block_indices.h

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// ---------------------------------------------------------------------
//
// Copyright (C) 2000 - 2020 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE.md at
// the top level directory of deal.II.
//
// ---------------------------------------------------------------------

#ifndef dealii_block_indices_h
#define dealii_block_indices_h


#include <deal.II/base/config.h>

#include <deal.II/base/exceptions.h>
#include <deal.II/base/logstream.h>
#include <deal.II/base/subscriptor.h>
#include <deal.II/base/utilities.h>

#include <cstddef>
#include <vector>

DEAL_II_NAMESPACE_OPEN


class BlockIndices : public Subscriptor
{
public:
  using size_type = types::global_dof_index;

  BlockIndices();

  BlockIndices(const std::vector<size_type> &block_sizes);

  BlockIndices(BlockIndices &&b) noexcept;

  BlockIndices(const BlockIndices &) = default;

  explicit BlockIndices(const unsigned int n_blocks,
                        const size_type    block_size = 0);

  void
  reinit(const unsigned int n_blocks, const size_type n_elements_per_block);

  void
  reinit(const std::vector<size_type> &block_sizes);

  void
  push_back(const size_type size);


  unsigned int
  size() const;

  size_type
  total_size() const;

  size_type
  block_size(const unsigned int i) const;

  std::string
  to_string() const;



  std::pair<unsigned int, size_type>
  global_to_local(const size_type i) const;

  size_type
  local_to_global(const unsigned int block, const size_type index) const;

  size_type
  block_start(const unsigned int i) const;

  BlockIndices &
  operator=(const BlockIndices &b);

  BlockIndices &
  operator=(BlockIndices &&) noexcept;

  bool
  operator==(const BlockIndices &b) const;

  void
  swap(BlockIndices &b);

  std::size_t
  memory_consumption() const;

private:
  unsigned int n_blocks;

  std::vector<size_type> start_indices;
};


inline LogStream &
operator<<(LogStream &s, const BlockIndices &bi)
{
  const unsigned int n = bi.size();
  s << n << ":[";
  // Write first size without leading space
  if (n > 0)
    s << bi.block_size(0);
  // Write all other sizes
  for (unsigned int i = 1; i < n; ++i)
    s << ' ' << bi.block_size(i);
  s << "]->" << bi.total_size();
  return s;
}



/* ---------------------- template and inline functions ------------------- */

inline void
BlockIndices::reinit(const unsigned int nb, const size_type block_size)
{
  n_blocks = nb;
  start_indices.resize(n_blocks + 1);
  for (size_type i = 0; i <= n_blocks; ++i)
    start_indices[i] = i * block_size;
}



inline void
BlockIndices::reinit(const std::vector<size_type> &block_sizes)
{
  if (start_indices.size() != block_sizes.size() + 1)
    {
      n_blocks = static_cast<unsigned int>(block_sizes.size());
      start_indices.resize(n_blocks + 1);
    }
  start_indices[0] = 0;
  for (size_type i = 1; i <= n_blocks; ++i)
    start_indices[i] = start_indices[i - 1] + block_sizes[i - 1];
}


inline BlockIndices::BlockIndices()
  : n_blocks(0)
  , start_indices(1, 0)
{}



inline BlockIndices::BlockIndices(const unsigned int n_blocks,
                                  const size_type    block_size)
  : n_blocks(n_blocks)
  , start_indices(n_blocks + 1)
{
  for (size_type i = 0; i <= n_blocks; ++i)
    start_indices[i] = i * block_size;
}



inline BlockIndices::BlockIndices(const std::vector<size_type> &block_sizes)
  : n_blocks(static_cast<unsigned int>(block_sizes.size()))
  , start_indices(block_sizes.size() + 1)
{
  reinit(block_sizes);
}



inline BlockIndices::BlockIndices(BlockIndices &&b) noexcept
  : n_blocks(b.n_blocks)
  , start_indices(std::move(b.start_indices))
{
  b.n_blocks      = 0;
  b.start_indices = std::vector<size_type>(1, 0);
}



inline void
BlockIndices::push_back(const size_type sz)
{
  start_indices.push_back(start_indices[n_blocks] + sz);
  ++n_blocks;
  AssertDimension(start_indices.size(), n_blocks + 1);
}


inline std::pair<unsigned int, BlockIndices::size_type>
BlockIndices::global_to_local(const size_type i) const
{
  AssertIndexRange(i, total_size());
  Assert(n_blocks > 0, ExcLowerRangeType<size_type>(i, size_type(1)));

  // start_indices[0] == 0 so we might as well start from the next one
  const auto it =
    --std::upper_bound(++start_indices.begin(), start_indices.end(), i);

  return {std::distance(start_indices.begin(), it), i - *it};
}


inline BlockIndices::size_type
BlockIndices::local_to_global(const unsigned int block,
                              const size_type    index) const
{
  AssertIndexRange(block, n_blocks);
  AssertIndexRange(index, start_indices[block + 1] - start_indices[block]);

  return start_indices[block] + index;
}


inline unsigned int
BlockIndices::size() const
{
  return n_blocks;
}



inline BlockIndices::size_type
BlockIndices::total_size() const
{
  if (n_blocks == 0)
    return 0;
  return start_indices[n_blocks];
}



inline BlockIndices::size_type
BlockIndices::block_size(const unsigned int block) const
{
  AssertIndexRange(block, n_blocks);
  return start_indices[block + 1] - start_indices[block];
}



inline std::string
BlockIndices::to_string() const
{
  std::string result = "[" + Utilities::int_to_string(n_blocks) + "->";
  for (unsigned int i = 0; i < n_blocks; ++i)
    {
      if (i > 0)
        result += ',';
      result += std::to_string(block_size(i));
    }
  result += "|" + std::to_string(total_size()) + ']';
  return result;
}



inline BlockIndices::size_type
BlockIndices::block_start(const unsigned int block) const
{
  AssertIndexRange(block, n_blocks);
  return start_indices[block];
}



inline BlockIndices &
BlockIndices::operator=(const BlockIndices &b)
{
  start_indices = b.start_indices;
  n_blocks      = b.n_blocks;
  return *this;
}



inline BlockIndices &
BlockIndices::operator=(BlockIndices &&b) noexcept
{
  start_indices = std::move(b.start_indices);
  n_blocks      = b.n_blocks;

  b.start_indices = std::vector<size_type>(1, 0);
  b.n_blocks      = 0;

  return *this;
}



inline bool
BlockIndices::operator==(const BlockIndices &b) const
{
  if (n_blocks != b.n_blocks)
    return false;

  for (size_type i = 0; i <= n_blocks; ++i)
    if (start_indices[i] != b.start_indices[i])
      return false;

  return true;
}



inline void
BlockIndices::swap(BlockIndices &b)
{
  std::swap(n_blocks, b.n_blocks);
  std::swap(start_indices, b.start_indices);
}



inline std::size_t
BlockIndices::memory_consumption() const
{
  return (sizeof(*this) + start_indices.size() * sizeof(start_indices[0]));
}



/* ----------------- global functions ---------------------------- */


inline void
swap(BlockIndices &u, BlockIndices &v)
{
  u.swap(v);
}



DEAL_II_NAMESPACE_CLOSE

#endif