Open source codes of each paper

Usually when you read a journal paper and happen to to like it. So you want to implement their idea. Now the problem occurs, how can I implement those ideas? I need to work out every detail to work it out. Also only when you work it out in detail, you can say you understand it since you make computer understand it.

Why do all papers have their code attached? I will do it for all my papers from now on.

• to make my code more organized
• to make my work better known by others if they can see how concrete results come out
• to improve the work if I can get the feedback from others.

To queue or not to queue

It is not about the book To queue or not to queue. It is about my experience today.

Today, I sit in the Wendy's from 10:30am to 2:50pm to read and think. When I realized that I soon need to have lunch, there is waiting line. Then it becomes an optimization problem. My hungry degree increases by time. I don't want to waiting in the line waste my time not doing meaningful things. The length of waiting line is changing. What should I do?!

It turns out that I was poor to make that decision. I waited until that I cannot stand more and joined a long line. What is the form of best strategy under this situation? What if I have perfect information or not? Is any similiar situation in the real business situation?

Two OR applications in Florida Trip

The first one is queueing theory.
When I was in Magic Kingdom, I found an interesting application of queueing theor - Fast Pass. The procedure is the following. 1) When you see a waiting line is quite long at one attraction say Space Mountain, you can insert your ticket in one machine to get a fast pass which indicates you return during the specific time usually one or two hours laters. 2) Then when you return after playing other stuffs, you can go through the fast pass line.
There are several key points. 1) Once you get your fast pass for one attraction, you cannot get fast pass for another attraction until your current fast pass expire. For example, if I get fast pass for Space Mountain from 1pm to 2pm. I can only get fast pass for Splash Mountain after 2pm. 2) The number of fast pass in one attraction must be limited. Since the available time for the fast pass is different at different attraction, the hotter the attraction is, the longer time difference between available time of fast pass and current will be. In the last attraction-Jungle Cruise we go at 5pm, its fast pass is unavailable. We need to wait 40mins to play.
The decision to make for the visitor. 1) What is the sequence of attraction I should follow. 2) Which attraction should I get the fast pass.
The decision to make for the Theme Park. 1) How much fast passes to available at each attraction and each time periods.
Game theory might not be suitable in this case. Probably, something like priority queue plus abandon and other customer behavior can be used to formulate the problem.

My experience of fast pass in Unversal Studio at CA is different. We got the fast pass after we experienced a half hour technique difficulty at Jurassic Park. Then we can get into fast pass line for every attraction. But actually, you need to spend 30$ to get one fast pass. So the decision for the theme park is how much fast pass to offer and how much to charge.

The second one is network flow. It is very wise decision to buy a GPS just before this trip. We don't need to print every map. And we can avoid the traffic jam in the high way by going through the local. It was very crucial when we tried to catch up our flight back. And the calculation of route is very fast, it is much faster than O(A) I learned last semester. But actually it can only calculate the route from two points. If I want to go several points a day, I need to manually choose the sequence of points I need to goal. If GPS can provide the function of solve small TSP problem such as 5 points, it will be wonderful. Since real map satisfy triangle inequality, there is heuristic to get solution within 1.5 time of optimal solution. So the calculation time won't increase a lot.

Arby's coupon

Yesterday night, I came to Arby's to have my dinner to save my time. I use the coupon Arby's sends out to me every month. I just raised my hypothesis before I order:
People eat insides are more price intensive so that more people use coupon than those who drive through.
Supposing my hypothesis is true, if Arby's send out the coupon to everyone no matter whether they prefers to eat inside or drive through, then it may lose potential revenue since it increases the chance of using coupon among the driving through persons. After I observe during my dinner, four transaction occurs all including coupon. That increases my confidence on my hypothesis.

A naive way is to replace current strategy with only putting coupon inside the store.

Again, we can build a model to help Arby's to improve their revenue

Diaper and Beer

From WSJ:

Tesco's computers often turn up counterintuitive results. Shoppers who buy diapers for the first time at a Tesco store can expect to receive coupons by mail for baby wipes, toys -- and beer. Tesco's analysis showed that new fathers tend to buy more beer because they are home with the baby and can't go to the pub.

Detailer can be founded in a blog called Data Doghouse.
Giving causation to the correlation given by the statistics is quite interesting:
More interesting and probable OR people can do is the following:
We have N items with correlation matrix, and we want to put them in the shelf togather to gain maximum profit. It is quite similar to the facility layout problem. And we may also hope to change the layout as little as we can, since the customer use to current layout.