I want to add a KPI to calculate the percentage of occupancy of vehicles: the total travel time of occupied arcs (where the capacity of a vehicle is non-zero) over the total travel time.
How can I represent that using three variables: the $x_{ij}$ variable equal to $1$ if there is an arc between $i$ and $j$, the $q_i$ the capacity of vehicle after serving vertex $i$ and the $b_i$ the starting time of service for vertex $i$?
from docplex.mp.model import Model
mdl = Model(name='buses')
nbbus40 = mdl.integer_var(name='nbBus40')
nbbus30 = mdl.integer_var(name='nbBus30')
nbbus=nbbus30+nbbus40
mdl.add_kpi(nbbus,"nbbus")
mdl.add_constraint(nbbus40*40 + nbbus30*30 >= 300, 'kids')
mdl.minimize(nbbus40*500 + nbbus30*400)
mdl.solve(log_output=True,)
mdl.export("c:\\temp\\buses.lp")
for v in mdl.iter_integer_vars():
print(v," = ",v.solution_value)
for k in mdl.iter_kpis():
print(k," = ",k.solution_value)
