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POwhat is the execution order of a threaded and non-threaded function call?
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  1. POwhat is the execution order of a threaded and non-threaded function call?
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    copied!<p>i have written a simple console application just to try boost::thread, i am a multithreading newbie by the way. here is the code</p> <pre><code>#include &lt;iostream&gt; #include &lt;boost/thread/thread.hpp&gt; #include &lt;windows.h&gt; using namespace std; void Avg(double * Src, double *Dst, int Per, int Len, string&amp; s ) { LARGE_INTEGER s1,s2,f; QueryPerformanceFrequency(&amp;f); QueryPerformanceCounter(&amp;s1); for(int i = Per-1; i &lt; Len ; i++) { double a = 0; for(int j = i; j &gt; i-Per ; j--) a += Src[j]; Dst[i] = a / Per; } QueryPerformanceCounter(&amp;s2); cout &lt;&lt; double(s2.QuadPart-s1.QuadPart)/f.QuadPart*1000 &lt;&lt; " ms : "+s &lt;&lt; endl; } int main(int argc, char* argv[]) { int L = 200000; double * a = new double[L], *b = new double[L] , *c = new double[L]; for(int i =0; i &lt; L;i++) { a[i] = i+2; } int x = 10000; boost::thread bAvg(Avg,a,b,x,L,string("T")); LARGE_INTEGER s1,s2,f; QueryPerformanceFrequency(&amp;f); QueryPerformanceCounter(&amp;s1); Avg(a,c,x,L,string("N")); // line 1 bAvg.join(); // line 2 QueryPerformanceCounter(&amp;s2); cout &lt;&lt; double(s2.QuadPart-s1.QuadPart)/f.QuadPart*1000 &lt;&lt; " ms : Total" &lt;&lt; endl; delete []a; delete []b; delete []c; system("PAUSE"); return 0; } </code></pre> <p>the output of that code is </p> <blockquote> <p>6621.1 ms : N<br> 6635.28 ms : T<br> 6638.29 ms : Total<br> Press any key to continue . . .</p> </blockquote> <p>But when i change the order of line 1 and line 2 the output becomes: </p> <blockquote> <p>6274.57 ms : T<br> 6250.56 ms : N<br> 12531.3 ms : Total<br> Press any key to continue . . .</p> </blockquote> <p>in case 1, bAvg.join() is fired just after Avg fired and before it is finished. i thought the results of case 1 and case 2 would be the opposite of each other. this has something to do with the execution order of threads i think. </p> <p><strong>edit:</strong><br> actually i am planning to write an application for trading purposes. i am going to create, say, at least 10 threads of calculations per upcoming signal for a single stock. the signals will be received via tcp connection. but if the main execution thread waits for the completion of other sub-threads', then a single signal may be easily missed, because the main thread is idle. how am i supposed to handle the signals and run the calculation threads?</p>
 

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