// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

//

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// modification, are permitted provided that the following conditions are met:

//

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//   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

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//

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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

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// Author: keir@google.com (Keir Mierle)

#ifndef CERES_INTERNAL_CGNR_SOLVER_H_

#define CERES_INTERNAL_CGNR_SOLVER_H_

#include "ceres/internal/scoped_ptr.h"

#include "ceres/linear_solver.h"

namespace ceres {

namespace internal {

class Preconditioner;

class BlockJacobiPreconditioner;

// A conjugate gradients on the normal equations solver. This directly solves

// for the solution to

//

//   (A^T A + D^T D)x = A^T b

//

// as required for solving for x in the least squares sense. Currently only

// block diagonal preconditioning is supported.

class CgnrSolver : public BlockSparseMatrixSolver {

 public:

  explicit CgnrSolver(const LinearSolver::Options& options);

  virtual Summary SolveImpl(

      BlockSparseMatrix* A,

      const double* b,

      const LinearSolver::PerSolveOptions& per_solve_options,

      double* x);

 private:

  const LinearSolver::Options options_;

  scoped_ptr<Preconditioner> preconditioner_;

  CERES_DISALLOW_COPY_AND_ASSIGN(CgnrSolver);

};

}  // namespace internal

}  // namespace ceres

#endif  // CERES_INTERNAL_CGNR_SOLVER_H_