// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2012 Google Inc. All rights reserved.
// http://code.google.com/p/ceres-solver/
//
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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.
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// Author: keir@google.com (Keir Mierle)

#ifndef CERES_INTERNAL_BLOCK_DIAGONAL_PRECONDITIONER_H_
#define CERES_INTERNAL_BLOCK_DIAGONAL_PRECONDITIONER_H_

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

namespace ceres {
namespace internal {

class CompressedRowBlockStructure;
class LinearOperator;
class SparseMatrix;

// A block diagonal preconditioner; also known as block-Jacobi.
class BlockDiagonalPreconditioner : public LinearOperator {
 public:
  BlockDiagonalPreconditioner(const LinearOperator& A);
  virtual ~BlockDiagonalPreconditioner();

  void Update(const LinearOperator& matrix);

  virtual void RightMultiply(const double* x, double* y) const;
  virtual void LeftMultiply(const double* x, double* y) const;

  virtual int num_rows() const { return size_; }
  virtual int num_cols() const { return size_; }

 private:
  std::vector<double*> blocks_;
  std::vector<double> block_storage_;
  int size_;
  const CompressedRowBlockStructure& block_structure_;
};

}  // namespace internal
}  // namespace ceres

#endif  // CERES_INTERNAL_LINEAR_OPERATOR_H_