Merge remote-tracking branch 'upstream/master'

1 files changed, 158 insertions, 0 deletions

diff --git a/extractor/target_phrase_extractor.cc b/extractor/target_phrase_extractor.cc
new file mode 100644
index 00000000..2b8a2e4a
--- /dev/null
+++ b/extractor/target_phrase_extractor.cc
@@ -0,0 +1,158 @@
+#include "target_phrase_extractor.h"
+
+#include <unordered_set>
+
+#include "alignment.h"
+#include "data_array.h"
+#include "phrase.h"
+#include "phrase_builder.h"
+#include "rule_extractor_helper.h"
+#include "vocabulary.h"
+
+using namespace std;
+
+namespace extractor {
+
+TargetPhraseExtractor::TargetPhraseExtractor(
+    shared_ptr<DataArray> target_data_array,
+    shared_ptr<Alignment> alignment,
+    shared_ptr<PhraseBuilder> phrase_builder,
+    shared_ptr<RuleExtractorHelper> helper,
+    shared_ptr<Vocabulary> vocabulary,
+    int max_rule_span,
+    bool require_tight_phrases) :
+    target_data_array(target_data_array),
+    alignment(alignment),
+    phrase_builder(phrase_builder),
+    helper(helper),
+    vocabulary(vocabulary),
+    max_rule_span(max_rule_span),
+    require_tight_phrases(require_tight_phrases) {}
+
+TargetPhraseExtractor::TargetPhraseExtractor() {}
+
+TargetPhraseExtractor::~TargetPhraseExtractor() {}
+
+vector<pair<Phrase, PhraseAlignment> > TargetPhraseExtractor::ExtractPhrases(
+    const vector<pair<int, int> >& target_gaps, const vector<int>& target_low,
+    int target_phrase_low, int target_phrase_high,
+    const unordered_map<int, int>& source_indexes, int sentence_id) const {
+  int target_sent_len = target_data_array->GetSentenceLength(sentence_id);
+
+  vector<int> target_gap_order = helper->GetGapOrder(target_gaps);
+
+  int target_x_low = target_phrase_low, target_x_high = target_phrase_high;
+  if (!require_tight_phrases) {
+    // Extend loose target phrase to the left.
+    while (target_x_low > 0 &&
+           target_phrase_high - target_x_low < max_rule_span &&
+           target_low[target_x_low - 1] == -1) {
+      --target_x_low;
+    }
+    // Extend loose target phrase to the right.
+    while (target_x_high < target_sent_len &&
+           target_x_high - target_phrase_low < max_rule_span &&
+           target_low[target_x_high] == -1) {
+      ++target_x_high;
+    }
+  }
+
+  vector<pair<int, int> > gaps(target_gaps.size());
+  for (size_t i = 0; i < gaps.size(); ++i) {
+    gaps[i] = target_gaps[target_gap_order[i]];
+    if (!require_tight_phrases) {
+      // Extend gap to the left.
+      while (gaps[i].first > target_x_low &&
+             target_low[gaps[i].first - 1] == -1) {
+        --gaps[i].first;
+      }
+      // Extend gap to the right.
+      while (gaps[i].second < target_x_high &&
+             target_low[gaps[i].second] == -1) {
+        ++gaps[i].second;
+      }
+    }
+  }
+
+  // Compute the range in which each chunk may start or end. (Even indexes
+  // represent the range in which the chunk may start, odd indexes represent the
+  // range in which the chunk may end.)
+  vector<pair<int, int> > ranges(2 * gaps.size() + 2);
+  ranges.front() = make_pair(target_x_low, target_phrase_low);
+  ranges.back() = make_pair(target_phrase_high, target_x_high);
+  for (size_t i = 0; i < gaps.size(); ++i) {
+    int j = target_gap_order[i];
+    ranges[i * 2 + 1] = make_pair(gaps[i].first, target_gaps[j].first);
+    ranges[i * 2 + 2] = make_pair(target_gaps[j].second, gaps[i].second);
+  }
+
+  vector<pair<Phrase, PhraseAlignment> > target_phrases;
+  vector<int> subpatterns(ranges.size());
+  GeneratePhrases(target_phrases, ranges, 0, subpatterns, target_gap_order,
+                  target_phrase_low, target_phrase_high, source_indexes,
+                  sentence_id);
+  return target_phrases;
+}
+
+void TargetPhraseExtractor::GeneratePhrases(
+    vector<pair<Phrase, PhraseAlignment> >& target_phrases,
+    const vector<pair<int, int> >& ranges, int index, vector<int>& subpatterns,
+    const vector<int>& target_gap_order, int target_phrase_low,
+    int target_phrase_high, const unordered_map<int, int>& source_indexes,
+    int sentence_id) const {
+  if (index >= ranges.size()) {
+    if (subpatterns.back() - subpatterns.front() > max_rule_span) {
+      return;
+    }
+
+    vector<int> symbols;
+    unordered_map<int, int> target_indexes;
+
+    // Construct target phrase chunk by chunk.
+    int target_sent_start = target_data_array->GetSentenceStart(sentence_id);
+    for (size_t i = 0; i * 2 < subpatterns.size(); ++i) {
+      for (size_t j = subpatterns[i * 2]; j < subpatterns[i * 2 + 1]; ++j) {
+        target_indexes[j] = symbols.size();
+        string target_word = target_data_array->GetWordAtIndex(
+            target_sent_start + j);
+        symbols.push_back(vocabulary->GetTerminalIndex(target_word));
+      }
+      if (i < target_gap_order.size()) {
+        symbols.push_back(vocabulary->GetNonterminalIndex(
+            target_gap_order[i] + 1));
+      }
+    }
+
+    // Construct the alignment between the source and the target phrase.
+    vector<pair<int, int> > links = alignment->GetLinks(sentence_id);
+    vector<pair<int, int> > alignment;
+    for (pair<int, int> link: links) {
+      if (target_indexes.count(link.second)) {
+        alignment.push_back(make_pair(source_indexes.find(link.first)->second,
+                                      target_indexes[link.second]));
+      }
+    }
+
+    Phrase target_phrase = phrase_builder->Build(symbols);
+    target_phrases.push_back(make_pair(target_phrase, alignment));
+    return;
+  }
+
+  subpatterns[index] = ranges[index].first;
+  if (index > 0) {
+    subpatterns[index] = max(subpatterns[index], subpatterns[index - 1]);
+  }
+  // Choose every possible combination of [start, end) for the current chunk.
+  while (subpatterns[index] <= ranges[index].second) {
+    subpatterns[index + 1] = max(subpatterns[index], ranges[index + 1].first);
+    while (subpatterns[index + 1] <= ranges[index + 1].second) {
+      GeneratePhrases(target_phrases, ranges, index + 2, subpatterns,
+                      target_gap_order, target_phrase_low, target_phrase_high,
+                      source_indexes, sentence_id);
+      ++subpatterns[index + 1];
+    }
+    ++subpatterns[index];
+  }
+}
+
+} // namespace extractor