www.pudn.com > bp_cpp.zip > sigmoid.cpp

/* 
 * public/ann/annfunc/sigmoid.c 
 * 2004-05-03 by ShanLanshan 
 */ 
#include "public/ann/annfunc/annfunc.h" 
#include "public/ann/annfunc/sigmoid.h" 
 
namespace ann { 
namespace annfunc { 
namespace sigmoid { 
 
	static bool init(); 
	static void finalize(); 
	static ann_float main_func(ann_float f); 
	static ann_float derivative_func(ann_float f); 
	static ann_float derivative_func2(ann_float f); 
	static void multi_main_func(ann_float *src, ann_int len, ann_float *dst); 
	static void multi_derivative_func(ann_float *src, ann_int len, ann_float *dst); 
	static void multi_derivative_func2(ann_float *src, ann_int len, ann_float *dst); 
 
	extern  AnnFuncGroup g_funcgroup = { 
		"sigmoid", 
		"双曲正切函数", 
		init, 
		finalize, 
		main_func, 
		derivative_func, 
		derivative_func2, 
		multi_main_func, 
		multi_derivative_func, 
		multi_derivative_func2 
	}; 
 
	static bool init() 
	{ 
		return true; 
	} 
 
	static void finalize() {} 
 
	/*  
	 * S型函数  
	 * w = 1 / ( 1 + e ^ (-f)) 
	 */ 
	static ann_float main_func(ann_float f) 
	{ 
		ann_float u; 
		u = pow(E, -f); 
		return 1 / (1 + u); 
	} 
 
	/* S型函数的导数 
	 * 
	 * w = 1 / (1 + e ^ -f) 
	 * Let u = e ^ -f, Then w = 1 / (1 + u), @u/@f = -u 
	 * @w/@u = -1/((1 + u) ^ 2) 
	 * @w/@f = @w/@u * @u/@f = u / ((1 + u) ^ 2), u = e ^ -f 
	 */ 
	static ann_float derivative_func(ann_float f) 
	{ 
		ann_float u; 
		u = pow(E, -f); 
		return u / ((1 + u) * (1 + u)); 
	} 
 
	/*  
	 * 求双曲正切函数的导数值，输入的参数是主函数的值 
	 * 	Let u(f) = e ^ (-f) 
	 * 	w = 1 / (1 + u) 
	 *	@w/@f = u / ((1 + u) ^ 2) 
	 *        = ((1 + u) - 1) / ((1 + u) ^ 2) 
	 *        = w * ((1 + u) - 1) / (1 + u) 
	 *        = w * (1 - w) 
	 */ 
	static ann_float derivative_func2(ann_float f) 
	{ 
		return f * (1 - f); 
	} 
 
	static void multi_main_func(ann_float *src, ann_int len, ann_float *dst) 
	{ 
		ann_float u, f; 
 
		assert(src != NULL); 
		if (dst == NULL) 
			dst = src; 
 
		for (int i=0; i