Mechanization of pomset languages in the Coq proof assistant for the specification of weak memory models

Abstract

Memory models define semantics of concurrent programs operating on shared memory. Theory of these models is an active research topic. As new models emerge, the problem of providing a rigorous formal specification of these models becomes relevant. In this paper we consider a problem of formalizing memory models in the interactive theorem proving systems. We use semantic domain of pomset languages to formalize memory models. We propose an encoding of pomset languages using quotient types and discuss advantages and shortcomings of this approach. We present a library developed in the Coq proof assistant that implements the proposed approach. As a part of this library, we establish a connection between pomset languages and operational semantics defined by labeled transition systems. With the help of this theory, it becomes possible to define in Coq memory models parameterized by the operational semantics of an abstract datatype, and thus to decouple the definition of a memory model from the definition of the datatype. The proposed library can be used to develop formal machine-checked specifications of a wide class of memory models. In order to demonstrate its applicability, we present specifications of several basic memory models: sequential, causal, and pipelined consistency.