The addition of __setstate__ and __getstate__ code below seems to have fixed the simple example (also revised, below). The resulting picked file is still large, suggesting further optimizations could be had by also adding __setstate__ and __getstate__ methods to the simtk.unit.Unit class to be more parsimonious in the information stored, but this is probably beyond my ken.

I'll test this more thoroughly before checking in a change. Thanks for the advice!

John

--

def __getstate__(self):
state = dict()
state['_value'] = self._value
state['unit'] = self.unit
return state

def __setstate__(self, state):
self._value = state['_value']
self.unit = state['unit']
return

--
# Simple test of pickling/unpickling

import simtk.unit
import numpy
import sys

x = numpy.zeros([10], numpy.float64)
quantity = simtk.unit.Quantity(x, simtk.unit.kilocalories_per_mole)

import pickle

print "pickling..."
outfile = open('pickle_test.pkl', 'wb')
pickle.dump(quantity, outfile)
outfile.close()
print str(quantity)

print "unpickling..."
infile = open('pickle_test.pkl', 'rb')
new_quantity = pickle.load(infile)
infile.close()

print str(new_quantity)