[ Misc ] Remove `fp8_shard_indexer` from Col/Row Parallel Linear (Simplify Weight Loading) (#5928)

Co-authored-by: Robert Shaw <rshaw@neuralmagic>

vllm/model_executor/layers/linear.py

@@ -269,10 +269,6 @@ class ColumnParallelLinear(LinearBase):
             self.register_parameter("bias", None)
 
     def weight_loader(self, param: Parameter, loaded_weight: torch.Tensor):
-        # Special case for Fp8 scales.
-        fp8_scales_shard_indexer = getattr(param, "fp8_scales_shard_indexer",
-                                           None)
-
         tp_rank = get_tensor_model_parallel_rank()
         output_dim = getattr(param, "output_dim", None)
         param_data = param.data
@@ -281,11 +277,11 @@ class ColumnParallelLinear(LinearBase):
             start_idx = tp_rank * shard_size
             loaded_weight = loaded_weight.narrow(output_dim, start_idx,
                                                  shard_size)
-        # Special case for Fp8 scales.
-        elif fp8_scales_shard_indexer is not None:
-            param_data, loaded_weight = fp8_scales_shard_indexer(param_data,
-                                                                 loaded_weight,
-                                                                 shard_id=0)
+
+        # Special case for loading scales off disk, which often do not
+        # have a shape (such as in the case of AutoFP8).
+        if len(loaded_weight.shape) == 0:
+            loaded_weight = loaded_weight.reshape(1)
 
         assert param_data.shape == loaded_weight.shape
         param_data.copy_(loaded_weight)
@@ -751,10 +747,6 @@ class RowParallelLinear(LinearBase):
             self.register_parameter("bias", None)
 
     def weight_loader(self, param: Parameter, loaded_weight: torch.Tensor):
-        # Special case for Fp8 scales.
-        fp8_scales_shard_indexer = getattr(param, "fp8_scales_shard_indexer",
-                                           None)
-
         tp_rank = get_tensor_model_parallel_rank()
         input_dim = getattr(param, "input_dim", None)
         param_data = param.data
@@ -764,13 +756,9 @@ class RowParallelLinear(LinearBase):
             loaded_weight = loaded_weight.narrow(input_dim, start_idx,
                                                  shard_size)
 
-        # Special case for Fp8 scales.
-        elif fp8_scales_shard_indexer is not None:
-            param_data, loaded_weight = fp8_scales_shard_indexer(param_data,
-                                                                 loaded_weight,
-                                                                 shard_id=0)
-
-        if fp8_scales_shard_indexer is None and len(loaded_weight.shape) == 0:
+        # Special case for loading scales off disk, which often do not
+        # have a shape (such as in the case of AutoFP8).
+        if len(loaded_weight.shape) == 0:
             loaded_weight = loaded_weight.reshape(1)
 
         assert param_data.shape == loaded_weight.shape