代做CSI3131、Virtual Campus代写、代做Java程序、代写Java编程

日期：2019-03-23 11:15

CSI3131

Assignment 2 Winter 2019

Semaphores/inter-thread synchronization

You must submit your assignment on-line with Virtual Campus. This is

the only method by which we accept assignment submissions. Do not send

any assignment by email. We will not accept them. We are not able to

enter a mark if the assignment is not submitted on Virtual Campus! The

deadline date is firm since you cannot submit an assignment passed the

deadline. You are responsible for the proper submission of your

assignments and you cannot appeal for having failed to do so. A mark of 0

will be assigned to any missing assignment.

Assignments must be done individually. Any team work, and any

work copied from a source external to the student (including solutions

of past year assignments) will be considered as an academic fraud and

will be forwarded to the Faculty of Engineering for imposition of

sanctions. Hence, if you are judged to be guilty of an academic fraud,

you should expect, at the very least, to obtain an F for this course.

Note that we will use sophisticated software to compare your

assignments (with other student's and with other sources...). This

implies that you must take all the appropriate measures to make sure

that others cannot copy your assignment (hence, do not leave your

workstation unattended).

Goal: Practise semaphore usage.

Posted:

Due:

Description (Please read the complete assignment document before starting.)

SIMULATING AN HARBOUR

Consider an Harbour used for launching international tourist ships. The Harbour has 2

launching/arriving docks. There are 4 ships offering trips to 2 possible destinations. The

ship destination is determined by the launching/arriving dock used. Each ship is capable

of taking 2 passengers, and can go to any of the destinations. At the beginning, all ships

start with zero passengers. There are 10 passengers. The behaviour of ships and

passengers is captured in the following pseudo code:

Ship:

for (;;) {

Wait until there is an empty launch/arriving dock.

Land at the Harbour on an empty dock.

The passengers currently in the ship (if any) leave the ship.

Announce that the passengers can board to the destination

determined by the dock used.

The waiting passengers sailing to that destination board the ship.

The ship is launched when it becomes full.

Wait for random time 500..2000ms /* sailing in the water */

}

Passenger:

for(;;) {

/* Makes some money to afford another ship. Note the ratio

between work and leisure. */

Wait for random time 0..700 ms

Choose a random destination 0,1.

Arrive to the Harbour and wait until there is an ship going to that

destination, then board it.

Enjoy the ship.

Leave the ship.

}

Correctness specification

The following conditions must be satisfied in order for the simulation to run correctly:

Each arriving/launching dock can at any time hold at most one ship. All other

ships are in the water doing the ship or waiting for landing.

At any moment, there are at most 2 passengers in an ship.

A passenger can board only an ship sitting on the launch/arriving dock, after all

passengers returning from a ride have already left, and after the ship has

announced boarding.

An ship launches into the water if and only if it is full of passengers (i.e. 2

passengers).

A passenger can leave an ship only after the ship has landed back at the Harbour.

The boarding starts only after the last passenger has left the ship.

Other minor restrictions, which follow from the comments in the provided

skeleton code.

Your goal:

Take the skeleton code and complete the classes defining the behaviour of the

ships and the Harbour (the passenger class is provided complete). The provided

code already creates and initializes the threads simulating the ships and the

passengers, as well as the object representing the Harbour. Your goal is to provide

proper synchronization between them, satisfying the conditions for correct

simulation. Use only semaphores (use the Semaphore class) to achieve the needed

synchronization.

Hints:

Take a look here for many semaphore problems and solutions.

Note that the number of passengers, destinations, ships and ship capacity has

been chosen in such a way that a deadlock will not occur in a correct

implementation – there are enough passengers to always fill at least one of the

ships waiting for launching.

On Unix/Linux systems (and on some Window systems as well), the following

commands might help you with debugging/verifying proper execution:

1. Launch the program with the output redirected to a log file, i.e. “java

Assignment2 > assignment2.log”

2. To see what passenger 5 did, type “cat assignment2.log | grep “Passenger

5”

3. To see what ship 3 did, type “cat assignment2.log | grep “Ship 3”

4. This way, you can rather easily see if your solution does not work yet.

5. You can figure out for yourself other ways to filter out useful information

from the log file, or simply study the log file to see whether everything

worked as specified

To submit your solution:

Submit single file assignment2.java, containing your solution. You will get partial marks

for partial solutions. Be sure to include your name and student number at the start of the

file.

Marking Criteria

Compiles and runs correctly by fulfilling the conditions below [100pts]. If any of the

points below fail to be implemented; deduct 5 points for each non-implemented part.

If it does not compile and/or run correctly; check the conditions below one by one:

· Each arriving/launching dock can at any time hold at most one ship. All other ships

are in the water doing the sailing or waiting for arriving. [15]

· At any moment, there are at most 2 passengers in an ship. [10]

· A passenger can board only a ship sitting on the launch/arriving dock after all

passengers returning from a ride have already left, and after the ship has announced

boarding. [15]

· An ship launches into the water if and only if it is full of passengers(i.e.2

passengers).[10]

· A passenger can leave a ship only after the ship has arrived back at the harbour.

[10]

· The boarding starts only after the last passenger has left the ship.[10]