Efficient Large-scale Trace Checking Using MapReduce

The problem of checking a logged event trace against a temporal logic specification arises in many practical cases. Unfortunately, known algorithms for an expressive logic like MTL (Metric Temporal Logic) do not scale with respect to two crucial dimensions: the length of the trace and the size of the time interval for which logged events must be buffered to check satisfaction of the specification. The former issue can be addressed by distributed and parallel trace checking algorithms that can take advantage of modern cloud computing and programming frameworks like MapReduce. Still, the latter issue remains open with current state-of-the-art approaches. In this paper we address this memory scalability issue by proposing a new semantics for MTL, called lazy semantics. This semantics can evaluate temporal formulae and boolean combinations of temporal-only formulae at any arbitrary time instant. We prove that lazy semantics is more expressive than standard point-based semantics and that it can be used as a basis for a correct parametric decomposition of any MTL formula into an equivalent one with smaller, bounded time intervals. We use lazy semantics to extend our previous distributed trace checking algorithm for MTL. We evaluate the proposed algorithm in terms of memory scalability and time/memory tradeoffs.Comment: 13 pages, 8 figure

On data skewness, stragglers, and MapReduce progress indicators

We tackle the problem of predicting the performance of MapReduce applications, designing accurate progress indicators that keep programmers informed on the percentage of completed computation time during the execution of a job. Through extensive experiments, we show that state-of-the-art progress indicators (including the one provided by Hadoop) can be seriously harmed by data skewness, load unbalancing, and straggling tasks. This is mainly due to their implicit assumption that the running time depends linearly on the input size. We thus design a novel profile-guided progress indicator, called NearestFit, that operates without the linear hypothesis assumption and exploits a careful combination of nearest neighbor regression and statistical curve fitting techniques. Our theoretical progress model requires fine-grained profile data, that can be very difficult to manage in practice. To overcome this issue, we resort to computing accurate approximations for some of the quantities used in our model through space- and time-efficient data streaming algorithms. We implemented NearestFit on top of Hadoop 2.6.0. An extensive empirical assessment over the Amazon EC2 platform on a variety of real-world benchmarks shows that NearestFit is practical w.r.t. space and time overheads and that its accuracy is generally very good, even in scenarios where competitors incur non-negligible errors and wide prediction fluctuations. Overall, NearestFit significantly improves the current state-of-art on progress analysis for MapReduce

Asymptotically Optimal Approximation Algorithms for Coflow Scheduling

Many modern datacenter applications involve large-scale computations composed of multiple data flows that need to be completed over a shared set of distributed resources. Such a computation completes when all of its flows complete. A useful abstraction for modeling such scenarios is a {\em coflow}, which is a collection of flows (e.g., tasks, packets, data transmissions) that all share the same performance goal. In this paper, we present the first approximation algorithms for scheduling coflows over general network topologies with the objective of minimizing total weighted completion time. We consider two different models for coflows based on the nature of individual flows: circuits, and packets. We design constant-factor polynomial-time approximation algorithms for scheduling packet-based coflows with or without given flow paths, and circuit-based coflows with given flow paths. Furthermore, we give an $O(\log n/\log \log n)$-approximation polynomial time algorithm for scheduling circuit-based coflows where flow paths are not given (here $n$ is the number of network edges). We obtain our results by developing a general framework for coflow schedules, based on interval-indexed linear programs, which may extend to other coflow models and objective functions and may also yield improved approximation bounds for specific network scenarios. We also present an experimental evaluation of our approach for circuit-based coflows that show a performance improvement of at least 22% on average over competing heuristics.Comment: Fixed minor typo

Dissociative recombination and electron-impact de-excitation in CH photon emission under ITER divertor-relevant plasma conditions

For understanding carbon erosion and redeposition in nuclear fusion devices, it is important to understand the transport and chemical break-up of hydrocarbon molecules in edge plasmas, often diagnosed by emission of the CH A^2\Delta - X^2\Pi Ger\"o band around 430 nm. The CH A-level can be excited either by electron-impact or by dissociative recombination (D.R.) of hydrocarbon ions. These processes were included in the 3D Monte Carlo impurity transport code ERO. A series of methane injection experiments was performed in the high-density, low-temperature linear plasma generator Pilot-PSI, and simulated emission intensity profiles were benchmarked against these experiments. It was confirmed that excitation by D.R. dominates at T_e < 1.5 eV. The results indicate that the fraction of D.R. events that lead to a CH radical in the A-level and consequent photon emission is at least 10%. Additionally, quenching of the excited CH radicals by electron impact de-excitation was included in the modeling. This quenching is shown to be significant: depending on the electron density, it reduces the effective CH emission by a factor of 1.4 at n_e=1.3*10^20 m^-3, to 2.8 at n_e=9.3*10^20 m^-3. Its inclusion significantly improved agreement between experiment and modeling

Chemical structure of methylmethacrylate-2-[2′,3′,5′-triiodobenzoyl]oxoethyl methacrylate copolymer, radio-opacity, in vitro and in vivo biocompatibility

The properties of copolymers (physical, chemical, biocompatibility, etc.) depend on their chemical structure and microstructural characteristics. We have prepared radio-opaque polymers based on the copolymers of methyl methacrylate (MMA) and 2-[2′,3′,5′-triiodobenzoyl]oxoethyl methacrylate (TIBOM). The copolymerization reaction between TIBOM and MMA showed that the reactivity ratios were r1 = 0.00029 and r2 = 1.2146. The composition diagram is typical for a practically non-homopolymerizable monomer (TIBOM) and a very reactive monomer (MMA). The copolymers were analyzed on an X-ray microcomputed tomograph and they proved to be radio-opaque even at low concentrations of TIBOM. The biocompatibility was tested both in vitro (with J774.2 macrophage and SaOS-2 osteoblast like cells) and in vivo in the rat. These materials were found to be non-toxic and were well tolerated by the organism. These combined results led to the suggestion that this type of polymer could be used as dental or bone cements in place of barium or zirconium particles, which are usually added to provide X-ray opacity

Tachyon: Reliable, Memory Speed Storage for Cluster Computing Frameworks

Tachyon is a distributed file system enabling reliable data sharing at memory speed across cluster computing frameworks. While caching today improves read workloads, writes are either network or disk bound, as replication is used for fault-tolerance. Tachyon eliminates this bottleneck by pushing lineage, a well-known technique, into the storage layer. The key challenge in making a long-running lineage-based storage system is timely data recovery in case of failures. Tachyon addresses this issue by introducing a checkpointing algorithm that guarantees bounded recovery cost and resource allocation strategies for recomputation under commonly used resource schedulers. Our evaluation shows that Tachyon outperforms in-memory HDFS by 110x for writes. It also improves the end-to-end latency of a realistic workflow by 4x. Tachyon is open source and is deployed at multiple companies.National Science Foundation (U.S.) (CISE Expeditions Award CCF-1139158)Lawrence Berkeley National Laboratory (Award 7076018)United States. Defense Advanced Research Projects Agency (XData Award FA8750-12-2-0331

The impact of columnar file formats on SQL‐on‐hadoop engine performance: A study on ORC and Parquet

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A carbazole-based self-assembled monolayer as the hole transport layer for efficient and stable Cs_0.25FA_0.75Sn_0.5Pb_0.5I₃ solar cells

Mixed tin/lead (Sn/Pb) perovskites have the potential to achieve higher performances in single junction solar cells compared to Pb-based compounds. The best Sn/Pb based devices are fabricated in a p-i-n structure, and PEDOT:PSS is frequently utilized as the hole transport layer, even if there are many doubts on a possible detrimental role of this conductive polymer. Here, we propose the use of [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) and [2-(3, 6-dibromo-9H-carbazol-9-yl) ethyl] phosphonic acid (Br-2PACz) as substitutes for PEDOT:PSS. By using Cs0.25FA0.75Sn0.5Pb0.5I3 as the active layer, we obtained record efficiencies as high as 19.51% on Br-2PACz, while 18.44% and 16.33% efficiencies were obtained using 2PACz and PEDOT:PSS, respectively. In addition, the implemented monolayers enhance both the shelf lifetime of the device as well as the operational stability. Finally, the Br-2PACz-based devices maintained 80% of their initial efficiency under continuous illumination for 230 h, and after being stored in a N2 atmosphere for 4224 h (176 days).</p

Diverticulii vezicii urinare

Summary The classification of diverticul of a urinary bladder till their etiology and localization is offered, on which further tactics of diagnostics and treatment depends. Surgical treatment requires diverticuls of the large sizes, at development of complications (urinary infection, infringement of miction, stones) and bladder-renal reflux. In a case of pseudodiverticul the basic pathology is treated. Introducere. În prezent lipseşte clasificarea diverticulilor vezicii urinare în funcţie de etiologie, localizare de care depind metodele de diagnostic şi de tratament. Material şi metode. În clinica de urologie s-au examinat 258 pacienţi cu patologia vezicii urinare. La 120 dintre ei au fost depistaţi diverticuli ai vezicii urinare, inclusiv băieţi - 94, fete - 40. Diverticulii au fost de diverse dimensiuni - de la 1 până la 15 cm în diametru, uneori de un volum mai mare ca vezica urinară, 80% fiind localizaţi dl partea stângă. Infecţia urinară s-a depistat la 68 pacienţi, hematurie - la 13, la 12 pacienţi - dureri suprapubiene. Numai la 6 copii - reziduu vezical şi micţiuni în doi timpi. La 14 copii diverticulii s-au depistat ocazional. La examinarea pacienţilor a fost utilizat un complex de investigaţii: sonografia, cistografia în 2 incidente, urografie, cistoscopie. În caz de pseudodiverticuli s-a aplicat şi cistometria, urofloumetria, calibrarea uretrei. Discuţii şi concluzii. Diverticulii congenitali în majoritatea lor sunt localizaţi în apropierea sau în regiunea meatului ureteral şi dl peretele latero- posterior, mai rar în regiunea vezico-uracală. Pseudodiverticulul poate fi prezent practic dl tot traiectul vezicii urinare şi este cauzat de diverse patologii: obstrucţie infravezicală, vezică neurogenă. Analiza materialului clinic ne demonstrează că, în caz de obstrucţie infravezicală, pseudodiverticulii apar în temei la băieţi şi foarte rar la fete. La o obstrucţie neînsemnată pseudodiverticulii sunt localizaţi dl peretele latero-posterior, în cazuri avansate - neuniform dl tot traiectul vezicii urinare. Din 162 băieţei cu obstrucţie infravezicală pronunţată, pseudodiverticuli s-au atestat numai la 38 bolnavi. Deoarece până în prezent lipseşte o clasificare care ar avea un rol important în diagnosticul şi alegerea metodelor de tratament aplicate, noi am încercat a clasifica diverticulii în funcţie de etiologie, localizare (după B.Curajos). Diverticulii congenitali localizaţi dl peretele latero-posterior, cu sau fără reflux vezico-renal, se înlătură prin metoda combinată - intra şi extravezicală, cei iatrogeni - numai în caz de recidivă de reflux vezico-renal. Diverticulii secundari necesită înlăturarea obstrucţiei şi tratamentul dereglărilor neurogene