Originally posted by: MachexC

Hi Alex,

I am modeling for 4 constraints, but the results of Xij is no value. Please help me.

{string} N = ...;
{string} M = ...;
//{string} D = ...;
//int      T=  ...;
//range    Time=1..T;

tuple vehicle_flow{
string vehicle;
string nodei;
string nodej;
}
{vehicle_flow} sub_vehicle_flow=...;
dvar boolean X[sub_vehicle_flow];

// demand
tuple demand {
string nodei;
}
{demand} sub_demand=...;
float D[sub_demand]=...;

// capacity
tuple capacity{
string vehicle;
}
{capacity} sub_capacity=...;
float q[sub_capacity]=...;   

subject to
{
// constraint(1)
forall (k  in  M ){
sum(<k1,"CT",j1> in sub_vehicle_flow:k1==k && 01==0 ) X[<k1,"CT",j1>] <= 1;
}
// constraint(2)
forall (k  in  M, i in N ){
sum(<k1,i1,j1> in sub_vehicle_flow:k1==k && i1==i ) X[<k1,i1,j1>]- sum(<k1,j1,i1> in sub_vehicle_flow) X[<k1,j1,i1>] == 0;
}
// constraint(3)
forall (i in N ){
sum(<k1,i1,j1> in sub_vehicle_flow:i1==i) X[<k1,i1,j1>]== 1;
}
// consatraint(4)
forall (k  in  M ){
sum(<i> in sub_demand ) D[<i>] * sum(<k1,i1,j1> in sub_vehicle_flow) X[<k1,i1,j1>]<= q[<k>];
}
}

Thanks,

Mac

Hi,

if you label your constraints

subject to
{
// constraint(1)
forall (k  in  M ){
ct1:sum(<k1,"CT",j1> in sub_vehicle_flow:k1==k && 01==0 ) X[<k1,"CT",j1>] <= 1;
}
// constraint(2)
forall (k  in  M, i in N ){
ct2:sum(<k1,i1,j1> in sub_vehicle_flow:k1==k && i1==i ) X[<k1,i1,j1>]- sum(<k1,j1,i1> in sub_vehicle_flow) X[<k1,j1,i1>] == 0;
}
// constraint(3)
forall (i in N ){
ct3:sum(<k1,i1,j1> in sub_vehicle_flow:i1==i) X[<k1,i1,j1>]== 1;
}
// consatraint(4)
forall (k  in  M ){
ct4:sum(<i> in sub_demand ) D[<i>] * sum(<k1,i1,j1> in sub_vehicle_flow) X[<k1,i1,j1>]<= q[<k>];
}
}

then CPLEX will give a relaxation

Line    Original    Relaxed    Element (4)
46    [1,1]    [0,1]    ct3["CT"]
46    [1,1]    [0,1]    ct3["VL"]
46    [1,1]    [0,1]    ct3["TG"]
46    [1,1]    [0,1]    ct3["TP.HCM"]

and some conflicts that will help you

Line    In conflict    Element (2)
42    Yes    ct2["truckA"]["VL"]
46    Yes    ct3["CT"]

NB:

In documentation I suggest

regards

Originally posted by: MachexC

Hi Alex,

I do not know how to fix it to have the results, Xij; maybe the constraints from OPL are not true. Please help me fix the constraints to give  results, Xij, you can fix the data from Excel file.

Thank you,

Bests,

Mac

Hi,

if you change the constraint

// constraint(3)
forall (i in N ){
ct3:sum(<k1,i1,j1> in sub_vehicle_flow:i1==i) X[<k1,i1,j1>]== 1;

into

// constraint(3)
forall (i in N ){
ct3:0<=sum(<k1,i1,j1> in sub_vehicle_flow:i1==i) X[<k1,i1,j1>]<= 1;

then you ll get a solution

regards