As an example, in a plant location related problem, which is an inexhaustible source of difficult problems, a polynomial time algorithm to solve the problem is often not known and it is not expected that such algorithm exists.
Por ejemplo, en un problema de localización de plantas, que es una fuente inagotable de problemas complicados, muchas veces resulta que no se conocen algoritmos de tiempo polinomial para resolver el problema y no se espera que tales algoritmos existan.