# Resizing the lattice¶

When you have mitosis in your simulation the numbers of cells usualy grows and cells need more space. Clearly, you need a bigger lattice. CC3D lets you enlarge, shrink and shift lattice content using one simple function. There are few caveats that you have to be aware of few issues before using this functionality:

1. When resizing lattice, the new lattice is created and existing lattice is kept alive until all the information from old lattice is transferred to the new lattice. This might strain memory of your computer and even crash CC3D. If you have enough RAM you should be fine
2. Shrinking operation may crop portion of the lattice occupied by cells. In this case shrinking operation will be aborted.
3. When shifting lattice content, some cells might end up outside lattice boundaries. In this case operation will fail.
4. When you are using a wall of frozen cells you have to first destroy the wall, do resize/shifting operation and rebuild a wall again.

The example in CompuCellPythonTutorial/BuildWall3D demonstrates how to deal with lattice resize in the presence of wall:

class BuildWall3DSteppable(SteppableBasePy):
def __init__(self, _simulator, _frequency=1):
SteppableBasePy.__init__(self, _simulator, _frequency)

def start(self):
self.buildWall(self.WALL)

def step(self, mcs):
if mcs == 4:
self.destroyWall()
self.resizeAndShiftLattice(_newSize=(80, 80, 80), _shiftVec=(10, 10, 10))
self.buildWall(self.WALL)


In the step function, during MCS=4 we first destroy the wall (we have built it in the start function), resize the lattice to dimension x, y, z = 80, 80, 80 and shift content of the old lattice (but without the wall , because we have just destroyed it) by a vector x, y, z = 10, 10, 10. Finally we rebuild the wall around bigger lattice.

Twedit++ offers help in case you forget the syntax – go to CC3D Python->Simulation menu and choose appropriate submenu option.

The ability to dynamically resize lattice can play an important role in improving performance of your simulation. If you expect that number of cells will grow significantly during the simulation you may start with small lattice and as the number of cells increases you keep increasing lattice size in a way that “comfortably” accommodates all cells. This significantly shortens simulation run times compared to the simulation where you start with big lattice. When you work with a big lattice but have few cell,s CC3D will spend a lot of time probing areas occupied by Medium and this wastes machine cycles.

Along with cell field CC3D will resize all PDE fields. When lattice grows all new pixels of the PDE field are initialized with 0.0.