TP/quantization/weight loading refactor part 2 - Refactor quantized linear logic and extend quantization support to all models (#1622)

Refactor the tensor parallelism, quantization, and weight-loading codes.

Summary of the new features enabled by this PR:
- **All models** are able to be quantized with AWQ and SqueezeLLM, and [soon GPTQ](#1580).
- Model loading code became much simpler.
- Support model parallelism for all MQA/GQA models when the number of key/value heads is smaller than the tensor parallel size.

Author: zhuohan123

vllm/config.py

@@ -140,8 +140,8 @@ def get_head_size(self) -> int:
         # FIXME(woosuk): This may not be true for all models.
         return self.hf_config.hidden_size // self.hf_config.num_attention_heads
 
-    def get_num_kv_heads(self, parallel_config: "ParallelConfig") -> int:
-        """Returns the number of KV heads per GPU worker."""
+    def get_total_num_kv_heads(self) -> int:
+        """Returns the total number of KV heads."""
         # For GPTBigCode & Falcon:
         # NOTE: for falcon, when new_decoder_architecture is True, the
         # multi_query flag is ignored and we use n_head_kv for the number of
@@ -155,23 +155,34 @@ def get_num_kv_heads(self, parallel_config: "ParallelConfig") -> int:
             # Multi-query attention, only one KV head.
             # Currently, tensor parallelism is not supported in this case.
             return 1
-        # For Falcon:
-        if getattr(self.hf_config, "n_head_kv", None) is not None:
-            return (self.hf_config.n_head_kv //
-                    parallel_config.tensor_parallel_size)
-        if getattr(self.hf_config, "num_kv_heads", None) is not None:
-            return (self.hf_config.num_kv_heads //
-                    parallel_config.tensor_parallel_size)
-        # For LLaMA-2:
-        if getattr(self.hf_config, "num_key_value_heads", None) is not None:
-            return (self.hf_config.num_key_value_heads //
-                    parallel_config.tensor_parallel_size)
-        # For ChatGLM-2:
-        if getattr(self.hf_config, "multi_query_group_num", None) is not None:
-            return (self.hf_config.multi_query_group_num //
-                    parallel_config.tensor_parallel_size)
-        total_num_attention_heads = self.hf_config.num_attention_heads
-        return total_num_attention_heads // parallel_config.tensor_parallel_size
+
+        attributes = [
+            # For Falcon:
+            "n_head_kv",
+            "num_kv_heads",
+            # For LLaMA-2:
+            "num_key_value_heads",
+            # For ChatGLM:
+            "multi_query_group_num",
+        ]
+        for attr in attributes:
+            num_kv_heads = getattr(self.hf_config, attr, None)
+            if num_kv_heads is not None:
+                return num_kv_heads
+
+        # For non-grouped-query attention models, the number of KV heads is
+        # equal to the number of attention heads.
+        return self.hf_config.num_attention_heads
+
+    def get_num_kv_heads(self, parallel_config: "ParallelConfig") -> int:
+        """Returns the number of KV heads per GPU."""
+        total_num_kv_heads = self.get_total_num_kv_heads()
+        # If tensor parallelism is used, we divide the number of KV heads by
+        # the tensor parallel size. We will replicate the KV heads in the
+        # case where the number of KV heads is smaller than the tensor
+        # parallel size so each GPU has at least one KV head.
+        return max(1,
+                   total_num_kv_heads // parallel_config.tensor_parallel_size)
 
     def get_num_layers(self, parallel_config: "ParallelConfig") -> int:
         total_num_hidden_layers = self.hf_config.num_hidden_layers

vllm/engine/async_llm_engine.py

@@ -142,10 +142,10 @@ def abort_request(self, request_id: str, *, verbose: bool = False) -> None:
 
         self._request_streams[request_id].finish()
 
-    def get_new_and_finished_requests(self) -> Tuple[List[dict], Set[str]]:
+    def get_new_and_finished_requests(self) -> Tuple[List[Dict], Set[str]]:
         """Get the new requests and finished requests to be
         sent to the engine."""
-        new_requests: List[dict] = []
+        new_requests: List[Dict] = []
         finished_requests: Set[str] = set()
 
         while not self._finished_requests.empty():