/*
 * Sample program for CDA5125
 *
 * One neuron neural network, able to learn logic and/or operation
 */

#include <iostream>
#include <math.h> 
#include <stdlib.h>

using namespace std;

double X[4][2] = {{0.0, 0.0}, {0.0, 1.0}, {1.0, 0.0}, {1.0, 1.0}};
double Y[4] = {0.0, 0.0, 0.0, 1.0};

double ii1, ii2;
double w1=0.0, w2=0.0, b=0;
double sum, o;
double err;

double rate = 0.1;

double sigmoid(double x)
{
	return 1/(1+exp(-x));
}

double forward(double i1, double i2)
{
        ii1 = i1; ii2 = i2;
        sum = w1*i1 + w2*i2 + b;
	o = sigmoid(sum);
	return o;
}

double derr_do, do_dsum, dsum_db, dsum_dw1, dsum_dw2;

double backward(double O, double Y)
{
	err = (Y-O) * (Y-O)/2; /* err = 1/2*(t-y)^2 */
	derr_do = O - Y;
        do_dsum = sigmoid(sum)*(1 - sigmoid(sum));
        dsum_db = 1;
        dsum_dw1 = ii1;
        dsum_dw2 = ii2;
        
        b = b - rate * derr_do * do_dsum * dsum_db;
        w1 = w1 - rate * derr_do * do_dsum * dsum_dw1;
        w2 = w2 - rate * derr_do * do_dsum * dsum_dw2;
	/*
        cout << "derr_do= " << derr_do <<  "do_dsum= " << do_dsum << 
                "dsum_db= " << dsum_db << "dsum_dw1= " << dsum_dw1 <<    
		"dsum_dw2= " << dsum_dw2 << "\n";
	*/
}  
	
void train(int iter)
{
	for (int i = 0; i< iter; i++) {
		int ii = random () % 4;
		forward(X[ii][0], X[ii][1]);
		backward(o, Y[ii]);
		/*	
                cout << "train (" << X[ii][0] << ", " << X[ii][1] << "), o=" << o << 
                        ", y=" << Y[ii] << "\n";
                cout << "b = " << b << ", w1=" << w1 << ", w2=" << w2 << "\n";
		*/

                if (i % 10000 == 0) 
			cout << "Iter " << i << ": err =" << err << "\n";
	}
}

int main(int argc, char *argv[]) 
{
        w1 = 0.45; w2 = 0.1; b = 0.3;

	if (argc == 2) train(atoi(argv[1]));
        else train(100000);

        cout << "w1 = " << w1 << ", w2 = " << w2 << ", b = " << b << "\n";

        cout << "0 0 -> " << forward(0, 0) << "\n";
        cout << "0 1 -> " << forward(0, 1) << "\n";
        cout << "1 0 -> " << forward(1, 0) << "\n";
        cout << "1 1 -> " << forward(1, 1) << "\n";
}