internal/ceres/block_structure.h

// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2015 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)
//
// Block structure objects are used to carry information about the
// dense block structure of sparse matrices. The BlockSparseMatrix
// object uses the BlockStructure objects to keep track of the matrix
// structure and operate upon it. This allows us to use more cache
// friendly block oriented linear algebra operations on the matrix
// instead of accessing it one scalar entry at a time.

#ifndef CERES_INTERNAL_BLOCK_STRUCTURE_H_
#define CERES_INTERNAL_BLOCK_STRUCTURE_H_

#include <cstdint>
#include <vector>

#include "ceres/internal/export.h"

namespace ceres::internal {

using BlockSize = int32_t;

struct CERES_NO_EXPORT Block {
  Block() = default;
  Block(int size_, int position_) : size(size_), position(position_) {}

  BlockSize size{-1};
  int position{-1};  // Position along the row/column.
};

struct CERES_NO_EXPORT Cell {
  Cell() = default;
  Cell(int block_id_, int position_)
      : block_id(block_id_), position(position_) {}

  // Column or row block id as the case maybe.
  int block_id{-1};
  // Where in the values array of the jacobian is this cell located.
  int position{-1};
};

// Order cell by their block_id;
CERES_NO_EXPORT bool CellLessThan(const Cell& lhs, const Cell& rhs);

struct CERES_NO_EXPORT CompressedList {
  CompressedList() = default;

  // Construct a CompressedList with the cells containing num_cells
  // entries.
  explicit CompressedList(int num_cells) : cells(num_cells) {}
  Block block;
  std::vector<Cell> cells;
};

using CompressedRow = CompressedList;
using CompressedColumn = CompressedList;

struct CERES_NO_EXPORT CompressedRowBlockStructure {
  std::vector<Block> cols;
  std::vector<CompressedRow> rows;
};

struct CERES_NO_EXPORT CompressedColumnBlockStructure {
  std::vector<Block> rows;
  std::vector<CompressedColumn> cols;
};

}  // namespace ceres::internal

#endif  // CERES_INTERNAL_BLOCK_STRUCTURE_H_