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Forum: Multithreading
Re: None MT migration problem (Alex Kav)
Re: Question Re: MT in hpcc problem (Alex Kav)
Date: 15 Sep, 2015
From: Alex Kav <Alex Kav>

Dear G4 experts! I still have a problem with MT simulation on computer cluster. I'll to try explain my problem once again . As I wrote in my question my software running in multithread (MT) mode on conventional laptop looks OK. I can run my simulation in parallel in all available computer’s cores. Number of available cores can be determinate by user G4int nThreads = 10; for instance or is determined by code G4int nThreads = G4Threading::G4GetNumberOfCores();. The speed up of simulation (if number of cores not too high) equal the number of cores. On laptop (which have 4 cores) all looks as expected. High Performance Compute Cluster (http://eng.auburn.edu/admin/ens/hpcc/hpcc-description.html), which I use, consists from 4 nodes with 128 core on each. The PBS-script is used for running the job. The number of nodes and the number of cores are ordered in script. When PBS-script ordered, for instance, n cores and code “nThreads = G4Threading::G4GetNumberOfCores();” the running goes on 128 threads, but on one core only (!) and load of this core 4000% or more. When PBS-script ordered n cores and code “nThreads = n;” the running goes on n threads, but on one core only (!) and load of this core is (~100 x n) %. Note, if my job runs on 128 cores, other jobs on hpcc are braked. Due to this reason I have quote for running 10 jobs in 2 thread mode now. My question is “how can I fixed this problem and run multithread job with 1 thread on each core of hpcc”.

Thanks in advance

Alex

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1 Warning: Re: MT in hpcc problem   (Andrea Dotti - 15 Sep, 2015)
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