Add an unit test for BleuScorer.

The test contains only ngram counting. More tests for calculating
BLEU score are reuiqred.

mert/BleuScorerTest.cpp

@@ -0,0 +1,155 @@
+#include "BleuScorer.h"
+
+#define BOOST_TEST_MODULE MertBleuScorer
+#include <boost/test/unit_test.hpp>
+
+#include "Ngram.h"
+#include "Vocabulary.h"
+#include "Util.h"
+
+namespace {
+
+NgramCounts* g_counts = NULL;
+
+NgramCounts* GetNgramCounts() {
+  assert(g_counts);
+  return g_counts;
+}
+
+void SetNgramCounts(NgramCounts* counts) {
+  g_counts = counts;
+}
+
+struct Unigram {
+  Unigram(const std::string& a) {
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(a));
+  }
+  NgramCounts::Key instance;
+};
+
+struct Bigram {
+  Bigram(const std::string& a, const std::string& b) {
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(a));
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(b));
+  }
+  NgramCounts::Key instance;
+};
+
+struct Trigram {
+  Trigram(const std::string& a, const std::string& b, const std::string& c) {
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(a));
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(b));
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(c));
+  }
+  NgramCounts::Key instance;
+};
+
+struct Fourgram {
+  Fourgram(const std::string& a, const std::string& b,
+           const std::string& c, const std::string& d) {
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(a));
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(b));
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(c));
+    instance.push_back(mert::VocabularyFactory::GetVocabulary()->Encode(d));
+  }
+  NgramCounts::Key instance;
+};
+
+void CheckUnigram(const std::string& str) {
+  Unigram unigram(str);
+  NgramCounts::Value v;
+  BOOST_CHECK(GetNgramCounts()->Lookup(unigram.instance, &v));
+}
+
+void CheckBigram(const std::string& a, const std::string& b) {
+  Bigram bigram(a, b);
+  NgramCounts::Value v;
+  BOOST_CHECK(GetNgramCounts()->Lookup(bigram.instance, &v));
+}
+
+void CheckTrigram(const std::string& a, const std::string& b,
+                  const std::string& c) {
+  Trigram trigram(a, b, c);
+  NgramCounts::Value v;
+  BOOST_CHECK(GetNgramCounts()->Lookup(trigram.instance, &v));
+}
+
+void CheckFourgram(const std::string& a, const std::string& b,
+                   const std::string& c, const std::string& d) {
+  Fourgram fourgram(a, b, c, d);
+  NgramCounts::Value v;
+  BOOST_CHECK(GetNgramCounts()->Lookup(fourgram.instance, &v));
+}
+
+} // namespace
+
+BOOST_AUTO_TEST_CASE(bleu_reference_type) {
+  BleuScorer scorer;
+  // BleuScorer will use "closest" by default.
+  BOOST_CHECK_EQUAL(scorer.GetReferenceLengthType(), BleuScorer::CLOSEST);
+
+  scorer.SetReferenceLengthType(BleuScorer::AVERAGE);
+  BOOST_CHECK_EQUAL(scorer.GetReferenceLengthType(), BleuScorer::AVERAGE);
+
+  scorer.SetReferenceLengthType(BleuScorer::SHORTEST);
+  BOOST_CHECK_EQUAL(scorer.GetReferenceLengthType(), BleuScorer::SHORTEST);
+}
+
+BOOST_AUTO_TEST_CASE(bleu_count_ngrams) {
+  BleuScorer scorer;
+
+  std::string line = "I saw a girl with a telescope .";
+  // In the above string, we will get the 25 ngrams.
+  //
+  // unigram: "I", "saw", "a", "girl", "with", "telescope", "."
+  // bigram:  "I saw", "saw a", "a girl", "girl with", "with a", "a telescope"
+  //          "telescope ."
+  // trigram: "I saw a", "saw a girl", "a girl with", "girl with a",
+  //          "with a telescope", "a telescope ."
+  // 4-gram:  "I saw a girl", "saw a girl with", "a girl with a",
+  //          "girl with a telescope", "with a telescope ."
+  NgramCounts counts;
+  BOOST_REQUIRE(scorer.CountNgrams(line, counts, kBleuNgramOrder) == 8);
+  BOOST_CHECK_EQUAL(25, counts.size());
+
+  mert::Vocabulary* vocab = scorer.GetVocab();
+  BOOST_CHECK_EQUAL(7, vocab->size());
+
+  std::vector<std::string> res;
+  Tokenize(line.c_str(), ' ', &res);
+  std::vector<int> ids(res.size());
+  for (std::size_t i = 0; i < res.size(); ++i) {
+    BOOST_CHECK(vocab->Lookup(res[i], &ids[i]));
+  }
+
+  SetNgramCounts(&counts);
+
+  // unigram
+  for (std::size_t i = 0; i < res.size(); ++i) {
+    CheckUnigram(res[i]);
+  }
+
+  // bigram
+  CheckBigram("I", "saw");
+  CheckBigram("saw", "a");
+  CheckBigram("a", "girl");
+  CheckBigram("girl", "with");
+  CheckBigram("with", "a");
+  CheckBigram("a", "telescope");
+  CheckBigram("telescope", ".");
+
+  // trigram
+  CheckTrigram("I", "saw", "a");
+  CheckTrigram("saw", "a", "girl");
+  CheckTrigram("a", "girl", "with");
+  CheckTrigram("girl", "with", "a");
+  CheckTrigram("with", "a", "telescope");
+  CheckTrigram("a", "telescope", ".");
+
+  // 4-gram
+  CheckFourgram("I", "saw", "a", "girl");
+  CheckFourgram("saw", "a", "girl", "with");
+  CheckFourgram("a", "girl", "with", "a");
+  CheckFourgram("girl", "with", "a", "telescope");
+  CheckFourgram("with", "a", "telescope", ".");
+}

mert/Jamfile

@@ -50,6 +50,7 @@ exe pro : pro.cpp mert_lib ..//boost_program_options ;
 
 alias programs : mert extractor evaluator pro ;
 
+unit-test bleu_scorer_test : BleuScorerTest.cpp mert_lib ..//boost_unit_test_framework ;
 unit-test feature_data_test : FeatureDataTest.cpp mert_lib ..//boost_unit_test_framework ;
 unit-test data_test : DataTest.cpp mert_lib ..//boost_unit_test_framework ;
 unit-test ngram_test : NgramTest.cpp mert_lib ..//boost_unit_test_framework ;