Chrono GPU Module Invalid SD Error

[Matthew Troemner]

Hello, 

I am trying to run a simple GPU Module particle generation and settling simulation based on the Moving Boundary demo code. When running the simulation I am encountering the error in the attached image noting that my spheres have an invalid SD (I'm guessing this means invalid small domain?). I've also attached a copy of the cpp code; but, I think that if someone could help explain better what the error actually means, I can solve the problem myself. 

Thank you in advance,

Matthew

[Ruochun Zhang]

Hi Matthew,

That error means, as you correctly noted, spheres have entered invalid subdomains (the simulation world is divided into subdomains for contact detection purposes), most likely out of bounds. This error admittedly did not specify the cause for that, but since it happens at the start, it is usually either because of the particles being initialized out-of-bound, or some simulation settings that will immediately disrupt the simulation (such as large initial particle penetration, initial particle--boundary overlap...), causing the particles to move at extreme velocities and go out-of-bound. 

I did not run your script, but I can see a few leads following what I said. For example, a plane is created at y=480 but faces positive y. In that case, all particles that have y coordinates lower than 480 will have contacts with this plane, and likely very large initial penetrations (for example 280, for a particle setting at y=200). This should kill the simulation. There could be other problems. You can debug based on the rendering of the initial frame. You can also start from a minimal working script, then gradually add the suspicious settings to discover which is creating problems.

By the way, it looks like you are running DEM simulations involving a few prescribed meshes. Chrono DEM-Engine can handle this better, giving you clearer error information, more complete mesh motion controls and of course, support for complex particles.

Thank you,

Ruochun

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Ruochun Zhang
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Email: ruochu...@alumni.rice.edu
Tel: 832-353-5111

[Matthew Troemner]

Hi Ruochun,

Thank you so much for the explanation, that helps clear things up a lot. Also, I'm almost sure the plane location is the problem - I had moved a lot of the items in the simulation but had forgotten to relocate the plane. 

Btw, I am hoping to move to DEM-Engine in the near future.

Thank you,

Matthew