def __promise__(data, domain, eps, delta, failure):
# TODO docstring
"""
:param data:
:param domain:
:param eps:
:param delta:
:param failure:
:return:
"""
const = log_star(2 * (domain + 1) * sqrt(data.shape[1]))
return 8**const * 144 * const / eps * log(24 * const / failure / delta)
def __rec_sanitize__(samples, domain_range, alpha, beta, eps, delta, dimension):
# print domain_range
# print calls
global calls
global san_data
# step 1
if calls == 0:
return
calls -= 1
# step 2
# the use of partial is redundant
samples_domain_points = partial(points_in_subset, samples)
noisy_points_in_range = samples_domain_points(subset=domain_range) + laplace(0, 1/eps, 1)
sample_size = len(samples)
# step 3
if noisy_points_in_range < alpha*sample_size/8:
base_range = domain_range
san_data.extend(base_range[1] * noisy_points_in_range)
return san_data
# step 4
domain_size = domain_range[1] - domain_range[0] + 1
log_size = int(ceil(log(domain_size, 2)))
# not needed
# size_tag = 2**log_size
# step 6
def quality(data, j):
return min(point_count_intervals_bounding(data, domain_range, j)-alpha * sample_size / 32,
3 * alpha * sample_size / 32 - point_count_intervals_bounding(data, domain_range, j-1))
# not needed if using exponential_mechanism
# step 7
# promise = alpha * sample_size / 32
# step 8
new_eps = eps/3/log_star(dimension)
# new_delta = delta/3/log_star(dimension)
# note the use of exponential_mechanism instead of rec_concave
z_tag = exponential_mechanism(samples, range(log_size+1), quality, new_eps)
z = 2 ** z_tag
# step 9
if z_tag == 0:
point_counter = Counter(samples)
def special_quality(data, b):
return point_counter[b]
b = choosing_mechanism(samples, range(domain_range[0], domain_range[1] + 1), special_quality,
1, alpha/64., beta, eps, delta)
a = b
# step 10
else:
first_intervals = __build_intervals_set__(samples, 2*z, domain_range[0], domain_range[1] + 1)
second_intervals = __build_intervals_set__(samples, 2*z_tag, domain_range[0], domain_range[1] + 1, True)
intervals = [(i, i+2*z-1) for i in first_intervals+second_intervals]
a, b = choosing_mechanism(samples, intervals, points_in_subset, 2, alpha/64., beta, eps, delta)
if type(a) == str:
raise ValueError("stability problem - choosing_mechanism returned 'bottom'")
# step 11
# although not mentioned I assume the noisy value should be rounded
noisy_count_ab = int(samples_domain_points((a, b)) + laplace(0, 1/eps, 1))
san_data.extend([b] * noisy_count_ab)
# step 12
if a > domain_range[0]:
rec_range = (domain_range[0], a - 1)
__rec_sanitize__(samples, rec_range, alpha, beta, eps, delta, dimension)
if b < domain_range[1]:
rec_range = (b + 1, domain_range[1])
__rec_sanitize__(samples, rec_range, alpha, beta, eps, delta, dimension)
return san_data
