def pagerank_reducer(node, values):
"""Compute the new PageRank for the node"""
try:
# sort because we want the 'infos' value at the end of the list
values = sorted([v for v in values]) # as values is a generator
damping = float(prince.get_parameters('damping'))
infos = values[-1].split()
pr_previous = float(infos[2])
nodes_adjacent = [int(n) for n in infos[3:]]
pageranks = [float(v) for v in values[:-1]]
nb_nodes = float(prince.get_parameters('nb_nodes'))
pr_new = (1.0 - damping) / nb_nodes + damping * sum(pageranks)
yield (node, make_value(pr_previous, pr_new, nodes_adjacent))
except ValueError:
pass
def pagerank_reducer(node, values):
"""Compute the new PageRank for the node"""
try:
# sort because we want the 'infos' value at the end of the list
values = sorted([v for v in values]) # as values is a generator
damping = float(prince.get_parameters('damping'))
infos = values[-1].split()
pr_previous = float(infos[2])
nodes_adjacent = [int(n) for n in infos[3:]]
pageranks = [float(v) for v in values[:-1]]
nb_nodes = float(prince.get_parameters('nb_nodes'))
pr_new = (1.0 - damping) / nb_nodes + damping * sum(pageranks)
yield (node, make_value(pr_previous, pr_new, nodes_adjacent))
except ValueError:
pass
def term_reducer(key, pagerank_changes):
"""Check whether the values are converging using the quadratic norm"""
try:
precision = float(prince.get_parameters('precision'))
if sum([float(p) ** 2 for p in pagerank_changes]) > precision ** 2:
return 0, 0 # let's do another iteration
except ValueError:
pass # the algorithm is stopped in case of error
return 1, 1
def term_reducer(key, pagerank_changes):
"""Check whether the values are converging using the quadratic norm"""
try:
precision = float(prince.get_parameters('precision'))
if sum([float(p)**2 for p in pagerank_changes]) > precision**2:
return 0, 0 # let's do another iteration
except ValueError:
pass # the algorithm is stopped in case of error
return 1, 1
def frontier_mapper(key, value):
"""Expand the frontier of one hop."""
(node, d_previous, d_current) = node_info(value)
if node != None:
yield node, '%d %d' % (d_current, d_current) # reinject itself
if d_current != d_previous: # expand only if distance has changed
graph = read_graph(prince.get_parameters('graph'))
for node_adjacent in graph[node]:
yield node_adjacent, '%d %d' % (sys.maxint, d_current + 1)
def frontier_mapper(key, value):
"""Expand the frontier of one hop."""
(node, d_previous, d_current) = node_info(value)
if node != None:
yield node, '%d %d' % (d_current, d_current) # reinject itself
if d_current != d_previous: # expand only if distance has changed
graph = read_graph(prince.get_parameters('graph'))
for node_adjacent in graph[node]:
yield node_adjacent, '%d %d' % (sys.maxint, d_current + 1)