diff options
Diffstat (limited to 'resources/libraries/python/jumpavg/BitCountingStats.py')
| -rw-r--r-- | resources/libraries/python/jumpavg/BitCountingStats.py | 110 |
1 files changed, 45 insertions, 65 deletions
diff --git a/resources/libraries/python/jumpavg/BitCountingStats.py b/resources/libraries/python/jumpavg/BitCountingStats.py index 7b5e659214..524ac952c8 100644 --- a/resources/libraries/python/jumpavg/BitCountingStats.py +++ b/resources/libraries/python/jumpavg/BitCountingStats.py @@ -1,4 +1,4 @@ -# Copyright (c) 2021 Cisco and/or its affiliates. +# Copyright (c) 2022 Cisco and/or its affiliates. # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at: @@ -13,11 +13,14 @@ """Module holding BitCountingStats class.""" +import dataclasses import math +import typing from .AvgStdevStats import AvgStdevStats +@dataclasses.dataclass class BitCountingStats(AvgStdevStats): """Class for statistics which include information content of a group. @@ -33,11 +36,20 @@ class BitCountingStats(AvgStdevStats): Only for_runs method calls the parent implementation, without using super(). """ - def __init__( - self, size=0, avg=None, stdev=0.0, max_value=None, prev_avg=None): - """Construct the stats object by computing from the values needed. + max_value: float = None + """Maximal sample value (real or estimated). + Default value is there just for argument ordering reasons, + leaving None leads to exceptions.""" + prev_avg: typing.Optional[float] = None + """Population average of the previous group (if any).""" + bits: float = None + """The computed information content of the group. + It is formally an argument to init function, just to keep repr string + a valid call. ut the init value is ignored and always recomputed. + """ - The values are not sanitized, faulty callers can cause math errors. + def __post_init__(self): + """Construct the stats object by computing from the values needed. The None values are allowed for stats for zero size data, but such stats can report arbitrary avg and max_value. @@ -54,91 +66,54 @@ class BitCountingStats(AvgStdevStats): (but not with floating point mechanic). The hope is the difference will have no real impact on the classification procedure. - - :param size: Number of values participating in this group. - :param avg: Population average of the participating sample values. - :param stdev: Population standard deviation of the sample values. - :param max_value: Maximal expected value. - TODO: This might be more optimal, - but max-invariant algorithm will be nicer. - :param prev_avg: Population average of the previous group. - If None, no previous average is taken into account. - If not None, the given previous average is used to discourage - consecutive groups with similar averages - (opposite triangle distribution is assumed). - :type avg: float - :type size: int - :type stdev: float - :type max_value: Union[float, NoneType] - :type prev_avg: Union[float, NoneType] """ - self.avg = avg - self.size = size - self.stdev = stdev - self.max_value = max_value - self.prev_avg = prev_avg # Zero size should in principle have non-zero bits (coding zero size), # but zero allows users to add empty groups without affecting bits. self.bits = 0.0 if self.size < 1: return - if avg is None: - raise ValueError(f"Avg is None: {self!r}") - if max_value is None or max_value <= 0.0: + if self.max_value <= 0.0: raise ValueError(f"Invalid max value: {self!r}") # Length of the sequence must be also counted in bits, # otherwise the message would not be decodable. # Model: probability of k samples is 1/k - 1/(k+1) == 1/k/(k+1) # This is compatible with zero size leading to zero bits. - self.bits += math.log(size * (size + 1), 2) - if prev_avg is None: + self.bits += math.log(self.size * (self.size + 1), 2) + if self.prev_avg is None: # Avg is considered to be uniformly distributed # from zero to max_value. - self.bits += math.log(max_value + 1.0, 2) + self.bits += math.log(self.max_value + 1.0, 2) else: # Opposite triangle distribution with minimum. self.bits += math.log( - max_value * (max_value + 1) / (abs(avg - prev_avg) + 1), 2) + (self.max_value * (self.max_value + 1)) + / (abs(self.avg - self.prev_avg) + 1), + 2, + ) if self.size < 2: return # Stdev is considered to be uniformly distributed # from zero to max_value. That is quite a bad expectation, # but resilient to negative samples etc. - self.bits += math.log(max_value + 1.0, 2) + self.bits += math.log(self.max_value + 1.0, 2) # Now we know the samples lie on sphere in size-1 dimensions. # So it is (size-2)-sphere, with radius^2 == stdev^2 * size. # https://en.wikipedia.org/wiki/N-sphere - sphere_area_ln = math.log(2) + math.log(math.pi) * ((size - 1) / 2.0) - sphere_area_ln -= math.lgamma((size - 1) / 2.0) - sphere_area_ln += math.log(stdev + 1.0) * (size - 2) - sphere_area_ln += math.log(size) * ((size - 2) / 2.0) + sphere_area_ln = math.log(2) + sphere_area_ln += math.log(math.pi) * ((self.size - 1) / 2.0) + sphere_area_ln -= math.lgamma((self.size - 1) / 2.0) + sphere_area_ln += math.log(self.stdev + 1.0) * (self.size - 2) + sphere_area_ln += math.log(self.size) * ((self.size - 2) / 2.0) self.bits += sphere_area_ln / math.log(2) - def __str__(self): - """Return string with human readable description of the group. - - :returns: Readable description. - :rtype: str - """ - return ( - f"size={self.size} avg={self.avg} stdev={self.stdev}" - f" bits={self.bits}" - ) - - def __repr__(self): - """Return string executable as Python constructor call. - - :returns: Executable constructor call. - :rtype: str - """ - return ( - f"BitCountingStats(size={self.size!r},avg={self.avg!r}" - f",stdev={self.stdev!r},max_value={self.max_value!r}" - f",prev_avg={self.prev_avg!r})" - ) - + # TODO: Rename, so pylint stops complaining about signature change. @classmethod - def for_runs(cls, runs, max_value=None, prev_avg=None): + def for_runs( + cls, + runs: typing.Iterable[typing.Union[float, AvgStdevStats]], + max_value: float, + prev_avg: typing.Optional[float] = None, + ): """Return new stats instance describing the sequence of runs. If you want to append data to existing stats object, @@ -164,6 +139,11 @@ class BitCountingStats(AvgStdevStats): :rtype: cls """ asd = AvgStdevStats.for_runs(runs) - ret_obj = cls(size=asd.size, avg=asd.avg, stdev=asd.stdev, - max_value=max_value, prev_avg=prev_avg) + ret_obj = cls( + size=asd.size, + avg=asd.avg, + stdev=asd.stdev, + max_value=max_value, + prev_avg=prev_avg, + ) return ret_obj |