Hello Wolfgang, The memory bus bandwidth seems the most reliable answer. But two more questions arise: - Matrix-free methods would have this problems minimised? - Will this affect also to MPI parallelization scalability in this computer?
Regards, Toni El dimarts, 11 febrer de 2020 22:37:31 UTC+1, Wolfgang Bangerth va escriure: > > On 2/11/20 2:27 PM, Toni Vidal wrote: > > > > That did not solve the problem with step 6. I got the same times. > > > > Indeed I have installed deal.II without threads (DEAL_II_WITH_THREADS = > > OFF) and I set in my .basrc OMP_NUM_THREADS=1. > > There are many other possible reasons for contention. For example, most > finite element programs are limited by the transfer of data from memory > to the processor. If you have just one program running, then only one > program is using the memory bus and is getting its full speed. But if > you have multiple programs running, then they are all competing for the > same bandwidth on the memory bus, and they will also be slowed down by > more than a single program would be. > > It could also be that you have, say, 4 cores on your processor but 3 > other programs currently running. Then running one instance of your code > will get a full core, but if you ran four, the total of 7 codes would > have to compete for 4 cores, and all would be slowed down. > > By the way, to see whether your program really is using only one thread, > you can run the program 'top' in a separate command line window. It will > show you which percentage of a processor each running job takes up. > > Best > W. > > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: bang...@colostate.edu > <javascript:> > www: http://www.math.colostate.edu/~bangerth/ > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/0dab48ed-19c0-4d99-af01-717d008cfdf2%40googlegroups.com.
