def add_ngram_arcs(fst, symtab, lm, n, sidtab):
"""
Add states and arcs for all N-grams in the language model, where
N=N (the order of the model, that is).
"""
for ng in lm.mgrams(n - 1):
wsym = symtab.Find(ng.words[n - 1])
if wsym == -1: # OOV
continue
if ng.words[n - 1] == '<s>': # non-event
continue
if '</s>' in ng.words[0:n - 1]:
continue
for w in ng.words[:n - 1]: # skip OOVs
if symtab.Find(w) == -1:
#print w, "not found"
continue
src = sidtab[tuple(ng.words[:n - 1])]
# Find longest suffix N-gram that exists
spos = 1
while tuple(ng.words[spos:]) not in sidtab:
spos += 1
if spos == n:
raise RuntimeError, "Unable to find suffix N-gram for", ng.wids
dest = sidtab[tuple(ng.words[spos:])]
fst.AddArc(src, openfst.StdArc(wsym, wsym, -ng.log_prob, dest))
def build_dictfst(lmfst):
"""
Build a character-to-word FST based on the symbol table of lmfst.
"""
insym = openfst.SymbolTable("letters")
insym.AddSymbol("ε")
outsym = lmfst.InputSymbols()
fst = openfst.StdVectorFst()
start = fst.AddState()
fst.SetStart(start)
final = fst.AddState()
fst.SetFinal(final, 0)
for w, wsym in outsym:
if wsym == 0:
continue
# Use a single symbol for end-of-sentence
if w == '</s>':
w = [
w,
]
for c in w:
csym = insym.AddSymbol(c)
for w, wsym in outsym:
if wsym == 0:
continue
wsym = outsym.Find(w)
# Add an epsilon:word arc to the first state of this word
prev = fst.AddState()
fst.AddArc(start, openfst.StdArc(0, wsym, 0, prev))
# Use a single symbol for end-of-sentence
if w == '</s>':
w = [
w,
]
for c in w:
csym = insym.Find(c)
next = fst.AddState()
fst.AddArc(prev, openfst.StdArc(csym, 0, 0, next))
prev = next
# And an epsilon arc to the final state
fst.AddArc(prev, openfst.StdArc(0, 0, 0, final))
fst.SetInputSymbols(insym)
fst.SetOutputSymbols(outsym)
return fst
from optparse import OptionParser
parser = OptionParser(usage="%prog CTL LATDIR")
parser.add_option("--prune", type="int", default=5)
parser.add_option("--errprune", type="float", default=1e-5)
parser.add_option("--errpen", type="float", default=1.0)
parser.add_option("--outext")
parser.add_option("--errfst")
opts, args = parser.parse_args(sys.argv[1:])
ctlfile, latdir = args
errfst = None
if opts.errfst:
errfst = openfst.StdVectorFst.Read(opts.errfst)
openfst.Prune(errfst, opts.errprune)
sigma = errfst.InputSymbols().Find("σ")
for node in errfst:
for ai in errfst.mutable_iterarcs(node):
arc = ai.Value()
if arc.ilabel == sigma:
continue
ai.SetValue(openfst.StdArc(arc.ilabel, arc.olabel,
arc.weight.Value() + opts.errpen,
arc.nextstate))
openfst.ArcSortInput(errfst)
if opts.outext == None:
opts.outext = ".fsg%d" % opts.prune
for spam in file(ctlfile):
latfile = os.path.join(latdir, spam.strip() + ".slf")
fsgfile = os.path.join(latdir, spam.strip() + opts.outext)
print spam,
ofst = lat2fsg_posterior(latfile, fsgfile, opts.prune, errfst)
def add_mgram_states(fst, symtab, lm, m, sidtab, bo_label=0):
"""
Add states and arcs for all M-grams in the language model, where M<N.
"""
for mg in lm.mgrams(m):
wsym = symtab.Find(mg.words[m])
if wsym == -1:
continue # skip mgrams ending in OOV
if m > 0 and mg.words[0] == '</s>':
continue # skip >1-grams starting with </s>
if m == 0:
src = 0 # 1-grams start in backoff state
elif tuple(mg.words[0:m]) not in sidtab:
continue # this means it has an OOV
else:
src = sidtab[tuple(mg.words[0:m])]
if mg.words[m] == '</s>':
# only one final state is allowed
final = True
newstate = False
if ('</s>', ) in sidtab:
dest = sidtab[('</s>', )]
else:
dest = fst.AddState()
fst.SetFinal(dest, 0)
sidtab[('</s>', )] = dest
#print "Final state", dest
#print "Entered state ID mapping (</s>,) =>", dest
else:
final = False
newstate = True
dest = fst.AddState()
if mg.words[m] == '<s>':
# <s> is a non-event
if m == 0:
# The destination state will be the initial state
fst.SetStart(dest)
#print "Initial state", dest
else:
fst.AddArc(src, openfst.StdArc(wsym, wsym, -mg.log_prob, dest))
#print "Added %d-gram arc %d => %d %s/%.4f" % (m+1, src, dest,
#mg.words[m], -mg.log_prob)
if newstate:
# Add a new state to the mapping if needed
sidtab[tuple(mg.words)] = dest
#print "Entered state ID mapping", tuple(mg.words), "=>", dest
if not final:
# Create a backoff arc to the suffix M-1-gram
# Note taht if mg.log_bowt == 0 it's particularly important to do this!
if m == 0:
bo_state = 0 # backoff state
elif tuple(mg.words[1:]) in sidtab:
bo_state = sidtab[tuple(mg.words[1:])]
else:
continue # Not a 1-gram, no suffix M-gram
fst.AddArc(
dest, openfst.StdArc(bo_label, bo_label, -mg.log_bowt,
bo_state))
