Originally posted by: SystemAdmin

[adji said:]

I would like to solve a parallel machine scheduling problem using IlLOG Scheduler 4.4 and ILOG Solver 4.4
Assume to schedule "n" tasks on 2 machines;
1. every task may be processed on a subset of all the machines;
2. between each task and one of its available machine, there are a series of time windows;
3. the task's span is shorter than one of its alternative time windows, i.e. there is slack time in the time

window;
4. the transition time is a function on the neighbouring two processing time of the respective tasks;


so the problem has to determine:
-whether a task should be processed;
-if so, it should be scheduled on which machine, and then which time window;
-and then the start time in the time window

the objective is to minimize makespan of all the scheduled tasks.

i tried to model it using ILOG Scheduler and ILOG Solver for several days, but got stuck in it.

Thank you in advance.

adji
#ConstraintProgramming-General
#DecisionOptimization

Originally posted by: SystemAdmin

[jfk said:]

Hello,
I don't have Scheduler+Solver anymore so I can't really help you but I remember that there are many examples in the doc with exactly the same features you describe. I guess it's worth taking a look...

cheers
#ConstraintProgramming-General
#DecisionOptimization

Originally posted by: SystemAdmin

[Didier Vidal said:]

Adj,

What makes the modeling difficult ? Is it the fact of deciding on which machine a task will be scheduled (ie can you model the problem if you ignore that there are different alternatives to perform a task)?


Didier.
#ConstraintProgramming-General
#DecisionOptimization

Originally posted by: SystemAdmin

[adji said:]

Dear Didier,

i have two machines to perform a task.assume that each task can be processed in both machines where time for processing a task between the two machines is not equal..
Just assume that the time for processing a task in the first machine is faster than the second.my problem is that how to divide the task between the two machines so that it can reach minimum processing time.But,not all tasks are processed in the first machine.

Fariz,
#ConstraintProgramming-General
#DecisionOptimization

Originally posted by: SystemAdmin

[Didier Vidal said:]

Fariz,

In case it is an option for you, that would be very easy to model this with CP Optimizer. This engine supports a notion of optional intervals that does just that.

Here is an example of a model in OPL that does that:


using CP;


int nbTasks = 5;
int nbMachines = 2;

range tasks = 1..nbTasks;
range machines = 1..nbMachines;

int duration[t in tasks][m in machines] = rand(5) + 1;


dvar interval tasksI[tasks];
dvar interval tasksOnMachineI[t in tasks][m in machines] optional size duration[t][m];

minimize max(t in tasks) endOf(tasksI[t]);

constraints {
  forall(m in machines)
    noOverlap(all(t in tasks) tasksOnMachineI[t][m]);
  forall(t in tasks)
    alternative(tasksI[t], all(m in machines) tasksOnMachineI[t][m]);
}


Didier.
#ConstraintProgramming-General
#DecisionOptimization