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Testing simple concurrent containers

, 25 Oct 2009 CPOL
This article illustrates simple approaches and test results when creating containers with concurrent flavor and running on a multi-core PC.
// The code of the hash() function in the critical section table
// came from the MSDN article written by Ian Emmons,
// "Multiprocessor Optimizations: Fine-Tuning Concurrent Access to Large Data Collections",
// http://msdn.microsoft.com/en-ca/magazine/cc301503.aspx

#pragma once 
#include "stdafx.h"
#include "rwlocks_helpers.h"

template <typename Lock_type>
struct CritSecTable_locker_t
{
	typedef ref_exclusive_lock_t<Lock_type> Exclusive_lock;
	typedef ref_shared_lock_t<Lock_type> Shared_lock;

	unsigned char hash(void* p)
	{
		unsigned char result;

		if (sizeof(void*) == 8)
		{
			assert(sizeof(unsigned long) == 4);
			assert(sizeof(unsigned short) == 2);

			unsigned long temp1 = ((unsigned long*) (&p))[0]
			^ ((unsigned long*) (&p))[1];
			unsigned short temp2 = ((unsigned short*) (&temp1))[0]
			^ ((unsigned short*) (&temp1))[1];
			result = ((unsigned char*) (&temp2))[0]
			^ ((unsigned char*) (&temp2))[1];
		}
		else if (sizeof(void*) == 4)
		{
			assert(sizeof(unsigned short) == 2);

			unsigned short temp = ((unsigned short*) (&p))[0]
			^ ((unsigned short*) (&p))[1];
			result = ((unsigned char*) (&temp))[0]
			^ ((unsigned char*) (&temp))[1];
			}
		else
		{
			result = ((unsigned char*) (&p))[0];
			for (unsigned i = 1; i < sizeof(void*); i++)
			{
				result ^= ((unsigned char*) (&p))[i];
			}
		}
		return result;
	}

	Lock_type& get_element_lock(void* p)
	{
		return m_element_locks[hash(p)]; 
	}

	enum {CSTABLE_SIZE = 256};
	Lock_type m_element_locks[CSTABLE_SIZE];

	CACHE_PADDING1
	Lock_type m_global_scope_lock;

	CritSecTable_locker_t& operator=(const CritSecTable_locker_t&); //C4512 warning
};


template <typename key_type, typename value_type, typename lock_type>
class CST_map_t 
{
public:
	
	bool insert( const std::pair<key_type, value_type>& pair) 
	{
		Container_locker::Exclusive_lock lock(m_map_lock.m_global_scope_lock);
		return m_map.insert(pair).second;
	}

	bool erase(const key_type& _key)
	{
		Container_locker::Exclusive_lock lock(m_map_lock.m_global_scope_lock);
		return (m_map.erase(_key) != 0);
	}

	bool update(const key_type& _key, const value_type& _val)
	{
		Container_locker::Shared_lock lock(m_map_lock.m_global_scope_lock);

		map_iterator iterator = m_map.find(_key);
		if (iterator != m_map.end())
		{
			Container_locker::Exclusive_lock lock(m_map_lock.get_element_lock(&iterator->second));
			iterator->second = _val; 
			return true;
		}
		else
		{
			return false;
		}
	}

	bool find(const key_type& _key, value_type& _val)
	{
		Container_locker::Shared_lock lock(m_map_lock.m_global_scope_lock);

		map_iterator iterator = m_map.find(_key);

		if (iterator != m_map.end())
		{
			Container_locker::Shared_lock lock(m_map_lock.get_element_lock(&iterator->second));
			_val = iterator->second; 
			return true;
		}
		else
		{
			return false;
		}
	}

private:	

	typedef CritSecTable_locker_t<lock_type> Container_locker;
	
#ifdef HAS_HASH_MAP
	typedef typename stdext::hash_map<key_type, value_type>::iterator map_iterator;
	stdext::hash_map<key_type, value_type> m_map;
#elif defined HAS_MAP
	typedef typename std::map<key_type, value_type>::iterator map_iterator;
	std::map<key_type, value_type> m_map;
#endif

	CACHE_PADDING1
	Container_locker m_map_lock;

};

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Valery Grebnev
Software Developer
Canada Canada
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