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[Reza Housseini <reza.housseini@xxxxxxxxx>]

I'm still wondering about some parts in this code.

1. Why will adding a vector of zeros [1] helps resetting the forces of clumps?
2. Why is the collected force of the clumps members added to the ForceContainer [2] ...
3. and why is this force then again retaken from the ForceContainer? [3]

There is no need to update the forces in the ForceContainer, because
there will be reset to zero at the next step. The force is only used to
calculate the acceleration in [4].

Can someone please clarify these points?


[1] https://github.com/yade/trunk/blob/master/pkg/dem/NewtonIntegrator.cpp#L93
[2] https://github.com/yade/trunk/blob/master/pkg/dem/NewtonIntegrator.cpp#L150
[3] https://github.com/yade/trunk/blob/master/pkg/dem/NewtonIntegrator.cpp#L157
[4] https://github.com/yade/trunk/blob/master/pkg/dem/NewtonIntegrator.cpp#L178

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https://bugs.launchpad.net/bugs/923929

Title:
  OMP force container fails to reset forces on clump members

Status in Yet Another Dynamic Engine:
  Incomplete

Bug description:
  When clumps are used and no gravity engine is present, force containers are not reseting the forces on clump members. Junk values are accumulated over time and the clump itself soon disappears.
  A workaround is to addForce(0,0,0) once at startup on all bodies, this is done in Newton::action() currently.
  This is most probably (still to check) because containers sizes are checked vs. body Id only in addForce, which is never applied on clump members before they are in contact with something. Not clear is why the same problem does not appear also on standalone bodies.
  The crashing example was obtained from a series of personal scripts from Klaus Thoeni, not disclosed here.

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