joddiy commented on a change in pull request #495: SINGA-475 add SoftSign
operator
URL: https://github.com/apache/incubator-singa/pull/495#discussion_r309593540
##########
File path: python/singa/autograd.py
##########
@@ -1828,3 +1828,26 @@ def backward(self, dy):
def leakyrelu(x, a=0.01):
return LeakyRelu(a)(x)[0]
+
+
+class SoftSign(Operation):
+ def __init__(self):
+ super(SoftSign, self).__init__()
+
+ def forward(self, x):
+ # y = x / (1 + np.abs(x))
+ if training:
+ self.input = x
+ x1 = singa.AddFloat(singa.Abs(x),1.0)
+ y = singa.__div__(x,x1)
+
+ return y
+
+ def backward(self, dy):
+ dx = singa.AddFloat(singa.Abs(self.input),1.0)
Review comment:
``` dy/dx = 1 / ( 1 + |x| ) ^ 2 ```
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