[Ode4j-users] multithreading crashes

[M@ <mat...@gm...>]

Spinning this out so as to not threadjack.

While starting my code on one particular machine (my advisor's) I get
either:

java.util.ConcurrentModificationException
[java] java.util.ArrayList$Itr.checkForComodification(ArrayList.java:819)
[java] java.util.ArrayList$Itr.next(ArrayList.java:791)
[java]
org.ode4j.ode.internal.DxSimpleSpace.cleanGeoms(DxSimpleSpace.java:63)
[java] org.ode4j.ode.internal.DxSimpleSpace.collide(DxSimpleSpace.java:82)
[java]
com.robotsim.model.World.checkForCollisions(World.jacom.mds.simulator.MdsSimComponent

or:

ODE INTERNAL ERROR 1: assertion failed

ODE INTERNAL ERROR 1: assertion failed
 java.lang.RuntimeException: #1: assertion failed ->
org.ode4j.ode.internal.ErrorHdl.dDebug(ErrorHdl.java:186)
org.ode4j.ode.internal.ErrorHandler.dDebug(ErrorHandler.java:89)
org.ode4j.ode.internal.Common.dIASSERT(Common.java:123)
org.ode4j.ode.internal.DxGeom.collideAABBs(DxGeom.java:1699)
org.ode4j.ode.internal.DxSimpleSpace.collide(DxSimpleSpace.java:93)
com.robotsim.model.World.checkForCollisions(World.java:197)
com.robotsim.model.World.checkForCollisions(World.java:187)
com.robotsim.model.LinearActuator.update(LinearActuator.java:60)
com.robotsim.model.Robot.tick(Robot.java:115)
com.robotsim.model.World.tick(World.java:128)
com.robotsim.model.World.tick(World.java:119)
com.robotsim.model.World$1.run(World.java:88)
java.util.TimerThread.mainLoop(Timer.java:555)
java.util.TimerThread.run(Timer.java:505)

(chosen seemingly randomly).  I managed to get it to stop on other machines
by pausing the main loop (that calls collisionSpace.collide) whenever I
need to add something to the collision space, but it's not clear why that
didn't fix the problem on the one machine.  It's also not clear exactly
what sorts of invariants I need to maintain to keep ODE happy, I can
certainly maintain them, I just need to know what they are.

--M@