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//===-- rosa/support/math.hpp -----------------------------------*- C++ -*-===//
//
// The RoSA Framework
//
//===----------------------------------------------------------------------===//
///
/// \file rosa/support/math.hpp
///
/// \author David Juhasz (david.juhasz@tuwien.ac.at)
///
/// \date 2017
///
/// \brief Math helpers.
///
//===----------------------------------------------------------------------===//
#ifndef ROSA_SUPPORT_MATH_HPP
#define ROSA_SUPPORT_MATH_HPP
#include <algorithm>
#include <cmath>
#include <cstdarg>
#include <cstdlib>
#include <limits>
#include <type_traits>
namespace rosa {
/// Computes log base 2 of a number.
///
/// \param N the number to compute log base 2 for
///
/// \return log base 2 of \p N
constexpr size_t log2(const size_t N) {
return ((N < 2) ? 1 : 1 + log2(N / 2));
}
/// Tells the next representable floating point value.
///
/// \tparam T type to operate on
///
/// \note The second type argument enforces \p T being a floating point type,
/// always use the default value!
///
/// \param V value to which find the next representable one
///
/// \return the next representable value of type \p T after value \p V
///
/// \pre Type \p T must be a floating point type, which is enforced by
/// `std::enable_if` in the second type argument.
template <typename T,
typename = std::enable_if_t<std::is_floating_point<T>::value>>
T nextRepresentableFloatingPoint(const T V) {
return std::nextafter(V, std::numeric_limits<T>::infinity());
}
// copied from the internet and adapted
// (https://stackoverflow.com/questions/1657883/variable-number-of-arguments-in-c)
/// Conjuncts two or more values with each other.
///
/// \param two or more values of the same datatype
///
/// \return the conjunction of the values given as parameter.
template <typename CONFDATATYPE>
CONFDATATYPE fuzzyAND(int n_args, ...) noexcept {
// TODO: check datatype, if there are at least two arguments, and if they are
// between 0 and 1
// David suggests: nstead of a variadic argument, you could pass the values as
// an std::array (with a template argument for the length). When you pass the
// values as a container, you can simply use std::max_element and
// std::min_element to have a one-liner implementation of the these fuzzy
// functions.
va_list ap;
va_start(ap, n_args);
CONFDATATYPE min = va_arg(ap, CONFDATATYPE);
for (int i = 2; i <= n_args; i++) {
CONFDATATYPE a = va_arg(ap, CONFDATATYPE);
min = std::min(a, min);
}
va_end(ap);
return min;
}
/// Disjuncts two or more values with each other.
///
/// \param two or more values of the same datatype
///
/// \return the disjunction of the values given as parameter.
// copied from the internet
// (https://stackoverflow.com/questions/1657883/variable-number-of-arguments-in-c)
template <typename CONFDATATYPE>
CONFDATATYPE fuzzyOR(int n_args, ...) noexcept {
// TODO: check datatype and if they are between 0 and 1
// David suggests: nstead of a variadic argument, you could pass the values as
// an std::array (with a template argument for the length). When you pass the
// values as a container, you can simply use std::max_element and
// std::min_element to have a one-liner implementation of the these fuzzy
// functions.
va_list ap;
va_start(ap, n_args);
CONFDATATYPE max = va_arg(ap, CONFDATATYPE);
for (int i = 2; i <= n_args; i++) {
CONFDATATYPE a = va_arg(ap, CONFDATATYPE);
max = std::max(a, max);
}
va_end(ap);
return max;
}
template <typename INDATATYPE, typename PROCDATATYPE>
PROCDATATYPE relativeDistance(INDATATYPE NewValue,
INDATATYPE HistoryValue) noexcept {
PROCDATATYPE Dist = HistoryValue - NewValue;
if (Dist == 0) {
return 0;
} else {
Dist = Dist / NewValue;
if (Dist < 0) {
// TODO: I guess this multiplication here should not be done because
// it could be that the distance fuzzy functions are not symetrical
//(negative and positive side)
Dist = Dist * (-1);
}
return (Dist);
}
}
} // End namespace rosa
#endif // ROSA_SUPPORT_MATH_HPP

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