[AMPL 2628] Re: Help with a constraint!

> I'm not entirely sure I understand this, but if you are saying that
> you want to fix DEMANDS_pd at zero for all cells not covered by the
> other two constraints, what about the following?
>
> subject to fix_zero {i in NODES, j in NODES, k in NODES, m in NODES :
> m <> i || (k <> i && k <> j)}:
> DEMANDS_pd[i,j,k,m] = 0;
>
> On Jul 2, 7:11 am, plozmar <lozano_pal...@...> wrote:
>
>
>
> > Hi,
>
> > I have a big problem trying to find a good constraint for the
> > following case:
>
> > ---------------------------------------
> > param DEMANDS{NODES};
>
> > var DEMANDS_pd {NODES, NODES, NODES, NODES};
>
> > subject to demands_per_node_per_demand {i in NODES, j in NODES}:
>
> >         DEMANDS_pd [i,j,j,i] = DEMANDS [i,j];
>
> > subject to demands_per_node_per_demand_2 {i in NODES, j in NODES}:
>
> >         DEMANDS_pd [i,j,i,i] = -DEMANDS[i,j];
> > -------------------------------------------
>
> > The result variable DEMANDS_pd has the following apparence,  for
> > example, for  DEMANDS_pd[1,2,*,*]
>
> >     1       2  3  4
> > 1   0.5   0  0  0
> > 2  -0.5   0  0  0
> > 3   0     0  0  0
> > 4   0    0  0  0
>
> > this table MUST have only two elements different from zero (the same
> > but opposite). I need a constraint that fixes the values of all the
> > elements a zero because with another contraints, the values can
> > change, and change all the result...
>
> > Thank you very much in advance,- Ocultar texto de la cita -
>
> - Mostrar texto de la cita -