4 research outputs found
FIFO anomaly is unbounded
Virtual memory of computers is usually implemented by demand paging. For some
page replacement algorithms the number of page faults may increase as the
number of page frames increases. Belady, Nelson and Shedler constructed
reference strings for which page replacement algorithm FIFO produces near twice
more page faults in a larger memory than in a smaller one. They formulated the
conjecture that 2 is a general bound. We prove that this ratio can be
arbitrarily large
Greedy D-Approximation Algorithm for Covering with Arbitrary Constraints and Submodular Cost
This paper describes a simple greedy D-approximation algorithm for any
covering problem whose objective function is submodular and non-decreasing, and
whose feasible region can be expressed as the intersection of arbitrary (closed
upwards) covering constraints, each of which constrains at most D variables of
the problem. (A simple example is Vertex Cover, with D = 2.) The algorithm
generalizes previous approximation algorithms for fundamental covering problems
and online paging and caching problems