Lignum vitae wood can also be used to brew a tea. Other names for lignum vitae include palo santo (Spanish for "holy wood") Aura palo santo and "bastard greenheart" (not to be confused with true greenheart "Chlorocardium rodiei", a popular wood in shipbuilding, cabinetry, and woodturning but a completely different timber). Lignum vitae is also one of the numerous hard, dense woods loosely referred to as "ironwood". Lignum vitae is hard and durable, and is also the densest wood traded (density: 1.23 g/cm); it will easily sink in water. On the Janka Scale of Hardness, which measures hardness of woods, lignum vitae
Hardness of approximation Hardness of approximation In computer science, hardness of approximation is a field that studies the algorithmic complexity of finding near-optimal solutions to optimization problems. Hardness of approximation complements the study of approximation algorithms by proving, for certain problems, a limit on the factors with which their solution can be efficiently approximated. Typically such limits show a factor of approximation beyond which a problem becomes NP-hard, implying that finding a polynomial time approximation for the problem is impossible unless NP=P. Some hardness of approximation results, however, are based on other hypotheses, a notable one among which is the unique games conjecture.