Tidy uses of torch.device in Pointclouds

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

Reviewed By: nikhilaravi

Differential Revision: D28970221

fbshipit-source-id: 3ca7104d4c0d9b20b0cff4f00e3ce931c5f1528a

pytorch3d/structures/pointclouds.py

@@ -2,6 +2,7 @@
 
 import torch
 
+from ..common.types import Device, make_device
 from . import utils as struct_utils
 
 
@@ -130,7 +131,7 @@ class Pointclouds:
         Refer to comments above for descriptions of List and Padded
         representations.
         """
-        self.device = None
+        self.device = torch.device("cpu")
 
         # Indicates whether the clouds in the list/batch have the same number
         # of points.
@@ -175,7 +176,6 @@ class Pointclouds:
         if isinstance(points, list):
             self._points_list = points
             self._N = len(self._points_list)
-            self.device = torch.device("cpu")
             self.valid = torch.zeros((self._N,), dtype=torch.bool, device=self.device)
             self._num_points_per_cloud = []
 
@@ -700,7 +700,7 @@ class Pointclouds:
                 setattr(other, k, v.detach())
         return other
 
-    def to(self, device, copy: bool = False):
+    def to(self, device: Device, copy: bool = False):
         """
         Match functionality of torch.Tensor.to()
         If copy = True or the self Tensor is on a different device, the
@@ -709,34 +709,39 @@ class Pointclouds:
         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.
 
         Returns:
           Pointclouds 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:
-            other.device = device
-            if other._N > 0:
-                other._points_list = [v.to(device) for v in other.points_list()]
-                if other._normals_list is not None:
-                    other._normals_list = [n.to(device) for n in other.normals_list()]
-                if other._features_list is not None:
-                    other._features_list = [f.to(device) for f in other.features_list()]
-            for k in self._INTERNAL_TENSORS:
-                v = getattr(self, k)
-                if torch.is_tensor(v):
-                    setattr(other, k, v.to(device))
+        if self.device == device_:
+            return other
+
+        other.device = device_
+        if other._N > 0:
+            other._points_list = [v.to(device_) for v in other.points_list()]
+            if other._normals_list is not None:
+                other._normals_list = [n.to(device_) for n in other.normals_list()]
+            if other._features_list is not None:
+                other._features_list = [f.to(device_) for f in other.features_list()]
+        for k in self._INTERNAL_TENSORS:
+            v = getattr(self, k)
+            if torch.is_tensor(v):
+                setattr(other, k, v.to(device_))
         return other
 
     def cpu(self):
-        return self.to(torch.device("cpu"))
+        return self.to("cpu")
 
     def cuda(self):
-        return self.to(torch.device("cuda"))
+        return self.to("cuda")
 
     def get_cloud(self, index: int):
         """

tests/test_pointclouds.py

@@ -633,6 +633,33 @@ class TestPointclouds(TestCaseMixin, unittest.TestCase):
         with self.assertRaises(ValueError):
             clouds.extend(N=-1)
 
+    def test_to(self):
+        cloud = self.init_cloud(5, 100, 10)  # Using device "cuda:0"
+
+        cuda_device = torch.device("cuda:0")
+
+        converted_cloud = cloud.to("cuda:0")
+        self.assertEqual(cuda_device, converted_cloud.device)
+        self.assertEqual(cuda_device, cloud.device)
+        self.assertIs(cloud, converted_cloud)
+
+        converted_cloud = cloud.to(cuda_device)
+        self.assertEqual(cuda_device, converted_cloud.device)
+        self.assertEqual(cuda_device, cloud.device)
+        self.assertIs(cloud, converted_cloud)
+
+        cpu_device = torch.device("cpu")
+
+        converted_cloud = cloud.to("cpu")
+        self.assertEqual(cpu_device, converted_cloud.device)
+        self.assertEqual(cuda_device, cloud.device)
+        self.assertIsNot(cloud, converted_cloud)
+
+        converted_cloud = cloud.to(cpu_device)
+        self.assertEqual(cpu_device, converted_cloud.device)
+        self.assertEqual(cuda_device, cloud.device)
+        self.assertIsNot(cloud, converted_cloud)
+
     def test_to_list(self):
         cloud = self.init_cloud(5, 100, 10)
         device = torch.device("cuda:1")