From a61bfd87c71ef6fc559729181726ed761ec50ee3 Mon Sep 17 00:00:00 2001
From: chenjianping <jpc.chen@huawei.com>
Date: Thu, 27 Aug 2020 19:23:25 +0800
Subject: [PATCH] optimize tanh

---
 mindspore/lite/nnacl/fp32/activation.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mindspore/lite/nnacl/fp32/activation.c b/mindspore/lite/nnacl/fp32/activation.c
index dbd61a7260..3cb34cd9ae 100644
--- a/mindspore/lite/nnacl/fp32/activation.c
+++ b/mindspore/lite/nnacl/fp32/activation.c
@@ -62,7 +62,14 @@ int Sigmoid(const float *src, int length, float *dst) {
 
 int Tanh(const float *src, int length, float *dst) {
   for (int i = 0; i < length; ++i) {
-    dst[i] = 1.0f - 2.0f / (exp(2 * src[i]) + 1);
+    float tmp_in = src[i];
+    if (tmp_in > 5.0) {
+      dst[i] = 1.0f;
+    } else if (tmp_in < -5.0) {
+      dst[i] = -1.0f;
+    } else {
+      dst[i] = 1.0f - 2.0f / (exp(2 * tmp_in) + 1);
+    }
   }
   return NNACL_OK;
 }