CODEWITHSUNDEEP
pythonvariablesgurobi
Sabreen
Sabreen

Reputation: 81

Gurobi/Python: Adding Binary Variables through addVars

I have these sets:

R = [1,2,3,4]
C = [10,11,12,13,14,15,16,17,18,19,20,21]
Cr = {1: C[0:3], 2 : C[3:6],3: C[6:9], 4: C[9:12] }

I want to write a code for adding the next variable shown in the image z variable

My trial is as next

z = m.addVars(R,Cr[r] for r in R,Cr[r] for r in R,vtype=GRB.BINARY)

When I tried to print z, I got this error: Generator expression must be parenthesized

Upvotes: 0

Views: 492

Answers (2)

Greg Glockner
Greg Glockner

Reputation: 5653

The first arguments to gurobipy.Model.addVars() are either some iterables (like R or C) or a generator expression; the generator expression must be parenthesized. So your code should be:

z = m.addVars(((i,j) for r in R for i in Cr[r] for j in Cr[r]),
              vtype=GRB.BINARY, name='z')

Alternately, you could use the Python itertools package as follows:

import itertools as it
z = m.addVars(it.chain.from_iterable(map(lambda x: it.product(x, repeat=2), Cr.values())),
              vtype=GRB.BINARY, name='z')

I prefer the first syntax but I suspect that itertools may be faster for large data sets.

Upvotes: 2

mattmilten
mattmilten

Reputation: 6716

You can use update() on Gurobi's tupledict to iteratively add the blocks of variables:

z = gp.tupledict()

for r in R:
    z.update(m.addVars(Cr[r], Cr[r], vtype=GRB.BINARY))

This will result in these variables:

{(10, 10): <gurobi.Var C0>,
 (10, 11): <gurobi.Var C1>,
 (10, 12): <gurobi.Var C2>,
 (11, 10): <gurobi.Var C3>,
 (11, 11): <gurobi.Var C4>,
 (11, 12): <gurobi.Var C5>,
 (12, 10): <gurobi.Var C6>,
 (12, 11): <gurobi.Var C7>,
 (12, 12): <gurobi.Var C8>,
 (13, 13): <gurobi.Var C9>,
 (13, 14): <gurobi.Var C10>,
 (13, 15): <gurobi.Var C11>,
 (14, 13): <gurobi.Var C12>,
 (14, 14): <gurobi.Var C13>,
 (14, 15): <gurobi.Var C14>,
 (15, 13): <gurobi.Var C15>,
 (15, 14): <gurobi.Var C16>,
 (15, 15): <gurobi.Var C17>,
 (16, 16): <gurobi.Var C18>,
 (16, 17): <gurobi.Var C19>,
 (16, 18): <gurobi.Var C20>,
 (17, 16): <gurobi.Var C21>,
 (17, 17): <gurobi.Var C22>,
 (17, 18): <gurobi.Var C23>,
 (18, 16): <gurobi.Var C24>,
 (18, 17): <gurobi.Var C25>,
 (18, 18): <gurobi.Var C26>,
 (19, 19): <gurobi.Var C27>,
 (19, 20): <gurobi.Var C28>,
 (19, 21): <gurobi.Var C29>,
 (20, 19): <gurobi.Var C30>,
 (20, 20): <gurobi.Var C31>,
 (20, 21): <gurobi.Var C32>,
 (21, 19): <gurobi.Var C33>,
 (21, 20): <gurobi.Var C34>,
 (21, 21): <gurobi.Var C35>}

Upvotes: 1

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