Use aten backend by default

Author: sovrasov

ptflops/flops_counter.py

@@ -31,7 +31,7 @@ def get_model_complexity_info(model: nn.Module,
                               verbose: bool = False,
                               ignore_modules: List[nn.Module] = [],
                               custom_modules_hooks: Dict[nn.Module, Any] = {},
-                              backend: Union[str, FLOPS_BACKEND] = FLOPS_BACKEND.PYTORCH,
+                              backend: Union[str, FLOPS_BACKEND] = FLOPS_BACKEND.ATEN,
                               flops_units: Optional[str] = None,
                               param_units: Optional[str] = None,
                               output_precision: int = 2) -> Tuple[Union[str, int, None],