Hi,

let ‘s start from https://www.ibm.com/developerworks/community/forums/html/topic?id=9748cb9c-fa58-471a-8f9b-fba546df609b&ps=25

At https://www.ibm.com/developerworks/community/forums/html/topic?id=4b0b67f3-bfb7-4a37-aef2-887c606153ce&ps=25

we saw

Very simple OPL : main block , flow control and incremental changes

But quite often those incremental changes are not enough for some changes and then we need to generate again the model. (regenerate)

Let’s see how  we can simply do that with the same tiny example.

We write sub.mod:

int nbKids=…;
float costBus40=…;
float costBus30=…;

int maxBus40=…;
int maxBus30=…;
     
dvar int+ nbBus40 in 0..maxBus40;
dvar int+ nbBus30 in 0..maxBus30;
     
minimize
     costBus40*nbBus40  +nbBus30*costBus30;
     
subject to
{
     ctKids:40*nbBus40+nbBus30*30>=nbKids;
}

execute
{
  writeln(“nbBus40 = “,nbBus40);
  writeln(“nbBus30 = “,nbBus30);
}

and then main.mod

main
{
  var source = new IloOplModelSource(“sub.mod”);
  var cplex = new IloCplex();
  var def = new IloOplModelDefinition(source);
 
  var opl1 = new IloOplModel(def,cplex);
  var data1=new IloOplDataElements();
  data1.costBus40=500;
  data1.costBus30=400;
  data1.maxBus40=100;
  data1.maxBus30=100;
  data1.nbKids=300;
 
 
  opl1.addDataSource(data1);
    
  opl1.generate();
  cplex.solve();
  opl1.postProcess();
 
//    //now 350 kids instead of 300
  writeln(“now 350 kids instead of 300”);
 
 
  data1.nbKids=350;
  var opl2 = new IloOplModel(def,cplex);
  opl2.addDataSource(data1);
    
  opl2.generate();
  cplex.solve();
  opl2.postProcess();

// no more than 4 buses 40 seats
  writeln(“no more than 4 buses 40 seats”);
  data1.maxBus40=4;
 
  var opl3 = new IloOplModel(def,cplex);
  opl3.addDataSource(data1);
    
  opl3.generate();
  cplex.solve();
  opl3.postProcess();
 
// change the objective so that cost for 40 seats is 450
// and remove the limit on the number of buses 40 seats

  writeln(“change the objective so that cost for 40 seats is 450”);
  writeln(“and remove the limit on the number of buses 40 seats”);    
 
  data1.maxBus40=100;
  data1.costBus40=450;
 
  var opl4 = new IloOplModel(def,cplex);
  opl4.addDataSource(data1);
    
  opl4.generate();
  cplex.solve();
  opl4.postProcess();

    }

 

which gives

nbBus40 = 6
nbBus30 = 2
now 350 kids instead of 300
nbBus40 = 8
nbBus30 = 1
no more than 4 buses 40 seats
nbBus40 = 2
nbBus30 = 9
change the objective so that cost for 40 seats is 450
and remove the limit on the number of buses 40 seats
nbBus40 = 8
nbBus30 = 1

regards

Many other very simple OPL models at https://www.linkedin.com/pulse/making-decision-optimization-simple-alex-fleischer/