[GitHub] [incubator-singa] nudles commented on a change in pull request #510: SINGA 475 - add min operator

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

nudles commented on a change in pull request #510: SINGA 475 - add min operator
URL: https://github.com/apache/incubator-singa/pull/510#discussion_r313761395
 
 

 ##########
 File path: python/singa/autograd.py
 ##########
 @@ -1945,3 +1945,29 @@ def backward(self, dy):
 
 def sub(a, b):
     return Sub()(a,b)[0]
+
+
+class Min(Operation):
+    def __init__(self):
+        super(Min, self).__init__()    
+    
+    def forward(self, a, b):
+        m = singa.__sub__(a,b)
+        mask0 = singa.LTFloat(m,0) 
+        mask00 = singa.__mul__(singa.LEFloat(m,0),a)
+        mask1 = singa.GTFloat(m,0)
+        mask11=singa.__mul__(mask1,b)
+        mask = singa.__add__(mask00,mask11)
+        
+        if training:
+            self.mask = mask
+            self.mask0 = mask0
+            self.mask1 = mask1
+        return mask
+
+    def backward(self, dy):
+        return (self.mask0,self.mask1)
 
 Review comment:
   dy is not multiplied in the backward?

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