def value_of(self, resource):
''' Given a resource, return the total value
of this resource to the current user.
:params resource: The resource to get the value of
:returns: The total value of the items
'''
(x0, span) = resource.value
value = integrate(self.function, x0, x0 + span, self.resolution)
return value / self.total
def __init__(self, user, function, resolution=1000):
''' Initialize a new preference class
:param user: The name or id of the participant
:param function: The function that describes the user's preference
:param resolution: The number of steps we will take in the integral
'''
self.user = user or self._get_user()
self.function = function
self.resolution = resolution
self.total = integrate(self.function, F(0), F(1), self.resolution)
#!/usr/bin/env python
from cakery.preference import ContinuousPreference
from cakery.utilities import integrate
#------------------------------------------------------------
# settings
#------------------------------------------------------------
tolerance = 0.005 # +/- off of 1 we accept
iterations = 1000 # the number of rounds to run
resolution = 1000 # higher means more precise integration
#------------------------------------------------------------
# initialize the test data
#------------------------------------------------------------
ps = [ContinuousPreference.random() for _ in range(iterations)]
ls = [integrate(p.function, 0.0, 0.5, resolution) for p in ps]
rs = [integrate(p.function, 0.5, 1.0, resolution) for p in ps]
ss = [l + r for l, r in zip(ls, rs)]
#------------------------------------------------------------
# test that the constraints hold
#------------------------------------------------------------
print "\n","=" * 60
print "Integration Stress Test"
print "=" * 60,"\n"
for left, right in zip(ls, rs):
print "left[%f]\t<= right[%f]" % (left, right)
assert(left != right)
assert(left > right or left < right)
assert(1.0 - tolerance < left + right < 1.0 + tolerance)
def test_integrate(self):
''' test that integrate method works correctly '''
self.assertEqual(5, int(integrate(lambda x: 1, 0.0, 5.0, 100)))
self.assertEqual(25, int(integrate(lambda x: 2 * x, 0.0, 5.0, 100)))
self.assertEqual(41, int(integrate(lambda x: x * x, 0.0, 5.0, 100)))
