1. Elevator Algorithm
B 楊定
B 王育軒
B 陳昶亦

2. At first…. At first , our goal is to find a efficient way for an
elevator model like 二活 , which has four elevators
and twelve floors.

3. Let’s do it
So we start our work like this… Student A is at 4F , he wants to go to 6F so elevator α come to A now additional student B is at 8F , he wants to go to 2F so elevator β come to B now another student C is at 3F , he wants to go to 10F so elevator γ come to C another student D is at 7F , he wants to go to 4F So elevator δ come to D

4. However
However , we sadly found that with more and more student , the situation is beyond our control.
Student D student E student F ….Student Z…StudentAA Student AB….StudentZZ…… 8F 4F 9F 11F

5. Q_____Q
That is goddamn hard……

6. We need change!!
In order to keep us alive , we have to try another way
Our model now is a twenty floors building with one elevator, we use the model to test the three elevator algorithm , to compare them , hoping the result is the same to our initial model

7. Algorithm we used
1.FCFS
Which means “First Come First Serve.” It is the most simple and traditional way to control elevators. The first one who sends the request can take the elevator first.
2.SSTF
Which means “Shortest Seek Time First” It works depending on the shortest distance. It will find out which floor is the closest to the elevator. The elevator goes to that floor, and search the next requested floor according to their distance.

8. Algorithm we used 3. SCAN&LOOK
LOOK is similiar to the SCAN. SCAN makes elevators moving from top to the bottom. Elevators turn back when they reach the top or the bottom. LOOK is an optimization of SCAN. The different is that the elevator turns back when there is no request in the elevator’s direction (up or down) in the time.

9. Our Code (1) struct Request{ int Where;
int When; // Have the same concept about order
// From 1~200
bool visited;
}request[100];
struct Elevator{
int now;
int sum;
int T;
}elevator;

10. Our Code (2) Concept of real time (causality) Other Useful Function
Use in SSTF and LOOK(SCAN)
Output at any time depends on input at the same time and in the past.
Elevators can only respond the request which is sent before now
Ex. if(request[i].When<=elevator.T)…..
Ex2. elevator.T+=step…..
Other Useful Function
bool AllRun()
bool AllRun2(int deraction, int Time)

11. Our Code (3) Three main functions Void FCFS() Void SSTF()
NOT real time algorithm
The most simple one
According to their orders
Void SSTF()
Real time algorithm
Search requests by their time and just finding which is the closest
Void LOOK(int z)
Search requests not only by their time but the elevator’s direction
z=0 means going up, z=1 means going down
Steadier than SSTF

12. Result

13. Conclusion
Obviously, according to our model , SCAN&LOOK is the best way among the three algorithm to manipulate an elevator.
So , we think SCAN&LOOK should be chosen when decide which algorithm to be chosen to manipulate an elevator.

14. Thank you~~~