Originally posted by: A.Omidi

hello

I have a project scheduling problem with below definition:

3 different resources and 5 tasks. (task 1 & 5 are dummy with pt=0).

task 2 use from resource 1 with pt=5, task 3 use from resource 2 with pt=5 & task 4 use from resource 3 with pt=2.

task 2,3 are precedence of task 4, and start in time 0, but task 4 can start in the specific time after task 2,3.

i used from rcpsp example code in the cplex for solved my problem, but, when solved it, in the solution, each task start after finished precedence task, but i want, task 4 start at 2 and not in the end of tasks 2,3.

cplex solution :

// solution with objective 7
Task 1 starts at 0
Task 2 starts at 0
Task 3 starts at 0
Task 4 starts at 5
Task 5 starts at 7  

pls. let me know, how can i solve this problem?

thanks so much

best regards

Hi,

why not attaching the model you have right now ?

regards
 

Originally posted by: A.Omidi

hi Alex

Pls. fine my model and it data in attached file.

best regards

Hi,

then you could try

minimize max(t in Tasks) endOf(itvs[t]);
subject to {
  forall (r in RsrcIds)
    rsrcUsage[r] <= Capacity[r];
  forall (t1 in Tasks, t2id in t1.succs:t2id!=4)
    endBeforeStart(itvs[t1], itvs[<t2id>]);
    
    startOf(itvs[<4>])==2;
}   

regards

Originally posted by: A.Omidi

Hi Alex

Thanks so much.

my problem solved correctly. 

but, if, i have some tasks that them condition are such as task 4 in my problem, i should definition them separately?( startOf(itvs[<4>])==2;)

regards