--- /dev/null
+# Copyright (c) 2019 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:
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Module holding BitCountingGroupList class."""
+
+import copy
+
+from .BitCountingGroup import BitCountingGroup
+
+
+class BitCountingGroupList:
+ # TODO: Inherit from collections.abc.Sequence in Python 3.
+ """List of data groups which tracks overall bit count.
+
+ The Sequence-like access is related to the list of groups,
+ for example group_list[0] returns the first group in the list.
+ Writable list-like methods are not implemented.
+
+ The overall bit count is the sum of bit counts of each group.
+ Group is a sequence of data samples accompanied by their stats.
+ Different partitioning of data samples into the groups
+ results in different overall bit count.
+ This can be used to group samples in various contexts.
+
+ As the group bit count depends on previous average
+ and overall maximal value, order of groups is important.
+ Having the logic encapsulated here spares the caller
+ the effort to pass averages around.
+
+ The data can be only added, and there is some logic to skip
+ recalculations if the bit count is not needed.
+ """
+
+ def __init__(self, group_list=None, bits_except_last=0.0, max_value=None):
+ """Set the internal state without any calculations.
+
+ The group list argument is copied deeply, so it is not a problem
+ if the value object is mutated afterwards.
+
+ A "group" stands for an Iterable of runs, where "run" is either
+ a float value, or a stats-like object (only size, avg and stdev
+ are accessed). Run is a hypothetical abstract class,
+ defining it in Python 2 is too much hassle.
+
+ It is not verified whether the user provided values are valid,
+ e.g. whether the cached bits values make sense.
+
+ The max_value is required and immutable,
+ it is recommended the callers find their maximum beforehand.
+
+ :param group_list: List of groups to compose this group list (or empty).
+ :param bits_except_last: Partial sum of all but one group bits.
+ :param max_value: Maximal sample value to base bits computation on.
+ :type group_list: Iterable[BitCountingGroup]
+ :type bits_except_last: float
+ :type max_value: float
+ """
+ self.group_list = copy.deepcopy(group_list) if group_list else list()
+ self.bits_except_last = bits_except_last
+ self.max_value = max_value
+
+ def __str__(self):
+ """Return string with human readable description of the group list.
+
+ :returns: Readable description.
+ :rtype: str
+ """
+ return u"group_list={self.group_list} bits={self.bits}"
+
+ def __repr__(self):
+ """Return string executable as Python constructor call.
+
+ :returns: Executable constructor call.
+ :rtype: str
+ """
+ return (
+ f"BitCountingGroupList(group_list={self.group_list!r}"
+ f",bits_except_last={self.bits_except_last!r}"
+ f",max_value={self.max_value!r})"
+ )
+
+ def __getitem__(self, index):
+ """Return the group at the index.
+
+ :param index: Index of the group to return.
+ :type index: int
+ :returns: The group at the index.
+ :rtype: BitCountingGroup
+ """
+ return self.group_list[index]
+
+ def __len__(self):
+ """Return the length of the group list.
+
+ :returns: The Length of group_list.
+ :rtype: int
+ """
+ return len(self.group_list)
+
+ def copy(self):
+ """Return a new instance with copied internal state.
+
+ :returns: The copied instance.
+ :rtype: BitCountingGroupList
+ """
+ return self.__class__(
+ group_list=self.group_list, bits_except_last=self.bits_except_last,
+ max_value=self.max_value
+ )
+
+ @property
+ def bits(self):
+ """Return overall bit content of the group list.
+
+ :returns: The overall information content in bits.
+ :rtype: float
+ """
+ if not self.group_list:
+ return 0.0
+ # TODO: Is it worth to cache the overall result?
+ return self.bits_except_last + self.group_list[-1].bits
+
+ def append_group_of_runs(self, runs):
+ """Mutate to add a new group based on the runs, return self.
+
+ The argument is copied before adding to the group list,
+ so further edits do not affect the grup list.
+ The argument can also be a group, only runs from it are used.
+
+ :param runs: Runs to form the next group to be appended to self.
+ :type runs: Union[Iterable[Run], BitCountingGroup]
+ :returns: The updated self.
+ :rtype: BitCountingGroupList
+ """
+ prev_avg = self.group_list[-1].stats.avg if self.group_list else None
+ if isinstance(runs, BitCountingGroup):
+ # It is faster to avoid stats recalculation.
+ new_group = runs.copy()
+ new_group.max_value = self.max_value
+ new_group.prev_avg = prev_avg
+ new_group.cached_bits = None
+ else:
+ new_group = BitCountingGroup(
+ run_list=runs, max_value=self.max_value, prev_avg=prev_avg)
+ self.bits_except_last = self.bits
+ self.group_list.append(new_group)
+ return self
+
+ def append_run_to_to_last_group(self, run):
+ """Mutate to add new run at the end of the last group.
+
+ Basically a one-liner, only returning group list instead of last group.
+
+ :param run: The run value to add to the last group.
+ :type run: Run
+ :returns: The updated self.
+ :rtype: BitCountingGroupList
+ :raises IndexError: If group list is empty, no last group to add to.
+ """
+ self.group_list[-1].append(run)
+ return self
+
+ def extend_runs_to_last_group(self, runs):
+ """Mutate to add new runs to the end of the last group.
+
+ A faster alternative to appending runs one by one in a loop.
+
+ :param runs: The runs to add to the last group.
+ :type runs: Iterable[Run]
+ :returns: The updated self
+ :rtype: BitCountingGroupList
+ :raises IndexError: If group list is empty, no last group to add to.
+ """
+ self.group_list[-1].extend(runs)
+ return self
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