Yade

About the precision in Yade

Asked by zhou qian

Hi:
I want to know if the precision of the output will change when using multiprocessing method?
I generated a cell using periodic boundary and run 1 step. All the input are the same, but the output has a little difference.
The only difference is that I used multiprocessing module.

Here is an example:
s = utils.getStress()
stress = .5*(s+s.transpose())
print(stress)

This is the output not using multiprocessing:
Matrix3(-3.2318083264549893e8,-1.0280421281453311e8,8.650857104999597e7, -1.0280421281453311e8,-2.711494053389691e8,5.1181854736692876e7, 8.650857104999597e7,5.1181854736692876e7,-3.063417307183882e8)

using multiprocessing:
Matrix3(-3.231808326454989e8,-1.0280421281453317e8,8.650857104999602e7, -1.0280421281453317e8,-2.711494053389688e8,5.1181854736692905e7, 8.650857104999602e7,5.1181854736692905e7,-3.063417307183884e8)

Yours,
Joe

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Solved by:
Jan Stránský
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Revision history for this message
Best Jan Stránský (honzik) said : 		#1

Hi Joe
https://yade-dem.org/doc/formulation.html#result-indeterminism
Jan

Revision history for this message
zhou qian (zhoug15) said : 		#2

Thanks Jan Stránský, that solved my question.

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Chareyre (bruno-chareyre-9) said : 		#3

The parallel result is different, yes, but not less accurate. The rounding
errors are just randomized.
Bruno

Le jeu. 28 mars. 2019 17:27, zhou qian <email address hidden>
a écrit :

> Question #679618 on Yade changed:
> https://answers.launchpad.net/yade/+question/679618
>
> Status: Answered => Solved
>
> zhou qian confirmed that the question is solved:
> Thanks Jan Stránský, that solved my question.
>
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Revision history for this message
zhou qian (zhoug15) said : 		#4

Hi：
Thanks for your reply!
I did a test with 480 periodic cells and it shows it has only a little difference when the strain is relatively large.
Yours,
Joe