text: // Boost.uBLAS
  //
  // Copyright (c) 2018 Fady Essam
  // Copyright (c) 2018 Stefan Seefeld
  //
  // Distributed under the Boost Software License, Version 1.0.
  // (See accompanying file LICENSE_1_0.txt or
  // copy at http://www.boost.org/LICENSE_1_0.txt)
  
  #ifndef boost_numeric_ublas_opencl_transpose_hpp_
  #define boost_numeric_ublas_opencl_transpose_hpp_
  
  #include <boost/numeric/ublas/opencl/library.hpp>
  #include <boost/numeric/ublas/opencl/vector.hpp>
  #include <boost/numeric/ublas/opencl/matrix.hpp>
  
  // Kernel for transposition of various data types
  #define OPENCL_TRANSPOSITION_KERNEL(DATA_TYPE)	\
  "__kernel void transpose(__global "  #DATA_TYPE "* in, __global " #DATA_TYPE "* result, unsigned int width, unsigned int height) \n"                       \
  "{ \n"								        \
  "  unsigned int column_index = get_global_id(0); \n"			\
  "  unsigned int row_index = get_global_id(1); \n"			\
  "  if (column_index < width && row_index < height) \n"			\
  "  { \n"							      	\
  "    unsigned int index_in = column_index + width * row_index; \n"	\
  "    unsigned int index_result = row_index + height * column_index; \n"	\
  "    result[index_result] = in[index_in]; \n"				\
  "  } \n"								\
  "} \n"
  
  
  namespace boost { namespace numeric { namespace ublas { namespace opencl {
  
  template<class T, class L1, class L2>
  typename std::enable_if<is_numeric<T>::value>::type
  change_layout(ublas::matrix<T, L1, opencl::storage> const &m,
  	      ublas::matrix<T, L2, opencl::storage> &result,
  	      compute::command_queue& queue)
  {
    assert(m.size1() == result.size1() && m.size2() == result.size2());
    assert(m.device() == result.device() && m.device() == queue.get_device());
    assert(!(std::is_same<L1, L2>::value));
    char const *kernel;
    if (std::is_same<T, float>::value)
      kernel = OPENCL_TRANSPOSITION_KERNEL(float);
    else if (std::is_same<T, double>::value)
      kernel = OPENCL_TRANSPOSITION_KERNEL(double);
    else if (std::is_same<T, std::complex<float>>::value)
      kernel = OPENCL_TRANSPOSITION_KERNEL(float2);
    else if (std::is_same<T, std::complex<double>>::value)
      kernel = OPENCL_TRANSPOSITION_KERNEL(double2);
    size_t len = strlen(kernel);
    cl_int err;
    cl_context c_context = queue.get_context().get();
    cl_program program = clCreateProgramWithSource(c_context, 1, &kernel, &len, &err);
    clBuildProgram(program, 1, &queue.get_device().get(), NULL, NULL, NULL);
    cl_kernel c_kernel = clCreateKernel(program, "transpose", &err);
    size_t width = std::is_same < L1, ublas::basic_row_major<>>::value ? m.size2() : m.size1();
    size_t height = std::is_same < L1, ublas::basic_row_major<>>::value ? m.size1() : m.size2();
    size_t global_size[2] = { width , height };
    clSetKernelArg(c_kernel, 0, sizeof(T*), &m.begin().get_buffer().get());
    clSetKernelArg(c_kernel, 1, sizeof(T*), &result.begin().get_buffer().get());
    clSetKernelArg(c_kernel, 2, sizeof(unsigned int), &width);
    clSetKernelArg(c_kernel, 3, sizeof(unsigned int), &height);
    cl_command_queue c_queue = queue.get();
    cl_event event = NULL;
    clEnqueueNDRangeKernel(c_queue, c_kernel, 2, NULL, global_size, NULL, 0, NULL, &event);
    clWaitForEvents(1, &event);
  }
  
  template<class T, class L1, class L2, class A>
  typename std::enable_if<is_numeric<T>::value>::type
  change_layout(ublas::matrix<T, L1, A> const &m,
  	      ublas::matrix<T, L2, A> &result,
  	      compute::command_queue& queue)
  {
    ublas::matrix<T, L1, opencl::storage> mdev(m, queue);
    ublas::matrix<T, L2, opencl::storage> rdev(result.size1(), result.size2(), queue.get_context());
    change_layout(mdev, rdev, queue);
    rdev.to_host(result, queue);
  }
  
  template<class T, class L>
  typename std::enable_if<is_numeric<T>::value>::type
  trans(ublas::matrix<T, L, opencl::storage> const &m,
        ublas::matrix<T, L, opencl::storage> &result,
        compute::command_queue& queue)
  {
    assert(m.size1() == result.size2() && m.size2() == result.size1());
    assert(m.device() == result.device() && m.device() == queue.get_device());
    char const *kernel;
    if (std::is_same<T, float>::value)
      kernel = OPENCL_TRANSPOSITION_KERNEL(float);
    else if (std::is_same<T, double>::value)
      kernel = OPENCL_TRANSPOSITION_KERNEL(double);
    else if (std::is_same<T, std::complex<float>>::value)
      kernel = OPENCL_TRANSPOSITION_KERNEL(float2);
    else if (std::is_same<T, std::complex<double>>::value)
      kernel = OPENCL_TRANSPOSITION_KERNEL(double2);
    size_t len = strlen(kernel);
    cl_int err;
    cl_context c_context = queue.get_context().get();
    cl_program program = clCreateProgramWithSource(c_context, 1, &kernel, &len, &err);
    clBuildProgram(program, 1, &queue.get_device().get(), NULL, NULL, NULL);
    cl_kernel c_kernel = clCreateKernel(program, "transpose", &err);
    size_t width = std::is_same <L, ublas::basic_row_major<>>::value ? m.size2() : m.size1();
    size_t height = std::is_same <L, ublas::basic_row_major<>>::value ? m.size1() : m.size2();
    size_t global_size[2] = { width , height };
    clSetKernelArg(c_kernel, 0, sizeof(T*), &m.begin().get_buffer().get());
    clSetKernelArg(c_kernel, 1, sizeof(T*), &result.begin().get_buffer().get());
    clSetKernelArg(c_kernel, 2, sizeof(unsigned int), &width);
    clSetKernelArg(c_kernel, 3, sizeof(unsigned int), &height);
    cl_command_queue c_queue = queue.get();
    cl_event event = NULL;
    clEnqueueNDRangeKernel(c_queue, c_kernel, 2, NULL, global_size, NULL, 0, NULL, &event);
    clWaitForEvents(1, &event);
  }
  
  template<class T, class L, class A>
  typename std::enable_if<is_numeric<T>::value>::type
  trans(ublas::matrix<T, L, A> const &m,
        ublas::matrix<T, L, A> &result,
        compute::command_queue& queue)
  {
    ublas::matrix<T, L, opencl::storage> mdev(m, queue);
    ublas::matrix<T, L, opencl::storage> rdev(result.size1(), result.size2(), queue.get_context());
    trans(mdev, rdev, queue);
    rdev.to_host(result, queue);
  }
  
  template<class T, class L, class A>
  typename std::enable_if<is_numeric<T>::value, ublas::matrix<T, L, A>>::type
  trans(ublas::matrix<T, L, A>& m, compute::command_queue& queue)
  {
    ublas::matrix<T, L, A> result(m.size2(), m.size1());
    trans(m, result, queue);
    return result;
  }
  
  }}}}
  
  #endif
  