week 8- iterative correctness

was quite confused about this week's lecture. Didn't understand the part about 7m+n=7a+b+i. The proof made a little sense to me but i just didn't understand the 1st part. This proof is rather similar to that of the previous week's proof. Just this time we have to count the i-th iteration in as well.

Do we have to make use of PWO at this point? To show that at the next iteration, we will always end up with a smaller variable and it will get smaller and smaller until it reaches 0. Is that how we are supposed to make use to PWO? How to apply PWO in this case?

A2 was a disaster. It took way longer than i expected. So as a result i did not finish it. But come to think of it, it was quite impossible for me to finish it. With 2 midterms on 22 and 23, 207 E3 and a group report due on monday then followed 207 midterm on wednesday, it was quite a challenge to finish my work on time. Just bad bad planning on my part.

I know danny reads our blogs...some help maybe? Haha. But oh well..can't ask for anything since i am responsible for my own work. Just hope to survive this course..........

week 7 - program corectness

Program correctness was taught this week. Proving correctness seemed rather straight forward. From what i understand, the key is to go slow and go line by line. We start at line 1 of the code and then probe deeper into the chunk of code. Since PS4 is about proving a python program, this is what i am going to do. I will start at the first line, and then just explain what the code will do at each iteration. It's rather similar to that example danny did in class but just not that complex. I just have to make sure my proof satisfies the postcondition.

We also did GCD. Nothing much to say about that.

Luckily PS4 is going to be due on monday instead. If not, with tests on wednesday and thursday, i wonder if i will complete PS4 on time without the extension.

week 6 - complexity of merge sort master theorem

This week we had a shorter lecture due to Thanksgiving. The proof of mergeSort looks simple. Again..it's Danny who is doing it. But after reading it over and over again, it makes more sense now. We also did the Master Theorem, a kind of strategy that works somewhat like the mergeSort. We divide a problem into smaller components then combine solutions. Since the solutions are now split up into smaller parts, it should be easier to solve.

But the question is, how to apply the general theorem? on slide 9 there T(n) is equal to 3 different formulas depending if its value relative to b^l.

Now for PS3, after reading the hint for PS3, it was a little easier to write out a proof. Just kept unwinding and unwinding. It's just a sum of 3^n, n starts at 0. I shall use that as a starting point for my proof then. Another PS done. 3 more PS and many many more tests to go.

week 5 - closed form of recurrence, structural induction, gcd

Just finished test 1 this week. I was so worried about test 1 since i had no clue about most of the material. I studied and studied a week ago but still felt that i was not properly prepared. But fortunately, the test was fair. Phew.

I did not attend lecture today since i really needed some sleep after studying all night for the two nights before the test. Too tired to attend lecture.

week 4 - recursive definitions

A1 was quite bad for me. Could not figure out how PWO worked for the golden ratio question. Luckily the bulletin board provided some answers. I won't expect much for A1 now. The second question about the repeating menus is interesting. I figured out the cycle for the 3 meals. But a technique? Whao...i feel stupid for not being able to answer that. Perhaps i started really really late. That's why i don't have enough time to figure it out.

Evening lectures are killing me. But i don't want to make the blog to vent my frustrations. I should use this blog as something to describe my experience for 236. I'll try to stop doing that now.

This week we did recursive definitions. As usual, i had no idea what danny was talking about during lecture. I did some reading up back at home and found that it was not as bad as it seems.It's all about unwinding etc...but i am rather confused about base cases. When do we need 2 or more of them? Oh well maybe i will ask danny when i have the chance to visit him during office hours. I need to check with him about my PS1 too. I think the TA lost it!!! I didn't get a grade for PS1. :(


ok hell season is officially starting for me. Starting from next week, i will have tests and assignments due every week and i am not only talking about 1...at least 2 per week. Let's hope i can keep up with my csc236 work. Test 1 is coming up next week too. I have to start early this time.