nn0.c

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

#define ROUNDS 100

float outval(float w, float x) {
	return w * x;
}

float err(float a, float b) {
	return (a-b)*(a-b);
}

float avg_err(float w) {
	const float dx = 0.001;
	int num_subdiv = 0;
	float sum = 0.0;

	for (float x = 0.0; x < 1.0; x += dx, num_subdiv++) {
		// got: outval(w, x)
		// expected: x
		sum += err(outval(w, x), x);
	}

	return sum / (float)num_subdiv;
}

float err_slope(float w) {
	const float dw = 0.0001;
	float err1 = avg_err(w), err2 = avg_err(w + dw);
	return (err2 - err1) / dw;
}

// returns a new value of w.
float epoch(float w) {
	const float learn_rate = 1.0;

	float slope = err_slope(w);
	printf("slope = %f; ", slope);
	// found local minimum

	return w - (learn_rate * slope);
}

int main() {
	float w = 0.0;
	int weight_correct;

	for (int i = 0; i < ROUNDS; i++) {
		printf("Round %d: w is %f; ", i, w);
		w = epoch(w);
		printf("w becomes %f\n", w);

	}

	printf("Final model: outval(0.3) = %f\n", outval(w, 0.3));

	return 0;
}