作業提交時間：10月9日上課前。
Design and implement an Elevator Scheduler to aim for both correctness and performance, in managed code.
Skills to learn and practice:
a) Peer to peer collaboration
b) Requirement Analysis
c) Design by contract, Interface design and comprehension
d) Test Driven Development, Unit Test
e) Algorithm design
f) Implementation
1. Background
Imagine we’re building a tall office building, it has the following configuration about elevators:
Building has 21 floors, 4 elevators, many passengers use these elevators everyday (passenger weight: average 70kg. max 120kg, min 45kg).
Other constant data: Elevator speed, door open/close time, passenger time for going in/out of the elevator. We can make reasonable assumptions about these.
The building has 21 floors, from floor 0, 1, ... to 20. Floor 0 is the underground parking level, floor 1 is the lobby level. Most people come in/out the building via these 2 floors.
| Elevator name |
Service floor list |
Passenger limit |
Weight limit |
| 1 |
All floors |
10 |
800 kg |
| 2 |
All floors |
12 |
1000 kg |
| 3 |
All floors |
20 |
1500 kg |
| 4 |
All floors |
20 |
2000 kg |
2. Requirement to Student pairs
A framework with a naive algorithm is prepared and shared to students. The core task for students is to design and implement the scheduling algorithm. Students need to write their own scheduler class (implements the IScheduler interface), Update the SchedulerFactory.CreateScheduler method so the test framework can instantiate your class.
TA will come up with a consistent testing model to test your program according to the “rush hour” scenario (see below), and record the total travel time of each passengers.
Total Travel Time = the time delta between the passenger appears in front of the elevator, and the time she gets off the elevator at this designated floor.
You (student pair) have:
1) A set of API
2) A naive solution (BUS program)
3) A set of test cases to run
Explanation of BUS program:
We can have a naive algorithm called “BUS”. BUS algorithm treats an elevator as a bus, it goes from bottom to top, stops at every floor, opens its door, to let people in and out (if any), then closes the door and moves on. After it reaches the top floor, it will go down and stop at each floor again. This algorithm can serve all requests, but it’s apparently not the fastest algorithm.
Your code is required to be managed code (C#, managed C++, etc).
It has to generate 0 (zero) VS Code Analysis warnings and errors.
It has to be correct
It has to be fast
Score guideline: TA will evaluate the “average total travel time” for all passengers in the same test case, the lower, the better. If your performance is slower than “bus” solution, you get 0 points; if your program can’t deliver any passenger to the correct destination, you get 0 points.
One hint about elevator scheduling: When total weight is within 45 kg of the max limit, or the number of passengers is already at maximum, the elevator doesn’t need to stop for more external requests.
The elevator scheduler program doesn’t know how many passengers are waiting on each floor, it doesn’t know how many passengers will show up either. This is the same with the real world situation.
3. Testing
TA will simulate a “rush hour” (上下班高峰時刻) test. The “rush hour” test is to simulate the come-to-work and leave-work scenario in a business building, which has the following 2 parts (they can be run next to each other).
1) Simple test. 20 passengers
20 people going thru random floors within 5 minutes.
2) Come-to-work. 1000 total passengers
a) 80% of them goes from floor 0 and 1 to all other floors, the destination is distributed evenly. The time each passenger arrives at the elevator can be emulated as a normal distribution.
b) 20% of them are going between any 2 floors of [2, 20], very few people travel between 2 adjacent floors (e.g. from floor 5 to 4). Other than this, the distribution is also even.
3) Leave-work. 1000 total passengers
a) 90% of them go from other floors to floor 1 or floor 0.
b) 10% of them travel between floors [2, 20], again, Very few people travel between 2 adjacent floors.
4. 作業步驟
| 作業 |
博客要求 (寫1個博客，附加題的解法寫另一個博客) 博客注明結對編程人員的名字/或學號后3位.
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| 看教科書和其它參考書, 網站中關於結對編程的章節。例如: |
照至少一張照片, 展現兩人在一起合作編程的情況。 說明結對編程的優點和缺點。 結對的每一個人的優點和缺點在哪里 (要列出至少三個優點和一個缺點)。 |
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| 看教科書和其它資料中關於 Information Hiding, interface design, loose coupling 的章節
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說明怎樣利用這些好的設計方法。 |
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| 看 Design by Contract, Code Contract 的內容: |
描述這些做法的優缺點, 說明你是如何把它們融入你的作業中的。 |
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| 看教科書中，網上有關 unit test 的內容 http://www.cnblogs.com/xinz/archive/2011/11/20/2255830.html
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通過截屏顯示你是如何用VS 的unit test 來保證你寫的類的質量的。顯示unit test 對你的寫的類(class) 的覆蓋率 |
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| 閱讀有關 UML 的內容 |
畫出UML 圖顯示各個實體之間的關系 (畫一個圖即可) |
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| 實現你的算法 |
說明你的算法的關鍵 （不必列出源代碼）, 以及獨到之處。
把你的代碼簽入TFS (問老師要權限及小組的路徑) |
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| [附加題] 改進電梯調度的interface 設計, 讓它更好地反映現實, 更能讓學生練習算法, 更好地實現信息隱藏和信息共享。 |
目前的設計有什么缺點, 你會如何改進它? Analyze the API design, and propose a better API so that Scheduler can have more freedom and students can do more realistic scheduling. |
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| [附加題] 目前的這個測試程序只有命令行界面, 請給它設計UI界面, 顯示乘客/電梯的運動, 並實現之。 |
Implement a UI to show how people/elevator moves (write a blog to show your code and UI)
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| [附加題] 閱讀有關 MVC 和 MVVM 設計模式的文章。 |
說明你寫的電梯調度的UI /Algorithm/interface 如何實現了MVC 或MVVM 的算法。 |
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| [附加題] 我們現在的題目是假設所有電梯到達所有的樓層。 在現實生活中, 多部電梯到達的樓層都不一樣。如果是這樣 (例如3號電梯能到達10 – 20 層, 4 號電梯能到達5-15 層)，整個程序框架和你的電梯調度模塊要做什么改變? |
請說明你的改進意見 |
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