Hello, I am actually running into the exact same problem.
For instance, with the scripts attached in the first post, and modifying the MAX_SPHERES_TOUCHED_BY_SPHERE to 32 (then rebuilding the solver), I get the "No available contact pair" error after around 40 steps. I am on the updated version of the feature/gpu branch, so I am a bit confused. Do you have any clue of what it could be? Best regards, Yves On Wednesday, June 8, 2022 at 7:07:16 PM UTC+3 Ruochun Zhang wrote: > Hi David, > > Thanks for sharing! > > Ruochun > > On Monday, June 6, 2022 at 10:34:24 AM UTC-5 [email protected] wrote: > >> Realized I forgot to share my changes to add the group functionality. I’m >> not super familiar with GitHub so I’ll just upload my chrono_gpu source >> files here. I believe that I only made changes to >> ChGPUDefines.h,,ChSystemGPU.h and .cpp, and ChSystemGpu_impl.h and .cpp to >> add the SetParticleGroup function. >> >> Thanks! >> David >> >> On Sunday, June 5, 2022 at 10:29:33 PM UTC-6 Ruochun Zhang wrote: >> >>> Hi Yves, >>> >>> If by "relocation" you mean something similar to the "particle source" >>> method mentioned in this thread, then you can already see how it's done >>> from the scripts shared therein: basically, adding more spheres to the >>> system then "re-initialize". If you meant establishing a periodic boundary, >>> then I don't believe it is discussed in this thread, and as I said this is >>> a more dedicated issue and worth a separated discussion. >>> >>> Thanks, >>> Ruochun >>> >>> On Saturday, June 4, 2022 at 2:02:14 PM UTC-5 [email protected] >>> wrote: >>> >>>> Hello, >>>> >>>> I would be very interested in this feature for my project, would it be >>>> possible to share the changes you made, especially for the particles >>>> relocation? >>>> Please let me know, we can exchange by email as well. >>>> >>>> Yves >>>> >>>> On Monday, May 16, 2022 at 5:55:47 PM UTC+3 [email protected] wrote: >>>> >>>>> Hi Ruochun, >>>>> >>>>> Thanks for the help, it seems to be working now! I was able to get the >>>>> particle relocation working as well. >>>>> >>>>> I am interested in the new solver. Let me know when a release/test >>>>> build is available for it, I’d like to try it out to see if it’s faster >>>>> for >>>>> these applications. >>>>> >>>>> Thanks! >>>>> David >>>>> >>>>> On Friday, May 13, 2022 at 3:43:36 PM UTC-6 Ruochun Zhang wrote: >>>>> >>>>>> Hi David, >>>>>> >>>>>> This issue is a weakness in the default assumption we made that a >>>>>> sphere can have at most 12 contacts. This assumption is made to save GPU >>>>>> memory and to help identify some large-penetration problems in >>>>>> simulation >>>>>> which is typical with insufficient time step size. This assumption is >>>>>> fine >>>>>> with near-rigid spherical contacts, but problematic when meshes are >>>>>> involved (each mesh facet in contact with a sphere eats up one slot as >>>>>> well). Imagine a sphere sitting on the tip of a needle made of mesh, it >>>>>> could have contacts with tens of mesh facets, and we haven't counted the >>>>>> sphere neighbors it can potentially have. >>>>>> >>>>>> The fix is easy, please go to the file *ChGpuDefines.h* (in >>>>>> chrono\src\chrono_gpu), and replace >>>>>> *#define MAX_SPHERES_TOUCHED_BY_SPHERE 12* >>>>>> by >>>>>> *#define MAX_SPHERES_TOUCHED_BY_SPHERE 20* >>>>>> or some even larger number if you need it. Rebuild it and your script >>>>>> should run fine. Note the error messages are hard-coded to say 12 is not >>>>>> enough if *MAX_SPHERES_TOUCHED_BY_SPHERE* is exceeded, so if 20 is >>>>>> not enough and you need even more, just change it and do not let the >>>>>> error >>>>>> messages confuse you. >>>>>> >>>>>> Another thing is that it is better to use meshes with relatively >>>>>> uniform triangle sizes. I attached a rebuilt mesh based on your original >>>>>> one. It's optional and does not seem to affect this simulation, but it's >>>>>> a >>>>>> good practice. >>>>>> >>>>>> To answer your other questions: Unfortunately C::GPU does not >>>>>> currently have an *efficient* way of streaming particles into the >>>>>> system. The method you are using (re-initialization) is probably what I >>>>>> would do too if I have to. With a problem size similar to yours, it >>>>>> should >>>>>> be fine. And C::GPU does not have an official API that enforces manual >>>>>> particle position changes. However this should be fairly straightforward >>>>>> to >>>>>> implement. The naive approach is of course, do it on the host side with >>>>>> a >>>>>> for loop. If you care about efficiency, then we should instead add one >>>>>> custom GPU kernel call at the end of each iteration, that scans the z >>>>>> coordinates of all particles, and add an offset to them if they are >>>>>> below a >>>>>> certain value. It would be nice if you can tailor it to your needs, but >>>>>> if >>>>>> you need help implementing this custom kernel you can let us know (it >>>>>> may >>>>>> be good to add it as a permanent feature). >>>>>> >>>>>> Lastly, I don't know if you are interested or not but in the new >>>>>> generation of DEM simulator that we are currently developing, apart from >>>>>> supporting non-trivial particle geometries, there will be *efficient* >>>>>> ways to do both things (sleeper and active entities; periodic boundary >>>>>> with >>>>>> no extra cost). It is not out yet, however. >>>>>> >>>>>> Thank you, >>>>>> Ruochun >>>>>> >>>>>> On Thursday, May 12, 2022 at 10:47:27 PM UTC-5 [email protected] >>>>>> wrote: >>>>>> >>>>>>> Hello, >>>>>>> >>>>>>> I have been working on trying to use the GPU module in project >>>>>>> chrono to fill a vessel with spherical particles. I have been able to >>>>>>> successfully do so by using the method in the demos of generating >>>>>>> particle >>>>>>> sheets and allowing them to settle in the vessel. I have recently, >>>>>>> however, >>>>>>> been attempting to fill the vessel with a "particle source" method that >>>>>>> continuously streams particles into the domain until a certain number >>>>>>> of >>>>>>> particles is reached. I am unsure if this method is officially >>>>>>> supported >>>>>>> with the GPU module, and I am encountering crash that continuously >>>>>>> seems to >>>>>>> happen. I receive the error *No available contact pair slots for >>>>>>> body # and body # *after the simulation has progressed. It seems to >>>>>>> occur sometime after the particles hit the bottom of the vessel. I have >>>>>>> tried reducing my timestep, reducing the "flow rate" of incoming >>>>>>> particles, >>>>>>> changing the height of the particle inflow, and altering some >>>>>>> stiffness/damping constants, but this error seems to always happen soon >>>>>>> after the particles make contact with the vessel. I have attached my >>>>>>> input >>>>>>> files, any help would be appreciated. >>>>>>> >>>>>>> An unrelated question, but does the GPU module support the changing >>>>>>> of particle positions during the simulation (i.e. taking all particles >>>>>>> below a certain z and moving them to the top to "recycle" them >>>>>>> continuously >>>>>>> during the simulation)? >>>>>>> >>>>>>> Thanks! >>>>>>> David >>>>>>> >>>>>>> >>>>>>> -- You received this message because you are subscribed to the Google Groups "ProjectChrono" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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