20160401, 14:44  #1 
"Ron"
Jan 2016
Fitchburg, MA
97 Posts 
Benchmark Variances
I'm having trouble deciding between 1 worker and 4 workers in terms of overall efficiency on a particular machine. I ran 30 minute benchmarks (BenchTime=1800) twice, and get close (but different) results. Is this the equivalent to a "statistical tie", and I should just randomly pick a configuration (1, 2, or 4 workers) and just forget about it?
Code:
Timings for 4096K FFT length (4 cpus, 1 worker): 5.85 ms. Throughput: 170.91 iter/sec. Timings for 4096K FFT length (4 cpus, 2 workers): 11.81, 11.74 ms. Throughput: 169.85 iter/sec. Timings for 4096K FFT length (4 cpus, 4 workers): 23.23, 23.36, 23.19, 23.23 ms. Throughput: 172.04 iter/sec. Code:
Timings for 4096K FFT length (4 cpus, 1 worker): 5.83 ms. Throughput: 171.43 iter/sec. Timings for 4096K FFT length (4 cpus, 2 workers): 11.57, 11.57 ms. Throughput: 172.89 iter/sec. Timings for 4096K FFT length (4 cpus, 4 workers): 23.56, 23.44, 23.46, 23.89 ms. Throughput: 169.60 iter/sec. Last fiddled with by Fred on 20160401 at 14:46 
20160401, 14:56  #2 
Undefined
"The unspeakable one"
Jun 2006
My evil lair
2·3·1,013 Posts 
If there is no clear difference then it doesn't matter what you choose. Just choose any one. Or choose the one that is the most "pretty". Or go to random.org and let noise choose for you.

20160401, 15:05  #3 
Jun 2003
2^{3}×607 Posts 
Pick the 1 worker setup. That way, if you want to take a break, you need to finish up just the 1 test (quickly) and you're done. Also, you'll become eligible for cat 0 (if it is ever created ;) ).
Or follow retina's advice. It's all good. 
20160401, 15:06  #4 
"Mike"
Aug 2002
2×13×307 Posts 
If you run enough benchmarks you will "waste" more time than any optimization will make up for.
Personally, we would run four cores on one job, so the work gets done faster. Our theory is the shorter the run is the less likely there will be a cosmic ray bitflip. 
20160401, 16:41  #5  
P90 years forever!
Aug 2002
Yeehaw, FL
2^{3}·919 Posts 
Quote:


20160401, 18:15  #6  
"Ron"
Jan 2016
Fitchburg, MA
97_{10} Posts 
Quote:
1 worker it is! 

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