Pointers versus arithmetic in PRAMs

A parallel pointer machine, (PPM) is a parallel model having pointers as its principal data type. PPMs have been characterized as PRAMs obeying two restrictions: restricted arithmetic capabilities and the CROW (concurrent read, owner write) memory access restriction. Results concerning the relative power of PPMs (and other arithmetically restricted PRAMs) versus CROW PRAMs having ordinary arithmetic capabilities are presented. First, lower bounds separating PPMs from CROW PRAMs are proved. Second, it is shown that this lower bound is tight. As a corollary, sharply improved PPM algorithms are obtained for a variety of problems, including deterministic context-free language recognition