gistfile1.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <windows.h>
#include <boost/thread.hpp>

class ConcurrentCounter {
	unsigned int* counters_;
	int length_;
public:
	ConcurrentCounter() {
		length_ = boost::thread::hardware_concurrency() * 0x100;
		counters_ = new unsigned int[length_];
		std::fill(counters_, counters_ + length_, 0);
	}
 
	unsigned int get_value() {
		return std::accumulate(counters_, counters_ + length_, 0);
	}
 
	void inc() {
		auto i = rand() % length_;
		InterlockedIncrement(counters_ + i);
	}
};
 
int main(int argc, char* argv[])
{
	{
		boost::thread_group tg;
		boost::barrier bar(4);
		unsigned int counter = 0;
		unsigned long startTime = 0;
		unsigned long stopTime = 0;
		auto threadFn = [&counter, &bar, &startTime] () {
			bar.wait();
			startTime = GetTickCount();
			for(int i = 0; i < 0x1000000; i++)
				InterlockedIncrement(&counter);
		};
		tg.create_thread(threadFn);
		tg.create_thread(threadFn);
		tg.create_thread(threadFn);
		tg.create_thread(threadFn);
		tg.join_all();
		stopTime = GetTickCount();
 
		printf("counter - %d\n", counter);
		printf("ticks - %d\n", stopTime - startTime);
	}
	{
		boost::thread_group tg;
		boost::barrier bar(4);
		ConcurrentCounter counter;
		unsigned long startTime = 0;
		unsigned long stopTime = 0;
		auto threadFn = [&counter, &bar, &startTime] () {
			bar.wait();
			startTime = GetTickCount();
			for(int i = 0; i < 0x1000000; i++)
				counter.inc();
		};
		tg.create_thread(threadFn);
		tg.create_thread(threadFn);
		tg.create_thread(threadFn);
		tg.create_thread(threadFn);
		tg.join_all();
		stopTime = GetTickCount();
 
		printf("counter - %d\n", counter.get_value());
		printf("ticks - %d\n", stopTime - startTime);
	}
	return 0;
}