Olea capensis wood materials. It is also the one of the world's hardest woods according to the Janka hardness test. The timber has a good abrasion resistance and is very strong. It is an excellent turnery wood, and is used for a wide range of decorative items. Olea capensis Olea capensis, also known by the common name black ironwood, is an African tree species belonging to the Olive family (Oleaceae). It is widespread in Sub-Saharan Africa from the east in Somalia, Ethiopia and Sudan, south to the tip of South Africa, and west to Cameroon, Sierra Leone and the Islands of the
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.