Abstract:Greedy algorithms are practitioners’ best friends—they are intuitive, are simple to implement, and often lead to very good solutions. However, implementing greedy algorithms in a distributed setting is challenging since the greedy choice is inherently sequential, and it is not clear how to take advantage of the extra processing power.
Our main result is a powerful sampling technique that aids in parallelization of sequential algorithms. Armed with this primitive, we then adapt a broad cl… Show more
“…The needs of the applications, and in particular the sheer bulk of large data sets, have brought into focus the development of fast algorithms for submodular optimization. Recent work on the theoretical side include the development of faster worst-case approximation algorithms in the traditional sequential model of computation [BV14,IJB13,CJV15], algorithms in the streaming model [BMKK14,CK14] as well as in the map-reduce model of computation [KMVV13].…”
Section: Introductionmentioning
confidence: 99%
“…Their algorithm extends to multiple passes, with an approximation bound of 1/(p + 1 + ) with O( −3 log p) passes. The main focus of [KMVV13] is on the map-reduce model although they claim some streaming results as well.…”
We consider the problem of maximizing a nonnegative submodular set function f : 2 N → R + subject to a p-matchoid constraint in the single-pass streaming setting. Previous work in this context has considered streaming algorithms for modular functions and monotone submodular functions. The main result is for submodular functions that are non-monotone. We describe deterministic and randomized algorithms that obtain a Ω( 1 p )-approximation using O(k log k)-space, where k is an upper bound on the cardinality of the desired set. The model assumes value oracle access to f and membership oracles for the matroids defining the p-matchoid constraint.
“…The needs of the applications, and in particular the sheer bulk of large data sets, have brought into focus the development of fast algorithms for submodular optimization. Recent work on the theoretical side include the development of faster worst-case approximation algorithms in the traditional sequential model of computation [BV14,IJB13,CJV15], algorithms in the streaming model [BMKK14,CK14] as well as in the map-reduce model of computation [KMVV13].…”
Section: Introductionmentioning
confidence: 99%
“…Their algorithm extends to multiple passes, with an approximation bound of 1/(p + 1 + ) with O( −3 log p) passes. The main focus of [KMVV13] is on the map-reduce model although they claim some streaming results as well.…”
We consider the problem of maximizing a nonnegative submodular set function f : 2 N → R + subject to a p-matchoid constraint in the single-pass streaming setting. Previous work in this context has considered streaming algorithms for modular functions and monotone submodular functions. The main result is for submodular functions that are non-monotone. We describe deterministic and randomized algorithms that obtain a Ω( 1 p )-approximation using O(k log k)-space, where k is an upper bound on the cardinality of the desired set. The model assumes value oracle access to f and membership oracles for the matroids defining the p-matchoid constraint.
“…The first three procedures (Table 1) implement the classical GR [9,[33][34][35] with a single objective (GR_S). The decision variable that provides the best objective function value is chosen first.…”
Wastewater quality monitoring is receiving growing interest with the necessity of developing new strategies for controlling accidental and intentional illicit intrusions. In designing a monitoring network, a crucial aspect is represented by the sensors' location. In this study, a methodology for the optimal placement of wastewater monitoring sensors in sewer systems is presented. The sensor location is formulated as an optimization problem solved using greedy algorithms (GRs). The Storm Water Management Model (SWMM) was used to perform hydraulic and water-quality simulations. Six different procedures characterized by different fitness functions are presented and compared. The performances of the procedures are tested on a real sewer system, demonstrating the suitability of GRs for the sensor-placement problem. The results show a robustness of the methodology with respect to the detection concentration parameter, and they suggest that procedures with multiple objectives into a single fitness function give better results. A further comparison is performed using previously developed multi-objective procedures with multiple fitness functions solved using a genetic algorithm (GA), indicating better performances of the GR. The existing monitoring network, realized without the application of any sensor design, is always suboptimal.
“…For maximizing submodular functions, there already exist a number of stream algorithms (Krause and Gomes, 2010;Badanidiyuru et al, 2014;Kumar et al, 2015). The heap substitution algorithm we designed in this work resembles the algorithm developed in (Krause and Gomes, 2010) that addresses cardinality constraints.…”
We study the task of constructing sports news report automatically from live commentary and focus on content selection. Rather than receiving every piece of text of a sports match before news construction, as in previous related work, we novelly verify the feasibility of a more challenging setting to generate news report on the fly by treating live text input as a stream. We design scoring functions to address different requirements of the task and use stream substitution for sentence selection. Experiments suggest that our proposed framework can already produce comparable results compared with previous work that relies on a supervised learning-to-rank model.
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