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Greg Tippitt

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Message 67233 - Posted: 9 Mar 2018, 10:06:29 UTC

Have others of you noticed that it takes 6 to 8 times as many CPU seconds for the same credit on N-Body OpenMP work units, than it takes for non-NBody Milkyway CPU jobs? I don't mean GPU versus CPU, but rather CPU versus CPU jobs?

In the past for Milkyway I have mainly run GPU work units, while running CPU tasks for other BOINC projects. I recently started running CPU tasks for Milkyway and have found that for given number of CPU seconds, I get more than 6 times as much credit for MilkyWay@Home v1.46 as I do for N-Body Simulation tasks.

On my machine (details at link below) that has 4 hex core AMD CPUs (26 real cores), I get 1 credit for every 30 CPU seconds on MW@Hv1.46 jobs, but it takes 175 CPU seconds to get 1 credit on N-Body Sim jobs. This disparity persists whether I am running 8, 10, or 16 core N-Body jobs.

http://milkyway.cs.rpi.edu/milkyway/show_host_detail.php?hostid=718220

I have triple checked, and I am not comparing the the Radeon GPU jobs with the N-Body OpenMP CPU tasks. This is CPU to CPU comparison. I run jobs for several BOINC projects, and I am accustomed to some projects giving lots more credit for the same processing time, whether CPU or GPU. On projects that have multiple types of jobs, a given project normally gives fairly comparable credit per their different applications unless there is a reason for doing otherwise.

Last year I was running work for another project that temporarily gave us double credit while they were testing a new application, because half of the work units would run for hours and then crash without us getting any credit. Once they debugged the new application and work units quit crashing, then they dropped the extra-credit on that application to be comparable to their other applications. Another project had one application where the work units required 4 times as much RAM as their other applications, so they gave a bit more credit for the RAM hungry application.

The very low credit for the N-Body application seems illogical, unless it's a private joke and "n-body" is a pun for the application "nobody" will want to run.

Greg
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Message boards : Number crunching : Low Credits for OpenMP N-Body work units?

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