functor_type  >::value( f , blockSize/vector_length );
      cudaOccupancyMaxActiveBlocksPerMultiprocessor(
              &numBlocks,
              cuda_parallel_launch_constant_memory<DriverType>,
              blockSize,
              sharedmem);
      if(maxOccupancy < numBlocks*blockSize) {
         maxOccupancy = numBlocks*blockSize;
         bestBlockSize = blockSize;
      }
    }
    return bestBlockSize;
  }
};

template<class DriverType>
struct CudaGetOptBlockSize<DriverType,false> {
  static int get_block_size(const typename DriverType::functor_type & f, const size_t vector_length,
                            const size_t shmem_extra_block, const size_t shmem_extra_thread) {
    int blockSize=16;
    int numBlocks;
    int sharedmem;
    int maxOccupancy=0;
    int bestBlockSize=0;

    while(blockSize<1024) {
      blockSize*=2;
      sharedmem = shmem_extra_block + shmem_extra_thread*(blockSize/vector_length) +
                  FunctorTeamShmemSize< typename DriverType::functor_type  >::value( f , blockSize/vector_length );

      cudaOccupancyMaxActiveBlocksPerMultiprocessor(
              &numBlocks,
              cuda_parallel_launch_local_memory<DriverType>,
              blockSize,
              sharedmem);

      if(maxOccupancy < numBlocks*blockSize) {
        maxOccupancy = numBlocks*blockSize;
        bestBlockSize = blockSize;
      }
    }
    return bestBlockSize;
  }
};

}} // namespace Kokkos::Impl

#endif // KOKKOS_HAVE_CUDA
#endif /* #ifndef KOKKOS_CUDA_INTERNAL_HPP */

