Bounding data races in space and time

© 2018 ACM. We propose a new semantics for shared-memory parallel programs that gives strong guarantees even in the presence of data races. Our local data race freedom property guarantees that all data-race-free portions of programs exhibit sequential semantics. We provide a straightforward operational semantics and an equivalent axiomatic model, and evaluate an implementation for the OCaml programming language. Our evaluation demonstrates that it is possible to balance a comprehensible memory model with a reasonable (no overhead on x86, ∼0.6% on ARM) sequential performance trade-off in a mainstream programming language

Turning down the lamp: Software specialisation for the cloud

© USENIX Workshop on Hot Topics in Cloud Computing, HotCloud 2010.All right reserved. The wide availability of cloud computing offers an unprecedented opportunity to rethink how we construct applications. The cloud is currently mostly used to package up existing software stacks and operating systems (e.g. LAMP) for scaling out websites. We instead view the cloud as a stable hardware platform, and present a programming framework which permits applications to be constructed to run directly on top of it without intervening software layers. Our prototype (dubbed Mirage) is unashamedly academic; it extends the Objective Caml language with storage extensions and a custom run-time to emit binaries that execute as a guest operating system under Xen. Mirage applications exhibit significant performance speedups for I/O and memory handling versus the same code running under Linux/Xen. Our results can be generalised to offer insight into improving more commonly used languages such as PHP, Python and Ruby, and we discuss lessons learnt and future directions

Optimal Algorithms For Dissemination Of Information In Generalized Communication Modes

Some generalized communication modes enabling the dissemination of information among processors of interconnection networks via vertex-disjoint or edge-disjoint paths in one communication step will be investigated. A thorough study of these communication modes will be presented by giving optimal algorithms for broadcasting, accumulation and gossiping in most of the well known parallel architectures. For those networks in which a Hamiltonian path exists (Hypercubes, Cube Connected Cycles, Butterflies, Shuffle Exchange, etc.) optimal algorithms can be obtained quite easily, but for complete binary trees, complete k-ary trees (k 3) and arbitrary degree bounded graphs, the optimal algorithms as well as the matching lower bound proofs are more involved. An interesting consequence of the presented algorithms is the fact that in almost all these interconnection networks the gossip problem cannot be solved in less time than the sum of time complexities of the accumulation problem and the bro..

Strategies for Minimizing the Average Cost of Paging on the Air Interface

Location Management of mobile users in a cellular network covers tracking and paging (searching) functionality. In this paper a sequential search strategy is proposed which reduces the signaling on the air interface and also considers the user’s privacy using implicit addresses. After introducing some related work on paging and reducing the costs of paging, the basic idea of the search strategy is described. The used paging methods are crucial for the effectiveness of this strategy. For that, three different paging methods are proposed using fixed and variable segment sizes. The methods are evaluated according to their costs in terms of delay, bandwidth and paging steps. For that the model is described we used for our simulations. Metrics are defined to evaluate the strategies before presenting our results using an event-driven simulation