// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
// http://code.google.com/p/ceres-solver/
//
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//
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#ifndef CERES_INTERNAL_BLOCK_RANDOM_ACCESS_SPARSE_MATRIX_H_
#define CERES_INTERNAL_BLOCK_RANDOM_ACCESS_SPARSE_MATRIX_H_

#include <set>
#include <vector>
#include <utility>
#include "ceres/mutex.h"
#include "ceres/block_random_access_matrix.h"
#include "ceres/collections_port.h"
#include "ceres/triplet_sparse_matrix.h"
#include "ceres/internal/macros.h"
#include "ceres/internal/port.h"
#include "ceres/internal/scoped_ptr.h"
#include "ceres/types.h"

namespace ceres {
namespace internal {

// A threaf safe square block sparse implementation of
// BlockRandomAccessMatrix. Internally a TripletSparseMatrix is used
// for doing the actual storage. This class augments this matrix with
// an unordered_map that allows random read/write access.
class BlockRandomAccessSparseMatrix : public BlockRandomAccessMatrix {
 public:
  // blocks is an array of block sizes. block_pairs is a set of
  // <row_block_id, col_block_id> pairs to identify the non-zero cells
  // of this matrix.
  BlockRandomAccessSparseMatrix(const vector<int>& blocks,
                                const set<pair<int, int> >& block_pairs);

  // The destructor is not thread safe. It assumes that no one is
  // modifying any cells when the matrix is being destroyed.
  virtual ~BlockRandomAccessSparseMatrix();

  // BlockRandomAccessMatrix Interface.
  virtual CellInfo* GetCell(int row_block_id,
                            int col_block_id,
                            int* row,
                            int* col,
                            int* row_stride,
                            int* col_stride);

  // This is not a thread safe method, it assumes that no cell is
  // locked.
  virtual void SetZero();
  virtual bool IsThreadSafe() const { return true; }

  // Since the matrix is square, num_rows() == num_cols().
  virtual int num_rows() const { return tsm_->num_rows(); }
  virtual int num_cols() const { return tsm_->num_cols(); }

  // Access to the underlying matrix object.
  const TripletSparseMatrix* matrix() const { return tsm_.get(); }
  TripletSparseMatrix* mutable_matrix() { return tsm_.get(); }

 private:
  long int IntPairToLong(int a, int b) {
    return a * kMaxRowBlocks + b;
  }

  const int kMaxRowBlocks;
  // row/column block sizes.
  const vector<int> blocks_;

  // A mapping from <row_block_id, col_block_id> to the position in
  // the values array of tsm_ where the block is stored.
  typedef HashMap<long int, CellInfo* > LayoutType;
  LayoutType layout_;

  // The underlying matrix object which actually stores the cells.
  scoped_ptr<TripletSparseMatrix> tsm_;

  DISALLOW_COPY_AND_ASSIGN(BlockRandomAccessSparseMatrix);
};

}  // namespace internal
}  // namespace ceres

#endif  // CERES_INTERNAL_BLOCK_RANDOM_ACCESS_SPARSE_MATRIX_H_