[GitHub] [incubator-singa] chrishkchris commented on a change in pull request #488: SINGA -475 add Sign operator to singa

[GitBox <gi...@apache.org>]

chrishkchris commented on a change in pull request #488: SINGA -475 add Sign operator to singa
URL: https://github.com/apache/incubator-singa/pull/488#discussion_r311601386
 
 

 ##########
 File path: python/singa/autograd.py
 ##########
 @@ -1828,3 +1828,18 @@ def backward(self, dy):
 
 def leakyrelu(x, a=0.01):
     return LeakyRelu(a)(x)[0]
+
+
+class Sign(Operation):
+    def forward(self, a):
+        if training:
+            self.input = a
+        return singa.Sign(a)
+
+    def backward(self, dy):
+        dx = singa.MultFloat(dy, 0.0)
+        return dx
+
+
+def sign(a):
+    return Sign()(a)[0]
 
 Review comment:
   change a to x
   def sign(x):
       return Sign()(x)[0]  
   

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