[Fix] Fix saconv (#1147)

* fix saconv

* update

* update

* fix

* use LooseVersion

mmcv/ops/saconv.py

@@ -100,6 +100,9 @@ class SAConv2d(ConvAWS2d):
         switch = self.switch(avg_x)
         # sac
         weight = self._get_weight(self.weight)
+        zero_bias = torch.zeros(
+            self.out_channels, device=weight.device, dtype=weight.dtype)
+
         if self.use_deform:
             offset = self.offset_s(avg_x)
             out_s = deform_conv2d(x, offset, weight, self.stride, self.padding,
@@ -108,6 +111,9 @@ class SAConv2d(ConvAWS2d):
             if (LooseVersion(TORCH_VERSION) < LooseVersion('1.5.0')
                     or TORCH_VERSION == 'parrots'):
                 out_s = super().conv2d_forward(x, weight)
+            elif LooseVersion(TORCH_VERSION) >= LooseVersion('1.8.0'):
+                # bias is a required argument of _conv_forward in torch 1.8.0
+                out_s = super()._conv_forward(x, weight, zero_bias)
             else:
                 out_s = super()._conv_forward(x, weight)
         ori_p = self.padding
@@ -123,8 +129,12 @@ class SAConv2d(ConvAWS2d):
             if (LooseVersion(TORCH_VERSION) < LooseVersion('1.5.0')
                     or TORCH_VERSION == 'parrots'):
                 out_l = super().conv2d_forward(x, weight)
+            elif LooseVersion(TORCH_VERSION) >= LooseVersion('1.8.0'):
+                # bias is a required argument of _conv_forward in torch 1.8.0
+                out_l = super()._conv_forward(x, weight, zero_bias)
             else:
                 out_l = super()._conv_forward(x, weight)
+
         out = switch * out_s + (1 - switch) * out_l
         self.padding = ori_p
         self.dilation = ori_d