Hi Ruochun, Sorry, I had made some changes to my script. I redownloaded the original scripts I provided here earlier, and rebuilt chrono with the feature/gpu branch from a fresh repo clone with the touched by sphere change. After doing all of this and running the exact same script that I had uploaded originally, I now got a “negative local pod in SD” error around frame 90. This is a bit strange since you had managed to run that script successfully, and everything was a clean install with the same script that I uploaded, so it should’ve had the same outcome as your run. Did you make any changes to the script/json?
On Monday, May 16, 2022 at 12:29:58 PM UTC-6 Ruochun Zhang wrote: > Hi David, > > Oh sorry before you do that, could you try this: I assume you cloned > Chrono and built from source. Then can you checkout the *feature/gpu* > branch first, then apply the MAX_SPHERES_TOUCHED_BY_SPHERE change, and > then build and try again with the script you failed to run initially? I did > apply a bug fix in *feature/gpu* branch and it is probably not in > *develop* branch yet, and I hope to rule out the possibility that this > bug was hurting you. > > Thank you, > Ruochun > > On Monday, May 16, 2022 at 1:23:06 PM UTC-5 Ruochun Zhang wrote: > >> Hi David, >> >> I am pretty sure that script worked for me until reaching a steady state, >> like in the picture attached. One thing is that I'd be quite surprised if >> MAX_SPHERES_TOUCHED_BY_SPHERE = 200 and the kernels did not fail to >> compile... I'd say something like 32 is the maximum that you should assign >> it. Maybe you should try something like 30 to see if it works. But if it >> still gives the same error, we have to have a look at the script. Is it >> still the same script you attached? >> >> Changing particle sizes has large impact on the physics and, "contacts >> over limit" problem can happen naturally (like in your first question), or >> happen as a result of non-physical behavior in the simulation, which is >> often related to improper sim parameters wrt the sphere radius. So it's >> hard to say without context. One thing you should do is of course, >> visualize simulation results before the crash and see if there is something >> non-physical. >> >> Thank you, >> Ruochun >> >> On Monday, May 16, 2022 at 10:41:03 AM UTC-5 [email protected] wrote: >> >>> Actually, it looks like the particle source still isn’t working, even >>> when increasing the MAX_SPHERES_TOUCHED_BY_SPHERE up to 200. The simulation >>> will run for longer, but still fail with the same contact pairs error. >>> Interestingly, it seems like it will fail sooner if I made the particle >>> source radius smaller (fails after 627 pebbles added (step 34) when the >>> source radius is 0.26 and fails after 31499 pebbles added (step 85) when >>> the source radius is 1.1.). Do I still just need to increase the number >>> further or is this a different issue? >>> >>> Thanks! >>> David >>> On Monday, May 16, 2022 at 8:55:47 AM UTC-6 David Reger 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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