libstdc++-v3/testsuite/experimental/simd/tests/reductions.cc

// Copyright (C) 2020-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3.  If not see
// <http://www.gnu.org/licenses/>.

// expensive: * [1-9] * *
#include "bits/verify.h"
#include "bits/metahelpers.h"
#include "bits/test_values.h"
#include <random>

template <typename V>
  void
  test()
  {
    using T = typename V::value_type;
    COMPARE(reduce(V(1)), T(V::size()));
    {
      V x = 1;
      COMPARE(reduce(x, std::multiplies<>()), T(1));
      x[0] = 2;
      COMPARE(reduce(x, std::multiplies<>()), T(2));
      if constexpr (V::size() > 1)
	{
	  x[V::size() - 1] = 3;
	  COMPARE(reduce(x, std::multiplies<>()), T(6));
	}
    }
    COMPARE(reduce(V([](int i) { return i & 1; })), T(V::size() / 2));
    COMPARE(reduce(V([](int i) { return i % 3; })),
	    T(3 * (V::size() / 3)   // 0+1+2 for every complete 3 elements in V
		+ (V::size() % 3) / 2 // 0->0, 1->0, 2->1 adjustment
	     ));
    if ((1 + V::size()) * V::size() / 2 <= std::__finite_max_v<T>)
      {
	COMPARE(reduce(V([](int i) { return i + 1; })),
		T((1 + V::size()) * V::size() / 2));
      }

    {
      const V y = 2;
      COMPARE(reduce(y), T(2 * V::size()));
      COMPARE(reduce(where(y > 2, y)), T(0));
      COMPARE(reduce(where(y == 2, y)), T(2 * V::size()));
    }

    {
      COMPARE(hmin(V(1)), T(1));
      COMPARE(hmax(V(1)), T(1));
      const V z([](T i) { return i + 1; });
      COMPARE(std::experimental::reduce(z,
					[](auto a, auto b) {
					  using std::min;
					  return min(a, b);
					}),
	      T(1))
	<< "z: " << z;
      COMPARE(std::experimental::reduce(z,
					[](auto a, auto b) {
					  using std::max;
					  return max(a, b);
					}),
	      T(V::size()))
	<< "z: " << z;
      COMPARE(std::experimental::reduce(where(z > 1, z), 117,
					[](auto a, auto b) {
					  using std::min;
					  return min(a, b);
					}),
	      T(V::size() == 1 ? 117 : 2))
	<< "z: " << z;
      COMPARE(hmin(z), T(1));
      COMPARE(hmax(z), T(V::size()));
      if (V::size() > 1)
	{
	  COMPARE(hmin(where(z > 1, z)), T(2));
	  COMPARE(hmax(where(z > 1, z)), T(V::size()));
	}
      COMPARE(hmin(where(z < 4, z)), T(1));
      COMPARE(hmax(where(z < 4, z)), std::min(T(V::size()), T(3)));
      const V zz = make_value_unknown(z);
      COMPARE(hmin(zz), T(1));
      COMPARE(hmax(zz), T(V::size()));
      if (V::size() > 1)
	{
	  COMPARE(hmin(where(zz > 1, zz)), T(2));
	  COMPARE(hmax(where(zz > 1, zz)), T(V::size()));
	}
      COMPARE(hmin(where(zz < 4, zz)), T(1));
      COMPARE(hmax(where(zz < 4, zz)), std::min(T(V::size()), T(3)));
    }

    test_values<V>({}, {1000}, [](V x) {
      // avoid over-/underflow on signed integers:
      if constexpr (std::is_signed_v<T> && std::is_integral_v<T>)
	x /= int(V::size());
      // The error in the following could be huge if catastrophic
      // cancellation occurs. (e.g. `a-a+b+b` vs. `a+b+b-a`).
      // Avoid catastrophic cancellation for floating point:
      if constexpr (std::is_floating_point_v<T>)
	x = abs(x);
      T acc = x[0];
      for (size_t i = 1; i < V::size(); ++i)
	acc += x[i];
      ULP_COMPARE(reduce(x), acc, V::size() / 2).on_failure("x = ", x);
    });
  }