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Feasibility of Fog Computing [article]

Blesson Varghese, Nan Wang, Dimitrios S. Nikolopoulos, Rajkumar Buyya
2017 arXiv   pre-print
As billions of devices get connected to the Internet, it will not be sustainable to use the cloud as a centralised server. The way forward is to decentralise computations away from the cloud towards the edge of the network closer to the user. This reduces the latency of communication between a user device and the cloud, and is the premise of 'fog computing' defined in this paper. The aim of this paper is to highlight the feasibility and the benefits in improving the Quality-of-Service and
more » ... f-Service and Experience by using fog computing. For an online game use-case, we found that the average response time for a user is improved by 20% when using the edge of the network in comparison to using a cloud-only model. It was also observed that the volume of traffic between the edge and the cloud server is reduced by over 90% for the use-case. The preliminary results highlight the potential of fog computing in achieving a sustainable computing model and highlights the benefits of integrating the edge of the network into the computing ecosystem.
arXiv:1701.05451v1 fatcat:vzqcosbqcncr5jj6hvhu7moj6y


Ioannis Manousakis, Dimitrios S. Nikolopoulos
2012 ACM SIGBED Review  
FFT CPU 64k input No Bzip2 CPU + I/O 1MB Compress No NAND Flash Read I/O {1,2,3,4}MB No Web Browsing CPU + I/O Konqueror Yes ADD -NOP CPU Scheduler Test No *T/S = Touchscreen On Figure Power behavior  ...  Power Consumption while browsing the Web via Touchschreen 4.25 4.2 Issue 4.15 Power [Watts] 4.05 4.1 Load Browser DNS Resolve Get Response Server Render Page 4 And Data [45 3.95 System KB/s]  ... 
doi:10.1145/2318836.2318841 fatcat:zee43doqfvawrl2of6bpipygxa

Cross Architectural Power Modelling [article]

Kai Chen and Peter Kilpatrick and Dimitrios S. Nikolopoulos and Blesson Varghese
2020 arXiv   pre-print
Existing power modelling research focuses on the model rather than the process for developing models. An automated power modelling process that can be deployed on different processors for developing power models with high accuracy is developed. For this, (i) an automated hardware performance counter selection method that selects counters best correlated to power on both ARM and Intel processors, (ii) a noise filter based on clustering that can reduce the mean error in power models, and (iii) a
more » ... odels, and (iii) a two stage power model that surmounts challenges in using existing power models across multiple architectures are proposed and developed. The key results are: (i) the automated hardware performance counter selection method achieves comparable selection to the manual method reported in the literature, (ii) the noise filter reduces the mean error in power models by up to 55%, and (iii) the two stage power model can predict dynamic power with less than 8% error on both ARM and Intel processors, which is an improvement over classic models.
arXiv:2003.08305v1 fatcat:lewj6gf2ovcvfi45nmtheky3mq

Confronting hip resurfacing and big femoral head replacement gait analysis

Panagiotis K. Karampinas, Dimitrios S. Evangelopoulos, John Vlamis, Konstantinos Nikolopoulos, Dimitrios S. Korres
2014 Orthopedic Reviews  
Improved hip kinematics and bone preservation have been reported after resurfacing total hip replacement (THRS). On the other hand, hip kinematics with standard total hip replacement (THR) is optimized with large diameter femoral heads (BFH-THR). The purpose of this study is to evaluate the functional outcomes of THRS and BFH-THR and correlate these results to bone preservation or the large femoral heads. Thirty-one patients were included in the study. Gait speed, postural balance,
more » ... lance, proprioception and overall performance. Our results demonstrated a non-statistically significant improvement in gait, postural balance and proprioception in the THRS confronting to BFH-THR group. THRS provide identical outcomes to traditional BFH-THR. The THRS choice as bone preserving procedure in younger patients is still to be evaluated.
doi:10.4081/or.2014.5221 pmid:24744841 pmcid:PMC3980157 fatcat:azsjc7dt7fhsjnr5qyzkrcnyse

Inference and Declaration of Independence in Task-Parallel Programs [chapter]

Foivos S. Zakkak, Dimitrios Chasapis, Polyvios Pratikakis, Angelos Bilas, Dimitrios S. Nikolopoulos
2013 Lecture Notes in Computer Science  
Benchmark LOC Tasks Total Args Scalar Args Analysis (s) Graph Nodes Safe Args Intruder is a Signature-based network intrusion detection systems (NIDS), from the STAMP benchmark suite [16] .  ... 
doi:10.1007/978-3-642-45293-2_1 fatcat:w5so2ucrybeetiga4xtjvhfcei

Evaluating Asymmetric Multicore Systems-on-Chip using Iso-Metrics [article]

Charalampos Chalios, Dimitrios S. Nikolopoulos, Enrique S. Quintana-Orti
2015 arXiv   pre-print
The end of Dennard scaling has pushed power consumption into a first order concern for current systems, on par with performance. As a result, near-threshold voltage computing (NTVC) has been proposed as a potential means to tackle the limited cooling capacity of CMOS technology. Hardware operating in NTV consumes significantly less power, at the cost of lower frequency, and thus reduced performance, as well as increased error rates. In this paper, we investigate if a low-power systems-on-chip,
more » ... r systems-on-chip, consisting of ARM's asymmetric big.LITTLE technology, can be an alternative to conventional high performance multicore processors in terms of power/energy in an unreliable scenario. For our study, we use the Conjugate Gradient solver, an algorithm representative of the computations performed by a large range of scientific and engineering codes.
arXiv:1503.08104v1 fatcat:w6m2azaplna2lku2hurlnaeeme

Implementing Efficient Message Logging Protocols as MPI Application Extensions [article]

Kiril Dichev, Dimitrios S. Nikolopoulos
2019 arXiv   pre-print
Message logging protocols are enablers of local rollback, a more efficient alternative to global rollback, for fault tolerant MPI applications. Until now, message logging MPI implementations have incurred the overheads of a redesign and redeployment of an MPI library, as well as continued performance penalties across various kernels. Successful research efforts for message logging implementations do exist, but not a single one of them can be easily deployed today by more than a few experts. In
more » ... a few experts. In contrast, in this work we build efficient message logging capabilities on top of an MPI library with no message logging capabilities; we do so for two different HPC kernels, one with a global exchange pattern (CG), and one with a neighbourhood exchange pattern (LULESH). While our library of choice ULFM detects failure and recovers MPI communicators, we build on that to then restore the intra- and inter-process data consistency of both applications. This task turns out to be challenging, and we present the methodology for doing so in this work. In the end, we achieve message logging capabilities for each kernel, without the need for an actual message logging runtime underneath. On the performance side, we match state-of-the-art solutions and (a) eliminate event logging and the event logger component altogether, and (b) design a hybrid protocol, which gracefully shifts between global and local rollback, depending on the available payload logging memory. Such a hybrid protocol between local and global rollback has not been previously proposed to our knowledge. Our extensions span a few hundred lines of code for each kernel, are open-sourced, and enable local and global rollback after process failure.
arXiv:1905.03184v1 fatcat:rqsr3nwuevdpjorgkuusevfaj4

Energy Optimization of Memory Intensive Parallel workloads [article]

Chhaya Trehan, Hans Vandierendonck, Georgios Karakonstantis, Dimitrios S. Nikolopoulos
2016 arXiv   pre-print
w 2 , ....w M ] and S = M m=1 w m is the sum of the parallelism vector.  ...  Note that the above scheduling criteria is different from the one suggested in [15] which suggests minimizing S = M m=1 π m w m , which the authors define as the weighted makespan.  ... 
arXiv:1605.04111v1 fatcat:vma7kk2csbfvbdqic4xw3yhspy

Intra-node Memory Safe GPU Co-Scheduling [article]

Carlos Reano, Federico Silla, Dimitrios S. Nikolopoulos, Blesson Varghese
2017 arXiv   pre-print
Dimitrios S. Nikolopoulos is Professor and Head of the School of Electronics, Electrical Engineering and Computer Science, at Queen's University of Belfast.  ...  Nikolopoulos and B. Varghese are with the Queen's University Belfast, UK.  ... 
arXiv:1712.04495v1 fatcat:mlth4j53wbcpdbyhfjdjiufbxe

Power Modelling for Heterogeneous Cloud-Edge Data Centers [article]

Kai Chen, Blesson Varghese, Peter Kilpatrick, Dimitrios S. Nikolopoulos
2017 arXiv   pre-print
Existing power modelling research focuses not on the method used for developing models but rather on the model itself. This paper aims to develop a method for deploying power models on emerging processors that will be used, for example, in cloud-edge data centers. Our research first develops a hardware counter selection method that appropriately selects counters most correlated to power on ARM and Intel processors. Then, we propose a two stage power model that works across multiple
more » ... ltiple architectures. The key results are: (i) the automated hardware performance counter selection method achieves comparable selection to the manual selection methods reported in literature, and (ii) the two stage power model can predict dynamic power more accurately on both ARM and Intel processors when compared to classic power models.
arXiv:1710.10325v1 fatcat:5f5dbrjetjg27lylvrdezcsz5a

Edge-as-a-Service: Towards Distributed Cloud Architectures [article]

Blesson Varghese, Nan Wang, Jianyu Li, Dimitrios S. Nikolopoulos
2017 arXiv   pre-print
The middle tier is the edge node layer in which edge node(s) are made available on-demand to support a collection of user devices that may be close to the node(s).  ... 
arXiv:1710.10090v1 fatcat:guoafqi2qvgwregwknwa24ucce

ENORM: A Framework For Edge NOde Resource Management [article]

Nan Wang, Blesson Varghese, Michail Matthaiou, Dimitrios S. Nikolopoulos
2017 arXiv   pre-print
Procedure 3: Deployment mechanism Data: s i , U i , S, R, r u 1 install software packages in s i ; 2 deploy partitioned server image in s i ; 3 launch s i ; 4 redirect U i to s i ; 5 autoScale(S, s i ,  ...  ype == multiple then 7 for ∀s i ∈ [s i , s n ] do 8 migrate and redirect U i to the cloud; 9 stop and destroy LXC container hosting s i ; 10 S = S − {s i }; Procedure 6 : 6 Scaling mechanism Data: r  ... 
arXiv:1709.04061v1 fatcat:b2rfsukd3bcmtbwndl7lp75lri

Inference and declaration of independence

Foivos S. Zakkak, Dimitrios Chasapis, Polyvios Pratikakis, Angelos Bilas, Dimitrios S. Nikolopoulos
2012 Proceedings of the 21st international conference on Parallel architectures and compilation techniques - PACT '12  
We present a set of static techniques that reduce runtime overheads in task-parallel programs with implicit synchronization. We use a static dependence analysis to detect nonconflicting tasks and remove unnecessary runtime checks. We further reduce overheads by statically optimizing task creation and management of runtime metadata. We implemented these optimizations in SCOOP, a source-to-source compiler for such a programming model and runtime system. We evaluate SCOOP on 10 representative
more » ... representative benchmarks and show that our approach can improve performance by 12% on average.
doi:10.1145/2370816.2370892 dblp:conf/IEEEpact/ZakkakCPBN12 fatcat:ibqbfrnvmjf7bcufcy7gpl45m4

TwinCG: Dual Thread Redundancy with Forward Recovery for Conjugate Gradient Methods [article]

Kiril Dichev, Dimitrios S. Nikolopoulos
2016 arXiv   pre-print
Even though iterative solvers like the Conjugate Gradients method (CG) have been studied for over fifty years, fault tolerance for such solvers has seen much attention in recent years. For iterative solvers, two major reliable strategies of recovery exist: checkpoint-restart for backward recovery, or some type of redundancy technique for forward recovery. Important redundancy techniques like ABFT techniques for sparse matrix-vector products (SpMxV) have recently been proposed, which increase
more » ... , which increase the resilience of CG methods. These techniques offer limited recovery options, and introduce a tolerable overhead. In this work, we study a more powerful resilience concept, which is redundant multithreading. It offers more generic and stronger recovery guarantees, including any soft faults in CG iterations (among others covering ABFT SpMxV), but also requires more resources. We carefully study this redundancy/efficiency conflict. We propose a fault tolerant CG method, called TwinCG, which introduces minimal wallclock time overhead, and significant advantages in detection and correction strategies. Our method uses Dual Modular Redundancy instead of the more expensive Triple Modular Redundancy; still, it retains the TMR advantages of fault correction. We describe, implement, and benchmark our iterative solver, and compare it in terms of efficiency and fault tolerance capabilities to state-of-the-art techniques. We find that before parallelization, TwinCG introduces around 5-6% runtime overhead compared to standard CG, and after parallelization efficiently uses BLAS. In the presence of faults, it reliably performs forward recovery for a range of problems, outperforming SpMxV ABFT solutions.
arXiv:1605.04580v1 fatcat:zmkv26ydjbe4lgyhcr3adif7m4

Challenges and Opportunities in Edge Computing [article]

Blesson Varghese and Nan Wang and Sakil Barbhuiya and Peter Kilpatrick and Dimitrios S. Nikolopoulos
2016 arXiv   pre-print
Many cloud-based applications employ a data centre as a central server to process data that is generated by edge devices, such as smartphones, tablets and wearables. This model places ever increasing demands on communication and computational infrastructure with inevitable adverse effect on Quality-of-Service and Experience. The concept of Edge Computing is predicated on moving some of this computational load towards the edge of the network to harness computational capabilities that are
more » ... es that are currently untapped in edge nodes, such as base stations, routers and switches. This position paper considers the challenges and opportunities that arise out of this new direction in the computing landscape.
arXiv:1609.01967v1 fatcat:ci234klfn5dv7h4mrnalwivzu4
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