Dynamic Algorithms for the Massively Parallel Computation Model

The Massive Parallel Computing (MPC) model gained popularity during the last decade and it is now seen as the standard model for processing large scale data. One significant shortcoming of the model is that it assumes to work on static datasets while, in practice, real-world datasets evolve continuously. To overcome this issue, in this paper we initiate the study of dynamic algorithms in the MPC model. We first discuss the main requirements for a dynamic parallel model and we show how to adapt the classic MPC model to capture them. Then we analyze the connection between classic dynamic algorithms and dynamic algorithms in the MPC model. Finally, we provide new efficient dynamic MPC algorithms for a variety of fundamental graph problems, including connectivity, minimum spanning tree and matching.Comment: Accepted to the 31st ACM Symposium on Parallelism in Algorithms and Architectures (SPAA 2019

Improved Algorithms for Decremental Single-Source Reachability on Directed Graphs

Recently we presented the first algorithm for maintaining the set of nodes reachable from a source node in a directed graph that is modified by edge deletions with $o(mn)$ total update time, where $m$ is the number of edges and $n$ is the number of nodes in the graph [Henzinger et al. STOC 2014]. The algorithm is a combination of several different algorithms, each for a different $m$ vs. $n$ trade-off. For the case of $m = \Theta(n^{1.5})$ the running time is $O(n^{2.47})$, just barely below $mn = \Theta(n^{2.5})$. In this paper we simplify the previous algorithm using new algorithmic ideas and achieve an improved running time of $\tilde O(\min(m^{7/6} n^{2/3}, m^{3/4} n^{5/4 + o(1)}, m^{2/3} n^{4/3+o(1)} + m^{3/7} n^{12/7+o(1)}))$. This gives, e.g., $O(n^{2.36})$ for the notorious case $m = \Theta(n^{1.5})$. We obtain the same upper bounds for the problem of maintaining the strongly connected components of a directed graph undergoing edge deletions. Our algorithms are correct with high probabililty against an oblivious adversary.Comment: This paper was presented at the International Colloquium on Automata, Languages and Programming (ICALP) 2015. A full version combining the findings of this paper and its predecessor [Henzinger et al. STOC 2014] is available at arXiv:1504.0795

2-Vertex Connectivity in Directed Graphs

We complement our study of 2-connectivity in directed graphs, by considering the computation of the following 2-vertex-connectivity relations: We say that two vertices v and w are 2-vertex-connected if there are two internally vertex-disjoint paths from v to w and two internally vertex-disjoint paths from w to v. We also say that v and w are vertex-resilient if the removal of any vertex different from v and w leaves v and w in the same strongly connected component. We show how to compute the above relations in linear time so that we can report in constant time if two vertices are 2-vertex-connected or if they are vertex-resilient. We also show how to compute in linear time a sparse certificate for these relations, i.e., a subgraph of the input graph that has O(n) edges and maintains the same 2-vertex-connectivity and vertex-resilience relations as the input graph, where n is the number of vertices.Comment: arXiv admin note: substantial text overlap with arXiv:1407.304

10261 Abstracts Collection -- Algorithm Engineering

From June 27 to July 2, the Dagstuhl Seminar 10261 ``Algorithm Engineering \u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Comportamento produtivo de cultivares de capim-elefante.

bitstream/item/131673/1/Comunicado-166-Comportamento-Produtivo-de-Cultivares-de-Capim-Elefante.pd

An overview of the geochemical characteristics of oceanic carbonatites: New insights from Fuerteventura carbonatites (Canary islands)

The occurrence of carbonatites in oceanic settings is very rare if compared with their continental counterpart, having been reported only in Cape Verde and Canary Islands. This paper provides an overview of the main geochemical characteristics of oceanic carbonatites, around which many debates still exist regarding their petrogenesis. We present new data on trace elements in minerals and whole-rock, together with the first noble gases isotopic study (He, Ne, Ar) in apatite, calcite, and clinopyroxene from Fuerteventura carbonatites (Canary Islands). Trace elements show a similar trend as Cape Verde carbonatites, almost tracing the same patterns on multi-element and REE abundance diagrams.3He/4He isotopic ratios of Fuerteventura carbonatites reflect a shallow (sub-continental lithospheric mantle, SCLM) He signature in their petrogenesis, and they clearly differ from Cape Verde carbonatites, i.e., fluids from a deep and low degassed mantle with a primitive plume-derived He signature are involved in their petrogenesis

Desempenho produtivo de ovinos deslanados da raça Santa Inês no Estado do Piauí.

Desempenho reprodutivo; Peso das matrizes; Peso das crias.bitstream/item/35788/1/Bol19.pd

Kajian Sistem Drainase Patukangan-pegulon Kabupaten Kendal

Kecamatan Patukangan – Pegulon adalah kawasan indsutri dan Perumahan yang berada di pusat Kota Kendal. Permasalahan banjir menyebabkan potensi ekonomi, sosial, dan lingkungan tidak dapat berkembang. Sistem draianse yang tepat adalah salah satu alternatif untuk menanggulangi permasalahan banjir di wilayah Kecamatan Patukangan – Pegulon. Kajian sistem drainase meliputi perencanaan ulang dimensi saluran, pintu air, dan sistem pipa – pompa.Data curah hujan yang digunakan untuk Sungai Kendal adalah data curah hujan dari tahun 2000 sampai 2015 dengan menggunakan stasiun hujan Sedayu, Karangtengah, dan Kedugsari. Analisis debit banjir di Sungai Kendal menggunakan metode HSS Nakayasu dengan periode ulang 20 tahun dan diperoleh debit banjir sebesar 68,19 m3/s.. Analisis pengaruh backwater dari Laut Jawa menggunakan metode tahapan langsung. Pengaruh backwater hanya sampai pada jarak 5543,88 meter dari muara sungai. Jarak outlet saluran drainase dari muara sungai adalah 6096 meter, sehingga titik outlet tidak terpengaruh backwater.Debit banjir rencana pada saluran drainase didapatkan dengan rumus Mononobe dengan periode ulang 5 tahun dan diperoleh debit banjir rencana sebesar 4,8 m3/s. Berdasar debit banjir rencana ini, dimensi saluran drainase yang baru adalah : 1,0 x 1,0 m ; 0,9 x 0,7 m ; 0,7 x 0,7 m ; 0,8 x 0,7 m ; 1,6 x 1,5 m ; 1,0 x 0,7 m ; dan 1,3 x 1,0 m. Pintu air direncanakan pada titik outlet saluran karena elevasi muka air Sungai Kendal lebih tinggi dibandingkan elevasi muka air di saluran drainase, dengan elevasi muka air Sungai Kendal + 5,9 m dan elevasi muka air saluran drainase adalah + 4,63 m. Dimensi pintu air yang direncanakan adalah 1,6 x 1,5 m. Sistem pipa - pompa direncanakan berjumlah 3 buah dengan kapasitas tiap pompa adalah 2,0 m3/s dan diameter pipa adalah 0,5 m

Finding 2-Edge and 2-Vertex Strongly Connected Components in Quadratic Time

We present faster algorithms for computing the 2-edge and 2-vertex strongly connected components of a directed graph, which are straightforward generalizations of strongly connected components. While in undirected graphs the 2-edge and 2-vertex connected components can be found in linear time, in directed graphs only rather simple $O(m n)$-time algorithms were known. We use a hierarchical sparsification technique to obtain algorithms that run in time $O(n^2)$. For 2-edge strongly connected components our algorithm gives the first running time improvement in 20 years. Additionally we present an $O(m^2 / \log{n})$-time algorithm for 2-edge strongly connected components, and thus improve over the $O(m n)$ running time also when $m = O(n)$. Our approach extends to k-edge and k-vertex strongly connected components for any constant k with a running time of $O(n^2 \log^2 n)$ for edges and $O(n^3)$ for vertices

Avaliação de clones de capim elefante para corte e pastejo na região Meio-Norte do Brasil.

bitstream/CPAMN-2009-09/16597/1/CT133.pd