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stan.py
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stan.py
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from _operator import itemgetter
from math import sqrt, exp
import random
import time
from pympler import asizeof
import numpy as np
import pandas as pd
from math import log10
from datetime import datetime as dt
from datetime import timedelta as td
import math
class STAN:
'''
STAN( k, sample_size=5000, sampling='recent', remind=True, extend=False, lambda_spw=1.02, lambda_snh=5, lambda_inh=2.05 , session_key = 'SessionId', item_key= 'ItemId', time_key= 'Time' )
Parameters
-----------
k : int
Number of neighboring session to calculate the item scores from. (Default value: 100)
sample_size : int
Defines the length of a subset of all training sessions to calculate the nearest neighbors from. (Default value: 500)
sampling : string
String to define the sampling method for sessions (recent, random). (default: recent)
remind : string
String to define the method for the similarity calculation (jaccard, cosine, binary, tanimoto). (default: jaccard)
extend : string
Decay function to determine the importance/weight of individual actions in the current session (linear, same, div, log, quadratic). (default: div)
lambda_spw : string
Decay function to lower the score of candidate items from a neighboring sessions that were selected by less recently clicked items in the current session. (linear, same, div, log, quadratic). (default: div_score)
lambda_snh : boolean
Experimental function to give less weight to items from older sessions (default: False)
lambda_inh : boolean
Experimental function to use the dwelling time for item view actions as a weight in the similarity calculation. (default: False)
session_key : string
Header of the session ID column in the input file. (default: 'SessionId')
item_key : string
Header of the item ID column in the input file. (default: 'ItemId')
time_key : string
Header of the timestamp column in the input file. (default: 'Time')
'''
def __init__( self, k, sample_size=5000, sampling='recent', remind=True, extend=False, lambda_spw=1.02, lambda_snh=5, lambda_inh=2.05 , session_key = 'SessionId', item_key= 'ItemId', time_key= 'Time' ):
self.k = k
self.sample_size = sample_size
self.sampling = sampling
self.lambda_spw = lambda_spw
self.lambda_snh = lambda_snh * 24 * 3600
self.lambda_inh = lambda_inh
self.session_key = session_key
self.item_key = item_key
self.time_key = time_key
self.extend = extend
self.remind = remind
#updated while recommending
self.session = -1
self.session_items = []
self.relevant_sessions = set()
# cache relations once at startup
self.session_item_map = dict()
self.item_session_map = dict()
self.session_time = dict()
self.min_time = -1
self.sim_time = 0
def fit(self, train, test=None, items=None):
'''
Trains the predictor.
Parameters
--------
data: pandas.DataFrame
Training data. It contains the transactions of the sessions. It has one column for session IDs, one for item IDs and one for the timestamp of the events (unix timestamps).
It must have a header. Column names are arbitrary, but must correspond to the ones you set during the initialization of the network (session_key, item_key, time_key properties).
'''
self.num_items = train[self.item_key].max()
index_session = train.columns.get_loc( self.session_key )
index_item = train.columns.get_loc( self.item_key )
index_time = train.columns.get_loc( self.time_key )
session = -1
session_items = []
time = -1
#cnt = 0
for row in train.itertuples(index=False):
# cache items of sessions
if row[index_session] != session:
if len(session_items) > 0:
self.session_item_map.update({session : session_items})
# cache the last time stamp of the session
self.session_time.update({session : time})
if time < self.min_time:
self.min_time = time
session = row[index_session]
session_items = []
time = row[index_time]
session_items.append(row[index_item])
# cache sessions involving an item
map_is = self.item_session_map.get( row[index_item] )
if map_is is None:
map_is = set()
self.item_session_map.update({row[index_item] : map_is})
map_is.add(row[index_session])
# Add the last tuple
self.session_item_map.update({session : session_items})
self.session_time.update({session : time})
if self.sample_size == 0: #use all session as possible neighbors
print('!!!!! runnig KNN without a sample size (check config)')
def predict_next( self, session_id, input_item_id, predict_for_item_ids, input_user_id=None, timestamp=0, skip=False, type='view'):
'''
Gives predicton scores for a selected set of items on how likely they be the next item in the session.
Parameters
--------
session_id : int or string
The session IDs of the event.
input_item_id : int or string
The item ID of the event. Must be in the set of item IDs of the training set.
predict_for_item_ids : 1D array
IDs of items for which the network should give prediction scores. Every ID must be in the set of item IDs of the training set.
Returns
--------
out : pandas.Series
Prediction scores for selected items on how likely to be the next item of this session. Indexed by the item IDs.
'''
# gc.collect()
# process = psutil.Process(os.getpid())
# print( 'cknn.predict_next: ', process.memory_info().rss, ' memory used')
if( self.session != session_id ): #new session
if( self.extend ):
self.session_item_map[self.session] = self.session_items;
for item in self.session_items:
map_is = self.item_session_map.get( item )
if map_is is None:
map_is = set()
self.item_session_map.update({item : map_is})
map_is.add(self.session)
ts = time.time()
self.session_time.update({self.session : ts})
self.session = session_id
self.session_items = list()
self.relevant_sessions = set()
if type == 'view':
self.session_items.append( input_item_id )
if skip:
return
neighbors = self.find_neighbors( self.session_items, input_item_id, session_id, timestamp )
scores = self.score_items( neighbors, self.session_items, timestamp )
# Create things in the format ..
predictions = np.zeros(len(predict_for_item_ids))
mask = np.in1d( predict_for_item_ids, list(scores.keys()) )
items = predict_for_item_ids[mask]
values = [scores[x] for x in items]
predictions[mask] = values
series = pd.Series(data=predictions, index=predict_for_item_ids)
return series
def vec(self, current, neighbor, pos_map):
'''
Calculates the ? for 2 sessions
Parameters
--------
first: Id of a session
second: Id of a session
Returns
--------
out : float value
'''
intersection = current & neighbor
vp_sum = 0
for i in intersection:
vp_sum += pos_map[i]
result = vp_sum / len(pos_map)
return result
def cosine(self, current, neighbor, pos_map):
'''
Calculates the cosine similarity for two sessions
Parameters
--------
first: Id of a session
second: Id of a session
Returns
--------
out : float value
'''
lneighbor = len(neighbor)
intersection = current & neighbor
if pos_map is not None:
vp_sum = 0
current_sum = 0
for i in current:
current_sum += pos_map[i] * pos_map[i]
if i in intersection:
vp_sum += pos_map[i]
else:
vp_sum = len( intersection )
current_sum = len( current )
result = vp_sum / (sqrt(current_sum) * sqrt(lneighbor))
return result
def items_for_session(self, session):
'''
Returns all items in the session
Parameters
--------
session: Id of a session
Returns
--------
out : set
'''
return self.session_item_map.get(session);
def sessions_for_item(self, item_id):
'''
Returns all session for an item
Parameters
--------
item: Id of the item session
Returns
--------
out : set
'''
return self.item_session_map.get( item_id ) if item_id in self.item_session_map else set()
def most_recent_sessions( self, sessions, number ):
'''
Find the most recent sessions in the given set
Parameters
--------
sessions: set of session ids
Returns
--------
out : set
'''
sample = set()
tuples = list()
for session in sessions:
time = self.session_time.get( session )
if time is None:
print(' EMPTY TIMESTAMP!! ', session)
tuples.append((session, time))
tuples = sorted(tuples, key=itemgetter(1), reverse=True)
#print 'sorted list ', sortedList
cnt = 0
for element in tuples:
cnt = cnt + 1
if cnt > number:
break
sample.add( element[0] )
#print 'returning sample of size ', len(sample)
return sample
#-----------------
# Find a set of neighbors, returns a list of tuples (sessionid: similarity)
#-----------------
def find_neighbors( self, session_items, input_item_id, session_id, timestamp ):
'''
Finds the k nearest neighbors for the given session_id and the current item input_item_id.
Parameters
--------
session_items: set of item ids
input_item_id: int
session_id: int
Returns
--------
out : list of tuple (session_id, similarity)
'''
possible_neighbors = self.possible_neighbor_sessions( session_items, input_item_id, session_id )
possible_neighbors = self.calc_similarity( session_items, possible_neighbors, timestamp )
possible_neighbors = sorted( possible_neighbors, reverse=True, key=lambda x: x[1] )
possible_neighbors = possible_neighbors[:self.k]
return possible_neighbors
def possible_neighbor_sessions(self, session_items, input_item_id, session_id):
'''
Find a set of session to later on find neighbors in.
A self.sample_size of 0 uses all sessions in which any item of the current session appears.
self.sampling can be performed with the options "recent" or "random".
"recent" selects the self.sample_size most recent sessions while "random" just choses randomly.
Parameters
--------
sessions: set of session ids
Returns
--------
out : set
'''
self.relevant_sessions = self.relevant_sessions | self.sessions_for_item( input_item_id )
if self.sample_size == 0: #use all session as possible neighbors
#print('!!!!! runnig KNN without a sample size (check config)')
return self.relevant_sessions
else: #sample some sessions
if len(self.relevant_sessions) > self.sample_size:
if self.sampling == 'recent':
sample = self.most_recent_sessions( self.relevant_sessions, self.sample_size )
elif self.sampling == 'random':
sample = random.sample( self.relevant_sessions, self.sample_size )
else:
sample = self.relevant_sessions[:self.sample_size]
return sample
else:
return self.relevant_sessions
def calc_similarity(self, session_items, sessions, timestamp ):
'''
Calculates the configured similarity for the items in session_items and each session in sessions.
Parameters
--------
session_items: set of item ids
sessions: list of session ids
Returns
--------
out : list of tuple (session_id,similarity)
'''
pos_map = None
if self.lambda_spw:
pos_map = {}
length = len( session_items )
pos = 1
for item in session_items:
if self.lambda_spw is not None:
pos_map[item] = self.session_pos_weight( pos, length, self.lambda_spw )
pos += 1
#print 'nb of sessions to test ', len(sessionsToTest), ' metric: ', self.metric
items = set(session_items)
neighbors = []
cnt = 0
for session in sessions:
cnt = cnt + 1
# get items of the session, look up the cache first
n_items = self.items_for_session( session )
similarity = self.cosine(items, set(n_items), pos_map)
if self.lambda_snh is not None:
sts = self.session_time[session]
decay = self.session_time_weight(timestamp, sts, self.lambda_snh)
similarity *= decay
neighbors.append((session, similarity))
return neighbors
def session_pos_weight(self, position, length, lambda_spw):
diff = position - length
return exp( diff / lambda_spw )
def session_time_weight(self, ts_current, ts_neighbor, lambda_snh):
diff = ts_current - ts_neighbor
return exp( - diff / lambda_snh )
def score_items(self, neighbors, current_session, timestamp):
'''
Compute a set of scores for all items given a set of neighbors.
Parameters
--------
neighbors: set of session ids
Returns
--------
out : list of tuple (item, score)
'''
# now we have the set of relevant items to make predictions
scores = dict()
s_items = set( current_session )
# iterate over the sessions
for session in neighbors:
# get the items in this session
n_items = self.items_for_session( session[0] )
pos_last = {}
pos_i_star = None
for i in range( len( n_items ) ):
if n_items[i] in s_items:
pos_i_star = i + 1
pos_last[n_items[i]] = i + 1
n_items = set( n_items )
for item in n_items:
if not self.remind and item in s_items:
continue
old_score = scores.get( item )
new_score = session[1]
if self.lambda_inh is not None:
new_score = new_score * self.item_pos_weight( pos_last[item], pos_i_star, self.lambda_inh )
if not old_score is None:
new_score = old_score + new_score
scores.update({item : new_score})
return scores
def item_pos_weight(self, pos_candidate, pos_item, lambda_inh):
diff = abs( pos_candidate - pos_item )
return exp( - diff / lambda_inh )
def clear(self):
self.session = -1
self.session_items = []
self.relevant_sessions = set()
self.session_item_map = dict()
self.item_session_map = dict()
self.session_time = dict()
def support_users(self):
'''
whether it is a session-based or session-aware algorithm
(if returns True, method "predict_with_training_data" must be defined as well)
Parameters
--------
Returns
--------
True : if it is session-aware
False : if it is session-based
'''
return False