How To Add Logical Constraints In Pulp

I am trying to solve FLP using PuLP. I want to add logical constraint for variable value. I have LpVariable f and C is list of LpVariables . I want to add f to the constraint of pr

Solution 1:

Three points:

(1) Your first constraint forces the lpsum to be equal to 2, so f will always be 1 in your example - are you sure your formulation is correct?

(2) If statements can't be used in combination with the lpSum - you should formulate it as an actual constraint.

For example, you could define f as a binary variable and add this constraint:

prob += lpSum(c[i]for i inrange(len(c)))-1<= M*f 

where M is a sufficiently large number. Then, if f==0 we have that "lpsum() <= 1" and if f==1 we have that lpsum can be anything. Play around with that type of constraints to get f to behave the way you want.

(3) The constraint "prob += lpSum(c[i] for i in range (len(c)) + f )" does nothing unless it's supposed to be the objective of your MILP? If so, you should add it immediately after prob = LpProblem("The MILP problem", LpMinimize)

Good luck