Concurrency: 2024-2025

Lecturer

Bill Roscoe

Degrees

Schedule A2(CS&P) — Computer Science and Philosophy

Schedule B1 (CS&P) — Computer Science and Philosophy

Schedule A2 — Computer Science

Schedule B1 — Computer Science

Schedule A2(M&CS) — Mathematics and Computer Science

Schedule B1(M&CS) — Mathematics and Computer Science

Term

Michaelmas Term 2024 (16 lectures)

Overview

Computer networks, multiprocessors and parallel algorithms, though radically different, all provide examples of processes acting in parallel to achieve some goal. All benefit from the efficiency of concurrency yet require careful design to ensure that they function correctly. The concurrency course introduces the fundamental concepts of concurrency using the notation of Communicating Sequential Processes. By introducing communication, parallelism, deadlock, livelock, etc., it shows how CSP represents, and can be used to reason about, concurrent systems. Students are taught how to design communicating processes, how to construct realistic models of real systems, and how to write specifications that can be used to verify the correctness of the system models. One important feature of the module is its use of both algebraic laws and semantic models to reason about reactive and concurrent designs. Another is its use of FDR to animate models and verify that they meet their specifications.

Learning outcomes

At the end of the course the student should:

understand some of the issues and difficulties involved in Concurrency;
be able to specify and model concuurent systems using CSP;
be able to reason about CSP models of systems using both algebraic laws and semantic models;
be able to analyse CSP models of systems using the model checker FDR.

Synopsis

Processes and observations of processes; point synchronisation, events, alphabets. Sequential processes: prefixing, choice, nondeterminism. Operational semantics; traces; algebraic laws.
Recursion. Fixed points as a means of explaining recursion; approximation, limits, least fixed points; guardedness and unique fixed points.
Concurrency. Hiding. Renaming.
Non-deterministic behaviours, refusals, failures.
Hiding and divergence, the failures-divergences model.
Specification and correctness.
Communication, buffers, sequential composition.

Syllabus

Deterministic processes: traces, operational semantics; prefixing, choice, concurrency and communication. Nondeterminism: failures and divergences; nondeterministic choice, hiding and interleaving. Advanced CSP operators. Refinement, specification and proof. Process algebra: equational and inequational reasoning.

Reading list

Lecture Notes: The lecture notes for this year's course appear online on the course materials page.

Course Text:

A. W. Roscoe, Understanding Concurrent Systems, Chapters 1-8, Springer 2010

Alternatives:

A.W. Roscoe, The Theory and Practice of Concurrency, Chapters 1-7, Prentice-Hall International, 1997; http://www.cs.ox.ac.uk/oucl/work/bill.roscoe/publications/68b.pdf.
C. A. R. Hoare, Communicating Sequential Processes, Prentice-Hall International, 1985; http://www.usingcsp.com.
S. A. Schneider, Concurrent and Real-time Systems, Chapters 1-8, Wiley, 2000; http://www.computing.surrey.ac.uk/personal/st/S.Schneider/books/CRTS.pdf.

Background reading:

S.D. Brookes and A.W. Roscoe. CSP: A practical process algebra: http://www.cs.ox.ac.uk/files/12724/cspfdrstory.pdf

Overheads: This year's slides will appear on the course materials page over the course of the term.

Link to downloadable CSPM scripts from Roscoe's book: http://www.cs.ox.ac.uk/ucs/CSPM.html

Related research

Activities

Concurrency

Taking our courses

This form is not to be used by students studying for a degree in the Department of Computer Science, or for Visiting Students who are registered for Computer Science courses

Other matriculated University of Oxford students who are interested in taking this, or other, courses in the Department of Computer Science, must complete this online form by 17.00 on Friday of 0th week of term in which the course is taught. Late requests, and requests sent by email, will not be considered. All requests must be approved by the relevant Computer Science departmental committee and can only be submitted using this form.