Parallel random access machines with both multiplication and shifts

Document Type

Article

Publication Date

1-1-1994

Abstract

We prove that the class of languages accepted in polynomial time by Parallel Random Access Machines with both multiplication and shifts using exponentially many processors (PRAM[*, {upwards double arrow}, {downwards double arrow}] - PTIME) includes the class of languages accepted in exponential time and polynomial alternations by an alternating Turing machine and is included in EXPSPACE. It follows that the class of languages accepted by a PRAM[*, {upwards double arrow}, {downwards double arrow}] in logarithmic time (using polynomially many processors) includes the polynomial hierarchy and is included in PSPACE. Thus, a PRAM[*, {upwards double arrow}, {downwards double arrow}] may be more powerful, to within a polynomial in time, than either a PRAM[*] or a PRAM[{upwards double arrow}, {downwards double arrow}], since PRAM[*] - PTIME = PRAM[{upwards double arrow}, {downwards double arrow}] - PTIME = PSPACE. © 1994 Academic Press, Inc.

Publication Source (Journal or Book title)

Information and Computation

First Page

96

Last Page

118

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