vivi's CSC236 SLoG

Wow, I can't believe the semester is nearly over! As of this morning, I have officially finished my last class of the semester. All I have left is one assignment due tonight, an essay, and exams. Speaking of class this morning, the test was not hard, but I wouldn't say it was easy either. I had some trouble with the question about the set of regular expressions that didn't have the concatenation property. Oh well, I guess I will have to do well on the final exam to make up for this (and previous tests/assignments.. :P). I was really hoping for a question to ask us to design and construct a DFSA rather than this proof question that I didn't get in the end :(

Well, answering my last question, we looked at how to prove a DFSA this week. It was a lot more straightforward than I thought. Everything was pretty much definition based, for which I am glad. Then things started getting a bit weirder. We began looking at NFSA's and how every regular expression has an FSA. And then how every NFSA can be rewritten as a DFSA. I could follow the pictures Prof. Heap drew, but I had a hard time trying to picture how to apply it to concrete examples. And then finally we learned the cartesian product so that we can build DFSAs for accepting strings with two different properties. Working through the last example at the end of Wednesday's lecture helped reinforce how it worked. I went home and filled in what we started in class. Building a machine that was a union of two different machines was surprisingly a lot easier than I had imagined.

Continuing formal languages, we looked at equivalent regular expressions and then finite state automata. Again, I've looked at finite state machines before while studying regular expressions last year so what Prof. Heap was describing in class was very straightforward. The only new part would be describing and essentially "drawing" the machine in words. Once it's explained, it's pretty easy to write out and understand though. I find it the easiest to draw first and then put it into words and definitions. I wonder how we're going prove that these DFSA's actually represent the regular expression?

So I finally decided to try printing out slides for once, and as expected, it beats copying down notes by a landslide. 

Midterms always turn out to be better than I had thought. Maybe with the exception of Stats...

Iterative program correctness requires a bit more work than recursive correctness. Although a bit trickier, I still prefer this over recurrences and time complexity. The lectures this week were pretty interesting. I am finding myself having trouble determining loop invariants, however. I tried reading the book, and even it says that determining these things just requires practice and thinking. There is no mechanical way of finding it unfortunately :( Also, I am not looking forward to proving iterative correctness on tests. After the double loop example we did in class, I can easily see myself rushing to write out a proof as there are so many steps. Hmm. I can't believe everything we've been doing so far involves induction. I knew we were going to work with induction, but I didn't realize that pretty much our entire course is based on it. 

Unfortunately, I missed the Monday lecture with the guest lecturer because I was frantically studying for another midterm. Anyway, we looked at program correctness this week. I think compared to the material we were covering the last couple of weeks, I find this a lot easier to take in and understand. There is something about time complexity that I just despise. Program correctness, on the other hand, feels more straightforward. I just need to follow the code and check if the postcondition is satisfied or not given the precondition. 

It has been a very stressful and busy midterm period. Although it's still not quite over yet for me, I am going to take some time and try to catch up on my slogging.

As I've mentioned before, I missed Week 5's lectures, and I am still having trouble understanding how to deal with closed form expressions. I had no trouble with Problem Set 3, but the notes on developing a closed form expression for the Fibonacci function haven't exactly 'clicked' for me. Perhaps the midterm stress is the cause, but I do have to admit that I haven't really sat down and investigated it thoroughly.

We looked at the complexity of merge-sort and the Mast Theorem last week. I really need to print out the slides and write on them instead. There were many slides of just text last week, and I tried to write them all down. In the end, I had "see slides online" written after trying to copy everything down, and I didn't get to hear anything Prof. Heap said as I was too busy writing. It's probably better that I print the notes, read them before lecture, and then just follow along the lecture. It's so simple, yet I feel that I need to continue writing up my notes since that is how all my notes for this class have been so far. Anyway, we proved that the time complexity of merge-sort was nlogn. We actually took the code and came up with a time complexity of which we proved by building on several smaller proofs. Or.. I think that's what we did. To be honest, I am somewhat lost at the moment in the course. As things die down, I think I will be able to make sense of everything again. Hopefully.

Well, besides catching up on the course, there's also another problem set and assignment due next Monday. I've looked at the problem set, and it should be somewhat similar to what we did in Wednesday's lecture. I'm having a bit of trouble wording what I want to say though. In fact, throughout this course, I seem to have some problems with the way I present anything. I'm going to have to work on that. The assignment.. won't be too bad, I hope.

I didn't know whether to put this under Week Three or Week Four, but anyway, I finished assignment 1 yesterday, a few hours before it was due. It wasn't all that bad in the end.. but I did have a lot of trouble starting the assignment and figuring out exactly what I needed to do. Question 2 really stumped me because I thought we actually had to prove that our technique works using induction. Instead, the TA told me just to use it to come up with a solution for n+1 meals. I sincerely hope that was what Prof. Heap wanted, otherwise I would have messed up a whole question. 

I'm still working on the assignment.. so I'm going to have to keep this entry short. 

So, the third week of classes are beginning already, yet I still feel an extreme lack of motivation and concentration. I know I should start focussing before I fall behind, but I'm constantly feeling tired from my super spread out schedule, 3 night classes, cooking, cleaning, and my part-time job. I need to work out some sort of schedule to be better organized :S

School has finally started again. It feels like only yesterday that I was still in first year...  except my memory seems to tell me otherwise; I've failed to retain anything after my brain turned off for four whole months. I guess what I meant to say was, summer sure went by quickly. I hope everyone has enjoyed their summer. I know I did. :)