// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2017 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)
//
// A solver for sparse linear least squares problem based on solving
// the normal equations via a sparse cholesky factorization.

#ifndef CERES_INTERNAL_SPARSE_NORMAL_CHOLESKY_SOLVER_H_
#define CERES_INTERNAL_SPARSE_NORMAL_CHOLESKY_SOLVER_H_

// This include must come before any #ifndef check on Ceres compile options.
#include "ceres/internal/port.h"

#include <vector>
#include "ceres/linear_solver.h"

namespace ceres {
namespace internal {

class CompressedRowSparseMatrix;
class InnerProductComputer;
class SparseCholesky;

// Solves the normal equations (A'A + D'D) x = A'b, using the sparse
// linear algebra library of the user's choice.
class SparseNormalCholeskySolver : public BlockSparseMatrixSolver {
 public:
  explicit SparseNormalCholeskySolver(const LinearSolver::Options& options);
  SparseNormalCholeskySolver(const SparseNormalCholeskySolver&) = delete;
  void operator=(const SparseNormalCholeskySolver&) = delete;

  virtual ~SparseNormalCholeskySolver();

 private:
  LinearSolver::Summary SolveImpl(
      BlockSparseMatrix* A,
      const double* b,
      const LinearSolver::PerSolveOptions& options,
      double* x) final;

  const LinearSolver::Options options_;
  Vector rhs_;
  std::unique_ptr<SparseCholesky> sparse_cholesky_;
  std::unique_ptr<InnerProductComputer> inner_product_computer_;
};

}  // namespace internal
}  // namespace ceres

#endif  // CERES_INTERNAL_SPARSE_NORMAL_CHOLESKY_SOLVER_H_