Hi, I am currently running into an issue when I try to carry out parallel projections with particle overlay. Also long as I don't use too many processors things run just fine but the projections only have some of the particles. Here is an example of the commands in my script: plotx = pc.add_projection("Density", 0, weight_field="Dust") plotx.add_callback(ParticleCallback(0, 1.0, p_size=1.0, col='k')) ploty = pc.add_projection("Density", 1, weight_field="Dust") ploty.add_callback(ParticleCallback(1, 1.0, p_size=1.0, col='k')) plotz = pc.add_projection("Density", 2, weight_field="Dust") plotz.add_callback(ParticleCallback(2, 1.0, p_size=1.0, col='k')) In addition, if I use too many processors and the one of the processors doesn't have any particles, I get the following error: Particle bounding box: 0.0 1.0 0.0 1.0 1.5 2.5 Traceback (most recent call last): Particle px extrema File "longbox.py", line 13, in <module> pc.save("DD%4.4d/DD%4.4d" % (i,i)) File "/home/solo/student/brittons/local/x86_64/lib/python2.5/site-packages/yt/raven/PlotCollection.py", line 80, in save override=override)) File "/home/solo/student/brittons/local/x86_64/lib/python2.5/site-packages/yt/raven/PlotTypes.py", line 110, in save_image self._redraw_image() File "/home/solo/student/brittons/local/x86_64/lib/python2.5/site-packages/yt/raven/PlotTypes.py", line 312, in _redraw_image self._run_callbacks() File "/home/solo/student/brittons/local/x86_64/lib/python2.5/site-packages/yt/raven/PlotTypes.py", line 183, in _run_callbacks cb(self) File "/home/solo/student/brittons/local/x86_64/lib/python2.5/site-packages/yt/raven/Callbacks.py", line 177, in __call__ print "Particle px extrema", particles_x.min(), particles_x.max(), \ ValueError: zero-size array to ufunc.reduce without identity Any help with this would be appreciated. Thanks, Devin -- Devin W. Silvia Graduate Student/Research Assistant Center for Astrophysics and Space Astronomy University of Colorado at Boulder http://mdbworks.net/devin