// g2o - General Graph Optimization
// Copyright (C) 2011 R. Kuemmerle, G. Grisetti, W. Burgard
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are
// met:
//
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#ifndef G2O_OPTIMIZATION_ALGORITHM_WITH_HESSIAN_H
#define G2O_OPTIMIZATION_ALGORITHM_WITH_HESSIAN_H

#include "optimization_algorithm.h"
#include "g2o_core_api.h"

namespace g2o {

  class Solver;

  /**
   * \brief Base for solvers operating on the approximated Hessian, e.g., Gauss-Newton, Levenberg
   */
  class G2O_CORE_API OptimizationAlgorithmWithHessian : public OptimizationAlgorithm
  {
    public:
      explicit OptimizationAlgorithmWithHessian(Solver* solver);
      virtual ~OptimizationAlgorithmWithHessian();

      virtual bool init(bool online = false);

      virtual bool computeMarginals(SparseBlockMatrix<MatrixXd>& spinv, const std::vector<std::pair<int, int> >& blockIndices);

      virtual bool buildLinearStructure();

      virtual void updateLinearSystem();

      virtual bool updateStructure(const std::vector<HyperGraph::Vertex*>& vset, const HyperGraph::EdgeSet& edges);

      //! return the underlying solver used to solve the linear system
      Solver* solver() { return _solver;}

      /**
       * write debug output of the Hessian if system is not positive definite
       */
      virtual void setWriteDebug(bool writeDebug);
      virtual bool writeDebug() const { return _writeDebug->value();}

    protected:
      Solver* _solver;
      Property<bool>* _writeDebug;

  };

}// end namespace

#endif
