C CreateThread() to slow? : i have a following code for matrix-vector multiplication:

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    std::chrono::steady_clock::time_point start, end2;
    void fillMatrixConditions(LPVOID lpv) {
    	end2 = std::chrono::steady_clock::now();
    	std::cout << "Time difference = " << std::chrono::duration_cast<std::chrono::microseconds>(end2 - start).count() << std::endl;
    	std::cout << "Time difference = " << std::chrono::duration_cast<std::chrono::nanoseconds> (end2 - start).count() << std::endl;
    	int i, j = horizontControl;
    	for (i = 0; i < horizontControl; i++, j++) {
    		b[i] = akcni - uMin;
    		b[j] = uMax - akcni;
    	}
    	j = 2 * horizontControl + N - N1 + 1;
    	int k = 0;
    	for (i = 2 * i; i < (2 * horizontControl + N - N1 + 1); i++, j++, k++) {
    		b[i] = MpDup[k] - yMin;
    		b[j] = yMax - MpDup[k];
    	};
    	RtPrintf("Thread");
    }

    int _tmain(int argc, _TCHAR * argv[])
    {
    	HANDLE hThread;
    	DWORD id;
    	int k = 0;
    	double temp;
    	double g[50];		
    	for (int j = 0; j < N - N1 + 1; j++)
    	{
    		temp = 0;
    		for (int m = 0; m < horizontPrediction - 1; m++, k++)
    		{
    			temp = temp + Mp[k] * dup[m];
    		}
    		MpDup[j] = temp;
    		tempMatrix[j] = setPoint - y - temp;
    	}
    	start = std::chrono::steady_clock::now();
    	hThread = CreateThread(NULL, NULL, (LPTHREAD_START_ROUTINE)fillMatrixConditions, NULL, NULL, &id);		
    	k = 0;
    	for (int j = 0; j < horizontControl; j++)
    	{
    		temp = 0;
    		for (int m = 0; m < N - N1 + 1; m++, k++)
    		{
    			temp = temp + Mtranspose[k] * tempMatrix[m];
    		}
    		g[j] = -2 * temp;
    	}
    	RtPrintf("Point\n");	
    	WaitForSingleObject(hThread, INFINITE);
    	CloseHandle(hThread);
        return 0;
    }

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But CreateThread() is to slow, because this is output program:

    Point
    Time difference = 247
    Time difference = 247261

I thought first will be write Time difference in thread and then "Point".  Or is it normal? I must use CreateThread. I can't pthread etc. Matrix Mtranspose has 2025 cells.

Thanks for help :-)