index_view.h

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/*
 * Copyright (c) 2010-2015:  G-CSC, Goethe University Frankfurt
 * Author: Martin Rupp
 * 
 * This file is part of UG4.
 * 
 * UG4 is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License version 3 (as published by the
 * Free Software Foundation) with the following additional attribution
 * requirements (according to LGPL/GPL v3 §7):
 * 
 * (1) The following notice must be displayed in the Appropriate Legal Notices
 * of covered and combined works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (2) The following notice must be displayed at a prominent place in the
 * terminal output of covered works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (3) The following bibliography is recommended for citation and must be
 * preserved in all covered files:
 * "Reiter, S., Vogel, A., Heppner, I., Rupp, M., and Wittum, G. A massively
 *   parallel geometric multigrid solver on hierarchically distributed grids.
 *   Computing and visualization in science 16, 4 (2013), 151-164"
 * "Vogel, A., Reiter, S., Rupp, M., Nägel, A., and Wittum, G. UG4 -- a novel
 *   flexible software system for simulating pde based models on high performance
 *   computers. Computing and visualization in science 16, 4 (2013), 165-179"
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 */
 
#ifndef __H__UG__LIB_ALGEBRA__INDEX_VIEW_H__
#define __H__UG__LIB_ALGEBRA__INDEX_VIEW_H__
 
namespace ug
{
 
 
template<typename index_type>
class IndexView
{
public:
  IndexView(const std::vector<index_type> &indices)
  {
    local_to_global = indices;
    init();
  }
 
  IndexView(index_type *indices, size_t size)
  {
    local_to_global.resize(size);
    for(size_t i=0; i<size; i++)
      local_to_global[i] = indices[i];
    init();
  }
 
  typedef std::vector<index_type> iterator;
 
  iterator begin()
  {
    return local_to_global.begin();
  }
 
  iterator end()
  {
    return local_to_global.end();
  }
 
  bool is_in_view(index_type i)
  {
    // we need this function to be very fast, because it is used often in matrix-vector-multiplication
    // this uses memory, but is faster than searching the local_to_global array, even with binary search
    if(i >= is_in_locals.size()) return false;
    return is_in_locals[i];
  }
 
private:
  void init()
  {
    index_type maxindex = (*max_element(local_to_global.begin(), local_to_global.end()));
    is_in_locals.clear();
    is_in_locals.resize(maxindex+1, false);
    for(size_t i=0; i<local_to_global.size(); i++)
      is_in_locals[local_to_global[i]] = true;
  }
  std::vector<index_type> local_to_global;
  std::vector<bool> is_in_locals;
  //std::vector<int> global_to_lobal;
};
template<typename index_type>
class SliceIndexView
{
public:
  SliceIndexView(index_type from, index_type to) : m_from(from), m_to(to) { }
 
  struct iterator
  {
    iterator(index_type from) : i(from) { }
    index_type i;
 
    bool operator != (const iterator &other) const { return i != other.i; }
    bool operator == (const iterator &other) const { return i == other.i; }
 
    void operator ++() { ++i; }
    int operator *() const { return i; }
  };
 
  inline iterator begin()
  {
    return iterator(m_from);
  }
 
  inline iterator end()
  {
    return iterator(m_to);
  }
 
  bool is_in_view(index_type i)
  {
    return i >= m_from && i < m_to;
  }
 
private:
  index_type m_from;
  index_type m_to;
};
 
/*
template<typename vector_t, typename view_t>
class VectorView
{
  VectorView(vector_t &vector, view_t &view) : m_vector(vector), m_view(view)
  { }
 
  typedef view_t::iterator index_iterator;
  index_iterator begin() { return m_view.begin(); }
  index_iterator end() { return m_view.end(); }
 
  typename vector_t::value_type operator[] (const index_iterator &it)
  {
    return vector_t::operator[] ( (*it) );
  }
}*/
 
 
/*
template<typename vector_t>
inline void VecScaleAssign(vector_t &dest, double alpha1, const vector_t &v1)
{
  for(dest::index_iterator it = dest.begin(); it != view.end(); ++it)
  {
  // so?
    size_t i = (*it);
    VecScaleAssign(dest[i], alpha1, v1[i]);
  // oder so
      VecScaleAssign(dest[it], alpha1, v1[it]);
  }
}
 
oder
 
template<typename vector_t, typename view_t>
inline void VecScaleAssign(vector_t &dest, double alpha1, const vector_t &v1, const view_t &view)
{
  for(view_t::index_iterator it = view.begin(); it != view.end(); ++it)
  {
    size_t i = (*it);
    VecScaleAssign(dest[i], alpha1, v1[i]);
  }
}
*/
 
 
template<typename index_type>
class BlockSliceIndexView
{
public:
  BlockSliceIndexView(index_type from, index_type to, index_type block) : m_from(from), m_to(to), m_block(block) { }
 
  struct iterator
  {
    iterator(index_type from, index_type block) : i(from), m_block(block) { }
    index_type i;
    index_type m_block;
 
    bool operator != (const iterator &other) const { return i != other.i; }
    bool operator == (const iterator &other) const { return i == other.i; }
 
    void operator ++() { ++i; }
    int index() const { return i; }
    int block() const { return block; }
  };
 
  inline iterator begin()
  {
    return iterator(m_from, m_block);
  }
 
  inline iterator end()
  {
    return iterator(m_to, m_block);
  }
 
  bool is_in_view(const iterator &i)
  {
    return is_in_view(i.i);
  }
  bool is_in_view(index_type i)
  {
    return i >= m_from && i < m_to;
  }
 
private:
  index_type m_from;
  index_type m_to;
};
 
/*
template<typename vector_t, typename view_t>
class BlockVectorView
{
  BlockVectorView(vector_t &vector, view_t &view) : m_vector(vector), m_view(view)
  { }
 
  typedef view_t::iterator index_iterator;
  index_iterator begin() { return m_view.begin(); }
  index_iterator end() { return m_view.end(); }
 
  typename vector_t::value_type::value_type operator[] (const index_iterator &it)
  {
    return BlockRef(vector_t::operator[] ( it.index() ), it.block());
  }
}*/
 
/*template<typename vector_t>
inline void VecScaleAssign(vector_t &dest, double alpha1, const vector_t &v1)
{
  for(dest::index_iterator it = dest.begin(); it != view.end(); ++it)
      VecScaleAssign(dest[it], alpha1, v1[it]); // automatically on BlockRef(index, block) if used with BlockVectorView(vec, BlockSliceIndexView(10, 20, 2))
}
*/
 
} // namespace ug
 
 
#endif // __H__UG__LIB_ALGEBRA__INDEX_VIEW_H__