Update Mish to default PyTorch 1.9 version (#2733)

* Update Mish to default PyTorch 1.9 version

monai/networks/blocks/activation.py

@@ -12,6 +12,19 @@
 import torch
 from torch import nn
 
+from monai.utils import optional_import
+
+if optional_import("torch.nn.functional", name="mish")[1]:
+
+ def monai_mish(x):
+ return torch.nn.functional.mish(x, inplace=True)
+
+
+else:
+
+ def monai_mish(x):
+ return x * torch.tanh(torch.nn.functional.softplus(x))
+
 
 class Swish(nn.Module):
  r"""Applies the element-wise function:
@@ -30,6 +43,8 @@ class Swish(nn.Module):
 
  Examples::
 
+ >>> import torch
+ >>> from monai.networks.layers.factories import Act
  >>> m = Act['swish']()
  >>> input = torch.randn(2)
  >>> output = m(input)
@@ -85,6 +100,8 @@ class MemoryEfficientSwish(nn.Module):
 
  Examples::
 
+ >>> import torch
+ >>> from monai.networks.layers.factories import Act
  >>> m = Act['memswish']()
  >>> input = torch.randn(2)
  >>> output = m(input)
@@ -111,10 +128,12 @@ class Mish(nn.Module):
 
  Examples::
 
+ >>> import torch
+ >>> from monai.networks.layers.factories import Act
  >>> m = Act['mish']()
  >>> input = torch.randn(2)
  >>> output = m(input)
  """
 
- def forward(self, input: torch.Tensor) -> torch.Tensor:
- return input * torch.tanh(torch.nn.functional.softplus(input))
+ def forward(self, input: torch.Tensor):
+ return monai_mish(input)