The communication semantics of the message passing interface

technical reportThe Message Passing Interface (MPI) standard is a natural language document that describes a software library for interprocess communication. Automatic reasoning about the reactive nature of programs communicating via MPI libraries is not possible without also analizing the library being used. Many distributed programs that use MPI are relatively brief compared to the libraries that implement MPI. A formal specification of the communication semantics of the MPI standard (i) enables modular automatic reasoning of MPI based parallel programs independent of the library implementation, (ii) provides a mathematically precise declaration of the natural language intent of the MPI specification, (iii) enables mathematical reasoning about libraries that implement the standard, and (iv) allows for reasoning about the standard itself. We have created such a specification of the point to point operations and present it in this report. We also discuss some preliminary efforts to accomplish (i) above

Formal specification of MPI 2.0: case study in specifying a practical concurrent programming API

technical reportWe describe the rst formal speci cation of a non-trivial subset of MPI, the dominant communication API in high performance computing. Engineering a formal speci cation for a non-trivial concurrency API requires the right combination of rigor, executability, and traceability, while also serving as a smooth elaboration of a pre-existing informal speci - cation. It also requires the modularization of reusable speci cation components to keep the length of the speci cation in check. Long-lived APIs such as MPI are not usually `textbook minimalistic' because they support a diverse array of applications, a diverse community of users, and have ef cient implementations over decades of computing hardware. We choose the TLA+ notation to write our speci cations, and describe how we organized the speci - cation of 150 of the 300 MPI 2.0 functions. We detail a handful of these functions in this paper, and assess our speci cation with respect to the aforesaid requirements. We close with a description of possible approaches that may help render the act of writing, understanding, and validating speci cations much more productive

A TLA solution to the RPC-Memory specification problem

We present a complete solution to the Broy-Lamport specification problem. Our specifications are written in TLA, a formal language based on TLA. We give the high levels of structured proofs an

Rigorous design of distributed transactions

Database replication is traditionally envisaged as a way of increasing fault-tolerance and availability. It is advantageous to replicate the data when transaction workload is predominantly read-only. However, updating replicated data within a transactional framework is a complex affair due to failures and race conditions among conflicting transactions. This thesis investigates various mechanisms for the management of replicas in a large distributed system, formalizing and reasoning about the behavior of such systems using Event-B. We begin by studying current approaches for the management of replicated data and explore the use of broadcast primitives for processing transactions. Subsequently, we outline how a refinement based approach can be used for the development of a reliable replicated database system that ensures atomic commitment of distributed transactions using ordered broadcasts. Event-B is a formal technique that consists of describing rigorously the problem in an abstract model, introducing solutions or design details in refinement steps to obtain more concrete specifications, and verifying that the proposed solutions are correct. This technique requires the discharge of proof obligations for consistency checking and refinement checking. The B tools provide significant automated proof support for generation of the proof obligations and discharging them. The majority of the proof obligations are proved by the automatic prover of the tools. However, some complex proof obligations require interaction with the interactive prover. These proof obligations also help discover new system invariants. The proof obligations and the invariants help us to understand the complexity of the problem and the correctness of the solutions. They also provide a clear insight into the system and enhance our understanding of why a design decision should work. The objective of the research is to demonstrate a technique for the incremental construction of formal models of distributed systems and reasoning about them, to develop the technique for the discovery of gluing invariants due to prover failure to automatically discharge a proof obligation and to develop guidelines for verification of distributed algorithms using the technique of abstraction and refinement.EThOS - Electronic Theses Online ServiceGBUnited Kingdo