Re: [Yade-users] [Question #665405]: Parallelism inconsistency
Question #665405 on Yade changed: https://answers.launchpad.net/yade/+question/665405 Bruno Chareyre posted a new comment: Hi, I would say this is not a misfeature that one wants to avoid. Instead it is an opportunity to assess indeterminism, which is in most cases inherent to the underlying physics. Re-ordering the bodies (i.e renumbering) while keeping everything else the same would give similar fluctuations in single thread yet I don't think anyone would claim that one numbering is better than another. The single thread result is like selecting one numbering and sticking to it, while parallel runs are like renumbering randomly each time. If the fluctuations are about 100% it is an interesting indication that the physical problem could be somehow ill-posed. Like asking in which direction a sphere will fall if you put it right on the top of a needle. Regards Bruno -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #665405]: Parallelism inconsistency
Question #665405 on Yade changed: https://answers.launchpad.net/yade/+question/665405 JOHN gave more information on the question: And now my new simulation is ~100% different. Reading the source i got the feeling that such large fluctuations are not normal -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #665405]: Parallelism inconsistency
Question #665405 on Yade changed: https://answers.launchpad.net/yade/+question/665405 Status: Open => Needs information Jan Stránský requested more information: Hi John, in general it depends very much on the problem and how you measure fluctuation. I am afraid there is no way to decrease the effect with current implementation.. Can you please post your example (ideally in the minimal form)? thanks Jan -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #665405]: Parallelism inconsistency
Question #665405 on Yade changed: https://answers.launchpad.net/yade/+question/665405 JOHN confirmed that the question is solved: Thanks Jan Stránský, that solved my question. -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #665405]: Parallelism inconsistency
Question #665405 on Yade changed: https://answers.launchpad.net/yade/+question/665405 Status: Needs information => Solved JOHN confirmed that the question is solved: Hi, thanks again. My example is unfortunately not easily given in minimal form. The simulation itself just creates a hexagonal packing, imports an stl, substracts spheres that are in or partially in the walls and runs with the following engine O.engines=[ ForceResetter(), InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]), InteractionLoop( # handle sphere+sphere and facet+sphere collisions [Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom()], [Ip2_FrictMat_FrictMat_FrictPhys()], [Law2_ScGeom_FrictPhys_CundallStrack()] ), NewtonIntegrator(gravity=(0,-9.81,0),damping=0.4, label='newtonInt'), the tricky part is an outside function that calculates rotations which is not easily given in minimal form -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #665405]: Parallelism inconsistency
Question #665405 on Yade changed: https://answers.launchpad.net/yade/+question/665405 Status: Answered => Open JOHN is still having a problem: Hi Jan, thanks for the info! That makes sense. Though it seems like there is no way around it, is it possible to decrease that effect? I am now seeing up to ~15% difference in some simulations Thanks again cheers John -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #665405]: Parallelism inconsistency
Question #665405 on Yade changed: https://answers.launchpad.net/yade/+question/665405 Status: Open => Answered Jan Stránský proposed the following answer: Hi John, yes, this is a known issue, see [1] cheers Jan [1] https://yade-dem.org/doc/formulation.html#result-indeterminism -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
