Add speed_exp.cpp

Author: BBuf

Algorithm optimization/README.md

@@ -5,4 +5,5 @@
 - speed_meanFilter_in_gray_image.cpp 使用x86循环展开，openmp优化均值滤波算法
 - speed_medianFilter_in_gray_image.cpp AVX和Openmp，优化中值滤波算法
 - speed_twoVector_distance.cpp AVX和x86循环展开，优化计算两个向量距离算法
-- Huang_Fast_MedianBlur.cpp 利用直方图实现快速中值滤波算法，算法原理：https://blog.csdn.net/just_sort/article/details/87994573
+- Huang_Fast_MedianBlur.cpp 利用直方图实现快速中值滤波算法，算法原理：https://blog.csdn.net/just_sort/article/details/87994573
+- speed_exp.cpp 在神经网络权值较小的情况下的快速exp算法，算法原理：https://blog.csdn.net/just_sort/article/details/88128200

Algorithm optimization/speed_exp.cpp

@@ -0,0 +1,14 @@
+inline float exp1(float x) {
+	x = 1.0 + x / 256.0;
+	x *= x; x *= x; x *= x; x *= x;
+	x *= x; x *= x; x *= x; x *= x;
+	return x;
+}
+
+inline float exp2(double x) { 
+	x = 1.0 + x / 1024;   
+	x *= x; x *= x; x *= x; x *= x;   
+	x *= x; x *= x; x *= x; x *= x;   
+	x *= x; x *= x;   
+	return x; 
+}