README

README
======

I did it as a part of homework problem in the Machine Learning class taught by Prof Daniel Gildea 
(https://www.cs.rochester.edu/~gildea/) in Spring 2014. In this code, I solved the primal problem of Support Vector
Machine (SVM) using Stochastic Gradient Descent (SGD).
==========================================================================================================

Name: Md. Iftekhar Tanveer
Email: itanveer@cs.rochester.edu  or  go2chayan@gmail.com
Course: CS446
Homework: Implement SVMs with SGD for the voting dataset, and compare results with the previous assignment. 
	Use the dev set to experiment with different values of the capacity parameter C and the learning rate.


************** Files ***************
README: This document
progAss2.py: The original python script. Just run the file using python. The main function will automatically called.
voting2.dat: Dataset file

************* Algorithm ************
1. repeat
2. for n = 1, ... N
3. if 1 - y(n)w'x(n) + b > 0
4.		w = w - eta*(1/N w - C*y(n)*x(n))
5. 		b = b - eta*(C/N)
6. else
7. 		w = w - eta*(w/N)
8. eta = eta0/time 


************* Results **************
Accuracy is ~89% ... (may change in each run due to random sampling)
To be honest, there is not much improvement from the last attempts.
Earlier, I got about 88% accuracy. Now it looks like 89% but sometimes,
it performs worse

************* Interpretations *****
I have noticed that low values of C gives better accuracy in test set.
May be it is because low C allows wider margin which eventually increases the accuracy
for unknown sample.

I tried random shuffling the data but looks like thats not a good
thing to do because in that case I am comparing the C and eta
on a variable basis. That means it is not legitimate to compare those
values anymore if I shuffle the dataset.

I tried many different maximum iteration. But looks like using a large max iteration
in fact reducing the accuracy

************* References ************
I used exponential grid search for C and learning rate. The idea of exponential grid
is actually borrowed from this libSVM tutorial:
http://www.csie.ntu.edu.tw/~cjlin/papers/guide/guide.pdf