[Fix] Check the version of torchvision in __init__ of DCN (open-mmlab…

…#2556)

mmcv/ops/deform_conv.py

@@ -438,12 +438,9 @@ def _load_from_state_dict(self, state_dict, prefix, local_metadata, strict,
 
 if IS_MLU_AVAILABLE:
     import torchvision
+    from torchvision.ops import deform_conv2d as tv_deform_conv2d
 
     from mmcv.utils import digit_version
-    assert digit_version(torchvision.__version__) >= digit_version(
-        '0.10.0a0'), 'the version of torchvision should be >= 0.10.0'
-
-    from torchvision.ops import deform_conv2d as tv_deform_conv2d
 
     @CONV_LAYERS.register_module('DCN', force=True)
     class DeformConv2dPack_MLU(DeformConv2d):
@@ -471,6 +468,8 @@ class DeformConv2dPack_MLU(DeformConv2d):
         """
 
         def __init__(self, *args, **kwargs):
+            assert digit_version(torchvision.__version__) >= digit_version(
+                '0.10.0a0'), 'the version of torchvision should be >= 0.10.0'
             super().__init__(*args, **kwargs)
 
             self.conv_offset = nn.Conv2d(
@@ -494,7 +493,6 @@ def forward(self, x: Tensor) -> Tensor:  # type: ignore
                     ) == 0, 'batch size must be divisible by im2col_step'
             offset = self.conv_offset(x)
             x = x.type_as(offset)
-            weight = self.weight
-            weight = weight.type_as(x)
+            weight = self.weight.type_as(x)
             return tv_deform_conv2d(x, offset, weight, None, self.stride,
                                     self.padding, self.dilation)

mmcv/ops/modulated_deform_conv.py

@@ -356,11 +356,9 @@ def _load_from_state_dict(self, state_dict, prefix, local_metadata, strict,
 
 if IS_MLU_AVAILABLE:
     import torchvision
+    from torchvision.ops import deform_conv2d as tv_deform_conv2d
 
     from mmcv.utils import digit_version
-    assert digit_version(torchvision.__version__) >= digit_version(
-        '0.10.0a0'), 'the version of torchvision should be >= 0.10.0'
-    from torchvision.ops import deform_conv2d as tv_deform_conv2d
 
     @CONV_LAYERS.register_module('DCNv2', force=True)
     class ModulatedDeformConv2dPack_MLU(ModulatedDeformConv2d):
@@ -383,6 +381,8 @@ class ModulatedDeformConv2dPack_MLU(ModulatedDeformConv2d):
         """
 
         def __init__(self, *args, **kwargs):
+            assert digit_version(torchvision.__version__) >= digit_version(
+                '0.10.0a0'), 'the version of torchvision should be >= 0.10.0'
             super().__init__(*args, **kwargs)
             self.conv_offset = nn.Conv2d(
                 self.in_channels,