sparse_vector.h

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//LIC// ====================================================================
//LIC// This file forms part of oomph-lib, the object-oriented, 
//LIC// multi-physics finite-element library, available 
//LIC// at http://www.oomph-lib.org.
//LIC// 
//LIC//    Version 1.0; svn revision $LastChangedRevision: 1097 $
//LIC//
//LIC// $LastChangedDate: 2015-12-17 11:53:17 +0000 (Thu, 17 Dec 2015) $
//LIC// 
//LIC// Copyright (C) 2006-2016 Matthias Heil and Andrew Hazel
//LIC// 
//LIC// This library is free software; you can redistribute it and/or
//LIC// modify it under the terms of the GNU Lesser General Public
//LIC// License as published by the Free Software Foundation; either
//LIC// version 2.1 of the License, or (at your option) any later version.
//LIC// 
//LIC// This library is distributed in the hope that it will be useful,
//LIC// but WITHOUT ANY WARRANTY; without even the implied warranty of
//LIC// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//LIC// Lesser General Public License for more details.
//LIC// 
//LIC// You should have received a copy of the GNU Lesser General Public
//LIC// License along with this library; if not, write to the Free Software
//LIC// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
//LIC// 02110-1301  USA.
//LIC// 
//LIC// The authors may be contacted at oomph-lib@maths.man.ac.uk.
//LIC// 
//LIC//====================================================================
#ifndef SPARSE_VECTOR_HEADER
#define SPARSE_VECTOR_HEADER


namespace oomph
{


//========================================================================
/// Sparse vector -- wrapper for map (but avoids filling map during
/// reads of zero/empty entries). Square bracket operator is read-only.
//========================================================================
template<class T>
class SparseVector
{

 public:
 /// Constructor
 SparseVector()
 {
  // Empty instance
  Empty_pt = new T(0);
 }

 /// Destructor
 ~SparseVector()
 {
  // Delete empty instance
  delete Empty_pt;
 }

 // Initialise the bin (only called by the create_bins_of_objects()
 // method)
 void initialise(const unsigned& size)
 {
  // Create a "large" bool vector indicating all entries are empty
  Has_entry.resize(size, false);
 }

 /// Wipe storage
 void clear()
 {
  Data.clear();

  // Get current size and reset all entries
  const unsigned size = Has_entry.size();
  Has_entry.resize(size, false);
 }

 /// Square bracket access (const version)
 const T& operator[](const unsigned& i) const
 {
  typedef typename std::map<unsigned, T>::const_iterator IT;
  IT it = Data.find(i);
  if (it == Data.end())
   {
    return *Empty_pt;
   }
  return (*it).second;
 }

 /// Set value of i-th entry
 void set_value(const unsigned& i, const T& value)
 {
  Data[i] = value;
  // Mark as having entry
  Has_entry[i] = true;
 }

 /// \short Number of nonzero entries stored in here (specifying the
 /// size of the vector (as a mathematical object)
 /// doesn't really make sense -- the thing could be infinitely
 /// big and we wouldn't know or care)
 unsigned nnz() const
  {
   return Data.size();
  }

 /// Read-only access to underlying map
 const std::map<unsigned,T>* map_pt() const
  {
   return &Data;
  }

 /// Read/write access to underlying map -- dangerous!
 std::map<unsigned,T>* map_pt()
  {
   return &Data;
  }

 /// \short Check if the bin has entries
 bool has_entry(const unsigned &nbin)
 {
  return Has_entry[nbin];
 }

 /// \short Return vector containing all values
 /// (without reference to their specific indices)
 /// for fast direct access
 void get_all_values(Vector<T>& all_values) const
 {
  all_values.clear();
  all_values.resize(nnz());
  typedef typename std::map<unsigned, T>::const_iterator IT;
  unsigned count = 0;
  for (IT it = Data.begin(); it != Data.end(); it++)
   {
    all_values[count++] = (*it).second;
   }
 }

 private:

 /// Internal storage in map.
 std::map<unsigned, T> Data;

 /// Empty instance
 const T* Empty_pt;

 /// Keep track of the filled and empty bins
 std::vector<bool> Has_entry;

};




#endif