GPU module error local pos in SD

[Dallas Wells]

While running a simulation based on the on the ballcosim_GPU_demo I ran into an error that I'm not sure the cause of after reducing my particle size to 0.001 m. I've attached the .cpp, .json files creating the error and a screenshot of the error. Any help as to what is causing the particles to produce a negative location and how I might fix that would be appreciated.

Best,

Dallas

[Dan Negrut]

Hi Dallas – we’ll talk internally at our end and do our best to help you… Stay tuned.

Dan

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Bernard A. and Frances M. Weideman Professor

NVIDIA CUDA Fellow

Director, Wisconsin Applied Computing Center

Department of Mechanical Engineering

Department of Computer Science

University of Wisconsin - Madison

4150ME, 1513 University Avenue

Madison, WI 53706-1572

608 772 0914

http://sbel.wisc.edu/

http://projectchrono.org/

http://homepages.cae.wisc.edu/~negrut

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[Ruochun Zhang]

Hi Dallas,

Almost all such problems are caused by some sort of inefficient contact event capture, so 2 particles tunnel through each other, leading to huge contact force being calculated, particles launched at extreme velocities, then crushing the simulation. Kinda like what happens every day in Source engine games.

You can do the following:

1. The best way is to reduce the simulation time step. I tried, 1e-7 would work for your test scenario. You can probably get away with something larger like 5e-7, but note 1mm radius particles are already very fine and a step size this small can be required. 

2. Increasing the damping can help, albeit not as much as time step size. And if your model mandates a selection of damping coefficients, then do not change it.

A different note: the Chrono version you are using is sort of old. If you decide to update to the newest, you can use my attached script, it just reflects a few API changes. The new Chrono::GPU version also allows checkpointing so you potentially don't have to use the same time step size all along.

Thank you,

Ruochun

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