Originally posted by: Almakhawi

Hello,

I m new to cplex, i would like to do program for scheduling n job on m machines with cplex and C++

i want to formulate the  job dependencies constraints, this menas if  job1 depends on job2 , job1 start time must be greater equal job2 start time + the computation time of job2 on that machine pointed by alloc matrix.

NumMatrix jobDep(env, n);                    // Matrix for Job Dependencies

  jobDep[0] = IloNumArray(env,n 0, 0, 0, 0 );   // in this example n = 4
    jobDep[1] = IloNumArray(env,n, 0, 0, 0, 0 );
    jobDep[2] = IloNumArray(env,n, 1, 1, 0, 0 );
    jobDep[3] = IloNumArray(env,n, 0, 0, 1, 0 );

 NumMatrix exec_time(env,n);                    // execution time of each node on each machine

// adding values for the matrix of the computation time
    exec_time[0] = IloNumArray(env,m, 1,3);                  // in this example m=2
    exec_time[1] = IloNumArray(env,m,16,8);
    exec_time[2] = IloNumArray(env,m,2,1);
    exec_time[3] = IloNumArray(env,m,2,4);

 IloNumVarArray ExecST(env, n, 0, 20, ILOINT);   // Startime for Jobs where cV is the number of jobs

 IloNumVarArray Alloc(env, n, 0, m-1, ILOINT);  //  Allocation matrix where cP is the number of machines

    // job dependencies test  
     for (int v1=0;v1<n;v1++) {
      for (int v2=0;v2<n;v2++) {
    if (jobDep[v1][v2]==1){    
      model.add(Alloc[v1]==Alloc[v2]);  //  this means if two jobs allocated to the same  machine  because every machine have differen exec time
      model.add(ExecST[v1] >= ExecST[v2] + exec_time[v2][Alloc[v2]]); // want to use the intermediate value of Alloc[v2] as index for exec_time[v2][ Alloc[v2] ]
    }
      
      }
    }

in the previous code Alloc[v2] will takes values from 0 to m-1 i need to retrive i would like to use the intermediate values as index of the column in the exec_time[v2][ Alloc[v2]] ..

in other form .. i want to use the  intermediate value of Alloc[v2] as index for the matrix exec_time [v2][ Alloc[v2] ];

any one have an idea?

You cannot use an IloNumVar as an index into an array.

One way to work around your problem would be the following:

1. Instead of using an ILOINT variable Alloc[v2] that can range from through m-1 use an array of m ILOBOOL variables and add the constraint that they must sum to 1 (so that v2 is allocated in exactly one slot):
     IloArray<IloNumVarArray> Alloc(env);
     for (int i = 0; i < n; ++i) {
        IloNumVarArray array(env, m, 0, 1, ILOBOOL);
        IloExpr sum(env);
        for (IloInt j = 0; j < array.getSize(); ++j)
           sum += array[j];
        model.add(sum == 1);
        sum.end();
     }
2. Instead of using exec_time[v2][Alloc[v2]] you can now use
     IloExpr exec_time_v2(env);
     for (IloInt j = 0; j < Alloc[v2].getSize(); ++j)
        exec_time_v2 += Alloc[v2][j] * exec_time[v2][j];
     model.add(ExecST[v1] >= ExecST[v2] + exec_time_v2;
     exec_time_v2.end();
   exec_time_v2 is exactly the exec_time in the slot to which v2 is allocated (only this slot as Alloc[v2][j] != 0).

Originally posted by: Almakhawi

hello,

thanks so much.. your idea did work

Originally posted by: Almakhawi

Hello,

thank you so much , your idea did work..