freeze solution value for next iteration

Question

I want to save some solution from iter=1 for iter=2 and so on. A part of the main block is placed here.

var x = opl.x.solutionValue;
  for (var k in data2.M){
    for (var r in data2.Links){
      if (x[k][r.N]==1){
       x[k][r.N]= opl.x[k][r.N].solutionValue;
       var data3 = new IloOplDataElements();
       var xnew =opl.x[k][r.N].solutionValue;
       xnew = x[k][r.N];
       data3.xnew = x[k][r.N];
       opl.addDataSource(data3);
       writeln("x[",k,"]","[",r.N,"]"," = ",x [k][r.N]);
       writeln("xnew[",k,"]","[",r.N,"]"," = ",data3.xnew [k][r.N]);
       }
       
       }}

when I run this model; Without any error, the xnew is not update and printed in scripting log xnew undefined. I have the same .mod file for each iteration and I defined xnew in the .mod file as follows:

{float} xnew [s][N]= [];

could you help me to solve this problem?

A really appreciate your comments.

Answer 1

Let me start from the example https://github.com/AlexFleischerParis/howtowithoplchange/blob/master/change2darray.mod to show how to freeze for next iteration.

if (k!=11)
      {opl.x.LB=output;
      opl.x.UB=output;
      }  

is doing the freeze

in

int a[1..2][1..2];

    main {
      var source = new IloOplModelSource("sub2d.mod");
      var cplex = new IloCplex();
      var def = new IloOplModelDefinition(source);
     
     var output=0;
     
      for(var k=11;k<=15;k++)
      {
      var opl = new IloOplModel(def,cplex);
     
     
        
      var data2= new IloOplDataElements();
     
      data2.y=thisOplModel.a;
      data2.y[1][1]=k;
      opl.addDataSource(data2);
     
      opl.generate();
      // if k!=11 then freeze x to the output value from last time
      if (k!=11)
      {opl.x.LB=output;
      opl.x.UB=output;
      }      

      if (cplex.solve()) {
         writeln("OBJ = " + cplex.getObjValue());
      } else {
         writeln("No solution");
      }
      opl.postProcess();
      output=opl.x.solutionValue;
      
      data2.end();
     opl.end();
     
     
    }  
     
    }

where sub2d.mod is

int y[1..2][1..2]=...;

execute
{
writeln("y=",y);
}

dvar float x;

maximize x;
subject to {
  x<=sum(i in 1..2, j  in 1..2) y[i][j];
}

and if you change sub2d.mod to

 int y[1..2][1..2]=...;

    execute
    {
    writeln("y=",y);
    }

    dvar boolean x[1..2][1..2];

    maximize sum(i in 1..2,j in 1..2)x[i][j];
    subject to {
      sum(i in 1..2,j in 1..2)  x[i][j]<=(sum(i in 1..2, j  in 1..2) y[i][j]) ;
    }  

then you can write

int a[1..2][1..2];

    main {
      var source = new IloOplModelSource("sub2d.mod");
      var cplex = new IloCplex();
      var def = new IloOplModelDefinition(source);
     
     var output=0;
     
      for(var k=11;k<=15;k++)
      {
      var opl = new IloOplModel(def,cplex);
     
     
        
      var data2= new IloOplDataElements();
     
      data2.y=thisOplModel.a;
      data2.y[1][1]=k;
      opl.addDataSource(data2);
     
      opl.generate();
      // if k!=11 then freeze x to the output value from last time
      if (k!=11)
      {opl.x[1][1].LB=output;
      opl.x[1][1].UB=output;
      }      

      if (cplex.solve()) {
         writeln("OBJ = " + cplex.getObjValue());
      } else {
         writeln("No solution");
      }
      opl.postProcess();
      output=opl.x[1][1].solutionValue;
      
      writeln("x[1][1]=",opl.x[1][1].solutionValue);
      writeln("x[2][1]=",opl.x[2][1].solutionValue);
      
      data2.end();
     opl.end();
     
     
    }  
     
    }