// g2o - General Graph Optimization
// Copyright (C) 2011 R. Kuemmerle, G. Grisetti, W. Burgard
// All rights reserved.
//
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// met:
//
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#ifndef G2O_ROBUST_KERNEL_H
#define G2O_ROBUST_KERNEL_H

#ifdef _MSC_VER
#include <memory>
#else
#include <tr1/memory>
#endif
#include <Eigen/Core>


namespace g2o {

  /**
   * \brief base for all robust cost functions
   *
   * Note in all the implementations for the other cost functions the e in the
   * funtions corresponds to the sqaured errors, i.e., the robustification
   * functions gets passed the squared error.
   *
   * e.g. the robustified least squares function is
   *
   * chi^2 = sum_{e} rho( e^T Omega e )
   */
  class  RobustKernel
  {
    public:
      RobustKernel();
      explicit RobustKernel(double delta);
      virtual ~RobustKernel() {}
      /**
       * compute the scaling factor for a error:
       * The error is e^T Omega e
       * The output rho is
       * rho[0]: The actual scaled error value
       * rho[1]: First derivative of the scaling function
       * rho[2]: Second derivative of the scaling function
       */
      virtual void robustify(double squaredError, Eigen::Vector3d& rho) const = 0;

      /**
       * set the window size of the error. A squared error above delta^2 is considered
       * as outlier in the data.
       */
      virtual void setDelta(double delta);
      double delta() const { return _delta;}

    protected:
      double _delta;
  };
  typedef std::tr1::shared_ptr<RobustKernel> RobustKernelPtr;

} // end namespace g2o

#endif
