This program is based on the following page
https://qiita.com/ufoo68/items/9e4ca04578ba0f5fa5ff
This program solves the XOR problem using MLP with one hidden layer.
#include <stdio.h>
#include <math.h>
#include <time.h>
#include <stdlib.h>
//num of units
#define NUM_INPUT 2
//#define NUM_HIDDEN 20
#define NUM_HIDDEN 2
double sigmoid(double x) {
return 1/(1+exp(-x));
}
//derivative of sigmoid function
double d_sigmoid(double x) {
double a = 0.1;
return a*x*(1-x);
}
int main(void) {
srand((unsigned)time(NULL));
//train data
double train_x[4][NUM_INPUT+1] = {{0, 0, -1},{0, 1, -1},{1, 0, -1},{1, 1, -1}};
double d[4] = {0, 1, 1, 0};
//net
double w[NUM_HIDDEN+1][NUM_INPUT+1];
double v[NUM_HIDDEN+1];
double y[4][NUM_HIDDEN+1];
double z[4];
double eta = 0.1;
int epoch = 1000000;
//other
int i, j, k, l;
double tmp = 0;
//update weights using rand()
for(l=0; l<NUM_HIDDEN+1; l++) {
for(i=0; i<NUM_INPUT+1; i++) {
w[l][i] = ((double)rand() / ((double)RAND_MAX + 1));
}
}
for(i=0; i<NUM_HIDDEN+1; i++) {
v[i] = ((double)rand() / ((double)RAND_MAX + 1));
}
//tain
for(k=0; k<epoch; k++) {
//feedforward
for(j=0; j<4; j++) {
//hidden
for(l=0; l<NUM_HIDDEN; l++) {
for(i=0; i<NUM_INPUT+1; i++) {
tmp += train_x[j][i] * w[l][i];
}
y[j][l] = sigmoid(tmp);
tmp = 0;
}
y[j][NUM_HIDDEN] = -1;
//output
for(i=0; i<NUM_HIDDEN+1; i++) {
tmp += y[j][i] * v[i];
}
z[j] = sigmoid(tmp);
tmp = 0;
//backward
//output
for(i=0; i<NUM_HIDDEN+1; i++) {
v[i] = v[i] - eta * y[j][i] * d_sigmoid(z[j]) * (z[j] - d[j]);
}
//hidden
for(l=0; l<NUM_INPUT+1; l++) {
for(i=0; i<NUM_HIDDEN+1; i++) {
w[i][l] = w[i][l] - eta * train_x[j][l] * d_sigmoid(y[j][i]) * d_sigmoid(z[j]) * (z[j] - d[j]) * v[i];
}
}
}
/*
//print detail
printf("z=");
for(i=0; i<4; i++) {
printf("%f ", z[i]);
}
printf("epoch:%d\n",k);
*/
}
//predict
for(j=0; j<4; j++) {
//hidden
for(l=0; l<NUM_HIDDEN; l++) {
for(i=0; i<NUM_INPUT+1; i++) {
tmp += train_x[j][i] * w[l][i];
}
y[j][l] = sigmoid(tmp);
tmp = 0;
}
y[j][NUM_HIDDEN] = -1;
//output
for(i=0; i<NUM_HIDDEN+1; i++) {
tmp += y[j][i] * v[i];
}
z[j] = sigmoid(tmp);
tmp = 0;
}
//print result
printf("z=");
for(i=0; i<4; i++) {
printf("%f ", z[i]);
}
printf("epoch:%d\n",k);
for(i=0; i<NUM_INPUT+1; i++) {
for(l=0; l<NUM_HIDDEN+1; l++) {
printf("w[%d][%d]:%f\n", i, l, w[i][l]);
}
}
for(i=0; i<NUM_HIDDEN+1; i++) {
printf("v[%d]:%f\n",i, v[i]);
}
return 0;
}
Save this program as a name "mlp.c", compile ">gcc mlp.c" and execute ">./a.exe"
