From 6d43674e6b224281e43ccefc87224a7ba2fbb99a Mon Sep 17 00:00:00 2001
From: Paul Baltescu <pauldb89@gmail.com>
Date: Sun, 10 Mar 2013 01:01:01 +0000
Subject: Added comments. Hooray!

---
 extractor/translation_table.cc | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

(limited to 'extractor/translation_table.cc')

diff --git a/extractor/translation_table.cc b/extractor/translation_table.cc
index 1852a357..45da707a 100644
--- a/extractor/translation_table.cc
+++ b/extractor/translation_table.cc
@@ -23,6 +23,8 @@ TranslationTable::TranslationTable(shared_ptr<DataArray> source_data_array,
   unordered_map<int, int> target_links_count;
   unordered_map<pair<int, int>, int, PairHash> links_count;
 
+  // For each pair of aligned source target words increment their link count by
+  // 1. Unaligned words are paired with the NULL token.
   for (size_t i = 0; i < source_data_array->GetNumSentences(); ++i) {
     vector<pair<int, int> > links = alignment->GetLinks(i);
     int source_start = source_data_array->GetSentenceStart(i);
@@ -40,25 +42,28 @@ TranslationTable::TranslationTable(shared_ptr<DataArray> source_data_array,
     for (pair<int, int> link: links) {
       source_linked_words[link.first] = 1;
       target_linked_words[link.second] = 1;
-      IncreaseLinksCount(source_links_count, target_links_count, links_count,
+      IncrementLinksCount(source_links_count, target_links_count, links_count,
           source_sentence[link.first], target_sentence[link.second]);
     }
 
     for (size_t i = 0; i < source_sentence.size(); ++i) {
       if (!source_linked_words[i]) {
-        IncreaseLinksCount(source_links_count, target_links_count, links_count,
-                           source_sentence[i], DataArray::NULL_WORD);
+        IncrementLinksCount(source_links_count, target_links_count, links_count,
+                            source_sentence[i], DataArray::NULL_WORD);
       }
     }
 
     for (size_t i = 0; i < target_sentence.size(); ++i) {
       if (!target_linked_words[i]) {
-        IncreaseLinksCount(source_links_count, target_links_count, links_count,
-                           DataArray::NULL_WORD, target_sentence[i]);
+        IncrementLinksCount(source_links_count, target_links_count, links_count,
+                            DataArray::NULL_WORD, target_sentence[i]);
       }
     }
   }
 
+  // Calculating:
+  //   p(e | f) = count(e, f) / count(f)
+  //   p(f | e) = count(e, f) / count(e)
   for (pair<pair<int, int>, int> link_count: links_count) {
     int source_word = link_count.first.first;
     int target_word = link_count.first.second;
@@ -72,7 +77,7 @@ TranslationTable::TranslationTable() {}
 
 TranslationTable::~TranslationTable() {}
 
-void TranslationTable::IncreaseLinksCount(
+void TranslationTable::IncrementLinksCount(
     unordered_map<int, int>& source_links_count,
     unordered_map<int, int>& target_links_count,
     unordered_map<pair<int, int>, int, PairHash>& links_count,
-- 
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