integrator_angle_cpu.hh

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#pragma once
 
// standard library
#include <future>
 
// external libraries
#include <tbb/tbb.h>
 
// DiFfRG
#include <DiFfRG/common/quadrature/quadrature_provider.hh>
 
namespace DiFfRG
{
  template <int d, typename NT, typename KERNEL> class IntegratorAngleTBB
  {
  public:
    using ctype = typename get_type::ctype<NT>;
 
    IntegratorAngleTBB(QuadratureProvider &quadrature_provider, const std::array<uint, 2> grid_sizes,
                       const ctype x_extent, const JSONValue &)
        : IntegratorAngleTBB(quadrature_provider, grid_sizes, x_extent)
    {
    }
 
    IntegratorAngleTBB(QuadratureProvider &quadrature_provider, std::array<uint, 2> grid_sizes, const ctype x_extent,
                       const uint max_block_size = 0)
        : grid_sizes(grid_sizes), x_extent(x_extent),
          x_quadrature_p(quadrature_provider.get_points<ctype>(grid_sizes[0])),
          x_quadrature_w(quadrature_provider.get_weights<ctype>(grid_sizes[0])),
          ang_quadrature_p(quadrature_provider.get_points<ctype>(grid_sizes[1])),
          ang_quadrature_w(quadrature_provider.get_weights<ctype>(grid_sizes[1]))
    {
      (void)max_block_size;
    }
 
    template <typename... T> NT get(const ctype k, const T &...t) const
    {
      constexpr ctype S_d = S_d_prec<ctype>(d);
      using std::sqrt;
 
      const auto constant = KERNEL::constant(k, t...);
      return constant + tbb::parallel_reduce(
                            tbb::blocked_range2d<uint, uint>(0, grid_sizes[0], 0, grid_sizes[1]), NT(0.),
                            [&](const tbb::blocked_range2d<uint, uint> &r, NT value) -> NT {
                              for (uint idx_x = r.rows().begin(); idx_x != r.rows().end(); ++idx_x) {
                                const ctype q = k * sqrt(x_quadrature_p[idx_x] * x_extent);
                                for (uint idx_y = r.cols().begin(); idx_y != r.cols().end(); ++idx_y) {
                                  const ctype cos = 2 * (ang_quadrature_p[idx_y] - (ctype)0.5);
                                  const ctype int_element =
                                      S_d                                        // solid nd angle
                                      * (powr<d - 2>(q) / (ctype)2 * powr<2>(k)) // x = p^2 / k^2 integral
                                      * (1 / (ctype)2)                           // divide the cos integral out
                                      / powr<d>(2 * (ctype)M_PI);                // fourier factor
                                  const ctype weight = 2 * ang_quadrature_w[idx_y] * x_quadrature_w[idx_x] * x_extent;
                                  value += int_element * weight * KERNEL::kernel(q, cos, k, t...);
                                }
                              }
                              return value;
                            },
                            [&](NT x, NT y) -> NT { return x + y; });
    }
 
    template <typename... T> std::future<NT> request(const ctype k, const T &...t) const
    {
      return std::async(std::launch::deferred, [=, this]() { return get(k, t...); });
    }
 
  private:
    const std::array<uint, 2> grid_sizes;
 
    const ctype x_extent;
 
    const std::vector<ctype> &x_quadrature_p;
    const std::vector<ctype> &x_quadrature_w;
    const std::vector<ctype> &ang_quadrature_p;
    const std::vector<ctype> &ang_quadrature_w;
  };
} // namespace DiFfRG