def reduce_nfa(aut, freq=None, ratio=.25, merge=True, th=.995, mf=.1):
'''
Approximate NFA reduction. The reduction consists of pruning and merging
based on packet frequency.
Parameters
----------
aut : Nfa class
the NFA to reduce
freq : str, None
PCAP filename, or file with packet frequencies, or None
ratio :
reduction ratio
merge :
use merging reduction before pruning
th :
merging threshold
mf :
maximal frequency merging parameter
Returns
-------
aut
reduced NFA
m
the number of merged states
'''
m = 0
if merge:
cnt = aut.state_count #modified!!!!
m = merging(aut, freq=freq, th=th, max_fr=mf)
ratio = ratio * float(cnt) / (cnt - m)
pruning(aut, ratio, freq=freq)
return aut, m
def reduce_nfa(aut,
freq=None,
ratio=.2,
merge=False,
freq_pruning=False,
th=.995,
mf=.1):
'''
Approximate NFA reduction. The reduction consists of pruning and merging
based on packet frequency.
Parameters
----------
aut : Nfa class
the NFA to reduce
freq : str, None
PCAP filename, or file with packet frequencies, or None
ratio :
reduction ratio
merge :
use merging reduction before pruning
freq_pruning:
frequency based pruning method
th :
merging threshold
mf :
maximal frequency merging parameter
Returns
-------
aut
reduced NFA
m
the number of merged states
max_err
in case of frequency pruning returns sum of frequencies of removed states, otherwise -1 (not computed)
'''
max_err = -1
m = 0
if merge:
cnt = aut.state_count #modified!!!!
m = merging(aut, freq=freq, th=th, max_fr=mf)
ratio = ratio * float(cnt) / (cnt - m)
# use of new_pruning and merging was not tested, NOT RECOMMENDED
if freq_pruning:
if merge:
sys.stderr.write(
"Use of freq_pruning and merging was not tested, NOT RECOMMENDED."
)
sys.exit()
# call my new cool function :) naskle
max_err = pruning_v2(aut, ratio, freq)
else:
# old pruning algorithm
pruning(aut, ratio, freq=freq)
return aut, m, max_err
def armc(aut, pcap, ratio=.25, th=.75, merge_empty=True):
'''
NFA reduction based on merging similar sets of prefixes.
Parameters
----------
aut : Nfa class
the NFA to reduce
pcap : str
PCAP filename
ratio :
reduction ratio
th :
merging threshold
merge_empty :
if set, reduction merges states with empty sets together
Returns
-------
aut
reduced NFA
m
the number of merged states
'''
empty, eq = aut.get_armc_groups(pcap, th)
mapping = {}
# merge similar
g = networkx.Graph(eq)
for cluster in networkx.connected_component_subgraphs(g):
l = list(cluster.nodes())
assert len(l) > 1
for i in l[1:]:
mapping[i] = l[0]
mapping.pop(aut._initial_state, None)
m = len(mapping)
if merge_empty:
# merge states with empty sets of prefixes together
fin = {s: f for f, ss in aut.fin_pred().items() for s in ss}
mapping.update(
{s: fin[s]
for s in empty if not s in aut._final_states})
mapping.pop(aut._initial_state, None)
aut.merge_states(mapping)
else:
aut.merge_states(mapping)
freq = aut.get_freq(pcap)
cnt = aut.state_count
ratio = ratio * cnt / (cnt - m)
pruning(aut, ratio, freq=freq)
return aut, m