remove printing functions from fasttext class

Summary:
This diff removes the print capabilities from fasttext and defines a new api.
- `predictLine` extracts predictions from exactly one line of the input stream.
- the deprecated `printLabelStats` is removed as [js bindings don't use it]( https://www.facebook.com/groups/1174547215919768/?multi_permalinks=2328051983902613&comment_id=2360179150689896 )
- `ngramVectors` is now deprecated by the addition of `getNgramVectors`. `Vector` class remains copy-free but move semantics has been added.
- `analogies` is now deprecated by `getAnalogies`. when called, fastText class lazy-precomputes word vectors
- `findNN` is now deprecated by `getNN`. when called, fastText class lazy-precomputes word vectors
- `trainThread` and `printInfo` functions are now private.
- `supervised`, `cbow`, `skipgram`, `selectEmbeddings`, `precomputeWordVectors` are now deprecated and will be private in the future.
- `saveVectors`, `saveOutput` and `saveModel` without arguments are now deprecated by their equivalent with filename as string argument.

Reviewed By: EdouardGrave

Differential Revision: D13083799

fbshipit-source-id: f557ed7c141a90a6171045fe118ac16c195c824f

python/fastText/FastText.py

@@ -130,12 +130,16 @@ def check(entry):
 
         if type(text) == list:
             text = [check(entry) for entry in text]
-            all_probs, all_labels = self.f.multilinePredict(text, k, threshold)
-            return all_labels, np.array(all_probs, copy=False)
+            predictions = self.f.multilinePredict(text, k, threshold)
+            dt = np.dtype([('probability', 'float64'), ('label', '<U32')])
+            result_as_pair = np.array(predictions, dtype=dt)
+
+            return result_as_pair['label'].tolist(), result_as_pair['probability']
         else:
             text = check(text)
-            pairs = self.f.predict(text, k, threshold)
-            probs, labels = zip(*pairs)
+            predictions = self.f.predict(text, k, threshold)
+            probs, labels = zip(*predictions)
+
             return labels, np.array(probs, copy=False)
 
     def get_input_matrix(self):

python/fastText/pybind/fasttext_pybind.cc

@@ -262,23 +262,30 @@ PYBIND11_MODULE(fasttext_pybind, m) {
              const std::string text,
              int32_t k,
              fasttext::real threshold) {
-            std::vector<std::pair<fasttext::real, int32_t>> predictions;
-            std::vector<std::pair<fasttext::real, std::string>> all_predictions;
             std::stringstream ioss(text);
-            std::shared_ptr<const fasttext::Dictionary> d = m.getDictionary();
-            std::vector<int32_t> words, labels;
-            d->getLine(ioss, words, labels);
-            m.predict(k, words, predictions, threshold);
-            std::transform(
-                predictions.begin(),
-                predictions.end(),
-                std::back_inserter(all_predictions),
-                [&d](const std::pair<fasttext::real, int32_t>& prediction) {
-                  return std::pair<fasttext::real, std::string>(
-                      std::exp(prediction.first),
-                      d->getLabel(prediction.second));
-                });
-            return all_predictions;
+            std::vector<std::pair<fasttext::real, std::string>> predictions;
+            m.predictLine(ioss, predictions, k, threshold);
+
+            return predictions;
+          })
+      .def(
+          "multilinePredict",
+          // NOTE: text needs to end in a newline
+          // to exactly mimic the behavior of the cli
+          [](fasttext::FastText& m,
+             const std::vector<std::string>& lines,
+             int32_t k,
+             fasttext::real threshold) {
+            std::vector<std::vector<std::pair<fasttext::real, std::string>>>
+                allPredictions;
+            std::vector<std::pair<fasttext::real, std::string>> predictions;
+
+            for (const std::string& text : lines) {
+              std::stringstream ioss(text);
+              m.predictLine(ioss, predictions, k, threshold);
+              allPredictions.push_back(predictions);
+            }
+            return allPredictions;
           })
       .def(
           "testLabel",
@@ -303,38 +310,6 @@ PYBIND11_MODULE(fasttext_pybind, m) {
 
             return returnedValue;
           })
-      .def(
-          "multilinePredict",
-          // NOTE: text needs to end in a newline
-          // to exactly mimic the behavior of the cli
-          [](fasttext::FastText& m,
-             const std::vector<std::string>& lines,
-             int32_t k,
-             fasttext::real threshold) {
-            std::pair<
-                std::vector<std::vector<fasttext::real>>,
-                std::vector<std::vector<std::string>>>
-                all_predictions;
-            std::vector<std::pair<fasttext::real, int32_t>> predictions;
-            std::shared_ptr<const fasttext::Dictionary> d = m.getDictionary();
-            std::vector<int32_t> words, labels;
-            for (const std::string& text : lines) {
-              std::stringstream ioss(text);
-              predictions.clear();
-              d->getLine(ioss, words, labels);
-              m.predict(k, words, predictions, threshold);
-              all_predictions.first.push_back(std::vector<fasttext::real>());
-              all_predictions.second.push_back(std::vector<std::string>());
-              for (auto& pair : predictions) {
-                pair.first = std::exp(pair.first);
-                all_predictions.first[all_predictions.first.size() - 1]
-                    .push_back(pair.first);
-                all_predictions.second[all_predictions.second.size() - 1]
-                    .push_back(d->getLabel(pair.second));
-              }
-            }
-            return all_predictions;
-          })
       .def(
           "getWordId",
           [](fasttext::FastText& m, const std::string word) {