mosesdecoder/moses/src/ObjectPool.h

// $Id$

/* ---------------------------------------------------------------- */
/* Copyright 2005 (c) by RWTH Aachen - Lehrstuhl fuer Informatik VI */
/* Richard Zens                                                     */
/* ---------------------------------------------------------------- */

#ifndef moses_ObjectPool_h
#define moses_ObjectPool_h

#include <vector>
#include <deque>
#include <string>
#include <iostream>
#include <iterator>
#include "Util.h"

/***
 * template class for pool of objects
 * - useful if many small objects are frequently created and destroyed
 * - allocates memory for N objects at a time
 * - separates memory allocation from constructor/destructor calls
 * - prevents memory leaks
 */
template<typename T> class ObjectPool {
 public:
  typedef T Object;
 private:
  std::string name;
  size_t idx,dIdx,N;
  std::vector<Object*> data;
  std::vector<size_t> dataSize;
  std::deque<Object*> freeObj;
  int mode;
 public:
  static const int cleanUpOnDestruction=1;
  static const int hasTrivialDestructor=2;

  // constructor arguments:
  //   N: initial number of objects to allocate memory at a time
  //   m & cleanUpOnDestruction = clean up objects in destructor
  //   m & hasTrivialDestructor = the object type has a trivial destructor,
  //            i.e. no sub-object uses dynamically allocated memory
  //            note: not equivalent to empty destructor
  //         -> more efficient (destructor calls can be omitted), 
  //            note: looks like memory leak, but is not
  ObjectPool(std::string name_="T",size_t N_=100000,int m=cleanUpOnDestruction)
    : name(name_),idx(0),dIdx(0),N(N_),mode(m) {allocate();}

		// main accesss functions:
		// get pointer to object via default or copy constructor
		Object* get() {return new (getPtr()) Object;}
		Object* get(const Object& x) {return new (getPtr()) Object(x);}
  
		// get pointer to uninitialized memory, 
		// WARNING: use only if you know what you are doing !
		// useful for non-default constructors, you have to use placement new
		Object* getPtr() {
			if(freeObj.size()) {
				Object* rv=freeObj.back();freeObj.pop_back();rv->~Object();return rv;}
			if(idx==dataSize[dIdx]) {idx=0; if(++dIdx==data.size()) allocate();}
			return data[dIdx]+idx++;
		}

		// return object(s) to pool for reuse
		// note: objects are not destroyed here, but in 'getPtr'/'destroyObjects',
		//       otherwise 'destroyObjects' would have to check the freeObj-stack 
		//       before each destructor call
		void freeObject(Object* x) {freeObj.push_back(x);}
		template<class fwiter> void freeObjects(fwiter b,fwiter e) {
			for(;b!=e;++b) this->free(*b);}

		// destroy all objects, but do not free memory
		void reset() {destroyObjects();idx=0;dIdx=0;freeObj.clear();}
		// destroy all objects and free memory
		void cleanUp() {
			reset(); for(size_t i=0;i<data.size();++i) free(data[i]);
			data.clear();dataSize.clear();
		}

		~ObjectPool() {if(mode & cleanUpOnDestruction) cleanUp();}

		void printInfo(std::ostream& out) const {
			out<<"OPOOL ("<<name<<") info: "<<data.size()<<" "<<dataSize.size()<<" "
				 <<freeObj.size()<<"\n"<<idx<<" "<<dIdx<<" "<<N<<"\n";
			std::copy(dataSize.begin(),dataSize.end(),
								std::ostream_iterator<size_t>(out," "));
			out<<"\n\n";
		}


 private:
		void destroyObjects() {
			if(mode & hasTrivialDestructor) return;
			for(size_t i=0;i<=dIdx;++i) {
				size_t lastJ= (i<dIdx ? dataSize[i] : idx);
				for(size_t j=0;j<lastJ;++j) (data[i]+j)->~Object();}
		}
		// allocate memory for a N objects, for follow-up allocations,
		// the block size is doubled every time
		// if allocation fails, block size is reduced by 1/4
		void allocate() {
			try {
				if(dataSize.empty()) dataSize.push_back(N); 
				else dataSize.push_back(dataSize.back()*2);
				void *m=malloc(sizeof(Object)*dataSize.back());
				while(!m) {
					dataSize.back()=static_cast<size_t>(dataSize.back()*0.75);
					m=malloc(sizeof(Object)*dataSize.back());
				}
				data.push_back(static_cast<Object*>(m)); 
			}
			catch (const std::exception& e) {
				TRACE_ERR("caught std::exception: "<<e.what()
								 <<" in ObjectPool::allocate(), name: "<<name<<", last size: "
								 <<dataSize.back()<<"\n");
				TRACE_ERR("OPOOL info: "<<data.size()<<" "<<dataSize.size()<<" "
								 <<freeObj.size()<<"\n"<<idx<<" "<<dIdx<<" "<<N<<"\n");
				std::copy(dataSize.begin(),dataSize.end(),
									std::ostream_iterator<size_t>(std::cerr," "));
				TRACE_ERR("\n");
				throw;
			}
		}
};

#endif