unshared nested_quant_map

bitsandbytes/functional.py

@@ -651,7 +651,7 @@ class QuantState:
     def as_dict(self, packed=False):
         """
         returns dict of tensors and strings to use in serialization via _save_to_state_dict()
-        param: packed -- returns dict[str, torch.Tensor] for state_dict
+        param: packed -- returns dict[str, torch.Tensor] for state_dict fit for safetensors saving
         """
         qs_dict = {
             'quant_type': self.quant_type,
@@ -665,13 +665,14 @@ class QuantState:
             qs_dict.update({
                 'nested_absmax': self.state2.absmax,
                 'nested_blocksize': self.state2.blocksize,
-                'nested_quant_map': self.state2.code,
+                'nested_quant_map': self.state2.code.clone(),  # un-shared to avoid restoring it after shared tensors are removed by safetensors
                 'nested_dtype': str(self.state2.dtype).strip('torch.'),
                 'nested_offset': self.offset.item(),
             })
         if not packed:
             return qs_dict
 
+        # packed format allows serialization of non-tensor components, critical for saving in safetensors format
         qs_packed_dict = {k: v for k, v in qs_dict.items() if isinstance(v, torch.Tensor)}
         non_tensor_dict = {k: v for k, v in qs_dict.items() if not isinstance(v, torch.Tensor)}
         qs_packed_dict["quant_state." + "bitsandbytes__" + self.quant_type] = pack_dict_to_tensor(non_tensor_dict)