text: // g2o - General Graph Optimization
  // Copyright (C) 2011 R. Kuemmerle, G. Grisetti, 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
  // HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
  // TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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  // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #include "linear_solver_pcg.h"
  
  #include "g2o/core/block_solver.h"
  #include "g2o/core/solver.h"
  #include "g2o/core/optimization_algorithm_factory.h"
  #include "g2o/stuff/macros.h"
  
  #include "g2o/core/optimization_algorithm_gauss_newton.h"
  #include "g2o/core/optimization_algorithm_levenberg.h"
  
  using namespace std;
  
  namespace g2o
  {
    namespace
    {
      template<int p, int l>
      std::unique_ptr<g2o::Solver> AllocateSolver()
      {
        std::cerr << "# Using PCG poseDim " << p << " landMarkDim " << l << std::endl;
  
        return g2o::make_unique<BlockSolverPL<p, l>>(
          g2o::make_unique<LinearSolverPCG<typename BlockSolverPL<p, l>::PoseMatrixType>>());
      }
    }
  
    static OptimizationAlgorithm* createSolver(const std::string& fullSolverName)
    {
      static const std::map<std::string, std::function<std::unique_ptr<g2o::Solver>()>> solver_factories{
          { "pcg", &AllocateSolver<-1, -1> },
          { "pcg3_2", &AllocateSolver<3, 2> },
          { "pcg6_3", &AllocateSolver<6, 3> },
          { "pcg7_3", &AllocateSolver<7, 3> },
      };
  
      string solverName = fullSolverName.substr(3);
      auto solverf = solver_factories.find(solverName);
      if (solverf == solver_factories.end())
        return nullptr;
  
      string methodName = fullSolverName.substr(0, 2);
  
      if (methodName == "gn") {
        return new OptimizationAlgorithmGaussNewton(solverf->second());
      }
      else if (methodName == "lm") {
        return new OptimizationAlgorithmLevenberg(solverf->second());
      }
  
      return nullptr;
    }
  
    class PCGSolverCreator : public AbstractOptimizationAlgorithmCreator
    {
      public:
        PCGSolverCreator(const OptimizationAlgorithmProperty& p) : AbstractOptimizationAlgorithmCreator(p) {}
        virtual OptimizationAlgorithm* construct()
        {
          return createSolver(property().name);
        }
    };
  
    G2O_REGISTER_OPTIMIZATION_LIBRARY(pcg);
  
    G2O_REGISTER_OPTIMIZATION_ALGORITHM(gn_pcg, new PCGSolverCreator(OptimizationAlgorithmProperty("gn_pcg", "Gauss-Newton: PCG solver using block-Jacobi pre-conditioner (variable blocksize)", "PCG", false, Eigen::Dynamic, Eigen::Dynamic)));
    G2O_REGISTER_OPTIMIZATION_ALGORITHM(gn_pcg3_2, new PCGSolverCreator(OptimizationAlgorithmProperty("gn_pcg3_2", "Gauss-Newton: PCG solver using block-Jacobi pre-conditioner (fixed blocksize)", "PCG", true, 3, 2)));
    G2O_REGISTER_OPTIMIZATION_ALGORITHM(gn_pcg6_3, new PCGSolverCreator(OptimizationAlgorithmProperty("gn_pcg6_3", "Gauss-Newton: PCG solver using block-Jacobi pre-conditioner (fixed blocksize)", "PCG", true, 6, 3)));
    G2O_REGISTER_OPTIMIZATION_ALGORITHM(gn_pcg7_3, new PCGSolverCreator(OptimizationAlgorithmProperty("gn_pcg7_3", "Gauss-Newton: PCG solver using block-Jacobi pre-conditioner (fixed blocksize)", "PCG", true, 7, 3)));
    G2O_REGISTER_OPTIMIZATION_ALGORITHM(lm_pcg, new PCGSolverCreator(OptimizationAlgorithmProperty("lm_pcg", "Levenberg: PCG solver using block-Jacobi pre-conditioner (variable blocksize)", "PCG", false, Eigen::Dynamic, Eigen::Dynamic)));
    G2O_REGISTER_OPTIMIZATION_ALGORITHM(lm_pcg3_2, new PCGSolverCreator(OptimizationAlgorithmProperty("lm_pcg3_2", "Levenberg: PCG solver using block-Jacobi pre-conditioner (fixed blocksize)", "PCG", true, 3, 2)));
    G2O_REGISTER_OPTIMIZATION_ALGORITHM(lm_pcg6_3, new PCGSolverCreator(OptimizationAlgorithmProperty("lm_pcg6_3", "Levenberg: PCG solver using block-Jacobi pre-conditioner (fixed blocksize)", "PCG", true, 6, 3)));
    G2O_REGISTER_OPTIMIZATION_ALGORITHM(lm_pcg7_3, new PCGSolverCreator(OptimizationAlgorithmProperty("lm_pcg7_3", "Levenberg: PCG solver using block-Jacobi pre-conditioner (fixed blocksize)", "PCG", true, 7, 3)));
  }
  