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

// Copyright 2015 Google Inc. All rights reserved.

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

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

// * Redistributions of source code must retain the above copyright notice,

//   this list of conditions and the following disclaimer.

// * Redistributions in binary form must reproduce the above copyright notice,

//   this list of conditions and the following disclaimer in the documentation

//   and/or other materials provided with the distribution.

// * Neither the name of Google Inc. nor the names of its contributors may be

//   used to endorse or promote products derived from this software without

//   specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

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// Author: keir@google.com (Keir Mierle)

//         sameeragarwal@google.com (Sameer Agarwal)

#ifndef CERES_INTERNAL_RANDOM_H_

#define CERES_INTERNAL_RANDOM_H_

#include <cmath>

#include <cstdlib>

#include "ceres/internal/port.h"

namespace ceres {

inline void SetRandomState(int state) {

  srand(state);

}

inline int Uniform(int n) {

  if (n) {

    return rand() % n;

  } else {

    return 0;

  }

}

inline double RandDouble() {

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

  return r / RAND_MAX;

}

// Box-Muller algorithm for normal random number generation.

// http://en.wikipedia.org/wiki/Box-Muller_transform

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 ceres

#endif  // CERES_INTERNAL_RANDOM_H_