Two changes here following the discussion in #122 (closed):
x_oldis replaced by
x_diff, i.e. the offset since the last tree-build. That makes the drift task a bit strange as they have to move
xin one direction and
x_diffin the other.
gpartstructure also gains an
x_oldfield. This is necessary for the cases where we only have gparts and no parts. If we don't do this, the tree reconstruction is never triggered in
A neat consequence is that we can store
x_diff as float and not as double. So the
xpart structure goes down to 32bytes in size (after alignment).