Hire Hard, Manage Easy

Easy Problems are Sometimes Hard

We present a detailed experimental investigation of the easy-hard-easy phase transition for randomly generated instances of satisfiability problems. Problems in the hard part of the phase transition have been extensively used for benchmarking satisfiability algorithms. This study demonstrates that problem classes and regions of the phase transition previously thought to be easy can sometimes be...

Easy and Hard Conformant Planning

Even under polynomial restrictions on plan length, conformant planning remains a very hard computational problem as plan verification itself can take exponential time. This heavy price cannot be avoided in general although in many cases conformant plans are verifiable efficiently by means of simple forms of disjunctive inference. We report an efficient but incomplete planner capable of solving ...

Distinguishing Easy and Hard Instances

2048 is (PSPACE) Hard, but Sometimes Easy

We prove that a variant of 2048, a popular online puzzle game, is PSPACE-Complete. Our hardness result holds for a version of the problem where the player has oracle access to the computer player’s moves. Specifically, we show that for an n × n game board G, computing a sequence of moves to reach a particular configuration C from an initial configuration C0 is PSPACE-Complete. Our reduction is ...

Authorship Attribution: What’s Easy and What’s Hard?

The simplest kind of authorship attribution problem—and the one that has received the most attention—is the one in which we are given a small, closed set of candidate authors and are asked to attribute an anonymous text to one of them. Usually, it is assumed that we have copious quantities of text by each candidate author and that the anonymous text is reasonably long. A number of recent survey...