Fix the KeyError when loading bloom-based models (vllm-project#441)

vllm/model_executor/models/bloom.py

@@ -284,10 +284,17 @@ def load_weights(self,
         state_dict = self.state_dict()
         for name, loaded_weight in hf_model_weights_iterator(
                 model_name_or_path, cache_dir, use_np_cache):
-            if not name.startswith("transformer."):
-                name = "transformer." + name
+            if name == "lm_head.weight":
+                # Since hidden_states are parallelized, we need to
+                # load lm_head.weight in parallel.
+                self._column_parallel_weights.append(name)
+                # If lm_head is provided, use it instead.
+                param = self.lm_head_weight
+            else:
+                if not name.startswith("transformer."):
+                    name = "transformer." + name
+                param = state_dict[name]
 
-            param = state_dict[name]
             if "query_key_value" in name:
                 # NOTE(woosuk): BLOOM's fused QKV has the shape of
                 # [num_heads * 3 * head_size, hidden_size], while the