fix flops count bug for ConvTranspose2d

imperative/python/megengine/utils/module_stats.py

@@ -84,7 +84,7 @@ def disable_receptive_field():
 
 
 @register_flops(
-    M.Conv1d, M.Conv2d, M.Conv3d, M.ConvTranspose2d, M.LocalConv2d, M.DeformableConv2d
+    M.Conv1d, M.Conv2d, M.Conv3d, M.LocalConv2d, M.DeformableConv2d
 )
 def flops_convNd(module: M.Conv2d, inputs, outputs):
     bias = 1 if module.bias is not None else 0
@@ -93,6 +93,15 @@ def flops_convNd(module: M.Conv2d, inputs, outputs):
         module.in_channels // module.groups * np.prod(module.kernel_size) + bias
     )
 
+@register_flops(
+    M.ConvTranspose2d
+)
+def flops_convNdTranspose(module: M.Conv2d, inputs, outputs):
+    bias = 1 if module.bias is not None else 0
+    # N x Cout x H x W x  (Cin x Kw x Kh + bias)
+    return np.prod(inputs[0].shape) * (
+        module.out_channels // module.groups * np.prod(module.kernel_size)
+    ) + np.prod(outputs[0].shape) * bias
 
 @register_flops(
     M.batchnorm._BatchNorm, M.SyncBatchNorm, M.GroupNorm, M.LayerNorm, M.InstanceNorm,