bbf.h

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/*
 * Copyright (c) 2018, the neonavigation authors
 * All rights reserved.
 *
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 * modification, are permitted provided that the following conditions are met:
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 *       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"
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#ifndef PLANNER_CSPACE_BBF_H
#define PLANNER_CSPACE_BBF_H

namespace bbf
{
constexpr float oddsToProbability(const float& o)
{
  return o / (1.0 + o);
}

constexpr float probabilityToOdds(const float& p)
{
  return p / (1.0 - p);
}

const float MIN_PROBABILITY = 0.1;
const float MAX_PROBABILITY = 1.0 - MIN_PROBABILITY;
const float MIN_ODDS = probabilityToOdds(MIN_PROBABILITY);
const float MAX_ODDS = probabilityToOdds(MAX_PROBABILITY);

class BinaryBayesFilter
{
protected:
  float odds_;

public:
  explicit BinaryBayesFilter(
      const float& initial_odds = 1.0) noexcept
      : odds_(initial_odds)
  {
  }
  float update(const float& odds)
  {
    odds_ *= odds;
    if (odds_ < MIN_ODDS)
      odds_ = MIN_ODDS;
    else if (odds_ > MAX_ODDS)
      odds_ = MAX_ODDS;
    return odds_;
  }
  float get() const
  {
    return odds_;
  }
  float getProbability() const
  {
    return oddsToProbability(odds_);
  }
  float getNormalizedProbability() const
  {
    return (getProbability() - MIN_PROBABILITY) / (MAX_PROBABILITY - MIN_PROBABILITY);
  }
};
};  // namespace bbf

#endif  // PLANNER_CSPACE_BBF_H