pynbody.gravity.pm#
- pynbody.gravity.pm(f: SimSnap, ipos: ndarray, ngrid: int = 10, x0=None, x1=None)[source]#
Calculate the potential and acceleration for a set of particles using a Particle-Mesh algorithm.
For large numbers of particles, this is faster than, but much less accurate than,
pynbody.gravity.direct(). It also takes into account periodicity of the box.- Parameters:
f – The snapshot to calculate the potential and acceleration for
ipos – The positions of the particles to calculate the potential and acceleration for
x0 – The lower bound of the grid in each dimension. If
None, the minimum of the snapshot’s positions will be used.x1 – The upper bound of the grid in each dimension. If
None,x0 + f.properties['boxsize']will be used.
- Returns:
phi (array.SimArray) – The gravitational potential at the specified positions
grad_phi (array.SimArray) – The gravitational acceleration at the specified positions