409 research outputs found

    On data skewness, stragglers, and MapReduce progress indicators

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    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

    Υπερβαση της πραγματικοτητας: Αλ. Παπαδιαμαντη’ Φονισσα’ - Ν. Νικολαιδη ‘Περα απ΄ το Καλο και το Κακο’

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    Please note: this article is in Greek. In this paper two novellas - The Murderess (1904) by Alex Papadiamantis and Beyond Good and Evil (1940) by Nikos Nikolaides - are analysed comparatively within the general theoretical framework of realism. More specifically, they are examined within the framework of Georg Lukacs' thesis on the relationship between Art and the historical-political reality

    Το τραγικό στοιχείο στα πεζογραφήματα της Βάσως Καλαμάρα

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    Please note: This article is in Greek. Vasso kalamara’s tragic vision: This paper explores the tragic vision of life as expressed in Vasso Kalmara’s collections of short stories Other Earth & Bitterness and in the play The Bread Trap. The paper identifies the significant features, which define literary works as “tragedies” and examines how the writer employs these features in her fiction. The emphasis is given to the function of the following: the tragic “heroes” (i.e. characters who initially show resistance and a will to change their life, which lead to hopelessness and their ultimate fall/destruction by fate); tragic peripeteia (i.e. the sudden change of fortune, which usually leads to suspense and ruin); tragic irony (i.e. the antithesis between action and result, between appearance and reality and between verbal word and true meaning of the situation); tragic anagnorisis (i.e. the moment of truth: when ignorance is replaced by knowledge). Finally, the debated element of catharsis is examined and its therapeutic effect through “pity and fear” as defined by Aristotle

    Λουκή Ακρίτα Ο Κάμπος: Ένα νατουραλιστικό μυθιστόρημα με αλληγορική λειτουργία

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    Please note: this article is in Greek. Loukis Akritas’ The Plain: A naturalistic novel and it’s allegorical function: This paper having as a point of reference Fredric Jameson’s thesis that all literary texts should be read and interpreted as political texts, as well as national allegories, examines whether this could be applied to the novel The Plain (1936), [Ο Κάμπος] written by the Cypriot writer Loukis Akritas. This is an important novel as it was written in the inter-World War period when Cyprus was a British colony. The upheaval and unrest on the island at the time prompted the enforcement of a dictatorship (including a censorship) by the British. The analysis of the novel reveals that the writer’s use of naturalism indeed functions as an allegory to depict the harsh conditions suffered by the agrarian sector of Cyprus at the time. The ruthless masters of the “Plain” could be paralleled to the colonial rulers. Furthermore the problems of this sector of the society could to a great extent be attributed to their rule. The allegory also helps the writer to overcome the problem of censorship. The political interpretation of this particular novel therefore affirms Jameson’s thesis

    Το αποικιοκρατικό παρελθόν στο μεταποικιοκρατικό παρόν στο μυθιστόρημα του Nίκου Ορφανίδη Ο Άγγελος έφυγε ευτυχισμένος

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    Please note: This article is in Greek. This paper is part of an extensive research project, which examines the Greek novels of Cyprus within the framework of postcolonial theory, in an attempt to add another paradigm to the universal body of postcolonial literature. It begins with a general introduction to postcolonial theory and critique and it then focuses on Frederic Jameson’s thesis that all literatures produced by ex-colonized countries are concerned with their nation’s situation in the decades that followed anti-colonial struggles and de-colonization and thus could be considered as “national allegories”. The main part of the paper analyses N. Orfanides’s novel, "Angelos Departed Happy", in order to establish the extent to which Jameson’s thesis applies to this novel. More specifically, it examines how the writer uses local history, symbolism and inertextuality in order to give a voice to a “subaltern” nation, to project national identity and to undermine the colonial perception of cultural superiority and local cultural inferiority. The conclusion drawn is that, indeed, Orfanides’s novel could be read as “a national allegory of the embattled situation” of the Greek nation

    The contestation of colonialism in Cypriot prose writings.

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    Please note: this article is in Greek. This paper examines the way in which two prose writings of Cyprus challenge the colonial thought and domination during a specific historical moment, i.e. while the armed struggle against the British colonial rule is being fought. It begins with a general introduction to the theme of challenging colonialism and then focuses on the examination of two specific literary works: "Liberty Street-Death Stop" (Kastaniotes, 1997) by Sophocles Lazarou and "My Brother the Traitor" (Kalendis, 2003) by Kostas Giorgallides. The aim of this examination is to add the paradigm of the Cyprus colonial experience to the general universal experience of colonialism. Today an increasing number of critics accept the view that the colonial experience is to a great extent a textual experience as well. Consequently, literary works can play a vital role in projecting contesting meanings, which are embedded in the colonial experience (rulers–oppressed, dominance–resistance, terrorism–heroism, nationalism–postnationalism, etc)
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