RealComparison.hpp

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///////////////////////////////////////////////////////////////////////////////
//
// File: RealComparison.hpp
//
// For more information, please see: http://www.nektar.info
//
// The MIT License
//
// Copyright (c) 2006 Division of Applied Mathematics, Brown University (USA),
// Department of Aeronautics, Imperial College London (UK), and Scientific
// Computing and Imaging Institute, University of Utah (USA).
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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//
// Description: simple routines to compare 2 real
//
///////////////////////////////////////////////////////////////////////////////
 
#ifndef NEKTAR_LIB_UTILITIES_REALCOMPARISON_H
#define NEKTAR_LIB_UTILITIES_REALCOMPARISON_H
 
#include <LibUtilities/BasicConst/NektarUnivConsts.hpp>
#include <LibUtilities/BasicUtils/ErrorUtil.hpp>
#include <boost/math/special_functions/relative_difference.hpp>
#include <limits>
#include <type_traits>
 
namespace Nektar::LibUtilities
{
/// compare reals of same type with relative tolerance
template <
    class T1, class T2,
    class = typename std::enable_if<
        std::is_floating_point<typename std::remove_cv<
            typename std::remove_reference<T1>::type>::type>::value &&
        std::is_same<typename std::remove_cv<
                         typename std::remove_reference<T1>::type>::type,
                     typename std::remove_cv<typename std::remove_reference<
                         T2>::type>::type>::value>::type>
inline bool IsRealEqual(
    T1 &&lhs, T2 &&rhs,
    const unsigned int factor = NekConstants::kNekFloatCompFact)
{
    // Check precondition in debug mode
    ASSERTL1(factor >= 1, "real comparison factor needs to be >= 1");
    // Relative distance normalized by machine epsilon
    return boost::math::epsilon_difference(lhs, rhs) < factor;
}
 
/// compare reals of same type with absolute tolerance
template <
    class T1, class T2,
    class = typename std::enable_if<
        std::is_floating_point<typename std::remove_cv<
            typename std::remove_reference<T1>::type>::type>::value &&
        std::is_same<typename std::remove_cv<
                         typename std::remove_reference<T1>::type>::type,
                     typename std::remove_cv<typename std::remove_reference<
                         T2>::type>::type>::value>::type>
inline bool IsRealClose(T1 &&lhs, T2 &&rhs,
                        const NekDouble tol = NekConstants::kNekMachineEpsilon)
{
    // Check if tolerance is positive
    ASSERTL1(tol >= 0, "real comparison tolerance needs to be >= 0");
    // Check if distance is within tolerance
    return std::abs(lhs - rhs) < tol;
}
 
} // namespace Nektar::LibUtilities
 
#endif