Rosiwal scale with corundum with a base value of 1000. The Rosiwal scale is used in mineralogy in the same way as Mohs scale and Knoop scale. Rosiwal scale The Rosiwal scale is a hardness scale, with its name given in memory of the Austrian geologist August Karl Rosiwal. The Rosiwal scale bases its measure on absolute values, unlike the Mohs scale whose values are relative values, its interest is relegated to the amateur or an approach that makes it useful in the research field ('in situ'). The Rosiwal method (also called Delesse and Rosiwal) is basically a method of petrographic analysis
Hardness of approximation polynomial time. In the early 1990s, with the development of PCP theory, it became clear that many more approximation problems were hard to approximate, and that (unless P = NP) many known approximation algorithms achieved the best possible approximation ratio. Hardness of approximation theory deals with studying the approximation threshold of such problems. For an example of an NP-hard optimization problem that is hard to approximate, see set cover. 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