https://community.intel.com/t5/Intel-Moderncode-for-Parallel/OpenMP-effectiveness/m-p/824339#M1335 Hi,<BR /><BR />Never Mind, Got it to work as expected.<BR /><BR />[uname -a : Linux dhcp- 2.6.18-194.11.1.el5 #1 SMP Tue Jul 27 05:45:06 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux]<BR /><BR /> I am trying to use OpenMP for a particular application and I am somewhat confused by the behavior. I am using Intel compiler 11.1 with -O3 - openmp options and processor is 2 X Intel Xeon CPU E5620 @ 2.40GHz with RHEL 5.5. I have included the parallel section below. If I use it as shown I don't get any speed up at all no matter how many cores I use. I was naively hoping that I will get decent speed up with this scheme. I have tried another scheme which roughly corresponds to parallelizing at the moleculeloop (line number 9) and I get decent speed up (100% on 4 cores) . Am I missing something? [I hope it is not related to cache misses]. At this point I would like to get some feedback from openmp experts, if I should just give up the first scheme and adopt the second scheme and move on. Thanks. <BR /><BR /><BR /><BR /><BR /><BR /> <BR /><BR /> Mon, 13 Sep 2010 15:28:35 GMT neernash 2010-09-13T15:28:35Z https://community.intel.com/t5/Intel-Moderncode-for-Parallel/OpenMP-effectiveness/m-p/824339#M1335 Hi,<BR /><BR />Never Mind, Got it to work as expected.<BR /><BR />[uname -a : Linux dhcp- 2.6.18-194.11.1.el5 #1 SMP Tue Jul 27 05:45:06 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux]<BR /><BR /> I am trying to use OpenMP for a particular application and I am somewhat confused by the behavior. I am using Intel compiler 11.1 with -O3 - openmp options and processor is 2 X Intel Xeon CPU E5620 @ 2.40GHz with RHEL 5.5. I have included the parallel section below. If I use it as shown I don't get any speed up at all no matter how many cores I use. I was naively hoping that I will get decent speed up with this scheme. I have tried another scheme which roughly corresponds to parallelizing at the moleculeloop (line number 9) and I get decent speed up (100% on 4 cores) . Am I missing something? [I hope it is not related to cache misses]. At this point I would like to get some feedback from openmp experts, if I should just give up the first scheme and adopt the second scheme and move on. Thanks. <BR /><BR /><BR /><BR /><BR /><BR /> <BR /><BR /> Mon, 13 Sep 2010 15:28:35 GMT https://community.intel.com/t5/Intel-Moderncode-for-Parallel/OpenMP-effectiveness/m-p/824339#M1335 neernash 2010-09-13T15:28:35Z https://community.intel.com/t5/Intel-Moderncode-for-Parallel/OpenMP-effectiveness/m-p/824340#M1336 Your sample code is missing from your post. Fri, 24 Sep 2010 04:30:21 GMT https://community.intel.com/t5/Intel-Moderncode-for-Parallel/OpenMP-effectiveness/m-p/824340#M1336 jimdempseyatthecove 2010-09-24T04:30:21Z