bool SparseOptimizerIncremental::updateInitialization(HyperGraph::VertexSet& vset, HyperGraph::EdgeSet& eset)
  {
    if (batchStep) {
      return SparseOptimizerOnline::updateInitialization(vset, eset);
    }

    //cerr << __PRETTY_FUNCTION__ << endl;

    for (HyperGraph::VertexSet::iterator it = vset.begin(); it != vset.end(); ++it) {
      OptimizableGraph::Vertex* v = static_cast<OptimizableGraph::Vertex*>(*it);
      v->clearQuadraticForm(); // be sure that b is zero for this vertex
    }

    // get the touched vertices
    _touchedVertices.clear();
    for (HyperGraph::EdgeSet::iterator it = eset.begin(); it != eset.end(); ++it) {
      OptimizableGraph::Edge* e = static_cast<OptimizableGraph::Edge*>(*it);
      OptimizableGraph::Vertex* v1 = static_cast<OptimizableGraph::Vertex*>(e->vertices()[0]);
      OptimizableGraph::Vertex* v2 = static_cast<OptimizableGraph::Vertex*>(e->vertices()[1]);
      if (! v1->fixed())
        _touchedVertices.insert(v1);
      if (! v2->fixed())
        _touchedVertices.insert(v2);
    }
    //cerr << PVAR(_touchedVertices.size()) << endl;

    // updating the internal structures
    std::vector<HyperGraph::Vertex*> newVertices;
    newVertices.reserve(vset.size());
    _activeVertices.reserve(_activeVertices.size() + vset.size());
    _activeEdges.reserve(_activeEdges.size() + eset.size());
    for (HyperGraph::EdgeSet::iterator it = eset.begin(); it != eset.end(); ++it)
      _activeEdges.push_back(static_cast<OptimizableGraph::Edge*>(*it));
    //cerr << "updating internal done." << endl;

    // update the index mapping
    size_t next = _ivMap.size();
    for (HyperGraph::VertexSet::iterator it = vset.begin(); it != vset.end(); ++it) {
      OptimizableGraph::Vertex* v=static_cast<OptimizableGraph::Vertex*>(*it);
      if (! v->fixed()){
        if (! v->marginalized()){
          v->setTempIndex(next);
          _ivMap.push_back(v);
          newVertices.push_back(v);
          _activeVertices.push_back(v);
          next++;
        } 
        else // not supported right now
          abort();
      }
      else {
        v->setTempIndex(-1);
      }
    }
    //cerr << "updating index mapping done." << endl;

    // backup the tempindex and prepare sorting structure
    VertexBackup backupIdx[_touchedVertices.size()];
    memset(backupIdx, 0, sizeof(VertexBackup) * _touchedVertices.size());
    int idx = 0;
    for (HyperGraph::VertexSet::iterator it = _touchedVertices.begin(); it != _touchedVertices.end(); ++it) {
      OptimizableGraph::Vertex* v = static_cast<OptimizableGraph::Vertex*>(*it);
      backupIdx[idx].tempIndex = v->tempIndex();
      backupIdx[idx].vertex = v;
      backupIdx[idx].hessianData = v->hessianData();
      ++idx;
    }
    sort(backupIdx, backupIdx + _touchedVertices.size()); // sort according to the tempIndex which is the same order as used later by the optimizer
    for (int i = 0; i < idx; ++i) {
      backupIdx[i].vertex->setTempIndex(i);
    }
    //cerr << "backup tempindex done." << endl;

    // building the structure of the update
    _updateMat.clear(true); // get rid of the old matrix structure
    _updateMat.rowBlockIndices().clear();
    _updateMat.colBlockIndices().clear();
    _updateMat.blockCols().clear();

    // placing the current stuff in _updateMat
    MatrixXd* lastBlock = 0;
    int sizePoses = 0;
    for (int i = 0; i < idx; ++i) {
      OptimizableGraph::Vertex* v = backupIdx[i].vertex;
      int dim = v->dimension();
      sizePoses+=dim;
      _updateMat.rowBlockIndices().push_back(sizePoses);
      _updateMat.colBlockIndices().push_back(sizePoses);
      _updateMat.blockCols().push_back(SparseBlockMatrix<MatrixXd>::IntBlockMap());
      int ind = v->tempIndex();
      //cerr << PVAR(ind) << endl;
      if (ind >= 0) {
        MatrixXd* m = _updateMat.block(ind, ind, true);
        v->mapHessianMemory(m->data());
        lastBlock = m;
      }
    }
    lastBlock->diagonal().array() += 1e-6; // HACK to get Eigen value > 0


    for (HyperGraph::EdgeSet::const_iterator it = eset.begin(); it != eset.end(); ++it) {
      OptimizableGraph::Edge* e = static_cast<OptimizableGraph::Edge*>(*it);
      OptimizableGraph::Vertex* v1 = (OptimizableGraph::Vertex*) e->vertices()[0];
      OptimizableGraph::Vertex* v2 = (OptimizableGraph::Vertex*) e->vertices()[1];

      int ind1 = v1->tempIndex();
      if (ind1 == -1)
        continue;
      int ind2 = v2->tempIndex();
      if (ind2 == -1)
        continue;
      bool transposedBlock = ind1 > ind2;
      if (transposedBlock) // make sure, we allocate the upper triangular block
        swap(ind1, ind2);

      MatrixXd* m = _updateMat.block(ind1, ind2, true);
      e->mapHessianMemory(m->data(), 0, 1, transposedBlock);
    }

    // build the system into _updateMat
    for (HyperGraph::EdgeSet::iterator it = eset.begin(); it != eset.end(); ++it) {
      OptimizableGraph::Edge * e = static_cast<OptimizableGraph::Edge*>(*it);
      e->computeError();
    }
    for (HyperGraph::EdgeSet::iterator it = eset.begin(); it != eset.end(); ++it) {
      OptimizableGraph::Edge* e = static_cast<OptimizableGraph::Edge*>(*it);
      e->linearizeOplus();
    }
    for (HyperGraph::EdgeSet::iterator it = eset.begin(); it != eset.end(); ++it) {
      OptimizableGraph::Edge* e = static_cast<OptimizableGraph::Edge*>(*it);
      e->constructQuadraticForm();
    }

    // restore the original data for the vertex
    for (int i = 0; i < idx; ++i) {
      backupIdx[i].vertex->setTempIndex(backupIdx[i].tempIndex);
      if (backupIdx[i].hessianData)
        backupIdx[i].vertex->mapHessianMemory(backupIdx[i].hessianData);
    }

    // update the structure of the real block matrix
    bool solverStatus = _solver->updateStructure(newVertices, eset);

    bool updateStatus = computeCholeskyUpdate();
    if (! updateStatus) {
      cerr << "Error while computing update" << endl;
    }

    cholmod_sparse* updateAsSparseFactor = cholmod_factor_to_sparse(_cholmodFactor, &_cholmodCommon);

    // convert CCS update by permuting back to the permutation of L
    if (updateAsSparseFactor->nzmax > _permutedUpdate->nzmax) {
      //cerr << "realloc _permutedUpdate" << endl;
      cholmod_reallocate_triplet(updateAsSparseFactor->nzmax, _permutedUpdate, &_cholmodCommon);
    }
    _permutedUpdate->nnz = 0;
    _permutedUpdate->nrow = _permutedUpdate->ncol = _L->n;
    {
      int* Ap = (int*)updateAsSparseFactor->p;
      int* Ai = (int*)updateAsSparseFactor->i;
      double* Ax = (double*)updateAsSparseFactor->x;
      int* Bj = (int*)_permutedUpdate->j;
      int* Bi = (int*)_permutedUpdate->i;
      double* Bx = (double*)_permutedUpdate->x;
      for (size_t c = 0; c < updateAsSparseFactor->ncol; ++c) {
        const int& rbeg = Ap[c];
        const int& rend = Ap[c+1];
        int cc = c / slamDimension;
        int coff = c % slamDimension;
        const int& cbase = backupIdx[cc].vertex->colInHessian();
        const int& ccol = _perm(cbase + coff);
        for (int j = rbeg; j < rend; j++) {
          const int& r = Ai[j];
          const double& val = Ax[j];

          int rr = r / slamDimension;
          int roff = r % slamDimension;
          const int& rbase = backupIdx[rr].vertex->colInHessian();
          
          int row = _perm(rbase + roff);
          int col = ccol;
          if (col > row) // lower triangular entry
            swap(col, row);
          Bi[_permutedUpdate->nnz] = row;
          Bj[_permutedUpdate->nnz] = col;
          Bx[_permutedUpdate->nnz] = val;
          ++_permutedUpdate->nnz;
        }
      }
    }
    cholmod_free_sparse(&updateAsSparseFactor, &_cholmodCommon);
    cholmod_sparse* updatePermuted = cholmod_triplet_to_sparse(_permutedUpdate, _permutedUpdate->nnz, &_cholmodCommon);
    //writeCCSMatrix("update-permuted.txt", updatePermuted->nrow, updatePermuted->ncol, (int*)updatePermuted->p, (int*)updatePermuted->i, (double*)updatePermuted2->x, false);

    _solverInterface->choleskyUpdate(updatePermuted);

    cholmod_free_sparse(&updatePermuted, &_cholmodCommon);

    return solverStatus;
  }
  void SparseOptimizer::computeInitialGuess()
  {
    OptimizableGraph::VertexSet emptySet;
    std::set<Vertex*> backupVertices;
    // these are the root nodes where to start the initialization
    HyperGraph::VertexSet fixedVertices;
    for (EdgeContainer::iterator
         it  = _activeEdges.begin();
         it != _activeEdges.end();
         ++it)
    {
      OptimizableGraph::Edge* e = *it;
      for (size_t i = 0; i < e->vertices().size(); ++i)
      {
        OptimizableGraph::Vertex* v =
           static_cast<OptimizableGraph::Vertex*>(e->vertices()[i]);

        if (v->fixed())   fixedVertices.insert(v);
        else
        {
          // check for having a prior which is able to fully initialize a vertex
          for (EdgeSet::const_iterator
               vedgeIt  = v->edges().begin();
               vedgeIt != v->edges().end();
               ++vedgeIt)
          {
            OptimizableGraph::Edge* vedge =
               static_cast<OptimizableGraph::Edge*>(*vedgeIt);
            if ( vedge->vertices().size() == 1
              && vedge->initialEstimatePossible(emptySet, v) > 0.)
            {
              //cerr << "Initialize with prior for " << v->id() << endl;
              vedge->initialEstimate(emptySet, v);
              fixedVertices.insert(v);
            }
          }
        }

        if (v->tempIndex() == -1)
        {
          std::set<Vertex*>::const_iterator foundIt = backupVertices.find(v);
          if (foundIt == backupVertices.end()) {
            v->push();
            backupVertices.insert(v);
          }
        }
      }
    }

    EstimatePropagator estimatePropagator(this);
    EstimatePropagator::PropagateCost costFunction(this);
    estimatePropagator.propagate(fixedVertices, costFunction);

    // restoring the vertices that should not be initialized
    for (std::set<Vertex*>::iterator
         it  = backupVertices.begin();
         it != backupVertices.end();
         ++it)
    {
      Vertex* v = *it;
      v->pop();
    }
    if (verbose())
    {
      computeActiveErrors();
      cerr << "iteration= -1\t chi2= " << activeChi2()
          << "\t time= 0.0"
          << "\t cumTime= 0.0"
          << "\t (using initial guess from spanning tree)" << endl;
    }
  }