How to remove a specific set of constraints from a bigger dictionary of constraints
AnsweredI have a constraint dictionary and a list of some infeasible arcs (i,j)
Given that the list PD is part of N.
'''
P = [1,2,3,4] #Pick-up nodes
D = [5,6,7,8] # drop-off nodes, the range function doesnot count the last number
PD = P + D
C = [10,11,12,13,14,15,16,17,18,19,20,21] # all transfer nodes
PDC = PD + C
O = [0,9]
N = O + P + D + C
m.addConstrs((quicksum(x[k,i,j] for j in N for k in K) == 1 for i in PD),'basic')
infeasible_arc4 = [(i, j ) for i in PD for j in PD if e[i] + d[i] + t[i,j] > l[j]]
'''
How to tell gurobi not to consider these infeasible arcs when working on the given constraints
I tried to create a variable to store the constraints as follows:
consts_basic = m.addConstrs((quicksum(x[k,i,j] for j in N for k in K) == 1 for i in PD),'basic')
However, this dictionnary can essentially be indexed by one symbol, for example, consts_basic[2].
To elaborate more, I want to tell gurobi to ignore any x[k,i,j] whenever i,j are found in the list infeasible_arc4
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Gurobi Staff
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Hi Sabrin,
You could define \(\texttt{infeasible_arc4}\) before you add the constraints and then add an \(\texttt{if}\)-statement to the quicksum. This should be similar to \(\texttt{quicksum(x[k,i,j] for j in N for k in K if (i,j) not in infeasible_arc4)}\).
Best regards,
Jaromił0 -
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Thank you Jaromil for your prompt response. I used the if - statement incorrectly. Now, I have applied your recommendations. and the model returns to work again. However, I faced another relevant issue please refer to this post.
Thanks a lot,
Sabreen
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