14,946 research outputs found
Actors vs Shared Memory: two models at work on Big Data application frameworks
This work aims at analyzing how two different concurrency models, namely the
shared memory model and the actor model, can influence the development of
applications that manage huge masses of data, distinctive of Big Data
applications. The paper compares the two models by analyzing a couple of
concrete projects based on the MapReduce and Bulk Synchronous Parallel
algorithmic schemes. Both projects are doubly implemented on two concrete
platforms: Akka Cluster and Managed X10. The result is both a conceptual
comparison of models in the Big Data Analytics scenario, and an experimental
analysis based on concrete executions on a cluster platform
Rumble: Data Independence for Large Messy Data Sets
This paper introduces Rumble, an engine that executes JSONiq queries on
large, heterogeneous and nested collections of JSON objects, leveraging the
parallel capabilities of Spark so as to provide a high degree of data
independence. The design is based on two key insights: (i) how to map JSONiq
expressions to Spark transformations on RDDs and (ii) how to map JSONiq FLWOR
clauses to Spark SQL on DataFrames. We have developed a working implementation
of these mappings showing that JSONiq can efficiently run on Spark to query
billions of objects into, at least, the TB range. The JSONiq code is concise in
comparison to Spark's host languages while seamlessly supporting the nested,
heterogeneous data sets that Spark SQL does not. The ability to process this
kind of input, commonly found, is paramount for data cleaning and curation. The
experimental analysis indicates that there is no excessive performance loss,
occasionally even a gain, over Spark SQL for structured data, and a performance
gain over PySpark. This demonstrates that a language such as JSONiq is a simple
and viable approach to large-scale querying of denormalized, heterogeneous,
arborescent data sets, in the same way as SQL can be leveraged for structured
data sets. The results also illustrate that Codd's concept of data independence
makes as much sense for heterogeneous, nested data sets as it does on highly
structured tables.Comment: Preprint, 9 page
Implementing atomic actions in Ada 95
Atomic actions are an important dynamic structuring technique that aid the construction of fault-tolerant concurrent systems. Although they were developed some years ago, none of the well-known commercially-available programming languages directly support their use. This paper summarizes software fault tolerance techniques for concurrent systems, evaluates the Ada 95 programming language from the perspective of its support for software fault tolerance, and shows how Ada 95 can be used to implement software fault tolerance techniques. In particular, it shows how packages, protected objects, requeue, exceptions, asynchronous transfer of control, tagged types, and controlled types can be used as building blocks from which to construct atomic actions with forward and backward error recovery, which are resilient to deserter tasks and task abortion
Atomic-SDN: Is Synchronous Flooding the Solution to Software-Defined Networking in IoT?
The adoption of Software Defined Networking (SDN) within traditional networks
has provided operators the ability to manage diverse resources and easily
reconfigure networks as requirements change. Recent research has extended this
concept to IEEE 802.15.4 low-power wireless networks, which form a key
component of the Internet of Things (IoT). However, the multiple traffic
patterns necessary for SDN control makes it difficult to apply this approach to
these highly challenging environments. This paper presents Atomic-SDN, a highly
reliable and low-latency solution for SDN in low-power wireless. Atomic-SDN
introduces a novel Synchronous Flooding (SF) architecture capable of
dynamically configuring SF protocols to satisfy complex SDN control
requirements, and draws from the authors' previous experiences in the IEEE EWSN
Dependability Competition: where SF solutions have consistently outperformed
other entries. Using this approach, Atomic-SDN presents considerable
performance gains over other SDN implementations for low-power IoT networks. We
evaluate Atomic-SDN through simulation and experimentation, and show how
utilizing SF techniques provides latency and reliability guarantees to SDN
control operations as the local mesh scales. We compare Atomic-SDN against
other SDN implementations based on the IEEE 802.15.4 network stack, and
establish that Atomic-SDN improves SDN control by orders-of-magnitude across
latency, reliability, and energy-efficiency metrics
Quantum Gates and Memory using Microwave Dressed States
Trapped atomic ions have been successfully used for demonstrating basic
elements of universal quantum information processing (QIP). Nevertheless,
scaling up of these methods and techniques to achieve large scale universal
QIP, or more specialized quantum simulations remains challenging. The use of
easily controllable and stable microwave sources instead of complex laser
systems on the other hand promises to remove obstacles to scalability.
Important remaining drawbacks in this approach are the use of magnetic field
sensitive states, which shorten coherence times considerably, and the
requirement to create large stable magnetic field gradients. Here, we present
theoretically a novel approach based on dressing magnetic field sensitive
states with microwave fields which addresses both issues and permits fast
quantum logic. We experimentally demonstrate basic building blocks of this
scheme to show that these dressed states are long-lived and coherence times are
increased by more than two orders of magnitude compared to bare magnetic field
sensitive states. This changes decisively the prospect of microwave-driven ion
trap QIP and offers a new route to extend coherence times for all systems that
suffer from magnetic noise such as neutral atoms, NV-centres, quantum dots, or
circuit-QED systems.Comment: 9 pages, 4 figure
Practical issues for the implementation of survivability and recovery techniques in optical networks
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