gistfile1.txt

#include <valarray>
#include <stdio.h>
#include <random>
#include <functional>

double MSE(const std::valarray<float>& target,
    const std::valarray<float>& lossy) {
  return ((target-lossy)*(target-lossy)).sum() / target.size();
}

int main() {
  int n = 100;
  std::valarray<float> target(n), lossy(n);
  std::mt19937::result_type seed = 0xDEADBEEF;
  auto real_rand = std::bind(std::uniform_real_distribution<double>(0,1),
                           std::mt19937(seed));
  for (int i = 0; i < n; ++i) {
    target[i] = real_rand();
  }

  // method 1: use mean
  lossy = target.sum() / n;
  printf("method 1: %.8f\n", MSE(target, lossy));

  // method 2: search for random seed
  double best = 1;
  for (int i = 0; i < 10000; ++i) {
    for (int j = 0; j < n; ++j) {
      lossy[j] = real_rand();
    }
    double mse = MSE(target, lossy);
    if (mse < best) {
      best = mse;
    }
  }
  printf("method 2: %.8f\n", best);

  // method 3: random seed + offset
  best = 1;
  for (int i = 0; i < 10000; ++i) {
    for (int j = 0; j < n; ++j) {
      lossy[j] = real_rand();
    }
    lossy += (target.sum() / n) - (lossy.sum() / n);
    for (int j = 0; j < n; ++j) {
      if (lossy[j] < 0) lossy[j] = 0;
      else if (lossy[j] > 1) lossy[j] = 1;
    }
    double mse = MSE(target, lossy);
    if (mse < best) {
      best = mse;
    }
  }
  printf("method 3: %.8f\n", best);

  // method 4: sample from Bates distribution
  best = 1;
  for (int i = 0; i < 1000; ++i) {
    for (int j = 0; j < n; ++j) {
      double val = 0;
      for (int k = 0; k < n; ++k) {
        val += real_rand();
      }
      lossy[j] = val / n;
    }
    double mse = MSE(target, lossy);
    if (mse < best) {
      best = mse;
    }
  }
  printf("method 4: %.8f\n", best);

  // method 5: sample from normal distribution
  best = 1;
  std::default_random_engine generator;
  std::normal_distribution<double> distribution(0.5, 0.01);
  for (int i = 0; i < 10000; ++i) {
    for (int j = 0; j < n; ++j) {
      lossy[j] = distribution(generator);
    }
    double mse = MSE(target, lossy);
    if (mse < best) {
      best = mse;
    }
  }
  printf("method 5: %.8f\n", best);
}