Deterministic parallelism via liquid effects

Abstract

Shared memory multithreading is a popular approach to parallel programming, but also fiendishly hard to get right. We present Liquid Effects, a type-and-effect system based on refinement types which allows for fine-grained, low-level, shared memory multithreading while statically guaranteeing that a program is deterministic. Liquid Effects records the effect of an expression as a formula in first-order logic, making our type-and-effect system highly expressive. Further, effects like Read and Write are recorded in Liquid Effects as ordinary uninterpreted predicates, leaving the effect system open to extension by the user. By building our system as an extension to an existing dependent refinement type system, our system gains precise value-and branch-sensitive reasoning about effects. Finally, our system exploits the Liquid Types refinement type inference technique to automatically infer refinement types and effects. We have implemented our type-and-effect checking techniques in CSOLVE, a refinement type inference system for C programs. We demonstrate how CSOLVE uses Liquid Effects to prove the determinism of a variety of benchmarks.

Rehearsal: a configuration verification tool for puppet

“…In the past few years, several tools have been developed that use static [6,19,31] and dynamic [8,24] techniques to check that multi-threaded programs are deterministic. Rehearsal is a static determinacy checker for Puppet and leverages an SMT solver, thus is most closely related to Liquid Effects [19]. Liquid Effects establishes determinism by showing that concurrent effects are disjoint, but there are common examples of deterministic Puppet programs that do not have disjoint effects.…”

Pabble: parameterised Scribble

“…The work [22] introduced an analyser for the C language in the low-level imperative environment based on Liquid Types and refinement types. The recent work on Liquid Types [15] applied the tool with SMT solvers to assist parallelisation of code regions by determining statically whether parallel threads will run on disjoint shared memory without races. Our work applies dependent session types to guarantee different kinds of safety, communication safety and deadlock freedom, in explicit message-passing based distributed and parallel programming rather than shared memory concurrency.…”

Java UI : Effects for Controlling UI Object Access

“…This is similar to what we would need to support qualifier-dependent effects (e.g., showWhile in Section 4.5). Other effect systems are designed to reason about more general safe concurrency properties [16,17], but we are the first to build a polymorphic effect system for the issue of safe UI updates. Another approach would be to encapsulate UI actions within a monad, since every effect system gives rise to a monad [18].…”