Tidy uses of torch.device in Volumes

Summary:
Tidy uses of `torch.device` in `Volumes`:
- Allow `str` or `torch.device` in `Volumes.to()` method
- Consistently use `torch.device` for internal type
- Fix comparison of devices

Reviewed By: nikhilaravi

Differential Revision: D28970876

fbshipit-source-id: c640cc22ced684a54cc450ac38a0f4b3435d47be

pytorch3d/structures/volumes.py

@@ -5,6 +5,7 @@ from typing import List, Optional, Tuple, Union
 
 import torch
 
+from ..common.types import Device, make_device
 from ..transforms import Scale, Transform3d
 from . import utils as struct_utils
 
@@ -694,7 +695,7 @@ class Volumes:
         """
         return copy.deepcopy(self)
 
-    def to(self, device, copy: bool = False) -> "Volumes":
+    def to(self, device: Device, copy: bool = False) -> "Volumes":
         """
         Match the functionality of torch.Tensor.to()
         If copy = True or the self Tensor is on a different device, the
@@ -703,30 +704,34 @@ class Volumes:
         then self is returned.
 
         Args:
-          **device**: Device id for the new tensor.
+            device: Device (as str or torch.device) for the new tensor.
-          **copy**: Boolean indicator whether or not to clone self. Default False.
+            copy: Boolean indicator whether or not to clone self. Default False.
 
         Returns:
             Volumes object.
         """
-        if not copy and self.device == device:
+        device_ = make_device(device)
+        if not copy and self.device == device_:
             return self
+
         other = self.clone()
-        if self.device != device:
+        if self.device == device_:
-            other.device = device
+            return other
+
+        other.device = device_
         # pyre-fixme[16]: `List` has no attribute `to`.
-            other._densities = self._densities.to(device)
+        other._densities = self._densities.to(device_)
         if self._features is not None:
             # pyre-fixme[16]: `Optional` has no attribute `to`.
-                other._features = self.features().to(device)
+            other._features = self.features().to(device_)
-            other._local_to_world_transform = (
+        other._local_to_world_transform = self.get_local_to_world_coords_transform().to(
-                self.get_local_to_world_coords_transform().to(device)
+            device_
         )
-            other._grid_sizes = self._grid_sizes.to(device)
+        other._grid_sizes = self._grid_sizes.to(device_)
         return other
 
     def cpu(self) -> "Volumes":
-        return self.to(torch.device("cpu"))
+        return self.to("cpu")
 
     def cuda(self) -> "Volumes":
-        return self.to(torch.device("cuda"))
+        return self.to("cuda")

tests/test_volumes.py

@@ -445,38 +445,65 @@ class TestVolumes(TestCaseMixin, unittest.TestCase):
         Test the moving of the volumes from/to gpu and cpu
         """
 
-        device = torch.device("cuda:0")
-        device_cpu = torch.device("cpu")
-
         features = torch.randn(
-            size=[num_volumes, num_channels, *size], device=device, dtype=torch.float32
+            size=[num_volumes, num_channels, *size], dtype=torch.float32
         )
-        densities = torch.rand(size=[num_volumes, 1, *size], device=device, dtype=dtype)
+        densities = torch.rand(size=[num_volumes, 1, *size], dtype=dtype)
+        volumes = Volumes(densities=densities, features=features)
+
+        # Test support for str and torch.device
+        cpu_device = torch.device("cpu")
+
+        converted_volumes = volumes.to("cpu")
+        self.assertEqual(cpu_device, converted_volumes.device)
+        self.assertEqual(cpu_device, volumes.device)
+        self.assertIs(volumes, converted_volumes)
+
+        converted_volumes = volumes.to(cpu_device)
+        self.assertEqual(cpu_device, converted_volumes.device)
+        self.assertEqual(cpu_device, volumes.device)
+        self.assertIs(volumes, converted_volumes)
+
+        cuda_device = torch.device("cuda:0")
+
+        converted_volumes = volumes.to("cuda:0")
+        self.assertEqual(cuda_device, converted_volumes.device)
+        self.assertEqual(cpu_device, volumes.device)
+        self.assertIsNot(volumes, converted_volumes)
+
+        converted_volumes = volumes.to(cuda_device)
+        self.assertEqual(cuda_device, converted_volumes.device)
+        self.assertEqual(cpu_device, volumes.device)
+        self.assertIsNot(volumes, converted_volumes)
+
+        # Test device placement of internal tensors
+        features = features.to(cuda_device)
+        densities = features.to(cuda_device)
 
         for features_ in (features, None):
-            v = Volumes(densities=densities, features=features_)
+            volumes = Volumes(densities=densities, features=features_)
 
-            v_cpu = v.cpu()
+            cpu_volumes = volumes.cpu()
-            v_cuda = v_cpu.cuda()
+            cuda_volumes = cpu_volumes.cuda()
-            v_cuda_2 = v_cuda.cuda()
+            cuda_volumes2 = cuda_volumes.cuda()
-            v_cpu_2 = v_cuda_2.cpu()
+            cpu_volumes2 = cuda_volumes2.cpu()
 
-            for v1, v2 in itertools.combinations(
+            for volumes1, volumes2 in itertools.combinations(
-                (v, v_cpu, v_cpu_2, v_cuda, v_cuda_2), 2
+                (volumes, cpu_volumes, cpu_volumes2, cuda_volumes, cuda_volumes2), 2
             ):
-                if v1 is v_cuda and v2 is v_cuda_2:
+                if volumes1 is cuda_volumes and volumes2 is cuda_volumes2:
                     # checks that we do not copy if the devices stay the same
                     assert_fun = self.assertIs
                 else:
                     assert_fun = self.assertSeparate
-                assert_fun(v1._densities, v2._densities)
+                assert_fun(volumes1._densities, volumes2._densities)
                 if features_ is not None:
-                    assert_fun(v1._features, v2._features)
+                    assert_fun(volumes1._features, volumes2._features)
-                for v_ in (v1, v2):
+                for volumes_ in (volumes1, volumes2):
-                    if v_ in (v_cpu, v_cpu_2):
+                    if volumes_ in (cpu_volumes, cpu_volumes2):
-                        self._check_vars_on_device(v_, device_cpu)
+                        self._check_vars_on_device(volumes_, cpu_device)
                     else:
-                        self._check_vars_on_device(v_, device)
+                        self._check_vars_on_device(volumes_, cuda_device)
 
     def _check_padded(self, x_pad, x_list, grid_sizes):
         """