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[Robert Caulk <question693370@xxxxxxxxxxxxxxxxxxxxx>]

Question #693370 on Yade changed:
https://answers.launchpad.net/yade/+question/693370

    Status: Open => Answered

Robert Caulk proposed the following answer:
Looks like you bumped into 2 bugs in FlowEngine. But neither bug is
catastrophic. You'll see below that I do not have time to debug these
for you - but you are more than welcome to chase them down yourself if
for some reason you find it worth while (probably only worth your time
if you want to learn how FlowEngine actually works, otherwise these two
bug fixes don't really improve much besides "quality of life").

>1. When I write "multithread=True" before the simulation begins, just
like the following, it reports that Segmentation fault (core dumped).

I just spent some time looking into this bug, it is not immediately
clear to me why this is happening. It is clearly a first run initiation
bug - but at the moment I do not have a lot of extra time to debug the
feature, especially since it works by activating multithread after 1
step. I would say, if it is working after running a single step then
activating multithread - just keep using it like that. There is no
computational gain from running multithread for a single extra step.

>After certain steps, all pore pressure turn to zero and the next step
everything is back to normal again. This error occurs at a fixed
interval.

It is a benign bug with saveVTK, if you ask for it to print too
frequently in addition to flow.multithread, there may be a period where
it hasn't updated itself to print from the correct triangulation despite
Yade still using the correct triangulation for pressure force
computations internally. In other words: I verify that the pore pressure
inside Yade is not actually 0, that is simply an artifact of carrying
around multiple solvers.  it is simply That is a low priority bug at the
moment. Again if you want to spend time learning the inner workings of
yade I will point you to the noCache flag - I believe that is the reason
saveVTK is incorrectly grabbing the triangulation periodically in such
case.

Cheers,

Robert

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