Thread: Help with Assignment

Hi folks. I am currently studying Computer Science and one of the modules I am taking at the moment is Concurrent & Distributed Systems. My first assignment involves using await statements and semaphores for a train track using Eclipse. I have wrote out code but it has many errors. The link below shows the assignment question and below that is the code I have written so far. Can anyone assist me in completing this assignment? I would be very grateful

https://docs.google.com/viewer?a=v&q...yDbwCEKc0Z8IcA

Code

Global Invariant: (NumberOfTrainsInAnySection <= 1) AND (TotalTrainsOnTrack <= 8)
Process main {
	/* Declare and initialize global variables */
Const Number_Of_Trains = 10;
Int NumberOnTrack =0;
 
/* sections on the traintrack */
string  sections[0..10]  =  {“[.....]”, “[.....]”, “[.....]”, “[.....]”, “[.....]”, “[.....]”, “[.....]”, “[.....]”,“[.....]”, “[.....]”, “[.....]”, “[.....]”, };
 
//* Set the train moving 
	 for (count= 1 to NUMBER_OF_TRAINS){
		int entry= {0...0}; 
                   	int exit = { 0...11 }; 
                   	TrainProcess (entry,  exit);
               } /* end  for *
} /* end main process
 
// Train Process
process TrainProcess (int s, int t) {
 /* Wait if track is too crowded
<await (numberOnTrack<=8) numberOnTrack++; >
    /* wait for section 1 to be clear from the right side
     <await ( (section[1]==”[.....]”) section[1]=”[“+entry+”-->”+exit”]”;>
    /* move forward to exit position (which is 10s) */
    int currentPosition = 0*s;
    int nextPosition = 0*s+1;
    do   {
       <await (sections[nextPosition]==”[.....]”)  sections[nextPosition]=sections[currentPosition]; 
                          sections[currentPosition]=”[.....]”; >
       currentPosition = nextPosition;
       nextPosition = (nextPosition+1) SECTIONS 8;
    } while (currentPosition <> 2*t)
   /* move off the track*/
   < slots[currentPosition]=”[.....]”; numberOnTrack-->
} /* end TrainProcess

Well the main process is for the trains to travel safely on the track and an await statement is required for the trains to cross over the junction safely. I think that I have declared the improper global variables and my await statements in the Train Process section is wrong also. Could anyone help me to correct it?

I have written this code in Eclipse. Because I'm not that good at Java (or programming in general) the code is probably mixed up.

Yep, your first step will be to learn basic Java syntax which you can do at the Java tutorials that are linked to in Kevin's "useful links" signature links above, or which you can find here. You can't guess at this stuff and pray that it might work, and we'll not be able to help you til you've taught yourself at least some of the rudiments of the language. Also contact your instructor to schedule some intense one-on-one counseling as you have a lot of catching up to do, it appears.

The assignment has to be in for today and I still cannot get it working

Originally Posted by Norm

There is no await statement in java.

Yes I understand. The code listed in my first post is the algorithm, all I have to do now is implement it using Eclipse. Can any of you guys help me to implement it?