[Omp] slow performance

[Dieter an Mey]

and there is not very much to do in side the parallel region...

regards
Dieter

Nils Smeds wrote:

> mcwang88 at hotmail.com said:
> 
>>But to my big suprise, I see that the result is quite different from what I
>>can  imagine. The more threads I have, the more slow the calculation is.
> 
> 
> You need to tell us more about the platform you are running on. How many processors
> are available? How many processors are in use? Is there any other processes running
> that may interfere with your application? What kind of processors? Operating system?
> 
> You enter and exit a parallel region 16200*50 times. The 39 second overhead then
> divides into 39s/(16200*50) = 48µs per fork-join which sounds a little high on a 
> modern system, but it is not outrageously high.
> 
> /Nils
> 
> 
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Dieter an Mey
High Performance Computing               Hochleistungsrechnen
RWTH Aachen University                   Rechen- und Kommunikations-
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