Hi,

let's go on with the example from https://www.linkedin.com/pulse/what-optimization-how-can-help-you-do-more-less-zoo-buses-fleischer/

Not all models are feasible so let's see how we can display relaxation and conflicts with the docplex python API.

from docplex.mp.model import Model
from docplex.mp.relaxer import Relaxer
from docplex.mp.conflict_refiner import ConflictRefiner
from docplex.mp.conflict_refiner import ConflictRefiner, VarUbConstraintWrapper, VarLbConstraintWrapper

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.add_constraint(nbbus40 + nbbus30 <= 7, 'maxTotalBuses')

mdl.minimize(nbbus40*500 + nbbus30*400)

mdl.solve()

print(mdl.report())
print("solve status =",mdl.get_solve_status()) #infeasible model

print()
print("relaxation")
print()

rx = Relaxer()
rx.relax(mdl)

print ("number_of_relaxations= " + str(rx.number_of_relaxations))
print(rx.relaxations())

print(mdl.report())
print(mdl.get_solve_status())
print(mdl.solution)

print()
print("conflict")
print()

cr=ConflictRefiner()
conflicts=cr.refine_conflict(mdl)
print(mdl.get_solve_status())

for conflict in conflicts:
    st = conflict.status
    ct = conflict.element
    label = conflict.name
    label_type = type(conflict.element)
    if isinstance(conflict.element, VarLbConstraintWrapper) \
            or isinstance(conflict.element, VarUbConstraintWrapper):
        ct = conflict.element.get_constraint()

    # Print conflict information in console
    print("Conflict involving constraint: %s" % label)
    print(" \tfor: %s" % ct)

gives

None
solve status = JobSolveStatus.INFEASIBLE_SOLUTION

relaxation

number_of_relaxations= 1
{docplex.mp.LinearConstraint[maxTotalBuses](nbBus40+nbBus30,LE,7): 1.0}
* model buses solved with objective = 3800
None
JobSolveStatus.INFEASIBLE_SOLUTION
solution for: buses
objective: 3800
nbBus40=6
nbBus30=2

conflict

JobSolveStatus.INFEASIBLE_SOLUTION
Conflict involving constraint: None
     for: nbBus30 >= 0
Conflict involving constraint: kids
     for: kids: 40nbBus40+30nbBus30 >= 300
Conflict involving constraint: maxTotalBuses
     for: maxTotalBuses: nbBus40+nbBus30 <= 7

regards

Many other very simple examples at https://www.linkedin.com/pulse/making-optimization-simple-python-alex-fleischer/