text: // g2o - General Graph Optimization
  // Copyright (C) 2011 R. Kuemmerle, G. Grisetti, H. Strasdat, W. Burgard
  // All rights reserved.
  //
  // 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.
  //
  // 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 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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  // TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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  #include "sparse_optimizer_terminate_action.h"
  
  #include "sparse_optimizer.h"
  
  #include <limits>
  
  namespace g2o {
  
    SparseOptimizerTerminateAction::SparseOptimizerTerminateAction() :
      HyperGraphAction(),
      _gainThreshold(cst(1e-6)), _lastChi(0), _auxTerminateFlag(false),
      _maxIterations(std::numeric_limits<int>::max())
    {
    }
  
    void SparseOptimizerTerminateAction::setGainThreshold(number_t gainThreshold)
    {
      _gainThreshold = gainThreshold;
    }
  
    HyperGraphAction* SparseOptimizerTerminateAction::operator()(const HyperGraph* graph, Parameters* parameters)
    {
      assert(dynamic_cast<const SparseOptimizer*>(graph) && "graph is not a SparseOptimizer");
      assert(dynamic_cast<HyperGraphAction::ParametersIteration*>(parameters) && "error casting parameters");
  
      const SparseOptimizer* optimizer = static_cast<const SparseOptimizer*>(graph);
      HyperGraphAction::ParametersIteration* params = static_cast<HyperGraphAction::ParametersIteration*>(parameters);
  
      const_cast<SparseOptimizer*>(optimizer)->computeActiveErrors();
      if (params->iteration < 0)
      {
        // let the optimizer run for at least one iteration
        // Hence, we reset the stop flag
        setOptimizerStopFlag(optimizer, false);
      } else if (params->iteration == 0) {
        // first iteration, just store the chi2 value
        _lastChi = optimizer->activeRobustChi2();
      } else {
        // compute the gain and stop the optimizer in case the
        // gain is below the threshold or we reached the max
        // number of iterations
        bool stopOptimizer = false;
        if (params->iteration < _maxIterations) {
          number_t currentChi = optimizer->activeRobustChi2();
          number_t gain = (_lastChi - currentChi) / currentChi;
          _lastChi = currentChi;
          if (gain >= 0 && gain < _gainThreshold)
            stopOptimizer = true;
        } else {
          stopOptimizer = true;
        }
        if (stopOptimizer) { // tell the optimizer to stop
          setOptimizerStopFlag(optimizer, true);
        }
      }
      return this;
    }
  
    void SparseOptimizerTerminateAction::setMaxIterations(int maxit)
    {
      _maxIterations = maxit;
    }
  
    void SparseOptimizerTerminateAction::setOptimizerStopFlag(const SparseOptimizer* optimizer, bool stop)
    {
      if (optimizer->forceStopFlag()) {
        *(optimizer->forceStopFlag()) = stop;
      } else {
        _auxTerminateFlag = stop;
        const_cast<SparseOptimizer*>(optimizer)->setForceStopFlag(&_auxTerminateFlag);
      }
    }
  
  } // end namespace
  