g2o 初始化

  typedef g2o::BlockSolver< g2o::BlockSolverTraits<6,3> > Block;  // pose 维度为 6, landmark 维度为 3
    Block::LinearSolverType* linearSolver = new g2o::LinearSolverCSparse<Block::PoseMatrixType>(); // 线性方程求解器
    Block* solver_ptr = new Block( std::unique_ptr<Block::LinearSolverType>(linearSolver) );     // 矩阵块求解器
    g2o::OptimizationAlgorithmLevenberg* solver = new g2o::OptimizationAlgorithmLevenberg(std::unique_ptr<Block>(solver_ptr) );
    g2o::SparseOptimizer optimizer;
    optimizer.setAlgorithm ( solver );  
    optimizer.setVerbose( true ); 

    typedef g2o::BlockSolver< g2o::BlockSolverTraits<6,3> > Block;  // pose维度为 6, landmark 维度为 3
    Block::LinearSolverType* linearSolver = new g2o::LinearSolverEigen<Block::PoseMatrixType>(); // 线性方程求解器
    Block* solver_ptr = new Block( std::unique_ptr<Block::LinearSolverType>(linearSolver) );      // 矩阵块求解器
    g2o::OptimizationAlgorithmGaussNewton* solver = new g2o::OptimizationAlgorithmGaussNewton( std::unique_ptr<Block::LinearSolverType>(linearSolver) );
    g2o::SparseOptimizer optimizer;
    optimizer.setAlgorithm( solver );