Simple gradient descent example using Codeblocks-EP in C language

The intention of this tutorial is to show you how to set up Codeblocks-EP and use the plotting software called KoolPlot to run a simple gradient descent example and plot it. This is workable in Windows.

First, download CodeBlocks-EP at http://codeblocks.codecutter.org/

Note that this is a different program than the regular CodeBlocks but I am pretty sure it has the same functionality. It seems to be a version to learn from. Install it and open it.

Step 1: Create a new project

Step 2: Select "koolplot project" and click "Go"

Step 3: Select "Add Console" It is not the default so make sure that you select it and then hit next.

Step 4: Name your project "GradientDescent" and click next. On the next screen, click finish.

Step 5: Go to File -> New -> Empty file. Name it GradientDescent.c

Step 6: Right click and select edit and paste the following code:

#include "koolplot.h"

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

int main(int argc, char**argv) {

    /*training set1.2
    1.1
    2.4 2.2
    3.1 3.3
    4.4 4.3
    5.3 5.4
    6.3 6.7
    7.6 7.7
    8.7 8.6
    9.7 9.8*/
    float x[] = {1.2, 2.4, 3.1, 4.4, 5.3, 6.3, 7.6, 8.7, 9.7};
    float y[] = {1.1, 2.2, 3.3, 4.3, 5.4, 6.7, 7.7, 8.6, 9.8};

    /*number of examples*/
    int m = 9;

    /*thetas and temp thetas*/
        float theta0, temp0, theta1, temp1;
        theta0 = 0.0; temp0 = 0.0;
        theta1 = 0.0; temp1 = 0.0;

    /*iterations and learning rate HIGHLY VARIABLE*/
        int iterations = 1000;
        float alpha = 0.03;

        int j = 0;
        float h0 = 0.0;
        float h1 = 0.0;
        int i = 0;
        for(i = 0; i < iterations; i++)
        {

            h0 = 0.0;
        h1 = 0.0;
            for(j = 0; j<m; j++)
            {
                h0 = h0 + ((theta0 + x[j]*theta1) - y[j]);
                    h1 = h1 + ((theta0 + x[j]*theta1) - y[j])*x[j];
            }

    //h0 = h0 / (float)m;
    //h1 = h1 / (float)m;
     temp0 = theta0 - (alpha*h0)/(float)m;
     temp1 = theta1 - (alpha*h1)/(float)m;
     theta0 = temp0;
    theta1 = temp1;
    }

    printf("Theta0: %f\n", theta0);
    printf("Theta1: %f\n", theta1);

    Plotdata xx(0.0, 3.0), yy = theta0 + xx*theta1;
    plot(xx, yy);

    return 0;
}

 Step 7: Select Build -> Build and then Build -> Run

Lastly, if you followed all of these steps it should run. The command console will show the values of theta0 and theta1 and the plot with plot out "y = theta0 + x*theta1" Note that I had to use "xx" and "yy" at the end because these are the variables that koolplot is using to plot and x and y were already used to store our training data. If you click on the plot, you will be able to see the x and y values above. Here is what the output should look like:

And that's it.