/***************************************************************************
                          CudaHost.h  -  description
                             -------------------
    begin                : Apr 8, 2019
    copyright            : (C) 2019 by Tomas Oberhuber et al.
    email                : tomas.oberhuber@fjfi.cvut.cz
 ***************************************************************************/

/* See Copyright Notice in tnl/Copyright */

// Implemented by: Jakub Klinkovsky

#pragma once

#include <TNL/Devices/Cuda.h>

namespace TNL {
namespace Allocators {

/**
 * \brief Allocator for page-locked memory on the host.
 *
 * The allocation is done using the `cudaMallocHost` function and the
 * deallocation is done using the `cudaFreeHost` function.
 */
template< class T >
struct CudaHost
{
   using value_type = T;
   using size_type = std::size_t;
   using difference_type = std::ptrdiff_t;

   CudaHost() = default;
   CudaHost( const CudaHost& ) = default;
   CudaHost( CudaHost&& ) = default;

   CudaHost& operator=( const CudaHost& ) = default;
   CudaHost& operator=( CudaHost&& ) = default;

   template< class U >
   CudaHost( const CudaHost< U >& )
   {}

   template< class U >
   CudaHost( CudaHost< U >&& )
   {}

   template< class U >
   CudaHost& operator=( const CudaHost< U >& )
   {
      return *this;
   }

   template< class U >
   CudaHost& operator=( CudaHost< U >&& )
   {
      return *this;
   }

   value_type* allocate( size_type n )
   {
#ifdef HAVE_CUDA
      TNL_CHECK_CUDA_DEVICE;
      value_type* result = nullptr;
      // cudaHostAllocPortable - The memory returned by this call will be considered as pinned memory by all
      //                       CUDA contexts, not just the one that performed the allocation.
      // cudaHostAllocMapped - Maps the allocation into the CUDA address space.
      // Also note that we assume that the cudaDevAttrCanUseHostPointerForRegisteredMem attribute is non-zero
      // on all devices visible to the application, in which case the pointer returned by cudaMallocHost can
      // be used directly by all devices without having to call cudaHostGetDevicePointer. See the reference:
      // https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__MEMORY.html#group__CUDART__MEMORY_1gc00502b44e5f1bdc0b424487ebb08db0
      if( cudaMallocHost( (void**) &result, n * sizeof(value_type), cudaHostAllocPortable | cudaHostAllocMapped ) != cudaSuccess )
         throw Exceptions::CudaBadAlloc();
      TNL_CHECK_CUDA_DEVICE;
      return result;
#else
      throw Exceptions::CudaSupportMissing();
#endif
   }

   void deallocate(value_type* ptr, size_type)
   {
#ifdef HAVE_CUDA
      TNL_CHECK_CUDA_DEVICE;
      cudaFreeHost( ptr );
      TNL_CHECK_CUDA_DEVICE;
#else
      throw Exceptions::CudaSupportMissing();
#endif
   }
};

template<class T1, class T2>
bool operator==(const CudaHost<T1>&, const CudaHost<T2>&)
{
   return true;
}

template<class T1, class T2>
bool operator!=(const CudaHost<T1>& lhs, const CudaHost<T2>& rhs)
{
   return !(lhs == rhs);
}

} // namespace Allocators
} // namespace TNL
