approximability造句

• Sudan has made important contributions to several areas of theoretical computer science, including probabilistically checkable proofs, non-approximability of list decoding, and error-correcting codes.
• Multifunctions arise in correspondence . ) This among many other properties loosely associated with approximability of upper hemicontinuous multifunctions via continuous functions explains why upper hemicontinuity is more preferred than lower hemicontinuity.
• The approximability of set covering is also well understood : a logarithmic approximation factor can be found by using a simple greedy algorithm, and finding a sublogarithmic approximation factor is NP-hard.
• Not all types of approximation-preserving reductions can be used to show membership in all approximability complexity classes, the most notable of which are completeness of a problem within a complexity class.
• NP-hard problems vary greatly in their approximability; some, such as the bin packing problem, can be approximated within any factor greater than 1 ( such a family of approximation algorithms is often called a polynomial time approximation scheme or " PTAS " ).
• However, David Zuckerman showed in 1996 that every one of these 21 problems has a constrained optimization version that is impossible to approximate within any constant factor unless P = NP, by showing that Karp's approach to reduction generalizes to a specific type of approximability reduction.