Week#7

I found it's easier to perform a proof with the implication format than conjunction or dis-junction formats.

During my tutorial this week on Tuesday, our TA told me the same thing and showed us how to prove the problems with a conjunction as the consequence.

For example,

this is not easy to prove under the original format. So, first we remove the negation.

Then change the conjunction part to the implication format.

De Morgan's Law is the most famous one to use for this situation. And by bi-implication, P(x) => Q(x) is equivalent to NOT P(x) V Q(x). Therefore NOT NOT (y > x) is simply (y > x), and NOT (Ay > Ax) can be re-written as (Ay <= Ax).

Voila!! Now we can pick x, assume y is a typical natural number and assume y > x, then find out if the sequence provided has an example of the existential; the sequence provided is A = 2,3,4,8,9,7,5,3,1,0,0,0,0,0,..... where Ai = 0 for i >= 10.

I have to remember this or I may screw up on the next mid-term again...

Week#6

Since I had a mid-term test, there is not much thing to note here for CSC165H1.

For Week#6, I want to note here about CSC200Y. First of all, I want to mention here about why I'm taking the 200 level course.

Most of the students who are taking CSC165H1 should be a first-year student. But my case is different. My official year of study is second year, because I already have bachelor's degree in economics from Glendon College. So I have one-year equivalent credits that are four 100 level and one 200 level; total is five full-year credits. This is sort of good and bad. Since I already have four 100 level courses in my status, the limitation to BSc regulation, saying I'm not supposed to take more than six 100 level courses, bothers me. I've already had CSC108H1 from summer 2014, and am currently taking CSC148H1, CSC165H1 and PSY100H1 (PSY for my general education requirement). H means half year course, so I'm stuck with the six-100-level-courses regulation right at the start. Then I had to choose whatever the course starts with 200. That is why I'm taking CSC200.

The thing is that the course (CSC200) is quite interesting. Some parts of the course cover Game Theory which I put much focus when I was at Glendon College.

So why am I studying Game Theory for computer science? Well... the course hasn't reached there yet, but basically CSC200 is about graph theory with nodes and edges.

My first impression was; what is it?? But the prof started to talk about social network such as Facebook and Twitter, and I realized that this is somehow related to computer science.

Since the course is year-long, I do not have much thing to update today. But I see the network nodes and edges in Linkedin. In Linkedin, there is a graph showing you how you connect with the friend. This graph as a whole must be huge. CSC200 teaches about this big graph.

http://www.cs.cornell.edu/home/kleinber/networks-book/

The material for CSC200 is online for free, by the way.

For WEEK#7, I will update about Game Theory and about CSC165 (proof).

Week#5

There was a mid-term exam for CSC165 this week. The test was not that hard, but I found how I was unable to think fast. I was quite good at exams in general, but fixing my 5-year blank of non-school life is still being in process.

I think I just have to get used to it.

There is not much new topic to note about CSC165 this week. We started to talk about proof. This is something I've done it when I was in high school over 2 decades ago. Again, I have to get used to this. My problem is I cannot find algebraic logic quickly, even though I was very good at mathematics. If you don't use math for a while, it's easy to forget it.

I think we will do more proofs next week. I think I will just have to practice more. I wish this course had a kind of bible type textbook like Calculus and Statistics...

Week#4

I remember when I was a marketing manager for Japanese food distributor, due dates flock into a single week. Is this nostalgia or nightmare? The due dates for all courses I'm taking are coming this week (including some quiz and term tests). There will be mid-term for this course too.

That's also the reason why my blog is late this week. I have been struggling to set up Linkedin and Piazza for summer internship. (I've never used Linkedin before, but it seems this is necessary to find a new job... (Ref: https://ca.linkedin.com/in/spencerogawa )

Actually, I'm quite good for this week except one transformation which I had misunderstood how it works.

P => (Q => (R => S))

P => (Q => (not R v S))

This transformation is true if R implies S, this is equivalent to not R or S. I totally misunderstood this transformation and I realized (fixed) it during the tutorial.

I think I'm ready for the mid-term.

Now the course is going to PROOF. To be honest, I've done PROOF when I was in highs school (almost two decades ago in Tokyo). Oh well... I have to refresh everything from a scratch...