def __init__(self, maxCardinality, error_rate):
"""Implementes a LogLog Sketch
*maxCardinality
this Sketch is able to count cardinalities up to cardinality *maxCardinality*
error_rate
the error_rate of the sketch when calculating the cardinality of the set
"""
if not (0 < error_rate < 1):
raise ValueError("Error_Rate must be between 0 and 1.")
if not maxCardinality > 0:
raise ValueError("maxCardinality must be > 0")
self._maxCardinality = maxCardinality
#k
self._k = int(round(log(pow(1.30/error_rate,2),2)))
# m = 2**k
self._bucketNumber = 1<<self._k
self._bucketSize = compute_wordsize(self._maxCardinality)
#M(1)... M(m) = 0
self._bucketList =[bitarray(self._bucketSize) for _ in xrange(self._bucketNumber)]
for barray in self._bucketList:
barray.setall(False)
self.__name = "LogLog"
def __init__(self, maxCardinality, error_rate):
"""Implementes a HyperLogLog Sketch
*maxCardinality
this Sketch is able to count cardinalities up to cardinality *maxCardinality*
error_rate
the error_rate of the sketch when calculating the cardinality of the set
"""
self.__ALPHA16=0.673
self.__ALPHA32=0.697
self.__ALPHA64=0.709
if not (0 < error_rate < 1):
raise ValueError("Error_Rate must be between 0 and 1.")
if not maxCardinality > 0:
raise ValueError("maxCardinality must be > 0")
self._maxCardinality = maxCardinality
#k
self._k = int(round(log(pow(1.04/error_rate,2),2)))
# m = 2**k
self._bucketNumber = 1<<self._k
self._bucketSize = compute_wordsize(self._maxCardinality)
#M(1)... M(m) = 0
self._bucketList =[0 for _ in xrange(self._bucketNumber)]
self.__name = "HyperLogLog"
self._alpha = self.__getALPHA(self._bucketNumber)
