CODEWITHSUNDEEP
pyomo
Ralph
Ralph

Reputation: 265

pyomo creating constraints via a loop

I am adding a series of constraints like this, one for each node (Node_A, Node_B, ... Node_L):

def NodeA(model):
    k = sum(
        model.ArcVar[i] * node_arc_matrix[i,0]
        for i in model.ArcVar
            )
    return k ==  2*model.NodeVar[1]
model.NodeAConstraint=Constraint(rule=NodeA)

Where the 0-index in node_arc_matrix refers to the column corresponding to Node_A, and model.NodeVar[1] refers to Node-A as well. Instead of creating a constraint for each node manually can I create constraints across both i (arcs) and j (nodes)?

Upvotes: 0

Views: 1006

Answers (1)

V. Brunelle
V. Brunelle

Reputation: 1068

No need to add a loop.

When you have elements in your constraint that are a "for all element in ...", Pyomo simply requires you to add the Sets that you want to iterate over in the Constraint construction line. 

model.NodeAConstraint=Constraint(model.set_of_arcs_A, model.set_of_node_N, rule=NodeA)

And your rule must include a and n as parameters (i seems to already be used in your function). 

def NodeA(model, a, n):
    k = sum(
        model.ArcVar[i] * node_arc_matrix[i,a]
        for i in model.ArcVar
    )
    return k ==  2 * model.NodeVar[n]

Notice where I put a and n in the previous code. It also needs to be parameters for your function. I tried replacing every 0 by a and every 1 by n, if I understood your needs correctly.

Link to documentation here: https://pyomo.readthedocs.io/en/stable/pyomo_modeling_components/Constraints.html

Upvotes: 2

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