アドカレ用

advent_calendar.cpp

#include <iostream>
#include <array>
#include <cmath>

template<typename T, typename U, size_t DATA_NUM>
using dataType = std::array<std::pair<T, U>, DATA_NUM>;

template<typename Array = std::array<double, 2>>
using Array = Array;

constexpr double operator*(Array<> a, Array<> b) {
  double num = 0;
  for(size_t i = 0; i < a.size(); ++i)
    num += a[i]*b[i];
  return num;
}

constexpr Array<> operator*(double a, Array<> b) {
  return {b[0]*a, b[1]*a};
}

constexpr Array<> operator+(Array<> a, Array<> b) {
  return {a[0]+b[0], a[1]+b[1]};
}

constexpr Array<> operator+(Array<> a, double b) {
  return {a[0]+b, a[1]+b};
}

constexpr Array<> operator/(Array<> a, double b) {
  return {a[0]/b, a[1]/b};
}

constexpr Array<> operator/(Array<> a, Array<> b) {
  return {a[0]/b[0], a[1]/b[1]};
}

constexpr Array<> operator-(Array<> a, Array<> b) {
  return {a[0]-b[0], a[1]-b[1]};
}

constexpr double pow(double num, int times){
  if(times == 0) return 1;
  return num*pow(num, times-1);
}

constexpr double constexpr_sqrt(double num){
  double current = num;
  double prev = 0;
  while(current-prev != 0) {
    prev = current;
    current = (current+num/current)/2;
  }
  return current;
}

constexpr std::uint64_t fact(int num){
  if(num == 0) return 1;
  return num*fact(num-1);
}

constexpr double constexpr_exp(double num){
  double result = 0;
  for(int i = 0; i < 10; ++i){
    result += (pow(num, i)/fact(i));
  }
  return result;
}

constexpr double sigmoid(Array<> _w,  Array<> _ed) {
  double num = _w*_ed;
  return 1 / (1 + constexpr_exp(-num));
}

constexpr Array<> pow(Array<> a, int b) {
  return {pow(a[0], 2), pow(a[1], 2)};
}

constexpr Array<> sqrt(Array<> a) {
  return {constexpr_sqrt(a[0]), constexpr_sqrt(a[1])};
}

constexpr Array<> train() {
  constexpr dataType<double, int, 12> data = {
    std::make_pair(1.0, 0), std::make_pair(1.15, 0), std::make_pair(1.2, 0),
    std::make_pair(1.25, 0), std::make_pair(1.3, 0), std::make_pair(1.35, 0),
    std::make_pair(1.4, 0), std::make_pair(1.45, 1), std::make_pair(1.5, 1),
    std::make_pair(1.55, 1), std::make_pair(1.6, 1), std::make_pair(1.65, 1),
  };

  Array<> w = {1.0, 0.0};
  double alpha = 0.001;
  double pred = 0.0;

  for(size_t time = 1; time <= 3000; ++time) {
    for(auto& d: data) {
      Array<> extended_data = {d.first, 1};
      pred = sigmoid(w, extended_data);    
      w = w-alpha*(pred-d.second)*pred*(1-pred)*extended_data;
    }
  }

  return w;
}

int main(int argc, char const *argv[]) {
  constexpr Array<> result = train();
  std::cout << result[0] << " " << result[1] << std::endl;
  return 0;
}