Tiling problems provide for a very simple and transparent mechanism for encod ing machine computations This gives rise to rather simple master reductions showing various versions of the tiling problem complete for various complexity classes We in vestigate the potential for using these tiling problems in subsequent reductions showing hardness of the combinatorial problems that really matter We ...

In social advertising, ads are targeted based on underlying social networks and their content is tailored with information that pertains to the social relationship. This paper explores the effectiveness of social advertising using data from field tests of different ads on Facebook. We find evidence that social advertising is effective, and that this efficacy seems to stem mainly from the abilit...