arXiv subjects

Marc Pouzet

Publications and source records attributed to Marc Pouzet.

5 recordsLinked to original sources

arXiv2026

Towards Formal Verification of Hybrid Synchronous Programs with Refinement Types

Cyber-physical systems (CPS) such as autonomous cars, aircraft, and robots are often also safety-critical; thus it is imperative that they operate as intended with a high degree of certainty. Formal verification has been employed to verify the software controlling these systems, but due to their complexity, is usually performed on an abstract model rather than the executable code. Synchronous programming languages extended with differential equations promise both rigorous modeling and sufficient expressiveness to implement executable controller code, and recent developments have introduced formal verification of strictly discrete-time programs. Extending these verification techniques to hybrid systems enables precise modeling of the environment for a wider variety of programs to be both verified and executed. We formalize the operational semantics of initial value problems and zero-crossing detection expressed in a synchronous programming language, extend its type system for verification thereof, and prove its soundness.

cs.PL↗

arXiv2025

PSM: Policy Synchronised Deterministic Memory

Concurrency and determinacy do not go well with each other when resources must be shared. Haskell provides parallel programming abstractions such as IVar and LVar in the Par monad and concurrent abstractions such as MVar and TVar in the in IO and STM monads, respectively. The former are determinate but have no destructive updates and the latter have destructive updates but do not guarantee determinacy. Programming patterns that are both concurrent and determinate, such as those provided by Kahn or Berry require memory abstractions at a higher level than is currently available. In this paper we describe a new type context PSM for policy synchronised memory in Haskell. Like STM and IO, the computations in PSM can access persistent state and, as a side-effect, update the memory in imperative style. Like the Par and IO monads, PSM supports concurrent threads and shared state. However, in contrast to IO, our PSM contexts are race-free since concurrent accesses are policy coordinated which guarantees determinacy.Well-typed transactions in the PSM context can accommodate abstract data structures that are imperative, concurrently shareable and still behave deterministically, by construction.

cs.PL↗

arXiv2020

Reactive Probabilistic Programming

Synchronous modeling is at the heart of programming languages like Lustre, Esterel, or Scade used routinely for implementing safety critical control software, e.g., fly-by-wire and engine control in planes. However, to date these languages have had limited modern support for modeling uncertainty -- probabilistic aspects of software's environment or behavior -- even though modeling uncertainty is a primary activity when designing a control system. In this paper we present ProbZelus the first synchronous probabilistic programming language. ProbZelus conservatively provides the facilities of a synchronous language to write control software, with probabilistic constructs to model uncertainties and perform inference-in-the-loop. We present the design and implementation of the language. We propose a measure-theoretic semantics of probabilistic stream functions and a simple type discipline to separate deterministic and probabilistic expressions. We demonstrate a semantics-preserving compilation into a first-order functional language that lends itself to a simple presentation of inference algorithms for streaming models. We also redesign the delayed sampling inference algorithm to provide efficient streaming inference. Together with an evaluation on several reactive applications, our results demonstrate that ProbZelus enables the design of reactive probabilistic applications and efficient, bounded memory inference.

cs.PL↗

arXiv2018

Sundials/ML: Connecting OCaml to the Sundials Numeric Solvers

This paper describes the design and implementation of a comprehensive OCaml interface to the Sundials library of numeric solvers for ordinary differential equations, differential algebraic equations, and non-linear equations. The interface provides a convenient and memory-safe alternative to using Sundials directly from C and facilitates application development by integrating with higher-level language features, like garbage-collected memory management, algebraic data types, and exceptions. Our benchmark results suggest that the interface overhead is acceptable: the standard examples are rarely twice as slow in OCaml than in C, and often less than 50% slower. The challenges in interfacing with Sundials are to efficiently and safely share data structures between OCaml and C, to support multiple implementations of vector operations and linear solvers through a common interface, and to manage calls and error signalling to and from OCaml. We explain how we overcame these difficulties using a combination of standard techniques such as phantom types and polymorphic variants, and carefully crafted data representations.

cs.PL↗

arXiv2012

A Type System for the Automatic Distribution of Higher-order Synchronous Dataflow Programs

We address the design of distributed systems with synchronous dataflow programming languages. As modular design entails handling both architectural and functional modularity, our first contribution is to extend an existing synchronous dataflow programming language with primitives allowing the description of a distributed architecture and the localization of some expressions onto some processors. We also present a distributed semantics to formalize the distributed execution of synchronous programs. Our second contribution is to provide a type system, in order to infer the localization of non-annotated values by means of type inference and to ensure, at compilation time, the consistency of the distribution. Our third contribution is to provide a type-directed projection operation to obtain automatically,from a centralized typed program, the local program to be executed by each computing resource. The type system as well as the automatic distribution mechanism has been fully implemented in the compiler of an existing synchronous data-flow programming language.

cs.PL↗