[shardformer] update gptj model (#5503)

Author: wangbluo

colossalai/shardformer/modeling/gptj.py

@@ -123,11 +123,9 @@ def gptj_model_forward(
         head_mask = self.get_head_mask(head_mask, self.config.n_layer)
 
         # position id to be assigned not just for the first stage for attn input
-        if position_ids is not None:
-            position_ids = position_ids.view(-1, seq_length)
-        else:
+        if position_ids is None:
             position_ids = torch.arange(0, seq_length, dtype=torch.long, device=device)
-            position_ids = position_ids.unsqueeze(0).view(-1, input_shape[-1])
+            position_ids = position_ids.unsqueeze(0)
         if stage_manager.is_first_stage():
             if inputs_embeds is None:
                 inputs_embeds = self.wte(input_ids)
@@ -172,21 +170,15 @@ def gptj_model_forward(
                 all_hidden_states = all_hidden_states + (hidden_states,)
 
             if self.gradient_checkpointing and self.training:
-
-                def create_custom_forward(module):
-                    def custom_forward(*inputs):
-                        # None for past_key_value
-                        return module(*inputs, use_cache, output_attentions)
-
-                    return custom_forward
-
-                outputs = torch.utils.checkpoint.checkpoint(
-                    create_custom_forward(block),
+                outputs = self._gradient_checkpointing_func(
+                    block.__call__,
                     hidden_states,
                     None,
                     attention_mask,
                     position_ids,
                     head_mask[i],
+                    use_cache,
+                    output_attentions,
                 )
             else:
                 outputs = block(
@@ -603,7 +595,9 @@ def forward(
             value = torch.cat((past_value, value), dim=1)
 
         if use_cache is True:
-            present = (key, value)
+            # Note that this cast is quite ugly, but is not implemented before ROPE as the original codebase keeps the key in float32 all along the computation.
+            # Reference: https://github.com/kingoflolz/mesh-transformer-jax/blob/f8315e3003033b23f21d78361b288953064e0e76/mesh_transformer/layers.py#L128
+            present = (key.to(hidden_states.dtype), value)
         else:
             present = None