pcl_util_impl.h

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/*
 * Copyright (c) 2010-2015:  G-CSC, Goethe University Frankfurt
 * Author: Sebastian Reiter
 * 
 * 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.
 */
 
 
#include "common/util/binary_buffer.h"
#include "common/serialization.h"
 
namespace pcl {
 
template <typename TKey, typename TValue, typename Compare>
void MinimalKeyValuePairAcrossAllProcs(TKey& keyInOut, TValue& valInOut, const Compare& cmp)
{
  // in the serial case, input key and value are already output key and value
#ifndef UG_PARALLEL
  return;
#endif
  size_t nProc = NumProcs();
  if (nProc == 1)
    return;
 
  // write key/value pair into binary buffer
  ug::BinaryBuffer buf;
  ug::Serialize(buf, keyInOut);
  ug::Serialize(buf, valInOut);
 
  // gather buffers on root
  ProcessCommunicator pc;
  pc.gather(buf, 0);
 
  // find minimum on root
  size_t rk = ProcRank();
  if (rk == 0)
  {
    TKey key;
    TValue val;
 
    for (size_t i = 0; i < nProc; ++i)
    {
      ug::Deserialize(buf, key);
      ug::Deserialize(buf, val);
 
      if (cmp(key, keyInOut))
      {
        keyInOut = key;
        valInOut = val;
      }
    }
 
    buf.clear();
    ug::Serialize(buf, keyInOut);
    ug::Serialize(buf, valInOut);
  }
 
  // communicate minimum to all procs
  pc.broadcast(buf, 0);
 
  // copy to return values
  ug::Deserialize(buf, keyInOut);
  ug::Deserialize(buf, valInOut);
}
 
 
} // end of namespace pcl