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-rwxr-xr-xpython/src/sa/online_extractor.py285
1 files changed, 285 insertions, 0 deletions
diff --git a/python/src/sa/online_extractor.py b/python/src/sa/online_extractor.py
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+++ b/python/src/sa/online_extractor.py
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+#!/usr/bin/env python
+
+import collections, sys
+
+import cdec.configobj
+
+CAT = '[X]' # Default non-terminal
+MAX_SIZE = 15 # Max span of a grammar rule (source)
+MAX_LEN = 5 # Max number of terminals and non-terminals in a rule (source)
+MAX_NT = 2 # Max number of non-terminals in a rule
+MIN_GAP = 1 # Min number of terminals between non-terminals (source)
+
+# Spans are _inclusive_ on both ends [i, j]
+# TODO: Replace all of this with bit vectors?
+def span_check(vec, i, j):
+ k = i
+ while k <= j:
+ if vec[k]:
+ return False
+ k += 1
+ return True
+
+def span_flip(vec, i, j):
+ k = i
+ while k <= j:
+ vec[k] = ~vec[k]
+ k += 1
+
+# Next non-terminal
+def next_nt(nt):
+ if not nt:
+ return 1
+ return nt[-1][0] + 1
+
+# Create a rule from source, target, non-terminals, and alignments
+def form_rule(f_i, e_i, f_span, e_span, nt, al):
+
+ # This could be more efficient but is unlikely to be the bottleneck
+
+ nt_inv = sorted(nt, cmp=lambda x, y: cmp(x[3], y[3]))
+
+ f_sym = f_span[:]
+ off = f_i
+ for next_nt in nt:
+ nt_len = (next_nt[2] - next_nt[1]) + 1
+ i = 0
+ while i < nt_len:
+ f_sym.pop(next_nt[1] - off)
+ i += 1
+ f_sym.insert(next_nt[1] - off, '[X,{0}]'.format(next_nt[0]))
+ off += (nt_len - 1)
+
+ e_sym = e_span[:]
+ off = e_i
+ for next_nt in nt_inv:
+ nt_len = (next_nt[4] - next_nt[3]) + 1
+ i = 0
+ while i < nt_len:
+ e_sym.pop(next_nt[3] - off)
+ i += 1
+ e_sym.insert(next_nt[3] - off, '[X,{0}]'.format(next_nt[0]))
+ off += (nt_len - 1)
+
+ # Adjusting alignment links takes some doing
+ links = [list(link) for sub in al for link in sub]
+ links_len = len(links)
+ nt_len = len(nt)
+ nt_i = 0
+ off = f_i
+ i = 0
+ while i < links_len:
+ while nt_i < nt_len and links[i][0] > nt[nt_i][1]:
+ off += (nt[nt_i][2] - nt[nt_i][1])
+ nt_i += 1
+ links[i][0] -= off
+ i += 1
+ nt_i = 0
+ off = e_i
+ i = 0
+ while i < links_len:
+ while nt_i < nt_len and links[i][1] > nt_inv[nt_i][3]:
+ off += (nt_inv[nt_i][4] - nt_inv[nt_i][3])
+ nt_i += 1
+ links[i][1] -= off
+ i += 1
+ a_str = ' '.join('{0}-{1}'.format(i, j) for (i, j) in links)
+
+ return '[X] ||| {0} ||| {1} ||| {2}'.format(' '.join(f_sym), ' '.join(e_sym), a_str)
+
+class OnlineGrammarExtractor:
+
+ def __init__(self, config=None):
+ if isinstance(config, str) or isinstance(config, unicode):
+ if not os.path.exists(config):
+ raise IOError('cannot read configuration from {0}'.format(config))
+ config = cdec.configobj.ConfigObj(config, unrepr=True)
+ elif not config:
+ config = collections.defaultdict(lambda: None)
+ self.category = CAT
+ self.max_size = MAX_SIZE
+ self.max_length = config['max_len'] or MAX_LEN
+ self.max_nonterminals = config['max_nt'] or MAX_NT
+ self.min_gap_size = MIN_GAP
+ # Hard coded: require at least one aligned word
+ # Hard coded: require tight phrases
+
+ # Phrase counts
+ self.phrases_f = collections.defaultdict(lambda: 0)
+ self.phrases_e = collections.defaultdict(lambda: 0)
+ self.phrases_fe = collections.defaultdict(lambda: collections.defaultdict(lambda: 0))
+
+ # Bilexical counts
+ self.bilex_f = collections.defaultdict(lambda: 0)
+ self.bilex_e = collections.defaultdict(lambda: 0)
+ self.bilex_fe = collections.defaultdict(lambda: collections.defaultdict(lambda: 0))
+
+ # Aggregate bilexical counts
+ def aggr_bilex(self, f_words, e_words):
+
+ for e_w in e_words:
+ self.bilex_e[e_w] += 1
+
+ for f_w in f_words:
+ self.bilex_f[f_w] += 1
+ for e_w in e_words:
+ self.bilex_fe[f_w][e_w] += 1
+
+ # Aggregate stats from a training instance:
+ # Extract hierarchical phrase pairs
+ # Update bilexical counts
+ def add_instance(self, f_words, e_words, alignment):
+
+ # Bilexical counts
+ self.aggr_bilex(f_words, e_words)
+
+ # Phrase pairs extracted from this instance
+ phrases = set()
+
+ f_len = len(f_words)
+
+ # Pre-compute alignment info
+ al = [[] for i in range(f_len)]
+ al_span = [[f_len + 1, -1] for i in range(f_len)]
+ for (f, e) in alignment:
+ al[f].append(e)
+ al_span[f][0] = min(al_span[f][0], e)
+ al_span[f][1] = max(al_span[f][1], e)
+
+ # Target side word coverage
+ # TODO: Does Cython do bit vectors?
+ cover = [0] * f_len
+
+ # Extract all possible hierarchical phrases starting at a source index
+ # f_ i and j are current, e_ i and j are previous
+ def extract(f_i, f_j, e_i, e_j, wc, links, nt, nt_open):
+ # Phrase extraction limits
+ if wc > self.max_length or (f_j + 1) >= f_len or \
+ (f_j - f_i) + 1 > self.max_size:
+ return
+ # Unaligned word
+ if not al[f_j]:
+ # Open non-terminal: extend
+ if nt_open:
+ nt[-1][2] += 1
+ extract(f_i, f_j + 1, e_i, e_j, wc, links, nt, True)
+ nt[-1][2] -= 1
+ # No open non-terminal: extend with word
+ else:
+ extract(f_i, f_j + 1, e_i, e_j, wc + 1, links, nt, False)
+ return
+ # Aligned word
+ link_i = al_span[f_j][0]
+ link_j = al_span[f_j][1]
+ new_e_i = min(link_i, e_i)
+ new_e_j = max(link_j, e_j)
+ # Open non-terminal: close, extract, extend
+ if nt_open:
+ # Close non-terminal, checking for collisions
+ old_last_nt = nt[-1][:]
+ nt[-1][2] = f_j
+ if link_i < nt[-1][3]:
+ if not span_check(cover, link_i, nt[-1][3] - 1):
+ nt[-1] = old_last_nt
+ return
+ span_flip(cover, link_i, nt[-1][3] - 1)
+ nt[-1][3] = link_i
+ if link_j > nt[-1][4]:
+ if not span_check(cover, nt[-1][4] + 1, link_j):
+ nt[-1] = old_last_nt
+ return
+ span_flip(cover, nt[-1][4] + 1, link_j)
+ nt[-1][4] = link_j
+ phrases.add(form_rule(f_i, new_e_i, f_words[f_i:f_j + 1], e_words[new_e_i:new_e_j + 1], nt, links))
+ extract(f_i, f_j + 1, new_e_i, new_e_j, wc, links, nt, False)
+ nt[-1] = old_last_nt
+ if link_i < nt[-1][3]:
+ span_flip(cover, link_i, nt[-1][3] - 1)
+ if link_j > nt[-1][4]:
+ span_flip(cover, nt[-1][4] + 1, link_j)
+ return
+ # No open non-terminal
+ # Extract, extend with word
+ collision = False
+ for link in al[f_j]:
+ if cover[link]:
+ collision = True
+ # Collisions block extraction and extension, but may be okay for
+ # continuing non-terminals
+ if not collision:
+ plus_links = []
+ for link in al[f_j]:
+ plus_links.append((f_j, link))
+ cover[link] = ~cover[link]
+ links.append(plus_links)
+ phrases.add(form_rule(f_i, new_e_i, f_words[f_i:f_j + 1], e_words[new_e_i:new_e_j + 1], nt, links))
+ extract(f_i, f_j + 1, new_e_i, new_e_j, wc + 1, links, nt, False)
+ links.pop()
+ for link in al[f_j]:
+ cover[link] = ~cover[link]
+ # Try to add a word to a (closed) non-terminal, extract, extend
+ if nt and nt[-1][2] == f_j - 1:
+ # Add to non-terminal, checking for collisions
+ old_last_nt = nt[-1][:]
+ nt[-1][2] = f_j
+ if link_i < nt[-1][3]:
+ if not span_check(cover, link_i, nt[-1][3] - 1):
+ nt[-1] = old_last_nt
+ return
+ span_flip(cover, link_i, nt[-1][3] - 1)
+ nt[-1][3] = link_i
+ if link_j > nt[-1][4]:
+ if not span_check(cover, nt[-1][4] + 1, link_j):
+ nt[-1] = old_last_nt
+ return
+ span_flip(cover, nt[-1][4] + 1, link_j)
+ nt[-1][4] = link_j
+ # Require at least one word in phrase
+ if links:
+ phrases.add(form_rule(f_i, new_e_i, f_words[f_i:f_j + 1], e_words[new_e_i:new_e_j + 1], nt, links))
+ extract(f_i, f_j + 1, new_e_i, new_e_j, wc, links, nt, False)
+ nt[-1] = old_last_nt
+ if new_e_i < nt[-1][3]:
+ span_flip(cover, link_i, nt[-1][3] - 1)
+ if link_j > nt[-1][4]:
+ span_flip(cover, nt[-1][4] + 1, link_j)
+ # Try to start a new non-terminal, extract, extend
+ if (not nt or f_j - nt[-1][2] > 1) and len(nt) < self.max_nonterminals:
+ # Check for collisions
+ if not span_check(cover, link_i, link_j):
+ return
+ span_flip(cover, link_i, link_j)
+ nt.append([next_nt(nt), f_j, f_j, link_i, link_j])
+ # Require at least one word in phrase
+ if links:
+ phrases.add(form_rule(f_i, new_e_i, f_words[f_i:f_j + 1], e_words[new_e_i:new_e_j + 1], nt, links))
+ extract(f_i, f_j + 1, new_e_i, new_e_j, wc, links, nt, False)
+ nt.pop()
+ span_flip(cover, link_i, link_j)
+ # TODO: try adding NT to start, end, both
+ # check: one aligned word on boundary that is not part of a NT
+
+ # Try to extract phrases from every f index
+ f_i = 0
+ while f_i < f_len:
+ # Skip if phrases won't be tight on left side
+ if not al[f_i]:
+ f_i += 1
+ continue
+ extract(f_i, f_i, f_len + 1, -1, 1, [], [], False)
+ f_i += 1
+
+ for rule in sorted(phrases):
+ print rule
+
+def main(argv):
+
+ extractor = OnlineGrammarExtractor()
+
+ for line in sys.stdin:
+ f_words, e_words, a_str = (x.split() for x in line.split('|||'))
+ alignment = sorted(tuple(int(y) for y in x.split('-')) for x in a_str)
+ extractor.add_instance(f_words, e_words, alignment)
+
+if __name__ == '__main__':
+ main(sys.argv) \ No newline at end of file