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Re: hello? -help with a spinning bucket!


> I assume it has only one core, and I certainly don't know how to hook
> up other ones, though I know people who surely do.

If there is just one core, you cannot add more (if you know someone who
does, he would be probably doing that all the time). 

Forget about running serious simulations (given size of simulation) on a
laptop. Get a decent 4core (or more) machine with DDR3 RAM (you need
several GB of RAM for compilation, probably not so much for running).

I am usually running with 4 cores (as I have only 4 ;-) ), but there is
not much speedup beyond 4 cores (depending on exact simulation setup; we
pretty suck at scalability on multicore machines).

> am I fighting what must surely be a loosing battle, my goal being to
> simulate up to 1 million particles (1 cubic millimeter glass beads in
> a volume of about 1 liter), for at least 4-10 seconds?  10 000
> particles? 1000?

Depends on the critical Δt (determined roughly by particle diameter and
stiffness). If it were 1e-6, then you need about 1e7 timesteps...

Read https://yade-dem.org/sphinx/formulation.html#cost , that gives an
esstimate of the order of magnitude, about 1e-6s of computation per
particle and per timestep. That gives you 10s with 1 particle :-) So
with 1k particles, you will be somewhere around 3hrs and with 10k around
a day. Keep in mind that it is very very very rough.

Cheers, vaclav

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