// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

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// Author: sameeragarwal@google.com (Sameer Agarwal)

#ifndef CERES_EXAMPLES_RANDOM_H_

#define CERES_EXAMPLES_RANDOM_H_

#include <math.h>

#include <stdlib.h>

namespace ceres {

namespace examples {

// Return a random number sampled from a uniform distribution in the range

// [0,1].

inline double RandDouble() {

  double r = static_cast<double>(rand());

  return r / RAND_MAX;

}

// Marsaglia Polar method for generation standard normal (pseudo)

// random numbers http://en.wikipedia.org/wiki/Marsaglia_polar_method

inline double RandNormal() {

  double x1, x2, w;

  do {

    x1 = 2.0 * RandDouble() - 1.0;

    x2 = 2.0 * RandDouble() - 1.0;

    w = x1 * x1 + x2 * x2;

  } while ( w >= 1.0 || w == 0.0 );

  w = sqrt((-2.0 * log(w)) / w);

  return x1 * w;

}

}  // namespace examples

}  // namespace ceres

#endif  // CERES_EXAMPLES_RANDOM_H_