class Pairwise(ForceCategory):
"""Pairwise force category. It handles constructing a neighbor-list at each time-step.
"""
instance = None
@staticmethod
def get_instance(*args):
if(len(args) == 0 or args[0] is None):
#doesn't care about cutoff
return Pairwise.instance
if(Pairwise.instance is None):
Pairwise.instance = Pairwise(args[0])
else:
#check cutoff
if(Pairwise.instance.cutoff - args[0] < 0):
raise RuntimeError("Incompatible cutoffs: Already set to %g, not %g" % (Pairwise.instance.cutoff,args[0]))
return Pairwise.instance
def __init__(self, cutoff=12):
super(Pairwise, self).__init__()
self.cutoff = cutoff
self.forces = []
self.nlist_obj = None
def _build_nlist(self, u):
if(self.nlist_obj is None):
self.nlist_obj = NeighborList(u, self.cutoff)
self.nlist, self.nlist_lengths = self.nlist_obj.build_nlist(u)
self.nlist_ready = True
def _setup(self, u):
if(not self.nlist_ready):
self._build_nlist(u)
def _teardown(self):
self.nlist_ready = False
def pair_exists(self, u, type1, type2):
return True
def __reduce__(self):
return Pairwise, (self.cutoff,)
def _build_nlist(self, u):
if(self.nlist_obj is None):
self.nlist_obj = NeighborList(u, self.cutoff)
self.nlist, self.nlist_lengths = self.nlist_obj.build_nlist(u)
self.nlist_ready = True
