yade-users team mailing list archive

[Anton Gladky <gladky.anton@xxxxxxxxx>]

Dear users/devs, who is working with clumps,

I have done a tiny modification in NewtonIntegrator [1], which
should fix numerical instability with clumps in a rare cases.

============================================
============================================
Subject: [PATCH] Do not use getTorqueUnsynced and forces.getForceUnsynced in
 clumps

It seems both of these commands are unsafe. It causes NaN velocities
in a very specific cases. From my point of view it is OK, because
addForceTorqueFromMembers does not modify data itself.
---
 pkg/dem/NewtonIntegrator.cpp | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/pkg/dem/NewtonIntegrator.cpp b/pkg/dem/NewtonIntegrator.cpp
index e961bf2..082add8 100644
--- a/pkg/dem/NewtonIntegrator.cpp
+++ b/pkg/dem/NewtonIntegrator.cpp
@@ -146,14 +146,8 @@ void NewtonIntegrator::action()
  // clumps forces
  if(b->isClump()) {
  b->shape->cast<Clump>().addForceTorqueFromMembers(state,scene,f,m);
- #ifdef YADE_OPENMP
- //it is safe here, since only one thread will read/write
- scene->forces.getTorqueUnsynced(id)+=m;
- scene->forces.getForceUnsynced(id)+=f;
- #else
  scene->forces.addTorque(id,m);
  scene->forces.addForce(id,f);
- #endif
  }
  //in most cases, the initial force on clumps will be zero and next
line is not changing f and m, but make sure we don't miss something
(e.g. user defined forces on clumps)
  f=scene->forces.getForce(id); m=scene->forces.getTorque(id);
-- 
1.9.3
============================================
============================================

Please, test you scripts with the newest version. Yadedaily should
get this fix tonight.

Comments are very welcome.

[1] https://github.com/yade/trunk/commit/5707bb55fb9a3605e10a82cdecbec8efcc7d906f

Best regards

Anton