CPLEX Binary Variable in Python

Question

I am trying to set up a binary variable for my optimization problem in Python by using the IBM CPLEX. In my objective function, I set up a line which turns on and off depending on the market price in t:

mdl.maximize(
mdl.sum( (1-b[t]) * (prod_diff[t] * price_diff[t]) + \
(b[t]) * (vol_t * price[t] + prod_diff[t] * price_spot[t]) for t in time
)

Subject to:

mdl.add_constraint(
if prod_diff[t] <= 0:
b= 0
else:
b= 1
)

Apparently, there is something called logical and conditional constraints; but, unfortunately, I was unable to set it up in Python.

I'm new to this; can anyone put some light on the problem?

Answer 1

In easy python optimization see

if then

from docplex.mp.model import Model

mdl = Model(name='buses')
nbbus40 = mdl.integer_var(name='nbBus40')
nbbus30 = mdl.integer_var(name='nbBus30')
mdl.add_constraint(nbbus40*40 + nbbus30*30 >= 300, 'kids')
mdl.minimize(nbbus40*500 + nbbus30*400)

mdl.solve()

for v in mdl.iter_integer_vars():
   print(v," = ",v.solution_value)

print()
print("with if nb buses 40 more than 3  then nbBuses30 more than 7")

#if then constraint
mdl.add(mdl.if_then(nbbus40>=3,nbbus30>=7))
mdl.minimize(nbbus40*500 + nbbus30*400)

mdl.solve()

 

for v in mdl.iter_integer_vars():
    print(v," = ",v.solution_value)