vireo/common/math.h

/*
 * MIT License
 *
 * Copyright (c) 2017 Twitter
 *
 * 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 THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#pragma once

#include <limits>
#include <math.h>
#include <vector>

#include "vireo/base_h.h"
#include "vireo/error/error.h"

namespace vireo {
namespace common {

using namespace std;

template <class T>
T mean(vector<T> values) {
  T acc = 0;
  for (auto v: values) {
    acc += v;
  }
  return acc / values.size();
}

template <class T>
double variance(vector<T> values) {
  T avg = mean(values);
  double acc = 0;
  for (auto v: values) {
    acc += v * v;
  }
  return (acc / values.size()) - avg * avg;
}

template <class T>
double std_dev(vector<T> values) {
  return sqrt(variance(values));
}

template <class T>
static inline typename std::enable_if<std::is_unsigned<T>::value & std::is_integral<T>::value, T>::type safe_umul(T x, T y) {
  THROW_IF(y && x > numeric_limits<T>::max() / y, Overflow);
  return x * y;
}

template <class T>
static inline T round_divide(T x, T num, T denom) {
  return (safe_umul(x, num) + (denom / 2)) / denom;
};

template <class T>
static inline T ceil_divide(T x, T num, T denom) {
  return (safe_umul(x, num) + (denom - 1)) / denom;
};

template <class T>
static inline T align_shift(T x, int shift) {
  return ((x + (1 << shift) - 1) >> shift) << shift;
};

template <class T>
static inline T align_divide(T x, T denom) {
  return ((x + (denom - 1)) / denom) * denom;
};

template <class T>
static T median(vector<T> values) {
  auto size = values.size();
  sort(values.begin(), values.end());
  auto mid = size / 2;
  return size ? ((size % 2 == 0) ? (values[mid - 1] + values[mid]) / 2 : values[mid]) : 0;
};

template <class T>
static inline T even(T x) {
  return x + (x & 0x01);
}

template <class T>
static inline T even_floor(T x) {
  return x - (x & 0x01);
}

}}