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Diffstat (limited to 'resources/libraries/python/search/MultipleLossRatioSearch.py')
| -rw-r--r-- | resources/libraries/python/search/MultipleLossRatioSearch.py | 501 |
1 files changed, 0 insertions, 501 deletions
diff --git a/resources/libraries/python/search/MultipleLossRatioSearch.py b/resources/libraries/python/search/MultipleLossRatioSearch.py deleted file mode 100644 index 0eb1d7da4c..0000000000 --- a/resources/libraries/python/search/MultipleLossRatioSearch.py +++ /dev/null @@ -1,501 +0,0 @@ -# Copyright (c) 2018 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 defining MultipleLossRatioSearch class.""" - -import logging -import math -import time - -from AbstractSearchAlgorithm import AbstractSearchAlgorithm -from NdrPdrResult import NdrPdrResult -from ReceiveRateInterval import ReceiveRateInterval - - -class MultipleLossRatioSearch(AbstractSearchAlgorithm): - """Optimized binary search algorithm for finding NDR and PDR bounds. - - Traditional binary search algorithm needs initial interval - (lower and upper bound), and returns final interval after bisecting - (until some exit condition is met). - The exit condition is usually related to the interval width, - (upper bound value minus lower bound value). - - The optimized algorithm contains several improvements - aimed to reduce overall search time. - - One improvement is searching for two intervals at once. - The intervals are for NDR (No Drop Rate) and PDR (Partial Drop Rate). - - Next improvement is that the initial interval does not need to be valid. - Imagine initial interval (10, 11) where 11 is smaller - than the searched value. - The algorithm will try (11, 13) interval next, and if 13 is still smaller, - (13, 17) and so on, doubling width until the upper bound is valid. - The part when interval expands is called external search, - the part when interval is bisected is called internal search. - - Next improvement is that trial measurements at small trial duration - can be used to find a reasonable interval for full trial duration search. - This results in more trials performed, but smaller overall duration - in general. - - Next improvement is bisecting in logarithmic quantities, - so that exit criteria can be independent of measurement units. - - Next improvement is basing the initial interval on receive rates. - - Final improvement is exiting early if the minimal value - is not a valid lower bound. - - The complete search consist of several phases, - each phase performing several trial measurements. - Initial phase creates initial interval based on receive rates - at maximum rate and at maximum receive rate (MRR). - Final phase and preceding intermediate phases are performing - external and internal search steps, - each resulting interval is the starting point for the next phase. - The resulting interval of final phase is the result of the whole algorithm. - - Each non-initial phase uses its own trial duration and width goal. - Any non-initial phase stops searching (for NDR or PDR independently) - when minimum is not a valid lower bound (at current duration), - or all of the following is true: - Both bounds are valid, bound bounds are measured at the current phase - trial duration, interval width is less than the width goal - for current phase. - - TODO: Review and update this docstring according to rst docs. - TODO: Support configurable number of Packet Loss Ratios. - """ - - class ProgressState(object): - """Structure containing data to be passed around in recursion.""" - - def __init__( - self, result, phases, duration, width_goal, packet_loss_ratio, - minimum_transmit_rate, maximum_transmit_rate): - """Convert and store the argument values. - - :param result: Current measured NDR and PDR intervals. - :param phases: How many intermediate phases to perform - before the current one. - :param duration: Trial duration to use in the current phase [s]. - :param width_goal: The goal relative width for the curreent phase. - :param packet_loss_ratio: PDR fraction for the current search. - :param minimum_transmit_rate: Minimum target transmit rate - for the current search [pps]. - :param maximum_transmit_rate: Maximum target transmit rate - for the current search [pps]. - :type result: NdrPdrResult - :type phases: int - :type duration: float - :type width_goal: float - :type packet_loss_ratio: float - :type minimum_transmit_rate: float - :type maximum_transmit_rate: float - """ - self.result = result - self.phases = int(phases) - self.duration = float(duration) - self.width_goal = float(width_goal) - self.packet_loss_ratio = float(packet_loss_ratio) - self.minimum_transmit_rate = float(minimum_transmit_rate) - self.maximum_transmit_rate = float(maximum_transmit_rate) - - def __init__(self, measurer, final_relative_width=0.005, - final_trial_duration=30.0, initial_trial_duration=1.0, - number_of_intermediate_phases=2, timeout=600.0): - """Store the measurer object and additional arguments. - - :param measurer: Rate provider to use by this search object. - :param final_relative_width: Final lower bound transmit rate - cannot be more distant that this multiple of upper bound [1]. - :param final_trial_duration: Trial duration for the final phase [s]. - :param initial_trial_duration: Trial duration for the initial phase - and also for the first intermediate phase [s]. - :param number_of_intermediate_phases: Number of intermediate phases - to perform before the final phase [1]. - :param timeout: The search will fail itself when not finished - before this overall time [s]. - :type measurer: AbstractMeasurer - :type final_relative_width: float - :type final_trial_duration: float - :type initial_trial_duration: int - :type number_of_intermediate_phases: int - :type timeout: float - """ - super(MultipleLossRatioSearch, self).__init__(measurer) - self.final_trial_duration = float(final_trial_duration) - self.final_relative_width = float(final_relative_width) - self.number_of_intermediate_phases = int(number_of_intermediate_phases) - self.initial_trial_duration = float(initial_trial_duration) - self.timeout = float(timeout) - - - @staticmethod - def double_relative_width(relative_width): - """Return relative width corresponding to double logarithmic width. - - :param relative_width: The base relative width to double. - :type relative_width: float - :returns: The relative width of double logarithmic size. - :rtype: float - """ - return 1.999 * relative_width - relative_width * relative_width - # The number should be 2.0, but we want to avoid rounding errors, - # and ensure half of double is not larger than the original value. - - @staticmethod - def double_step_down(relative_width, current_bound): - """Return rate of double logarithmic width below. - - :param relative_width: The base relative width to double. - :param current_bound: The current target transmit rate to move [pps]. - :type relative_width: float - :type current_bound: float - :returns: Transmit rate smaller by logarithmically double width [pps]. - :rtype: float - """ - return current_bound * ( - 1.0 - MultipleLossRatioSearch.double_relative_width( - relative_width)) - - @staticmethod - def double_step_up(relative_width, current_bound): - """Return rate of double logarithmic width above. - - :param relative_width: The base relative width to double. - :param current_bound: The current target transmit rate to move [pps]. - :type relative_width: float - :type current_bound: float - :returns: Transmit rate larger by logarithmically double width [pps]. - :rtype: float - """ - return current_bound / ( - 1.0 - MultipleLossRatioSearch.double_relative_width( - relative_width)) - - @staticmethod - def half_relative_width(relative_width): - """Return relative width corresponding to half logarithmic width. - - :param relative_width: The base relative width to halve. - :type relative_width: float - :returns: The relative width of half logarithmic size. - :rtype: float - """ - return 1.0 - math.sqrt(1.0 - relative_width) - - @staticmethod - def half_step_up(relative_width, current_bound): - """Return rate of half logarithmic width above. - - :param relative_width: The base relative width to halve. - :param current_bound: The current target transmit rate to move [pps]. - :type relative_width: float - :type current_bound: float - :returns: Transmit rate larger by logarithmically half width [pps]. - :rtype: float - """ - return current_bound / ( - 1.0 - MultipleLossRatioSearch.half_relative_width(relative_width)) - - def narrow_down_ndr_and_pdr( - self, minimum_transmit_rate, maximum_transmit_rate, - packet_loss_ratio): - """Perform initial phase, create state object, proceed with next phases. - - :param minimum_transmit_rate: Minimal target transmit rate [pps]. - :param maximum_transmit_rate: Maximal target transmit rate [pps]. - :param packet_loss_ratio: Fraction of packets lost, for PDR [1]. - :type minimum_transmit_rate: float - :type maximum_transmit_rate: float - :type packet_loss_ratio: float - :returns: Structure containing narrowed down intervals - and their measurements. - :rtype: NdrPdrResult - :raises RuntimeError: If total duration is larger than timeout. - """ - minimum_transmit_rate = float(minimum_transmit_rate) - maximum_transmit_rate = float(maximum_transmit_rate) - packet_loss_ratio = float(packet_loss_ratio) - line_measurement = self.measurer.measure( - self.initial_trial_duration, maximum_transmit_rate) - initial_width_goal = self.final_relative_width - for _ in range(self.number_of_intermediate_phases): - initial_width_goal = self.double_relative_width(initial_width_goal) - max_lo = maximum_transmit_rate * (1.0 - initial_width_goal) - mrr = max( - minimum_transmit_rate, - min(max_lo, line_measurement.receive_rate)) - mrr_measurement = self.measurer.measure( - self.initial_trial_duration, mrr) - # Attempt to get narrower width. - if mrr_measurement.loss_fraction > 0.0: - max2_lo = mrr * (1.0 - initial_width_goal) - mrr2 = min(max2_lo, mrr_measurement.receive_rate) - else: - mrr2 = mrr / (1.0 - initial_width_goal) - if mrr2 > minimum_transmit_rate and mrr2 < maximum_transmit_rate: - line_measurement = mrr_measurement - mrr_measurement = self.measurer.measure( - self.initial_trial_duration, mrr2) - if mrr2 > mrr: - buf = line_measurement - line_measurement = mrr_measurement - mrr_measurement = buf - starting_interval = ReceiveRateInterval( - mrr_measurement, line_measurement) - starting_result = NdrPdrResult(starting_interval, starting_interval) - state = self.ProgressState( - starting_result, self.number_of_intermediate_phases, - self.final_trial_duration, self.final_relative_width, - packet_loss_ratio, minimum_transmit_rate, maximum_transmit_rate) - state = self.ndrpdr(state) - return state.result - - def _measure_and_update_state(self, state, transmit_rate): - """Perform trial measurement, update bounds, return new state. - - :param state: State before this measurement. - :param transmit_rate: Target transmit rate for this measurement [pps]. - :type state: ProgressState - :type transmit_rate: float - :returns: State after the measurement. - :rtype: ProgressState - """ - # TODO: Implement https://stackoverflow.com/a/24683360 - # to avoid the string manipulation if log verbosity is too low. - logging.info("result before update: %s", state.result) - logging.debug( - "relative widths in goals: %s", state.result.width_in_goals( - self.final_relative_width)) - measurement = self.measurer.measure(state.duration, transmit_rate) - ndr_interval = self._new_interval( - state.result.ndr_interval, measurement, 0.0) - pdr_interval = self._new_interval( - state.result.pdr_interval, measurement, state.packet_loss_ratio) - state.result = NdrPdrResult(ndr_interval, pdr_interval) - return state - - @staticmethod - def _new_interval(old_interval, measurement, packet_loss_ratio): - """Return new interval with bounds updated according to the measurement. - - :param old_interval: The current interval before the measurement. - :param measurement: The new meaqsurement to take into account. - :param packet_loss_ratio: Fraction for PDR (or zero for NDR). - :type old_interval: ReceiveRateInterval - :type measurement: ReceiveRateMeasurement - :type packet_loss_ratio: float - :returns: The updated interval. - :rtype: ReceiveRateInterval - """ - old_lo, old_hi = old_interval.measured_low, old_interval.measured_high - # Priority zero: direct replace if the target Tr is the same. - if measurement.target_tr in (old_lo.target_tr, old_hi.target_tr): - if measurement.target_tr == old_lo.target_tr: - return ReceiveRateInterval(measurement, old_hi) - else: - return ReceiveRateInterval(old_lo, measurement) - # Priority one: invalid lower bound allows only one type of update. - if old_lo.loss_fraction > packet_loss_ratio: - # We can only expand down, old bound becomes valid upper one. - if measurement.target_tr < old_lo.target_tr: - return ReceiveRateInterval(measurement, old_lo) - else: - return old_interval - # Lower bound is now valid. - # Next priorities depend on target Tr. - if measurement.target_tr < old_lo.target_tr: - # Lower external measurement, relevant only - # if the new measurement has high loss rate. - if measurement.loss_fraction > packet_loss_ratio: - # Returning the broader interval as old_lo - # would be invalid upper bound. - return ReceiveRateInterval(measurement, old_hi) - elif measurement.target_tr > old_hi.target_tr: - # Upper external measurement, only relevant for invalid upper bound. - if old_hi.loss_fraction <= packet_loss_ratio: - # Old upper bound becomes valid new lower bound. - return ReceiveRateInterval(old_hi, measurement) - else: - # Internal measurement, replaced boundary - # depends on measured loss fraction. - if measurement.loss_fraction > packet_loss_ratio: - # We have found a narrow valid interval, - # regardless of whether old upper bound was valid. - return ReceiveRateInterval(old_lo, measurement) - else: - # In ideal world, we would not want to shrink interval - # if upper bound is not valid. - # In the real world, we want to shrink it for - # "invalid upper bound at maximal rate" case. - return ReceiveRateInterval(measurement, old_hi) - # Fallback, the interval is unchanged by the measurement. - return old_interval - - def ndrpdr(self, state): - """Pefrom trials for this phase. Return the new state when done. - - :param state: State before this phase. - :type state: ProgressState - :returns: The updated state. - :rtype: ProgressState - :raises RuntimeError: If total duration is larger than timeout. - """ - start_time = time.time() - if state.phases > 0: - # We need to finish preceding intermediate phases first. - saved_phases = state.phases - state.phases -= 1 - # Preceding phases have shorter duration. - saved_duration = state.duration - duration_multiplier = state.duration / self.initial_trial_duration - phase_exponent = float(state.phases) / saved_phases - state.duration = self.initial_trial_duration * math.pow( - duration_multiplier, phase_exponent) - # Shorter durations do not need that narrow widths. - saved_width = state.width_goal - state.width_goal = self.double_relative_width(state.width_goal) - # Recurse. - state = self.ndrpdr(state) - # Restore the state for current phase. - state.duration = saved_duration - state.width_goal = saved_width - state.phases = saved_phases # Not needed, but just in case. - logging.info( - "starting iterations with duration %s and relative width goal %s", - state.duration, state.width_goal) - while 1: - if time.time() > start_time + self.timeout: - raise RuntimeError("Optimized search takes too long.") - # Order of priorities: invalid bounds (nl, pl, nh, ph), - # then narrowing relative Tr widths. - # Durations are not priorities yet, - # they will settle on their own hopefully. - ndr_lo = state.result.ndr_interval.measured_low - ndr_hi = state.result.ndr_interval.measured_high - pdr_lo = state.result.pdr_interval.measured_low - pdr_hi = state.result.pdr_interval.measured_high - ndr_rel_width = max( - state.width_goal, state.result.ndr_interval.rel_tr_width) - pdr_rel_width = max( - state.width_goal, state.result.pdr_interval.rel_tr_width) - # If we are hitting maximal or minimal rate, we cannot shift, - # but we can re-measure. - if ndr_lo.loss_fraction > 0.0: - if ndr_lo.target_tr > state.minimum_transmit_rate: - new_tr = max( - state.minimum_transmit_rate, - self.double_step_down(ndr_rel_width, ndr_lo.target_tr)) - logging.info("ndr lo external %s", new_tr) - state = self._measure_and_update_state(state, new_tr) - continue - elif ndr_lo.duration < state.duration: - logging.info("ndr lo minimal re-measure") - state = self._measure_and_update_state( - state, state.minimum_transmit_rate) - continue - if pdr_lo.loss_fraction > state.packet_loss_ratio: - if pdr_lo.target_tr > state.minimum_transmit_rate: - new_tr = max( - state.minimum_transmit_rate, - self.double_step_down(pdr_rel_width, pdr_lo.target_tr)) - logging.info("pdr lo external %s", new_tr) - state = self._measure_and_update_state(state, new_tr) - continue - elif pdr_lo.duration < state.duration: - logging.info("pdr lo minimal re-measure") - state = self._measure_and_update_state( - state, state.minimum_transmit_rate) - continue - if ndr_hi.loss_fraction <= 0.0: - if ndr_hi.target_tr < state.maximum_transmit_rate: - new_tr = min( - state.maximum_transmit_rate, - self.double_step_up(ndr_rel_width, ndr_hi.target_tr)) - logging.info("ndr hi external %s", new_tr) - state = self._measure_and_update_state(state, new_tr) - continue - elif ndr_hi.duration < state.duration: - logging.info("ndr hi maximal re-measure") - state = self._measure_and_update_state( - state, state.maximum_transmit_rate) - continue - if pdr_hi.loss_fraction <= state.packet_loss_ratio: - if pdr_hi.target_tr < state.maximum_transmit_rate: - new_tr = min( - state.maximum_transmit_rate, - self.double_step_up(pdr_rel_width, pdr_hi.target_tr)) - logging.info("pdr hi external %s", new_tr) - state = self._measure_and_update_state(state, new_tr) - continue - elif pdr_hi.duration < state.duration: - logging.info("ndr hi maximal re-measure") - state = self._measure_and_update_state( - state, state.maximum_transmit_rate) - continue - # If we are hitting maximum_transmit_rate, - # it is still worth narrowing width, - # hoping large enough loss fraction will happen. - # But if we are hitting the minimal rate (at current duration), - # no additional measurement will help with that, - # so we can stop narrowing in this phase. - if (ndr_lo.target_tr <= state.minimum_transmit_rate - and ndr_lo.loss_fraction > 0.0): - ndr_rel_width = 0.0 - if (pdr_lo.target_tr <= state.minimum_transmit_rate - and pdr_lo.loss_fraction > state.packet_loss_ratio): - pdr_rel_width = 0.0 - if ndr_rel_width > state.width_goal: - # We have to narrow NDR width first, as NDR internal search - # can invalidate PDR (but not vice versa). - new_tr = self.half_step_up(ndr_rel_width, ndr_lo.target_tr) - logging.info("Bisecting for NDR at %s", new_tr) - state = self._measure_and_update_state(state, new_tr) - continue - if pdr_rel_width > state.width_goal: - # PDR iternal search. - new_tr = self.half_step_up(pdr_rel_width, pdr_lo.target_tr) - logging.info("Bisecting for PDR at %s", new_tr) - state = self._measure_and_update_state(state, new_tr) - continue - # We do not need to improve width, but there still might be - # some measurements with smaller duration. - # We need to re-measure with full duration, possibly - # creating invalid bounds to resolve (thus broadening width). - if ndr_lo.duration < state.duration: - logging.info("re-measuring NDR lower bound") - self._measure_and_update_state(state, ndr_lo.target_tr) - continue - if pdr_lo.duration < state.duration: - logging.info("re-measuring PDR lower bound") - self._measure_and_update_state(state, pdr_lo.target_tr) - continue - # Except when lower bounds have high loss fraction, in that case - # we do not need to re-measure _upper_ bounds. - if ndr_hi.duration < state.duration and ndr_rel_width > 0.0: - logging.info("re-measuring NDR upper bound") - self._measure_and_update_state(state, ndr_hi.target_tr) - continue - if pdr_hi.duration < state.duration and pdr_rel_width > 0.0: - logging.info("re-measuring PDR upper bound") - self._measure_and_update_state(state, pdr_hi.target_tr) - continue - # Widths are narrow (or lower bound minimal), bound measurements - # are long enough, we can return. - logging.info("phase done") - break - return state |