[Seq2Seq Generation] Call encoder before expanding input_ids (#3370)

src/transformers/modeling_bart.py

@@ -113,6 +113,7 @@ class PretrainedBartModel(PreTrainedModel):
     config_class = BartConfig
     base_model_prefix = "model"
     pretrained_model_archive_map = BART_PRETRAINED_MODEL_ARCHIVE_MAP
+    encoder_outputs_batch_dim_idx = 1  # outputs shaped (seq_len, bs, ...)
 
     def _init_weights(self, module):
         std = self.config.init_std
@@ -888,7 +889,6 @@ class BartForConditionalGeneration(PretrainedBartModel):
             encoder_outputs, decoder_cached_states = past, None
         else:
             encoder_outputs, decoder_cached_states = past
-
         return {
             "input_ids": None,  # encoder_outputs is defined. input_ids not needed
             "encoder_outputs": encoder_outputs,