xor_nn.cpp

BP模型逼近异或问题

#include <dos.h>
#include <iostream.h>
#include <math.h>
#include<stdlib.h>
#include<time.h>
#include<stdio.h>

#define INPUT 2
#define OUTPUT 1
#define HIDELAYER 2
#define SAMPLES 4
#define NTA 0.5

double w1[INPUT][HIDELAYER];
double w2[HIDELAYER][OUTPUT];
double sample[SAMPLES][INPUT];
double teacher[SAMPLES][OUTPUT];

double Ep[SAMPLES];  //误差
int K[SAMPLES];

double realuniform(double a,double b){//定义随机函数
	double c;
	c=rand()%int(b)/(b-a)+a;
	return c;
}
		
int intuniform(int a,int b){
	int c;
	c=rand()%(b-a)+a;
	return c;
}

double f(double x)          //激活函数
{
    double val;
    val=1.0/(1.0+exp(-0.5*x));
    return val;
}

void init_sample()          //样本初始化
{
    sample[0][0]=0;
    sample[0][1]=0;
    teacher[0][0]=0;

    sample[1][0]=0;
    sample[1][1]=1;
    teacher[1][0]=1;

    sample[2][0]=1;
    sample[2][1]=0;
    teacher[2][0]=1;

    sample[3][0]=1;
    sample[3][1]=1;
    teacher[3][0]=0;
}

void initialize()           //权值初始化
{
    int i,j;
    for(i=0;i<INPUT;i++)
        for(j=0;j<HIDELAYER;j++)
            w1[i][j]=realuniform(0.1,2.0);
    for(i=0;i<HIDELAYER;i++)
        for(j=0;j<OUTPUT;j++)
            w2[i][j]=realuniform(0.1,2.0);
}



void BP()                   //BP算法
{
    int i,j,k,m;
    bool cont;

    double net1[HIDELAYER];
    double net2[OUTPUT];
    double o1[HIDELAYER];
    double o2[OUTPUT];

    double delta2[OUTPUT];
    double delta1[HIDELAYER];
    double deltaW2[HIDELAYER][OUTPUT];
    double deltaW1[INPUT][HIDELAYER];

    k=0;
    cont=false;
    while(k<SAMPLES)
    {
        //正向计算
        for(i=0;i<HIDELAYER;i++){
            net1[i]=0;
            for(j=0;j<INPUT;j++)
                net1[i]+=sample[K[k]][j]*w1[j][i];
            o1[i]=f(net1[i]);
        }
        for(i=0;i<OUTPUT;i++){
            net2[i]=0;
            for(j=0;j<HIDELAYER;j++)
                net2[i]+=o1[j]*w2[j][i];
            o2[i]=f(net2[i]);
        }
        //误差计算
        Ep[K[k]]=0;
        for(i=0;i<OUTPUT;i++)
            Ep[K[k]]+=pow(teacher[K[k]][i]-o2[i],2);
        Ep[K[k]]=1.0/2*sqrt(Ep[K[k]]);
        if(Ep[K[k]]>0.02){
            cont=true;
            //反向计算
            for(j=0;j<OUTPUT;j++){   //输出层
                delta2[j]=-(teacher[K[k]][j]-o2[j])*(1-o2[j])*o2[j];
                for(i=0;i<HIDELAYER;i++)
                    deltaW2[i][j]=(-1)*NTA*delta2[j]*o1[i];
            }
            for(j=0;j<HIDELAYER;j++){    //隐层
                double temp;
                temp=0.0;
                for(m=0;m<OUTPUT;m++)
                    temp+=delta2[m]*w2[j][m];
                delta1[j]=(1-o1[j])*o1[j]*temp;
                for(i=0;i<INPUT;i++)
                    deltaW1[i][j]=(-1)*NTA*delta1[j]*sample[K[k]][i];
            }
            for(i=0;i<INPUT;i++)
                for(j=0;j<HIDELAYER;j++)
                    w1[i][j]+=deltaW1[i][j];
            for(i=0;i<HIDELAYER;i++)
                for(j=0;j<OUTPUT;j++)
                    w2[i][j]+=deltaW2[i][j];
				 cout<<i<<","<<j<<": "<<w1[i][j]<<endl;
				 cout<<i<<","<<j<<": "<<w2[i][j]<<endl;
				 cout<<"EP["<<K[k]<<"]="<<Ep[K[k]]<<endl;
        }
        k++;
        if(k==SAMPLES && cont){
            k=0;
            cont=false;
        }
    }
}

int main(int argc, char* argv[])
{
   
      
    initialize();
    init_sample();
        BP();
     return 0;
}
//---------------------------------------------------------------------------