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Node Arc constraint declaration AMPL

I'm using AMPL to build a reverse logistics model. The model is rather simple and has a series of nodes: from production to recycling facility, the node are defined as follows:

node Plant: net_out = p_supply;
node Dist {i in D_CITY};
node Whse {j in W_CITY};
node Recy {k in R_CITY}: net_in = r_demand[k];

I would like to a have a constraint in Whse but i do not know how to apply it directly. I get by with the following "unelegant" way:

subject to dw_objd{j in W_CITY}: sum {(i,j) in DW_LINKS} DW_Ship[i,j] = w_demand[j];

Is there a way to do it directly in the node declaration?

Solution

  • Unfortunately, there's no way to declare it inside the node-arc environment since each node statement defines constraints on "flow in minus flow out".