fix bf16 load, TODO: refactor cpu dequant

ktransformers/util/custom_gguf.py

@@ -314,10 +314,12 @@ class GGUFLoader:
 
         return values
 
-    def load_gguf_tensor(self, name: str, device:str = "cpu", target_dtype = torch.get_default_dtype())->torch.Tensor:
+    def load_gguf_tensor(self, name: str, device:str = "cpu", target_dtype = None)->torch.Tensor:
         t = self.tensor_info[name]
         if device.lower() == "cpu":
             print(f"loading {name} with CPU")
+        if target_dtype == None:
+            target_dtype = torch.get_default_dtype()
         
         shape = t["shape"]
         ggml_type = t["ggml_type"]
@@ -336,7 +338,7 @@ class GGUFLoader:
         
         blocks_per_iter = 16384
         if num_blocks > blocks_per_iter: # dequant large tensor
-            values = torch.empty((num_blocks, elements_per_block), dtype=torch.float, device=device)
+            values = torch.empty((num_blocks, elements_per_block), dtype=target_dtype, device=device)
             for i in range( (num_blocks + blocks_per_iter - 1) // blocks_per_iter):
                 blocks_begin = i * blocks_per_iter
                 blocks_end = min(blocks_begin + blocks_per_iter, num_blocks)
@@ -347,6 +349,8 @@ class GGUFLoader:
                     cur_values = torch.from_numpy(cur_values.copy())
                 
                 cur_values = cur_values.view(-1, elements_per_block)
+                if ggml_name == "BF16":
+                    cur_values = cur_values.view(torch.bfloat16)
                 values[blocks_begin : blocks_end] = cur_values
         else:
             if "cuda" in device.lower():