param 2n;
param c{i in 1..2n, j in 1..2n};
set S1;
var x{i in 1..2n, j in 1..2n: i<>j} >=0, <=1;
maximize Value:
.5*sum{i in 1..2n, j in 1..2n: i<>j}c[i,j]*x[i,j];
s.t. symmetry{i in 1..2n, j in 1..2n: i<>j}:
x[i,j]=x[j,i];
s.t. assign{i in 1..2n}:
sum{j in 1..2n: i<>j}x[i,j]=1;
#s.t. oddsubsets: sum{i in S1, j in 1..2n diff S1} x[i,j] >= 1;
data;
param 2n:=6;
set S1:= 1 2 3;
param c[*,*]:
1 2 3 4 5 6 :=
1 0 10 10 1 1 1
2 10 0 10 1 1 1
3 10 10 0 1 1 1
4 1 1 1 0 10 10
5 1 1 1 10 0 10
6 1 1 1 10 10 0 ;