<s> import time <EOL> import random <EOL> import math <EOL> import heapq <EOL> from . snapshot import Snapshot <EOL> DEFAULT_SIZE = <NUM_LIT> <EOL> DEFAULT_ALPHA = <NUM_LIT> <EOL> class ExpDecayingSample ( object ) : <EOL> """<STR_LIT>""" <EOL> RESCALE_THREASHOLD = <NUM_LIT> <EOL> def __init__ ( self , size = DEFAULT_SIZE , alpha = DEFAULT_ALPHA , clock = time ) : <EOL> """<STR_LIT>""" <EOL> super ( ExpDecayingSample , self ) . __init__ ( ) <EOL> self . clock = clock <EOL> self . size = size <EOL> self . alpha = alpha <EOL> self . clear ( ) <EOL> def clear ( self ) : <EOL> self . values = { } <EOL> self . priorities = [ ] <EOL> self . counter = <NUM_LIT:0> <EOL> self . start_time = self . clock . time ( ) <EOL> self . next_time = self . clock . time ( ) + ExpDecayingSample . RESCALE_THREASHOLD <EOL> def get_size ( self ) : <EOL> return self . counter if self . counter < self . size else self . size <EOL> def update ( self , value ) : <EOL> """<STR_LIT>""" <EOL> if self . size == <NUM_LIT:0> : <EOL> return <EOL> self . _rescale_if_necessary ( ) <EOL> priority = self . _weight ( <EOL> self . clock . time ( ) - self . start_time ) / random . random ( ) <EOL> new_counter = self . counter + <NUM_LIT:1> <EOL> self . counter = new_counter <EOL> if new_counter <= self . size : <EOL> self . values [ priority ] = value <EOL> heapq . heappush ( self . priorities , priority ) <EOL> else : <EOL> first = heapq . heappop ( self . priorities ) <EOL> if first < priority : <EOL> if priority not in self . values : <EOL> self . values [ priority ] = value <EOL> heapq . heappush ( self . priorities , priority ) <EOL> while first not in self . values : <EOL> first = heapq . heappop ( self . priorities ) <EOL> del self . values [ first ] <EOL> else : <EOL> heapq . heappush ( self . priorities , first ) <EOL> def _rescale_if_necessary ( self ) : <EOL> if self . clock . time ( ) >= self . next_time : <EOL> self . _rescale ( ) <EOL> def _rescale ( self ) : <EOL> self . next_time = self . clock . time ( ) + ExpDecayingSample . RESCALE_THREASHOLD <EOL> old_start_time = self . start_time <EOL> self . start_time = self . clock . time ( ) <EOL> new_values = { } <EOL> new_priorities = [ ] <EOL> for key , val in self . values . items ( ) : <EOL> priority = key * math . exp ( - self . alpha * ( self . start_time - old_start_time ) ) <EOL> new_values [ priority ] = val <EOL> heapq . heappush ( new_priorities , priority ) <EOL> self . values = new_values <EOL> self . priorities = new_priorities <EOL> self . counter = len ( self . values ) <EOL> def _weight ( self , value ) : <EOL> return math . exp ( self . alpha * value ) <EOL> def get_snapshot ( self ) : <EOL> return Snapshot ( self . values . values ( ) ) </s>
