vc_aos_approximately_equal.hpp

// This file is part of the ACTS project.
//
// Copyright (C) 2016 CERN for the benefit of the ACTS project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
#pragma once
 
// Project include(s)
#include "detray/algebra/concepts.hpp"
#include "detray/definitions/detail/qualifiers.hpp"
 
// Vc include(s).
#ifdef _MSC_VER
#pragma warning(push, 0)
#endif  // MSVC
#include <Vc/Vc>
#ifdef _MSC_VER
#pragma warning(pop)
#endif  // MSVC
 
// System include(s)
#include <concepts>
#include <limits>
 
namespace detray::algebra {

template <typename simd1_t, typename simd2_t>
  requires((Vc::is_simd_vector<simd1_t>::value &&
            std::convertible_to<simd2_t, simd1_t>) ||
           (Vc::is_simd_vector<simd2_t>::value &&
            std::convertible_to<simd1_t, simd2_t>))
DETRAY_HOST_DEVICE constexpr auto approx_equal(
    const simd1_t a, const simd2_t b,
    const typename simd1_t::value_type rel_error =
        16.f * std::numeric_limits<typename simd1_t::value_type>::epsilon(),
    const typename simd1_t::value_type max_error =
        std::numeric_limits<typename simd1_t::value_type>::epsilon()) {
  static_assert(
      std::same_as<typename simd1_t::value_type, typename simd2_t::value_type>);
 
  if constexpr (std::integral<typename simd1_t::value_type>) {
    return (a == b).isFull();
  } else {
    // Calculate the difference.
    const simd1_t diff{Vc::abs(a - b)};
 
    // If the numbers are is close to zero
    if ((diff <= simd1_t(max_error)).isFull()) {
      return true;
    }
 
    // Find the largest entries and scale the epsilon
    const simd1_t largest = Vc::max(Vc::abs(a), Vc::abs(b));
 
    return (diff <= (largest * rel_error)).isFull();
  }
}
 
}  // namespace detray::algebra