2,954 research outputs found
Which Problems Does a Multi-Language Virtual Machine Need to Solve in the Multicore/Manycore Era?
While parallel programming for very regular problems has been used in the scientific community by non-computer-scientists successfully for a few decades now, concurrent programming and solving irregular problems remains hard. Furthermore, we shift from few expert system programmers mastering concurrency for a constrained set of problems to mainstream application developers being required to master concurrency for a wide variety of problems. Consequently, high-level language virtual machine (VM) research faces interesting questions. What are processor design changes that have an impact on the abstractions provided by VMs to provide platform independence? How can application programmers' diverse needs be facilitated to solve concurrent programming problems? We argue that VMs will need to be ready for a wide range of different concurrency models that allow solving concurrency problems with appropriate abstractions. Furthermore, they need to abstract from heterogeneous processor architectures, varying performance characteristics, need to account for memory access cost and inter-core communication mechanisms but should only expose the minimal useful set of notions like locality, explicit communication, and adaptable scheduling to maintain their abstracting nature. Eventually, language designers need to be enabled to guarantee properties like encapsulation, scheduling guarantees, and immutability also when an interaction between different problem-specific concurrency abstractions is required
Causality in concurrent systems
Concurrent systems identify systems, either software, hardware or even
biological systems, that are characterized by sets of independent actions that
can be executed in any order or simultaneously. Computer scientists resort to a
causal terminology to describe and analyse the relations between the actions in
these systems. However, a thorough discussion about the meaning of causality in
such a context has not been developed yet. This paper aims to fill the gap.
First, the paper analyses the notion of causation in concurrent systems and
attempts to build bridges with the existing philosophical literature,
highlighting similarities and divergences between them. Second, the paper
analyses the use of counterfactual reasoning in ex-post analysis in concurrent
systems (i.e. execution trace analysis).Comment: This is an interdisciplinary paper. It addresses a class of causal
models developed in computer science from an epistemic perspective, namely in
terms of philosophy of causalit
History-Preserving Bisimilarity for Higher-Dimensional Automata via Open Maps
We show that history-preserving bisimilarity for higher-dimensional automata
has a simple characterization directly in terms of higher-dimensional
transitions. This implies that it is decidable for finite higher-dimensional
automata. To arrive at our characterization, we apply the open-maps framework
of Joyal, Nielsen and Winskel in the category of unfoldings of precubical sets.Comment: Minor updates in accordance with reviewer comments. Submitted to MFPS
201
Harnessing the Power of Many: Extensible Toolkit for Scalable Ensemble Applications
Many scientific problems require multiple distinct computational tasks to be
executed in order to achieve a desired solution. We introduce the Ensemble
Toolkit (EnTK) to address the challenges of scale, diversity and reliability
they pose. We describe the design and implementation of EnTK, characterize its
performance and integrate it with two distinct exemplar use cases: seismic
inversion and adaptive analog ensembles. We perform nine experiments,
characterizing EnTK overheads, strong and weak scalability, and the performance
of two use case implementations, at scale and on production infrastructures. We
show how EnTK meets the following general requirements: (i) implementing
dedicated abstractions to support the description and execution of ensemble
applications; (ii) support for execution on heterogeneous computing
infrastructures; (iii) efficient scalability up to O(10^4) tasks; and (iv)
fault tolerance. We discuss novel computational capabilities that EnTK enables
and the scientific advantages arising thereof. We propose EnTK as an important
addition to the suite of tools in support of production scientific computing
Higher-Dimensional Timed Automata
We introduce a new formalism of higher-dimensional timed automata, based on
van Glabbeek's higher-dimensional automata and Alur's timed automata. We prove
that their reachability is PSPACE-complete and can be decided using zone-based
algorithms. We also show how to use tensor products to combat state-space
explosion and how to extend the setting to higher-dimensional hybrid automata
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