授業で作ったNeural Networkでxの二乗を学習するやつ #cpp #NN

nn.cpp

#include <bits/stdc++.h>
#define FOR(i,a,b) for (auto i=(a);i<(b);i++)
#define REP(i,n) for (auto i=0;i<(n);i++)
#define EPS 1e-15

#define I 1
#define H 4
#define O 1
#define N 500
#define alpha 0.35
double x[N][I], y[N][O];
double w[H][I+1], wt[O][H+1];

using namespace std;

double xrand(){
    return (double) rand()/RAND_MAX;
}

void datainit(){
  srand(1);
  REP(i, N){
    x[i][0]=(double) xrand();
    /* y = x * x + NOISE */
    y[i][0]=x[i][0]*x[i][0]+EPS*xrand();
  }
}

void netinit(){
  /* initialize weights at random */
  REP(i, I+1){
    REP(j, H) w[j][i]=xrand();
  }
  REP(i, H+1){
    REP(j, O) wt[j][i]=xrand();
  }
  /* learning rate */
}

double f(double x){
    double t, ti;
    if(fabs(x) > 20.0) return (x>0 ? 1.0:-1.0);
    else{
        t = exp(x);
        ti = 1/exp(x);
        return (t - ti)/(t+ti);
    }
}

double fp(double x){
    return 1 - pow(f(x),2);
}

double g(double x){
    return x;
}

double gp(double x){
    return 1;
}



double ynet(double x[]){
    double s[H],st[H],h[H],t,y[O];
    REP(j, H){
        t = w[j][0]*1; // add bias
        FOR(i,1, I+1) t+=w[j][i]*x[i-1];
        s[j] = t; //sum
        h[j] = f(s[j]);
    }
    REP(j, O){
        t= wt[j][0];
        FOR(i, 1, H+1)t +=wt[j][i]*h[i-1];
        st[j] = t;
        y[j] =  g(st[j]);
    }
    return y[0];
}

void netstep(double x[], double yd[]){
    double z, s[H], st[O], h[H], t, y[O];
    REP(j, H){
        t = w[j][0];
        FOR(i,1, I+1){
            t+=w[j][i]*x[i-1];
        }
        s[j] = t;
        h[j] = f(s[j]);
    } //hidden layer

    REP(j, O){
        t = wt[j][0];
        FOR(i,1, H+1){
            t+=wt[j][i]*h[i-1];
        }
        st[j] = t;
        y[j] = g(st[j]);
    } //output
    /* update weight */
    REP(j, O){
        wt[j][0] += alpha*(yd[j]-y[j])*gp(st[j]);
        FOR(i,1, H+1){
            wt[j][i]+=alpha*(yd[j]-y[j])*gp(st[j])*h[i-1];
        }
    }

    REP(i, I+1){
        REP(j, H){
            z = 0;
            REP(k, O)z+=gp(st[k])*wt[k][j+1]*(yd[k]-y[k]);
            z=z*fp(s[j]);
            if(i==0)w[j][i]+=alpha*z;
            else w[j][i] +=alpha*z*x[i-1];
        }
    }

}

int main(int argc, char const *argv[]) {
    srand((unsigned)time(NULL));
    int j=0, jstep=400;
    double xt[1];
    datainit();
    netinit();
    while(j<jstep){
        REP(i, N){
            netstep(x[i],y[i]);
        }
    j++;
  }
  /* check the network */

  REP(i, 10+1){
    xt[0]=i*0.1;
    printf("x=%7.5f y=%7.5f ynet=%+7.5f\n",xt[0],xt[0]*xt[0],ynet(xt));
  }
    return 0;
}