Hello, The misbehave affects only the parallel performance. It returns correct calculation results, is faster than the simple algorithm, but the runtime doesn't improve compared to the serial execution. Unfortunately I don't have an explaination yet because I just had to replace a for-loop with a forall-loop; there is no loop dependence. I really wonder about this effect because it's the same program I had to parallelize with MPI in a practical lesson and there it worked well, so the algorithm itself is correct. Parallelizing it in Chapel (at first for one locale until it works) needs much less effort, hereby programming mistakes become virtually impossible (which I really appreciate :-) ).
bye Zitat von Lydia Duncan <[email protected]>: > Hi Michael, > > By behaves incorrectly, were you referring to the performance > timings or some other issue not mentioned here? > > Thanks, > Lydia Duncan > ________________________________________ > From: Michael Dietrich [[email protected]] > Sent: Friday, August 15, 2014 12:29 PM > To: Tom MacDonald > Cc: [email protected] > Subject: Re: Missing performance improvement at parallel execution > > Hello, > > thank you for your fast answer. > No, I didn't use any further options for compiling because I was not > sure about it when it already behaves uncorrectly without. > Should I maybe let the compiler do the optimizations? I can give you > feedback about this next week when I'm back in university. > > bye > > > Zitat von Tom MacDonald <[email protected]>: > >> Hi Michael, >> >> Thank you for your interest in Chapel! It's good to hear you are >> studying high performance programming languages. >> >> Are you compiling your Chapel program with the --fast option? >> >> We need to know that before looking deeper. >> >> Thanks >> >> Tom MacDonald >> >> On Fri, 15 Aug 2014, Michael Dietrich wrote: >> >>> Hello, >>> >>> I'm working with Chapel due to my bachelor thesis about high >>> performance programming languages. My current task is to implement a >>> particle simulation program of which I already have the code in C. It >>> includes two possible algorithms for calculating the force acting onto >>> the particles: A simple but ineffective one and the >>> Barnes-Hut-Algorithm [1] which is much faster but a bit more >>> complicated. The other calculations aren't that complex so for me only >>> the calculation of force is important. >>> >>> I implemented the simple algorithm at first. For comparing the serial >>> and parallel execution time I surrounded everything with a >>> serial-statement, evaluating a bool variable I have to set in the >>> command line. I didn't implement the multi locale improvement yet so >>> it runs only on a dual core PC, using forall-loops. Finally the >>> parallel one only needed half of the time of the serial, yay. >>> >>> I continued with Barnes-Hut. This one was a bit more work because the >>> maintenance of the tree-structure leaves a lot of opportunities for >>> mistakes. After a bit more time it was working as well. >>> My issue is about the parallel execution time of this algorithm. Like >>> in the other one I replaced the crucial for-loop with a forall-loop >>> (the serial-statement surrounds the whole program). The problem is, >>> that the parallel execution time is similar to the serial one, >>> sometimes even longer. >>> Of course I don't want you to read through all my code, but could you >>> tell me some possible reasons, why this effect may occur? >>> >>> thank you very much >>> bye >>> Michael >>> >>> >>> [1] http://beltoforion.de/barnes_hut/barnes_hut_en.html >>> >>> >>> ------------------------------------------------------------------------------ >>> _______________________________________________ >>> Chapel-users mailing list >>> [email protected] >>> https://lists.sourceforge.net/lists/listinfo/chapel-users >>> > > > > > ------------------------------------------------------------------------------ > _______________________________________________ > Chapel-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/chapel-users ------------------------------------------------------------------------------ _______________________________________________ Chapel-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/chapel-users
