[Fix] BaseModel & BaseDataPreprocessor `to` method to be consistent with torch.nn.Module (#783)

* fix BaseModel `to` method to be consistent with torch.nn.Module

* fix data_preprocessor as well

* fix docstring alignment

* fix docstring alignment

mmengine/model/base_model/base_model.py

@@ -155,9 +155,9 @@ class BaseModel(BaseModule):
 
         Returns:
             tuple[Tensor, dict]: There are two elements. The first is the
-            loss tensor passed to optim_wrapper which may be a weighted sum of
-            all losses, and the second is log_vars which will be sent to the
-            logger.
+            loss tensor passed to optim_wrapper which may be a weighted sum
+            of all losses, and the second is log_vars which will be sent to
+            the logger.
         """
         log_vars = []
         for loss_name, loss_value in losses.items():
@@ -177,23 +177,17 @@ class BaseModel(BaseModule):
 
         return loss, log_vars  # type: ignore
 
-    def to(self,
-           device: Optional[Union[int, str, torch.device]] = None,
-           *args,
-           **kwargs) -> nn.Module:
+    def to(self, *args, **kwargs) -> nn.Module:
         """Overrides this method to call :meth:`BaseDataPreprocessor.to`
         additionally.
 
-        Args:
-            device (int, str or torch.device, optional): the desired device
-                of the parameters and buffers in this module.
-
         Returns:
             nn.Module: The model itself.
         """
+        device = torch._C._nn._parse_to(*args, **kwargs)[0]
         if device is not None:
             self._set_device(torch.device(device))
-        return super().to(device)
+        return super().to(*args, **kwargs)
 
     def cuda(
         self,
@@ -244,7 +238,7 @@ class BaseModel(BaseModule):
 
         Args:
             device (torch.device): the desired device of the parameters and
-                    buffers in this module.
+                buffers in this module.
         """
 
         def apply_fn(module):

mmengine/model/base_model/data_preprocessor.py

@@ -84,19 +84,16 @@ class BaseDataPreprocessor(nn.Module):
     def device(self):
         return self._device
 
-    def to(self, device: Optional[Union[int, torch.device]], *args,
-           **kwargs) -> nn.Module:
+    def to(self, *args, **kwargs) -> nn.Module:
         """Overrides this method to set the :attr:`device`
 
-        Args:
-            device (int or torch.device, optional): The desired device of the
-                parameters and buffers in this module.
-
         Returns:
             nn.Module: The model itself.
         """
-        self._device = torch.device(device)
-        return super().to(device)
+        device = torch._C._nn._parse_to(*args, **kwargs)[0]
+        if device is not None:
+            self._device = torch.device(device)
+        return super().to(*args, **kwargs)
 
     def cuda(self, *args, **kwargs) -> nn.Module:
         """Overrides this method to set the :attr:`device`

tests/test_model/test_base_model/test_base_model.py

 # Copyright (c) OpenMMLab. All rights reserved.
+import itertools
 import unittest
 from unittest import TestCase
 
 import torch
 import torch.nn as nn
+from parameterized import parameterized
 from torch.optim import SGD
 
 from mmengine.model import BaseDataPreprocessor, BaseModel
@@ -11,6 +13,18 @@ from mmengine.optim import OptimWrapper
 from mmengine.registry import MODELS
 from mmengine.testing import assert_allclose
 
+dtypes_to_test = [torch.float16, torch.float32, torch.float64, torch.half]
+
+cpu_devices = ['cpu', torch.device('cpu')]
+cuda_devices = ['cuda', 0, torch.device('cuda')]
+devices_to_test = cpu_devices
+if torch.cuda.is_available():
+    devices_to_test += cuda_devices
+
+
+def list_product(*args):
+    return list(itertools.product(*args))
+
 
 @MODELS.register_module()
 class CustomDataPreprocessor(BaseDataPreprocessor):
@@ -158,3 +172,32 @@ class TestBaseModel(TestCase):
         self.assertEqual(model.data_preprocessor._device, torch.device('cuda'))
         self.assertEqual(model.toy_model.data_preprocessor._device,
                          torch.device('cuda'))
+
+    @parameterized.expand(list_product(devices_to_test))
+    def test_to_device(self, device):
+        model = ToyModel().to(device)
+        self.assertTrue(
+            all(p.device.type == torch.device(device).type
+                for p in model.parameters())
+            and model.data_preprocessor._device == torch.device(device))
+
+    @parameterized.expand(list_product(dtypes_to_test))
+    def test_to_dtype(self, dtype):
+        model = ToyModel().to(dtype)
+        self.assertTrue(all(p.dtype == dtype for p in model.parameters()))
+
+    @parameterized.expand(
+        list_product(devices_to_test, dtypes_to_test,
+                     ['args', 'kwargs', 'hybrid']))
+    def test_to_device_and_dtype(self, device, dtype, mode):
+        if mode == 'args':
+            model = ToyModel().to(device, dtype)
+        elif mode == 'kwargs':
+            model = ToyModel().to(device=device, dtype=dtype)
+        elif mode == 'hybrid':
+            model = ToyModel().to(device, dtype=dtype)
+        self.assertTrue(
+            all(p.dtype == dtype for p in model.parameters())
+            and model.data_preprocessor._device == torch.device(device)
+            and all(p.device.type == torch.device(device).type
+                    for p in model.parameters()))