Merge pull request #4395 from zhouxiao-coder/elu-activation

ELU activation

paddle/operators/activation_op.cc

@@ -201,6 +201,27 @@ class SoftReluOpMaker : public framework::OpProtoAndCheckerMaker {
   }
 };
 
+template <typename AttrType>
+class ELUOpMaker : public framework::OpProtoAndCheckerMaker {
+ public:
+  ELUOpMaker(framework::OpProto *proto, framework::OpAttrChecker *op_checker)
+      : OpProtoAndCheckerMaker(proto, op_checker) {
+    AddInput("X",
+             "(Tensor) The input of ELU operator, it shouldn't be empty. Input "
+             "is flattened and treated as a 1D array.");
+    AddOutput("Y",
+              "(Tensor) The output of ELU operator. It has the same shape as "
+              "the input.");
+    AddAttr<AttrType>(
+        "alpha", "(float, default 1.0) Alpha value in the elu formulation.")
+        .SetDefault(static_cast<AttrType>(1.));
+    AddComment(R"DOC(
+        ELU activation operator. It applies this element-wise computation on
+        the input: f(x) = max(0, x) + min(0, alpha * (exp(x) - 1)).
+        Check .. _Link: https://arxiv.org/abs/1511.07289 for more details.)DOC");
+  }
+};
+
 template <typename AttrType>
 class Relu6OpMaker : public framework::OpProtoAndCheckerMaker {
  public:
@@ -289,6 +310,9 @@ REGISTER_OP(leaky_relu, ops::ActivationOp, ops::LeakyReluOpMaker<float>,
 REGISTER_OP(soft_relu, ops::ActivationOp, ops::SoftReluOpMaker<float>,
             soft_relu_grad, ops::ActivationOpGrad);
 
+REGISTER_OP(elu, ops::ActivationOp, ops::ELUOpMaker<float>, elu_grad,
+            ops::ActivationOpGrad);
+
 REGISTER_OP(relu6, ops::ActivationOp, ops::Relu6OpMaker<float>, relu6_grad,
             ops::ActivationOpGrad);
 

paddle/operators/activation_op.h

@@ -384,6 +384,35 @@ struct LeakyReluGradFunctor : public BaseActivationFunctor<T> {
   }
 };
 
+template <typename T>
+struct ELUFunctor : public BaseActivationFunctor<T> {
+  float alpha;
+  typename BaseActivationFunctor<T>::AttrPair GetAttrs() {
+    return {{"alpha", &alpha}};
+  }
+
+  template <typename Device, typename X, typename Y>
+  void operator()(Device d, X x, Y y) const {
+    y.device(d) =
+        x.cwiseMax(static_cast<T>(0)) +
+        (alpha * (x.exp() - static_cast<T>(1))).cwiseMin(static_cast<T>(0));
+  }
+};
+
+template <typename T>
+struct ELUGradFunctor : public BaseActivationFunctor<T> {
+  float alpha;
+  typename BaseActivationFunctor<T>::AttrPair GetAttrs() {
+    return {{"alpha", &alpha}};
+  }
+  template <typename Device, typename X, typename Y, typename dY, typename dX>
+  void operator()(Device d, X x, Y y, dY dy, dX dx) const {
+    dx.device(d) =
+        dy * (x > static_cast<T>(0)).template cast<T>() +
+        dy * (y + alpha) * (x < static_cast<T>(0)).template cast<T>();
+  }
+};
+
 template <typename T>
 struct PowFunctor : public BaseActivationFunctor<T> {
   float factor;
@@ -455,6 +484,7 @@ struct STanhGradFunctor : public BaseActivationFunctor<T> {
   __macro(pow, PowFunctor, PowGradFunctor);                       \
   __macro(stanh, STanhFunctor, STanhGradFunctor);                 \
   __macro(softsign, SoftsignFunctor, SoftsignGradFunctor);        \
-  __macro(relu6, Relu6Functor, Relu6GradFunctor);                \
   __macro(leaky_relu, LeakyReluFunctor, LeakyReluGradFunctor);    \
-  __macro(tanh_shrink, TanhShrinkFunctor, TanhShrinkGradFunctor)
+  __macro(relu6, Relu6Functor, Relu6GradFunctor);                 \
+  __macro(tanh_shrink, TanhShrinkFunctor, TanhShrinkGradFunctor); \
+  __macro(elu, ELUFunctor, ELUGradFunctor)

python/paddle/v2/framework/tests/test_activation_op.py

@@ -181,6 +181,26 @@ class TestSoftRelu(OpTest):
         self.check_grad(['X'], 'Y', max_relative_error=0.02)
 
 
+class TestELU(OpTest):
+    def setUp(self):
+        self.op_type = "elu"
+        x = np.random.uniform(-3, 3, [4, 4]).astype("float32")
+        alpha = 1.
+        # Note: unlike other Relu extensions, point 0 on standard ELU function (i.e. alpha = 1)
+        # is differentiable, so we can skip modifications like x[np.abs(x) < 0.005] = 0.02 here
+        self.inputs = {'X': x}
+        self.attrs = {'alpha': alpha}
+        self.outputs = {
+            'Y': np.maximum(0, x) + np.minimum(0, alpha * (np.exp(x) - 1))
+        }
+
+    def test_check_output(self):
+        self.check_output()
+
+    def test_check_grad(self):
+        self.check_grad(['X'], 'Y', max_relative_error=0.02)
+
+
 class TestReciprocal(OpTest):
     def setUp(self):
         self.op_type = "reciprocal"