456 research outputs found
Efficient and Reasonable Object-Oriented Concurrency
Making threaded programs safe and easy to reason about is one of the chief
difficulties in modern programming. This work provides an efficient execution
model for SCOOP, a concurrency approach that provides not only data race
freedom but also pre/postcondition reasoning guarantees between threads. The
extensions we propose influence both the underlying semantics to increase the
amount of concurrent execution that is possible, exclude certain classes of
deadlocks, and enable greater performance. These extensions are used as the
basis an efficient runtime and optimization pass that improve performance 15x
over a baseline implementation. This new implementation of SCOOP is also 2x
faster than other well-known safe concurrent languages. The measurements are
based on both coordination-intensive and data-manipulation-intensive benchmarks
designed to offer a mixture of workloads.Comment: Proceedings of the 10th Joint Meeting of the European Software
Engineering Conference and the ACM SIGSOFT Symposium on the Foundations of
Software Engineering (ESEC/FSE '15). ACM, 201
Handling Parallelism in a Concurrency Model
Programming models for concurrency are optimized for dealing with
nondeterminism, for example to handle asynchronously arriving events. To shield
the developer from data race errors effectively, such models may prevent shared
access to data altogether. However, this restriction also makes them unsuitable
for applications that require data parallelism. We present a library-based
approach for permitting parallel access to arrays while preserving the safety
guarantees of the original model. When applied to SCOOP, an object-oriented
concurrency model, the approach exhibits a negligible performance overhead
compared to ordinary threaded implementations of two parallel benchmark
programs.Comment: MUSEPAT 201
On the dynamic toroidal multipoles from localized electric current distributions
We analyze the dynamic toroidal multipoles and prove that they do not have an
independent physical meaning with respect to their interaction with
electromagnetic waves. We analytically show how the split into electric and
toroidal parts causes the appearance of non-radiative components in each of the
two parts. These non-radiative components, which cancel each other when both
parts are summed, preclude the separate determination of each part by means of
measurements of the radiation from the source or of its coupling to external
electromagnetic waves. In other words, there is no toroidal radiation or
independent toroidal electromagnetic coupling. The formal meaning of the
toroidal multipoles is clear in our derivations. They are the higher order
terms of an expansion of the multipolar coefficients of electric parity with
respect to the electromagnetic size of the source
Contract-Based General-Purpose GPU Programming
Using GPUs as general-purpose processors has revolutionized parallel
computing by offering, for a large and growing set of algorithms, massive
data-parallelization on desktop machines. An obstacle to widespread adoption,
however, is the difficulty of programming them and the low-level control of the
hardware required to achieve good performance. This paper suggests a
programming library, SafeGPU, that aims at striking a balance between
programmer productivity and performance, by making GPU data-parallel operations
accessible from within a classical object-oriented programming language. The
solution is integrated with the design-by-contract approach, which increases
confidence in functional program correctness by embedding executable program
specifications into the program text. We show that our library leads to modular
and maintainable code that is accessible to GPGPU non-experts, while providing
performance that is comparable with hand-written CUDA code. Furthermore,
runtime contract checking turns out to be feasible, as the contracts can be
executed on the GPU
Exact dipolar moments of a localized electric current distribution
The multipolar decomposition of current distributions is used in many
branches of physics. Here, we obtain new exact expressions for the dipolar
moments of a localized electric current distribution. The typical integrals for
the dipole moments of electromagnetically small sources are recovered as the
lowest order terms of the new expressions in a series expansion with respect to
the size of the source. All the higher order terms can be easily obtained. We
also provide exact and approximated expressions for dipoles that radiate a
definite polarization handedness (helicity). Formally, the new exact
expressions are only marginally more complex than their lowest order
approximations
Exact dipolar moments of a localized electric current distribution
The multipolar decomposition of current distributions is used in many
branches of physics. Here, we obtain new exact expressions for the dipolar
moments of a localized electric current distribution. The typical integrals for
the dipole moments of electromagnetically small sources are recovered as the
lowest order terms of the new expressions in a series expansion with respect to
the size of the source. All the higher order terms can be easily obtained. We
also provide exact and approximated expressions for dipoles that radiate a
definite polarization handedness (helicity). Formally, the new exact
expressions are only marginally more complex than their lowest order
approximations
The 101 translation problems between Japanese and German/English
We investigate differences between Japanese and German/English and explain characteristic phenomena to Japanese. The study helps us to realize what can be problematic when translating Japanese into German/English and vice versa
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