Correct truncation for RoBERTa in 2-input GLUE

examples/utils_glue.py

@@ -422,8 +422,9 @@ def convert_examples_to_features(examples, label_list, max_seq_length,
             tokens_b = tokenizer.tokenize(example.text_b)
             # Modifies `tokens_a` and `tokens_b` in place so that the total
             # length is less than the specified length.
-            # Account for [CLS], [SEP], [SEP] with "- 3"
-            _truncate_seq_pair(tokens_a, tokens_b, max_seq_length - 3)
+            # Account for [CLS], [SEP], [SEP] with "- 3". " -4" for RoBERTa.
+            special_tokens_count = 4 if sep_token_extra else 3
+            _truncate_seq_pair(tokens_a, tokens_b, max_seq_length - special_tokens_count)
         else:
             # Account for [CLS] and [SEP] with "- 2" and with "- 3" for RoBERTa.
             special_tokens_count = 3 if sep_token_extra else 2