CODEWITHSUNDEEP
optimizationconstraintsmathematical-optimizationpyomo
cerofrais
cerofrais

Reputation: 1337

How to write constraint which says if p or q then r in pyomo?

Hi I am learning optimization using pyomo and i have a problem where one variable should get value only when one of the other two variables or both get a value.

it's like (P V Q) => R in tautology. can someone please help how to write it as a constraint in pyomo.

example : if i am using 3 ingredients to make a product, 3rd one should always be used if any of 1,2 are used or both 1,2 are used.

Upvotes: 0

Views: 191

Answers (2)

Erwin Kalvelagen
Erwin Kalvelagen

Reputation: 16797

I don't know what "get a value" is in optimization. All variables in the model "get a value". Look at it as a system of equations + an objective.

But, of course,

 (P V Q) => R

is equivalent to

  R >= P
  R >= Q

where R,P and Q are binary variables.

Upvotes: 1

Qi Chen
Qi Chen

Reputation: 1718

What you are describing is disjunctive programming. Pyomo provides support for that through Pyomo.GDP: https://pyomo.readthedocs.io/en/latest/modeling_extensions/gdp.html, with more logical expression support upcoming.

For simple problems, the direct algebraic formulation suggested by Erwin is probably easiest.

Upvotes: 0

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