xtensor-advanced-example.cpp

#include <iostream>

#include "xtensor/xio.hpp"
#include "xtensor/xnpy.hpp"
#include "xtensor/xrandom.hpp"
#include "xtensor/xtensor.hpp"
#include "xtensor/xview.hpp"

using farray = xt::xtensor<float, 2, xt::layout_type::row_major>;

const int B = 4;
const int M = 4;
const int N = 4;

template <class E>
auto transform(E& x) {
  auto x_reshaped = xt::reshape_view(x, {B, M, N});
  x_reshaped = x_reshaped * 2;
}

int main() {
  const farray x_orig = xt::random::randn<float>({B, 2 * M * N});
  const size_t split = M * N;
  using namespace xt::placeholders;

  {
    // Processing without copying
    farray x_view = x_orig;
    auto x1 = xt::view(x_view, xt::all(), xt::range(_, split));
    transform(x1);
    auto x2 = xt::view(x_view, xt::all(), xt::range(split, _));
    transform(x2);
    std::cout << "Same with views? " << xt::allclose(x_view, 2 * x_orig)
              << std::endl;
  }

  {
    // Processing with copying
    farray x_view = x_orig;
    auto x1 = xt::view(x_view, xt::all(), xt::range(_, split));
    {
      farray tmp = x1;
      transform(tmp);
      x1 = tmp;
    }
    auto x2 = xt::view(x_view, xt::all(), xt::range(split, _));
    {
      farray tmp = x2;
      transform(tmp);
      x2 = tmp;
    }
    std::cout << "Same with copies? " << xt::allclose(x_view, 2 * x_orig)
              << std::endl;
  }

  return 0;
}