Originally posted by: JCPawlowski

Hi,

I have a problem extracting the dual variables of a constraint in a post process opl script. I already did it on easy constraints and it works well but I can't figure out how to do it for this one:

// Temporal capacity constraints
    forall (<i,j,c,b> in Arcs, e in Epochs)
      ctLinkCapacity:
          sum (d in Demands, f in 1 .. d.td : f <= e) d.bw * (dArc[d, <i,j,c,b>, (e-f+1)] + dArc[d, <j,i,c,b>, (e-f+1)]) <= b;

I tried this way: (that's what I did in the past for "easier" constraints and it worked)

float Duals[Arcs][Epochs];

    for (a in Arcs) {
        for (var e in Epochs) {
            Duals[a][e] = ctLinkCapacity[a][e].dual;
          }
     } 

I have the following error: 

Erreur d'exécution du script : Index hors bornes pour le tableau "ctLinkCapacity", " <1 3 804 32000>".   (out of bound index)

Unfortunately the <1 3 804 32000> tuple exists in my Arcs set. I'm guessing I have wrongly written the export but I can't find how to do it differently in the manual.

Thanks in advance,

JC

Hi,

the index you use for the array has to be exactly the same as the one in the constraints:

tuple arc
 {
 int a;
 int b;
 }
 
 {int} Epochs=asSet(1..10);
 
 {arc} Arcs={<1,2>,<2,3>};
 
 dvar float x[Arcs][Epochs];
 
 maximize sum(a in Arcs, e in Epochs) x[a][e];
 subject to
 {
    forall (<a,b> in Arcs, e in Epochs)
      ctLinkCapacity:
          x[<a,b>][e]<=10;
          
        }          
 

 

float Duals[Arcs][Epochs];
execute
{
    for (a in Arcs) {
        for (var e in Epochs) {
            Duals[a][e] = ctLinkCapacity[a][e].dual;
          }
        }          
     } 

gives an out of bound wheras if I turn

forall (<a,b> in Arcs, e in Epochs)
      ctLinkCapacity:
          x[<a,b>][e]<=10;

into

forall (a in Arcs, e in Epochs)
      ctLinkCapacity:
          x[a][e]<=10;

then it works fine.

tuple arc
 {
 int a;
 int b;
 }
 
 {int} Epochs=asSet(1..10);
 
 {arc} Arcs={<1,2>,<2,3>};
 
 dvar float x[Arcs][Epochs];
 
 maximize sum(a in Arcs, e in Epochs) x[a][e];
 subject to
 {
    forall (a in Arcs, e in Epochs)
      ctLinkCapacity:
          x[a][e]<=10;
          
        }          
 

 

float Duals[Arcs][Epochs];
execute
{
    for (a in Arcs) {
        for (var e in Epochs) {
            Duals[a][e] = ctLinkCapacity[a][e].dual;
          }
        }          
     } 

works fine

regards

Originally posted by: JCPawlowski

Thank you a lot  Alex !

That is what I tought but unfortunately I cannot use exactly this version as you can see in my constraint I use my tuple <i,j,c,b> and also <j,i,c,b>, therefore I cannot use the short "a" and have to put the whole tuple !

I also tried to put the whole tuple in my saving command as follow but somehow it doesn't work :

    for (<i,j,c,b> in Arcs) {
        for (var e in Epochs) {
            Duals[<i,j,c,b>][e] = ctLinkCapacity[<i,j,c,b>][e].dual;
          }
     }      

The script doesn't accept it ! Is there a way to do it ? or do i have to change the constraint itself ?

can I slice in the constraint using two arc a1 and a2 ? and setting the tuples like this: item(a1,0) == item(a2,1) and item(a1,1) == item(a2,0) and item(a1,2) == item(a2,2) and item(a1,3) == item(a2,3)

// Temporal capacity constraints
    forall (a1 in Arcs, a2 in Arcs, e in Epochs : item(a1,0) == item(a2,1) and item(a1,1) == item(a2,0) and item(a1,2) == item(a2,2) and item(a1,3) == item(a2,3))
      ctLinkCapacity:
          sum (d in Demands, f in 1 .. d.td : f <= e) d.bw * (dArc[d, a1, (e-f+1)] + dArc[d, a2, (e-f+1)]) <= b;

I remember something about not slicing with decision variables.

Thanks in advance

Regards,

JC

Hi,

you could have a look at

http://www.ibm.com/support/knowledgecenter/SSSA5P_12.6.3/ilog.odms.ide.help/OPL_Studio/opllangref/topics/opl_langref_formalParams_filtering.html

about implicit and explicit slicing

Plus

{int} s={1,2,3};

    tuple arc
     {
     int a;
     int b;
     }
     
     {int} Epochs=asSet(1..10);
     
     {arc} Arcs={<1,2>,<2,3>};
     
     dvar float x[Arcs][Epochs];
     
     maximize sum(a in Arcs, e in Epochs) x[a][e];
     subject to
     {
        forall (<a,b> in Arcs, e in Epochs)
          ctLinkCapacity:
              x[<a,b>][e]<=10;
              
            }          
     

     

    float Duals[Arcs][Epochs];
    execute
    {
        for (var a in s) for (var b in s) {
            if (Arcs.contains(a,b)) for (var e in Epochs) {
                Duals[Arcs.find(a,b)][e] = ctLinkCapacity[a][b][e].dual;
              }
            }          
         }
 

works fine

regards