Sorry, I just have a quick follow-up on this subject, to clarify. Am I misinterpreting when I read "num-threads is larger than the value for cores or procs"? The cluster I am using (ThornyFlat) gives me the formula: procs* num-stm = np*num-threads Disregarding simultaneous multithreading (num-stm = 1) and considering np>1, gives procs>num-threads What I heard at the last ETK meeting was that procs is nr. processes, and it will be divided by the num threads. I thought that if we divide procs by num-threads, we get np. Indeed, testing it, I get: --procs=24 --num-threads=1 <=> np=24 --procs =24 --num-threads=2 <=> np=12 _______________________ Maria C. Babiuc Hamilton, Ph.D. Professor, Department of Physics College of Science, Marshall University, 1 John Marshall Drive, Huntington, WV, 25755 Room S 257, Phone: (304)696-2754
________________________________ From: [email protected] <[email protected]> on behalf of Roland Haas <[email protected]> Sent: Monday, January 18, 2021 5:17 PM To: KARIMA SHAHZAD <[email protected]> Cc: [email protected] <[email protected]> Subject: Re: [Users] TAT/ Slab Error Hello Karima, > Here is the error attached I encountered while evolving black holes > binary. The work-around I guess is to increase the number of > processes (if I am not wrong), but I am not quite sure how to do > that. I need some help to get around this issue. Assuming you use simulation factory you need to pass options to make sure it creates multiple MPI processes. The auto-detection code tends to choose a number of threads equal to the the number of cores on your laptop and and a single MPI rank. Eg if you have a 4 core laptop then you have to use: ./simfactory/bin/sim submit testrun01 --cores 4 --num-threads 2 --parfile ... which uses a total of 4 cores and starts 2 threads per MPI rank so that you end up with 4 / 2 = 2 MPI ranks each of which uses 2 threads. Similarly on clusters, the basic idea is to set --num-threads so that there are more than 1 MPI rank started (ie --num-threads is larger than the value for --cores or --procs [which are synonyms for each other]). If not using simulation factory you have to manually use mpirun and OMP_NUM_THREADS. Eg: export OMP_NUM_THREADS=2 mpirun -np 2 /home/karima/simulations/bbhHr/SIMFACTORY/exe/cactus_sim -L 3 /home/karima/simulations/bbhHr/output-0000/BBHHigherRes.par which starts 2 MPI ranks each will use 2 OpenMP threads. Yours, Roland -- My email is as private as my paper mail. I therefore support encrypting and signing email messages. Get my PGP key from https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpgp.mit.edu%2F&data=04%7C01%7Cbabiuc%40marshall.edu%7C6164afef3f5144f4e6ad08d8bbfee273%7C239ab2783bba4c78b41d8508a541e025%7C0%7C0%7C637466050685932327%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=bIBVt8EYRo%2FekfxirOK1RXSZyr5K8aAReTD76%2FpaLHk%3D&reserved=0 .
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