Comparing MapReduce and pipeline implementations for counting triangles

A common method to define a parallel solution for a computational problem consists in finding a way to use the Divide and Conquer paradigm in order to have processors acting on its own data and scheduled in a parallel fashion. MapReduce is a programming model that follows this paradigm, and allows for the definition of efficient solutions by both decomposing a problem into steps on subsets of the input data and combining the results of each step to produce final results. Albeit used for the implementation of a wide variety of computational problems, MapReduce performance can be negatively affected whenever the replication factor grows or the size of the input is larger than the resources available at each processor. In this paper we show an alternative approach to implement the Divide and Conquer paradigm, named dynamic pipeline. The main features of dynamic pipelines are illustrated on a parallel implementation of the well-known problem of counting triangles in a graph. This problem is especially interesting either when the input graph does not fit in memory or is dynamically generated. To evaluate the properties of pipeline, a dynamic pipeline of processes and an ad-hoc version of MapReduce are implemented in the language Go, exploiting its ability to deal with channels and spawned processes. An empirical evaluation is conducted on graphs of different topologies, sizes, and densities. Observed results suggest that dynamic pipelines allows for an efficient implementation of the problem of counting triangles in a graph, particularly, in dense and large graphs, drastically reducing the execution time with respect to the MapReduce implementation.Peer ReviewedPostprint (published version

Euripides’ Electra 1351-1352: A New Interpretation

Eur. El. 1351–1352 has always been problematic for editors and translators. Usually, they supply the article τό with ὅσιον in order to translate ὅσιον (“piety”) and τὸ δίκαιον (“justice) as coordinated nouns. At the same time, editors never add the article to their texts because it gives a metrically incorrect line. Another issue is that there are no examples in Greek where the article governing two coordinated nouns is given with the second noun but has to be supplied for the first (where it is strictly necessary). This paper proposes that ὅσιον is in fact an adjective (i.e., “pious”), which is not connected to the noun τὸ δίκαιον but to the adjective ϕίλον (“loved”). This interpretation can be justified through the work itself and also by exploring the use of the adjective ὅσιος in different tragedies by Euripides and in other authors. Les vers 1351-1352 de l’Électre d’Euripide ont toujours été problématiques pour les éditeurs et traducteurs. Généralement, ils suppléent l’article τό devant ὅσιον afin de traduire ὅσιον (« piété ») et τὸ δίκαιον (« la justice ») comme des noms coordonnés. En même temps, les éditeurs n’ajoutent jamais l’article à leur texte car il serait incorrect métriquement. Par ailleurs, il n’existe pas d’exemple en grec de situation où l’article coordonnant deux noms est donné pour le deuxième tandis qu’il doit être suppléé pour le premier (alors qu’il est strictement nécessaire). Dans cet article, nous suggérons donc que le mot ὅσιον est en réalité un adjectif (« pieux ») qui n’est pas lié au nom τὸ δίκαιον mais à l’adjectif ϕίλον (« aimé »). Cette interprétation peut être justifiée par l’œuvre elle-même, mais aussi en étudiant l’usage de l’adjectif ὅσιος dans les différentes tragédies d’Euripide et chez d’autres auteurs

Haloglomus irregulare gen. nov., sp. nov., a New Halophilic Archaeon Isolated from a Marine Saltern

A halophilic archaeal strain, designated F16-60T, was isolated from Isla Cristina marine saltern in Huelva, Spain. Cells were pleomorphic, irregular, non-motile, and Gram-stain-negative. It produced red-pigmented colonies on agar plates. Strain F16-60T was extremely halophilic (optimum at 30% (w/v) NaCl) and neutrophilic (optimum pH 7.5). Phylogenetic tree reconstructions based on 16S rRNA and rpoB´ gene sequences revealed that strain F16-60T was distinct from species of the related genera Natronomonas, Halomarina, and Halomicrobium, of the order Halobacteriales. The polar lipids are phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), phosphatidylglycerol sulfate (PGS), and one glycolipid chromatographically identical to sulfated mannosyl glucosyl diether (S-DGD-1). The DNA G+C content is 68.0 mol%. The taxonomic study, based on a combination of phylogenetic, genomic, chemotaxonomic, and phenotypic analyses, suggest that strain F16-60T (= CECT 9635T = JCM 33318T), represents a novel species of a new genus within the family Haloarculaceae and the order Halobacteriales, for which the name Haloglomus irregulare gen. nov., sp. nov. is proposed. Metagenomic fragment recruitment analysis revealed the worldwide distribution of members of this genus and suggested the existence of other closely related species to be isolated.España, MINECO project CGL2017-83385-PEspaña, Junta de Andalucía (BIO-213, US-1263771

Comparing MapReduce and pipeline implementations for counting triangles

A generalized method to define the Divide & Conquer paradigm in order to have processors acting on its own data and scheduled in a parallel fashion. MapReduce is a programming model that follows this paradigm, and allows for the definition of efficient solutions by both decomposing a problem into steps on subsets of the input data and combining the results of each step to produce final results. Albeit used for the implementation of a wide variety of computational problems, MapReduce performance can be negatively affected whenever the replication factor grows or the size of the input is larger than the resources available at each processor. In this paper we show an alternative approach to implement the Divide & Conquer paradigm, named pipeline. The main features of pipeline are illustrated on a parallel implementation of the well-known problem of counting triangles in a graph. This problem is especially interesting either when the input graph does not fit in memory or is dynamically generated. To evaluate the properties of pipeline, a dynamic pipeline of processes and an ad-hoc version of MapReduce are implemented in the language Go, exploiting its ability to deal with channels and spawned processes. An empirical evaluation is conducted on graphs of different sizes and densities. Observed results suggest that pipeline allows for the implementation of an efficient solution of the problem of counting triangles in a graph, particularly, in dense and large graphs, drastically reducing the execution time with respect to the MapReduce implementation.Peer ReviewedPostprint (published version

Dynamic Pipeline: an adaptive solution for big data

The Dynamic Pipelineis a concurrent programming pattern amenable to be parallelized. Furthermore, the number of processing units used in the parallelization is adjusted to the size of the problem, and each processing unit uses a reduced memory footprint. Contrary to other approaches, the Dynamic Pipeline can be seen as ageneralization of the (parallel) Divide and Conquer schema, where systems can be reconfigured depending on the particular instance of the problem to be solved. We claim that the Dynamic Pipelines is useful to deal with Big Data related problems. In particular, we have designed and implemented algorithms for computing graphs parameters as number of triangles, connected components, and maximal cliques, among others. Currently, we are focused on designing and implementing an efficient algorithm to evaluate conjunctive query.Peer ReviewedPostprint (author's final draft

Multi-agent simulations for emergency situations in an airport scenario

This paper presents a multi-agent framework using Net- Logo to simulate humanand collective behaviors during emergency evacuations. Emergency situationappears when an unexpected event occurs. In indoor emergency situation, evacuation plans defined by facility manager explain procedure and safety ways tofollow in an emergency situation. A critical and public scenario is an airportwhere there is an everyday transit of thousands of people. In this scenario theimportance is related with incidents statistics regarding overcrowding andcrushing in public buildings. Simulation has the objective of evaluating buildinglayouts considering several possible configurations. Agents could be based onreactive behavior like avoid danger or follow other agent, or in deliberative behaviorbased on BDI model. This tool provides decision support in a real emergencyscenario like an airport, analyzing alternative solutions to the evacuationprocess.Publicad

Increasing the stability of Empeltre olive oils by aromatization with rosemary (Rosmarinus officinalis) and garlic (Allium sativum)

A strategy to increase shelf life of Empeltre olive oils could consist in the incorporation of flavoring agents (rich in antioxidant compounds). The aim of this study was to describe the quality of Empeltre olive oils flavored with rosemary and garlic at different concentrations and methods (maceration and co-processing during malaxation). The incorporation of garlic during malaxation increased total phenol content and antioxidant capacity. Aromatization with rosemary (added during malaxation) increased total phenol content more than 50%. Changes in individual phenols were observed after garlic and rosemary aromatization. Slight increases in α-tocopherol were also observed at 5 and 7% concentration. Pigment content increased with rosemary concentration. As a consequence, antioxidant capacity and oxidative stability increased. Aromatization with rosemary by co-processing during malaxation was more effective in increasing antioxidant compounds than the maceration method. Empeltre olive oils aromatized with garlic achieved a greater sensory acceptance and better scores than with rosemary

Moduli Spaces of Semistable Sheaves on Singular Genus One Curves

We find some equivalences of the derived category of coherent sheaves on a Gorenstein genus one curve that preserve the (semi)-stability of pure dimensional sheaves. Using them we establish new identifications between certain Simpson moduli spaces of semistable sheaves on the curve. For rank zero, the moduli spaces are symmetric powers of the curve whilst for a fixed positive rank there are only a finite number of non-isomorphic spaces. We prove similar results for the relative semistable moduli spaces on an arbitrary genus one fibration with no conditions either on the base or on the total space. For a cycle $E_N$ of projective lines, we show that the unique degree 0 stable sheaves are the line bundles having degree 0 on every irreducible component and the sheaves $\mathcal{O}(-1)$ supported on one irreducible component. We also prove that the connected component of the moduli space that contains vector bundles of rank $r$ is isomorphic to the $r$-th symmetric product of the rational curve with one node.Comment: 26 pages, 4 figures. Added the structure of the biggest component of the moduli space of sheaves of degree 0 on a cycle of projective lines. Final version; to appear en IMRS (International Mathematics Research Notices 2009