def get_register_value(raw_value, log2m):
"""
Extracts the HLL register value from a raw value.
"""
substream_value = BitUtil.unsigned_right_shift_long(raw_value, log2m)
if substream_value == 0:
# The paper does not cover p(0x0), so the special value 0 is used.
# 0 is the original initialization value of the registers, so by
# doing this the HLL simply ignores it. This is acceptable
# because the probability is 1/(2^(2^register_size_in_bits)).
p_w = 0
else:
p_w = BitUtil.to_signed_byte(
min(1 + BitUtil.least_significant_bit(substream_value), 31))
return p_w
def _add_raw_sparse_probabilistic(self, raw_value):
"""
Adds the raw value to the ``sparseProbabilisticStorage``.
``type`` ``HLLType.SPARSE``.
:param long raw_value: the raw value to add to the sparse storage.
:rtype: void
"""
# p(w): position of the least significant set bit (one-indexed)
# By contract: p(w) <= 2^(register_value_in_bits) - 1 (the max register value)
#
# By construction of pw_max_mask (see constructor),
# lsb(pw_max_mask) = 2^(register_value_in_bits) - 2,
# thus lsb(any_long | pw_max_mask) <= 2^(register_value_in_bits) - 2,
# thus 1 + lsb(any_long | pw_max_mask) <= 2^(register_value_in_bits) -1.
sub_stream_value = BitUtil.unsigned_right_shift_long(
raw_value, self._log2m)
p_w = None
if sub_stream_value == 0:
# The paper does not cover p(0x0), so the special value 0 is used.
# 0 is the original initialization value of the registers, so by
# doing this the multiset simply ignores it. This is acceptable
# because the probability is 1/(2^(2^register_size_in_bits)).
p_w = 0
else:
p_w = BitUtil.to_signed_byte(1 + BitUtil.least_significant_bit(
sub_stream_value | self._pw_max_mask))
# Short-circuit if the register is being set to zero, since algorithmically
# this corresponds to an "unset" register, and "unset" registers aren't
# stored to save memory. (The very reason this sparse implementation
# exists.) If a register is set to zero it will break the algorithm_cardinality
# code.
if p_w == 0:
return
# NOTE: no +1 as in paper since 0-based indexing
j = int(raw_value & self._m_bits_mask)
current_value = self._sparse_probabilistic_storage.get(j, 0)
if p_w > current_value:
self._sparse_probabilistic_storage[j] = p_w
