main.cpp

// Static dispatch SSE2
#include <hwy/highway.h>
#include <hwy/timer.h>  // Now()

#include <iostream>
#include <numeric>
#include <vector>

#include "dynamic_dispatch.h"

namespace hn = hwy::HWY_NAMESPACE;

using T = float;

void MulAddLoop(const T* HWY_RESTRICT mul_array,
                const T* HWY_RESTRICT add_array, const size_t size,
                T* HWY_RESTRICT x_array) {
  const hn::ScalableTag<T> d;

  for (size_t i = 0; i < size; i += hn::Lanes(d)) {
    const auto mul = hn::Load(d, mul_array + i);
    const auto add = hn::Load(d, add_array + i);

    // hwy::PrintArray(x_array, size);

    auto x = hn::Load(d, x_array + i);
    x = hn::Add(mul, add);
    hn::Store(x, d, x_array + i);
  }
}

int main() {
  using namespace std;
  std::vector<float> v_mult(100000000, 2.0);
  std::vector<float> v_add(100000000, 1.0);
  std::iota(v_add.begin(), v_add.end(), 1);
  std::vector<float> x_arr(100000000, 3.0);

  // for(auto i : v_mult) cout << i  << ' ';

  {
    const double t0 = hwy::platform::Now();
    for (auto i = 0; i < v_mult.size(); i++) {
      x_arr[i] = v_mult[i] + v_add[i];
    }
    const double elapsed = hwy::platform::Now() - t0;
    cout << "elapsed single: " << elapsed << endl;
  }

  {
    // Static dispatch
    const double t0 = hwy::platform::Now();
    MulAddLoop(&v_mult[0], &v_add[0], x_arr.size(), &x_arr[0]);
    const double elapsed = hwy::platform::Now() - t0;
    cout << "elapsed SSE2: " << elapsed << endl;
    // for(auto i : x_arr) cout << i  << ' ';
  }

  {
    // Dynamic dispatch
    const double t0 = hwy::platform::Now();
    EXAMPLE_DYNAMIC::CallMulAddLoop(&v_mult[0], &v_add[0], x_arr.size(),
                                    &x_arr[0]);
    const double elapsed = hwy::platform::Now() - t0;
    cout << "elapsed AVX: " << elapsed << endl;
    // for(auto i : x_arr) cout << i  << ' ';
  }

  /*
  Approx:
  elapsed single: 0.109093
  elapsed SSE2: 0.0911126
  elapsed AVX: 0.0868143
  */

  std::cout << "DONE" << std::endl;
}