Pyomo constraints for specific range

Question

Following is a part from an optimization code I'm trying to run.

from pyomo.environ import *
model = ConcreteModel()

## Define sets 
model.k = Set(initialize=['Diesel','Diesel_hybrid', 'Battery_electric'], doc='Vehicle Type')
model.i = Set(initialize=[0,1,2,3,4,5], doc='Age')
model.t = Set(initialize=[2018,2019,2020,2021,2022,2023], doc='Years')

## Define variables 
model.P = Var(model.k, model.t, bounds=(0,None), doc='number of k type vehicle purchased in year t')
model.A = Var(model.k, model.i, model.t, bounds=(0,None), doc='number of k type i year old bus in use at the end of year t')
model.R = Var(model.k, model.i, model.t, bounds=(0,20), doc='number of k type i year old bus salvaged at year t')

I'm trying to write a constraint that says, for age of bus i<=4, salvaged number of buses R[k,i,t] = 0 I tried the following. It doesn't seem to work.

def constraint_5(model,k,t):
    if (i<=4):
        return model.R[k,i,t] == 0

I've also tried defining a subset. That doesn't work as well.

model.sal = Set(initialize=[0,1,2,3,4], doc='Minimum age in usage')
def constraint_5(model,k,t):
    for i in model.w:
        return model.R[k,i,t] == 0

Can anyone help me? Thanks

I am glad to see people working with promo. I have similar interests and I work on similar problems. Do you mind sending me a private message? You can find my email in my profile page — oz123
– oz123, Commented Jul 25, 2017 at 21:30

Bethany Nicholson · Accepted Answer · 2017-07-25 21:14:50Z

4

You can do this by indexing your constraints over all of the sets and using Constraint.Skip to skip adding the constraint for undesired indices

def constraint_5(model,k,i,t):
    if i<=4:
        return model.R[k,i,t] == 0
    return Constraint.Skip
model.con5 = Constraint(model.k,model.i,model.t,rule=constraint_5)

Or you could index the constraint over the subset that you created

def constraint_5(model,k,i,t):
    return model.R[k,i,t] == 0
model.con5 = Constraint(model.k,model.sal,model.t,rule=constraint_5)

answered Jul 25, 2017 at 21:14

Bethany Nicholson

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