From 154a6ed29c13eeab9c4f785cf5ca1520ba8ca999 Mon Sep 17 00:00:00 2001
From: Kavya Srinet <kavyasrinet@baidu.com>
Date: Thu, 5 Oct 2017 17:52:10 -0700
Subject: [PATCH] Implementing tanhshrink operator

---
 paddle/operators/activation_op.cc             | 14 +++++++++++++
 paddle/operators/activation_op.h              | 21 ++++++++++++++++++-
 .../v2/framework/tests/test_activation_op.py  | 15 +++++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/paddle/operators/activation_op.cc b/paddle/operators/activation_op.cc
index 5f2ecc2673..66e9d2c401 100644
--- a/paddle/operators/activation_op.cc
+++ b/paddle/operators/activation_op.cc
@@ -97,6 +97,17 @@ class TanhOpMaker : public framework::OpProtoAndCheckerMaker {
   }
 };
 
+class TanhShrinkOpMaker : public framework::OpProtoAndCheckerMaker {
+ public:
+  TanhShrinkOpMaker(framework::OpProto *proto,
+                    framework::OpAttrChecker *op_checker)
+      : OpProtoAndCheckerMaker(proto, op_checker) {
+    AddInput("X", "Input of TanhShrink operator");
+    AddOutput("Y", "Output of TanhShrink operator");
+    AddComment("TanhShrink activation operator, tanhshrink(x) = x - tanh(x)");
+  }
+};
+
 class SqrtOpMaker : public framework::OpProtoAndCheckerMaker {
  public:
   SqrtOpMaker(framework::OpProto *proto, framework::OpAttrChecker *op_checker)
@@ -235,6 +246,9 @@ REGISTER_OP(relu, ops::ActivationOp, ops::ReluOpMaker, relu_grad,
 REGISTER_OP(tanh, ops::ActivationOp, ops::TanhOpMaker, tanh_grad,
             ops::ActivationOpGrad);
 
+REGISTER_OP(tanh_shrink, ops::ActivationOp, ops::TanhShrinkOpMaker,
+            tanh_shrink_grad, ops::ActivationOpGrad);
+
 REGISTER_OP(sqrt, ops::ActivationOp, ops::SqrtOpMaker, sqrt_grad,
             ops::ActivationOpGrad);
 
diff --git a/paddle/operators/activation_op.h b/paddle/operators/activation_op.h
index dae66cc77d..2450601742 100644
--- a/paddle/operators/activation_op.h
+++ b/paddle/operators/activation_op.h
@@ -146,6 +146,24 @@ struct TanhGradFunctor : public BaseActivationFunctor<T> {
   }
 };
 
+// tanhshrink(x) = x - tanh(x)
+// where tanh(x) = (exp(x) - exp(-x)) / (exp(x) + exp(-x))
+template <typename T>
+struct TanhShrinkFunctor : public BaseActivationFunctor<T> {
+  template <typename Device, typename X, typename Y>
+  void operator()(Device d, X x, Y y) const {
+    y.device(d) = x - x.tanh();
+  }
+};
+
+template <typename T>
+struct TanhShrinkGradFunctor : public BaseActivationFunctor<T> {
+  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.tanh() * x.tanh());
+  }
+};
+
 // sqrt(x) = x^(1/2)
 template <typename T>
 struct SqrtFunctor : public BaseActivationFunctor<T> {
@@ -407,4 +425,5 @@ struct STanhGradFunctor : public BaseActivationFunctor<T> {
   __macro(pow, PowFunctor, PowGradFunctor);                      \
   __macro(stanh, STanhFunctor, STanhGradFunctor);                \
   __macro(softsign, SoftsignFunctor, SoftsignGradFunctor);       \
-  __macro(leaky_relu, LeakyReluFunctor, LeakyReluGradFunctor)
+  __macro(leaky_relu, LeakyReluFunctor, LeakyReluGradFunctor);   \
+  __macro(tanh_shrink, TanhShrinkFunctor, TanhShrinkGradFunctor)
diff --git a/python/paddle/v2/framework/tests/test_activation_op.py b/python/paddle/v2/framework/tests/test_activation_op.py
index f232996a55..701e1a1aee 100644
--- a/python/paddle/v2/framework/tests/test_activation_op.py
+++ b/python/paddle/v2/framework/tests/test_activation_op.py
@@ -48,6 +48,21 @@ class TestTanh(OpTest):
         self.check_grad(['X'], 'Y', max_relative_error=0.007)
 
 
+class TestTanhShrink(OpTest):
+    def setUp(self):
+        self.op_type = "tanh_shrink"
+        self.inputs = {
+            'X': np.random.uniform(0.1, 1, [10, 17]).astype("float32")
+        }
+        self.outputs = {'Y': self.inputs['X'] - np.tanh(self.inputs['X'])}
+
+    def test_check_output(self):
+        self.check_output()
+
+    def test_check_grad(self):
+        self.check_grad(['X'], 'Y', max_relative_error=0.008)
+
+
 class TestSqrt(OpTest):
     def setUp(self):
         self.op_type = "sqrt"
-- 
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