97,548 research outputs found

    Semi-Streaming Algorithms for Annotated Graph Streams

    Get PDF
    Considerable effort has been devoted to the development of streaming algorithms for analyzing massive graphs. Unfortunately, many results have been negative, establishing that a wide variety of problems require Ω(n2)\Omega(n^2) space to solve. One of the few bright spots has been the development of semi-streaming algorithms for a handful of graph problems -- these algorithms use space O(n⋅polylog(n))O(n\cdot\text{polylog}(n)). In the annotated data streaming model of Chakrabarti et al., a computationally limited client wants to compute some property of a massive input, but lacks the resources to store even a small fraction of the input, and hence cannot perform the desired computation locally. The client therefore accesses a powerful but untrusted service provider, who not only performs the requested computation, but also proves that the answer is correct. We put forth the notion of semi-streaming algorithms for annotated graph streams (semi-streaming annotation schemes for short). These are protocols in which both the client's space usage and the length of the proof are O(n⋅polylog(n))O(n \cdot \text{polylog}(n)). We give evidence that semi-streaming annotation schemes represent a substantially more robust solution concept than does the standard semi-streaming model. On the positive side, we give semi-streaming annotation schemes for two dynamic graph problems that are intractable in the standard model: (exactly) counting triangles, and (exactly) computing maximum matchings. The former scheme answers a question of Cormode. On the negative side, we identify for the first time two natural graph problems (connectivity and bipartiteness in a certain edge update model) that can be solved in the standard semi-streaming model, but cannot be solved by annotation schemes of "sub-semi-streaming" cost. That is, these problems are just as hard in the annotations model as they are in the standard model.Comment: This update includes some additional discussion of the results proven. The result on counting triangles was previously included in an ECCC technical report by Chakrabarti et al. available at http://eccc.hpi-web.de/report/2013/180/. That report has been superseded by this manuscript, and the CCC 2015 paper "Verifiable Stream Computation and Arthur-Merlin Communication" by Chakrabarti et a

    Analysis of Intel's Haswell Microarchitecture Using The ECM Model and Microbenchmarks

    Full text link
    This paper presents an in-depth analysis of Intel's Haswell microarchitecture for streaming loop kernels. Among the new features examined is the dual-ring Uncore design, Cluster-on-Die mode, Uncore Frequency Scaling, core improvements as new and improved execution units, as well as improvements throughout the memory hierarchy. The Execution-Cache-Memory diagnostic performance model is used together with a generic set of microbenchmarks to quantify the efficiency of the microarchitecture. The set of microbenchmarks is chosen such that it can serve as a blueprint for other streaming loop kernels.Comment: arXiv admin note: substantial text overlap with arXiv:1509.0311

    Streaming cold cosmic ray back-reaction and thermal instabilities across the background magnetic field

    Full text link
    Using the multi-fluid approach, we investigate streaming and thermal instabilities of the electron-ion plasma with homogeneous cold cosmic rays drifting perpendicular to the background magnetic field. Perturbations across the magnetic field are considered. The back-reaction of cosmic rays resulting in the streaming instability is taken into account. The thermal instability is shown not to be subject to the action of cosmic rays in the model under consideration. The dispersion relation for the thermal instability has been derived which includes sound velocities of plasma and cosmic rays, Alfv\'{e}n and cosmic ray drift velocities. The relation between these parameters determines the kind of thermal instability from Parker's to Field's type instability. The results obtained can be useful for a more detailed the investigation of electron-ion astrophysical objects such as galaxy clusters including the dynamics of streaming cosmic rays.Comment: Submitted to MNRAS. arXiv admin note: substantial text overlap with arXiv:1203.573

    MODEL SINEKTIK BERBASIS MENGALIRKAN BAYANGAN DALAM PEMBELAJARAN MENULIS TEKS NARASI FABEL : Kuasi Eksperimen pada Kelas VII SMP Negeri 1 Suliki Tahun Pelajaran 2016/2017

    Get PDF
    Penelitian ini dilatarbelakangi masih rendahnya kemampuan siswa dalam menulis teks narasi fabel di sekolah. Batasan masalah yang dikaji dalam penelitian ini meliputi: 1) profil pembelajaran menulis; 2) kemampuan awal menulis teks narasi fabel di kelas kontrol dan di kelas eksperimen; 3) proses pembelajaran model sinektik berbasis mengalirkan bayangan di kelas eksperimen; dan 4) keefektifan model sinektik berbasis mengalirkan bayangan dalam meningkatkan kemampuan menulis teks narasi fabel di kelas eksperimen. Metode penelitian yang digunakan adalah metode kuasi eksperimen dengan desain the Maching Only Pretes–Postes Control Group. Populasi penelitian ini adalah seluruh siswa kelas VII SMP Negeri 1 Suliki dengan sampel siswa kelas VII-1 dan siswa kelas VII-3. Perlakuan model sinektik berbasis mengalirkan bayangan fokus pada analogi langsung, analogi personal, konflik padat yang diperoleh dengan proses mengalirkan bayangan. Hasil penelitian model sinektik berbasis mengalirkan bayangan dapat meningkatkan kemampuan menulis teks fabel dari beberapa aspek yang dinilai yaitu: unsur teks narasi fabel, isi teks narasi fabel, struktur teks narasi fabel dan ciri kebahasaan teks narasi fabel dengan hasil t_tabel -3,267 ˂ t_(hitung 0.975) 2.02. kesimpulannya terdapat perbedaan yang signifikan antara model sinektik berbasis mengalirkan bayangan dengan model terlangsung dalam meningkatkan kemampuan menulis teks narasi fabel. Artinya model sinektik berbasis mengalirkn bayangan lebih efektif dari pada model terlangsung. ----------- This study was back grounded by students ability in fable narration text writing in school which is still low. The scope of problem studied in this study comprised: 1) the profile of writing learning; 2) initial ability of fable narration text writing in control class and experiment class; 3) the process of sinectic model learning based on image streaming in enhancing fable narration text writing ability in experiment class. The method study used was experiment quasi with the Matching Only Pretest-Posttest Control Group design. The population of this study were all 7th grade students of SMPN 1 Suliki with sample of students of class VII-1 and class VII-3. The treatment of sinectic model based on image streaming focused on direct analogy, personal analogy, dense conflict which were acquired by process of flowing the shadow. The study result of sinectic model based on Image Streaming was able to enhance fable text writing ability from some aspects assessed, namely: the element of fable narration text, the content of fable narration text, the structure of fable narration text and the linguistic characteristic of fable narration text with the result of ttable -3.267 < tcalculate0.975 2.02. It can be concluded that there is significant difference between sinectic model based on image streaming and direct model in enhancing fable narration text writing ability. It means that sinectic model based on image streaming is more effective than direct mode
    • …
    corecore