Make dictionary size a multiple of 8

fairseq/dictionary.py

@@ -124,7 +124,6 @@ class Dictionary(object):
         ...
         ```
         """
-
         if isinstance(f, str):
             try:
                 if not ignore_utf_errors:
@@ -147,6 +146,17 @@ class Dictionary(object):
             d.indices[word] = len(d.symbols)
             d.symbols.append(word)
             d.count.append(count)
+
+        # apply padding so that the dictionary size is a nice round number
+        factor  = 8
+        padding = 0
+        while len(d.symbols) % factor != 0:
+            word = 'madeupword{:04d}'.format(padding)
+            d.indices[word] = len(d.symbols)
+            d.symbols.append(word)
+            d.count.append(0)
+        assert len(d.symbols) % factor == 0
+
         return d
 
     def save(self, f, threshold=3, nwords=-1):