joddiy commented on a change in pull request #480: SINGA-474 ELU operator
URL: https://github.com/apache/incubator-singa/pull/480#discussion_r309766714
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File path: python/singa/autograd.py
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@@ -358,6 +358,48 @@ def relu(x):
return ReLU()(x)[0]
+class Elu(Operation):
+ def __init__(self,alpha=1):
+ super(Elu, self).__init__()
+ self.alpha=alpha
+
+ def forward(self, x):
+ """Do forward propgation.
+ Store the x if requires gradient.
+ Args:
+ x (CTensor): matrix
+ Returns:
+ a CTensor for the result
+ """
+ #f(x) = alpha * (exp(x) - 1.) for x < 0, f(x) = x for x >= 0
+ if training:
+ self.input = x
+ x1 = singa.LTFloat(x, 0.0)
+ x1 = singa.__mul__(x, x1)
+ x1 = singa.SubFloat(singa.Exp(x1),self.alpha)
Review comment:
I think this formula doesn't correspond to alpha * (exp(x) - 1.)
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