MPIType.h

/****************************************************************/
/* Parallel Combinatorial BLAS Library (for Graph Computations) */
/* version 1.4 -------------------------------------------------*/
/* date: 1/17/2014 ---------------------------------------------*/
/* authors: Aydin Buluc (abuluc@lbl.gov), Adam Lugowski --------*/
/****************************************************************/
/*
 Copyright (c) 2010-2014, The Regents of the University of California
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:
 
 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */

#ifndef _MPI_TYPE_H
#define _MPI_TYPE_H

#include <iostream>
#include <typeinfo>
#include <map>
#include <mpi.h>
#include <stdint.h>

using namespace std;


// A datatype cache inspired by (mostly copied from) Boost http://www.boost.org/LICENSE_1_0.txt)

/// @brief comparison function object for two std::type_info pointers
/// is implemented using the before() member function of the std::type_info class
struct type_info_compare
{
  bool operator()(std::type_info const* lhs, std::type_info const* rhs) const
  {
    return lhs->before(*rhs);
  }
};


class MPIDataTypeCache
{
private:
  typedef std::map<std::type_info const*,MPI_Datatype,type_info_compare> stored_map_type;
  stored_map_type map;

public:
  void clear()
  {
	int is_finalized=0;
	MPI_Finalized(&is_finalized);
	if (! is_finalized ) 	// do not free after call to MPI_FInalize
	{
		// ignore errors in the destructor
		for (stored_map_type::iterator it=map.begin(); it != map.end(); ++it)
		{
			MPI_Type_free(&(it->second));
		}
	}
  }
  ~MPIDataTypeCache()
  {
    	clear();
  }
  MPI_Datatype get(const std::type_info* t)
  {
      	stored_map_type::iterator pos = map.find(t);
      	if (pos != map.end())
          	return pos->second;
      	else
        	return MPI_DATATYPE_NULL;
  }

  void set(const std::type_info* t, MPI_Datatype datatype)
  {
#ifdef NOTGNU
	if (map.find(t) != map.end()) map.erase(key);
    	map.insert(make_pair(t, datatype));
#else
     	 map[t] = datatype;
#endif
  }

  MPIDataTypeCache& mpi_datatype_cache()
  {
    	static MPIDataTypeCache cache;
    	return cache;
  }
};


/**
  * C++ type to MPIType conversion is done through functions returning the mpi types
  * The templated function is explicitly instantiated for every C++ type 
  * that has a correspoinding MPI type. For all others, a data type is created
  * assuming it's some sort of struct. Each created data type is committed only once
  **/

extern MPIDataTypeCache mpidtc;	// global variable
// Global variables have program scope, which means they can be accessed everywhere in the program, and they are only destroyed when the program ends.

template <typename T> 
MPI_Datatype MPIType ( void )
{
	std::type_info const* t = &typeid(T);
	MPI_Datatype datatype = mpidtc.get(t);

	if (datatype == MPI_DATATYPE_NULL) 
	{
		MPI_Type_contiguous(sizeof(T), MPI_CHAR, &datatype );
		MPI_Type_commit(&datatype);
		int myrank;
		MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
		if(myrank == 0)
			cout << "Creating a new MPI data type for " << t->name() << endl;
		mpidtc.set(t, datatype);
	}
   	return datatype;
};

template<> MPI_Datatype MPIType< signed char >( void );
template<> MPI_Datatype MPIType< signed short int >( void );
template<> MPI_Datatype MPIType< unsigned char >( void );
template<> MPI_Datatype MPIType< unsigned short int >( void );
template<> MPI_Datatype MPIType< int32_t >( void );
template<> MPI_Datatype MPIType< uint32_t >( void );
template<> MPI_Datatype MPIType< int64_t >( void );
template<> MPI_Datatype MPIType< uint64_t >( void );
template<> MPI_Datatype MPIType< float >( void );
template<> MPI_Datatype MPIType< double >( void );
template<> MPI_Datatype MPIType< long double >( void );
template<> MPI_Datatype MPIType< bool >( void );



#endif