## Computer Science Technical Reports

#### Title

On the Power of Multi-Objects

Technical Report

2-28-1997

PCS-TR97-311

#### Abstract

In the standard single-object'' model of shared-memory computing, it is assumed that a process accesses at most one shared object in each of its steps. In this paper, we consider a more powerful variant---the multi-object'' model---in which each process may access *any* finite number of shared objects atomically in each of its steps. We present results that relate the synchronization power of a type in the multi-object model to its synchronization power in the single-object model. Although the types fetch&add and swap have the same synchronization power in the single-object model, Afek, Merritt, and Taubenfeld showed that their synchronization powers differ in the multi-object model. We prove that this divergence phenomenon is exhibited {\em only\/} by types at levels 1 and 2; all higher level types have the same unbounded synchronization power in the multi-object model stated above. This paper identifies all possible relationships between a type's synchronization power in the single-object model and its synchronization power in the multi-object model.