Since Tassiulas and Ephremides proposed the maximum weight scheduling algorithm of throughput-optimality for constrained queueing networks in 1992, extensive research efforts have been made for resolving its high complexity issue under various directions. In this paper, we resolve this issue by developing a generic framework for designing throughput-optimal and low-complexity scheduling algorithms. Under the framework, an algorithm updates current schedules via an interaction with a given oracle system that generates a solution of a certain discrete optimization problem in a finite number of interactive queries. The complexity of the resulting algorithm is decided by the number of operations required for an oracle processing a single query, which is typically very small. Somewhat surprisingly, we prove that an algorithm using any such oracle is throughput-optimal for general constrained queueing network models that arise in the context of emerging large-scale communication networks. To our best knowledge, our result is the first that establishes a rigorous connection between iterative optimization methods and low-complexity scheduling algorithms, which we believe provides various future directions and new insights in both areas.
{"title":"Scheduling using interactive oracles: connection between iterative optimization and low-complexity scheduling","authors":"Jinwoo Shin, T. Suk","doi":"10.1145/2591971.2592026","DOIUrl":"https://doi.org/10.1145/2591971.2592026","url":null,"abstract":"Since Tassiulas and Ephremides proposed the maximum weight scheduling algorithm of throughput-optimality for constrained queueing networks in 1992, extensive research efforts have been made for resolving its high complexity issue under various directions. In this paper, we resolve this issue by developing a generic framework for designing throughput-optimal and low-complexity scheduling algorithms. Under the framework, an algorithm updates current schedules via an interaction with a given oracle system that generates a solution of a certain discrete optimization problem in a finite number of interactive queries. The complexity of the resulting algorithm is decided by the number of operations required for an oracle processing a single query, which is typically very small. Somewhat surprisingly, we prove that an algorithm using any such oracle is throughput-optimal for general constrained queueing network models that arise in the context of emerging large-scale communication networks. To our best knowledge, our result is the first that establishes a rigorous connection between iterative optimization methods and low-complexity scheduling algorithms, which we believe provides various future directions and new insights in both areas.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126177257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sequentially arriving jobs share a MapReduce cluster, each desiring a fair allocation of computing resources to serve its associated map and reduce tasks. The model of such a system consists of a processor sharing queue for the MapTasks and a multi-server queue for the ReduceTasks. These two queues are dependent through a constraint that the input data of each ReduceTask are fetched from the intermediate data generated by the MapTasks belonging to the same job. A more generalized form of MapReduce queueing model can capture the essence of other distributed data processing systems that contain interdependent processor sharing queues and multi-server queues. Through theoretical modeling and extensive experiments, we show that, this dependence, if not carefully dealt with, can cause non-work-conserving effects that negatively impact system performance and scalability. First, we characterize the heavy-traffic approximation. Depending on how tasks are scheduled, the number of jobs in the system can even exhibit jumps in diffusion limits, resulting in prolonged job execution times. This problem can be mitigated through carefully applying a tie-breaking rule for ReduceTasks, which as a theoretical finding has direct engineering implications. Second, we empirically validate a criticality phenomenon using experiments. MapReduce systems experience an undesirable performance degradation when they have reached certain critical points, another finding that offers fundamental guidance on managing MapReduce systems.
{"title":"Non-work-conserving effects in MapReduce: diffusion limit and criticality","authors":"Jian Tan, Yandong Wang, Weikuan Yu, Li Zhang","doi":"10.1145/2591971.2592007","DOIUrl":"https://doi.org/10.1145/2591971.2592007","url":null,"abstract":"Sequentially arriving jobs share a MapReduce cluster, each desiring a fair allocation of computing resources to serve its associated map and reduce tasks. The model of such a system consists of a processor sharing queue for the MapTasks and a multi-server queue for the ReduceTasks. These two queues are dependent through a constraint that the input data of each ReduceTask are fetched from the intermediate data generated by the MapTasks belonging to the same job. A more generalized form of MapReduce queueing model can capture the essence of other distributed data processing systems that contain interdependent processor sharing queues and multi-server queues.\u0000 Through theoretical modeling and extensive experiments, we show that, this dependence, if not carefully dealt with, can cause non-work-conserving effects that negatively impact system performance and scalability. First, we characterize the heavy-traffic approximation. Depending on how tasks are scheduled, the number of jobs in the system can even exhibit jumps in diffusion limits, resulting in prolonged job execution times. This problem can be mitigated through carefully applying a tie-breaking rule for ReduceTasks, which as a theoretical finding has direct engineering implications. Second, we empirically validate a criticality phenomenon using experiments. MapReduce systems experience an undesirable performance degradation when they have reached certain critical points, another finding that offers fundamental guidance on managing MapReduce systems.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116029599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Demand response is crucial for the incorporation of renewable energy into the grid. In this paper, we focus on a particularly promising industry for demand response: data centers. We use simulations to show that, not only are data centers large loads, but they can provide as much (or possibly more) flexibility as large-scale storage if given the proper incentives. However, due to the market power most data centers maintain, it is difficult to design programs that are efficient for data center demand response. To that end, we propose that prediction-based pricing is an appealing market design, and show that it outperforms more traditional supply function bidding mechanisms in situations where market power is an issue. However, prediction-based pricing may be inefficient when predictions are inaccurate, and so we provide analytic, worst-case bounds on the impact of prediction error on the efficiency of prediction-based pricing. These bounds hold even when network constraints are considered, and highlight that prediction-based pricing is surprisingly robust to prediction error.
{"title":"Pricing data center demand response","authors":"Zhenhua Liu, Iris Liu, S. Low, A. Wierman","doi":"10.1145/2591971.2592004","DOIUrl":"https://doi.org/10.1145/2591971.2592004","url":null,"abstract":"Demand response is crucial for the incorporation of renewable energy into the grid. In this paper, we focus on a particularly promising industry for demand response: data centers. We use simulations to show that, not only are data centers large loads, but they can provide as much (or possibly more) flexibility as large-scale storage if given the proper incentives. However, due to the market power most data centers maintain, it is difficult to design programs that are efficient for data center demand response. To that end, we propose that prediction-based pricing is an appealing market design, and show that it outperforms more traditional supply function bidding mechanisms in situations where market power is an issue. However, prediction-based pricing may be inefficient when predictions are inaccurate, and so we provide analytic, worst-case bounds on the impact of prediction error on the efficiency of prediction-based pricing. These bounds hold even when network constraints are considered, and highlight that prediction-based pricing is surprisingly robust to prediction error.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116411806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Today, big and small organizations alike collect huge amounts of data, and they do so with one goal in mind: extract "value" through sophisticated exploratory analysis, and use it as the basis to make decisions as varied as personalized treatment and ad targeting. Unfortunately, existing data analytics tools are slow in answering queries, as they typically require to sift through huge amounts of data stored on disk, and are even less suitable for complex computations, such as machine learning algorithms. These limitations leave the potential of extracting value of big data unfulfilled. To address this challenge, we are developing Berkeley Data Analytics Stack (BDAS), an open source data analytics stack that provides interactive response times for complex computations on massive data. To achieve this goal, BDAS supports efficient, large-scale in-memory data processing, and allows users and applications to trade between query accuracy, time, and cost. In this talk, I'll present the architecture, challenges, results, and our experience with developing BDAS, with a focus on Apache Spark, an in-memory cluster computing engine that provides support for a variety of workloads, including batch, streaming, and iterative computations. In a relatively short time, Spark has become the most active big data project in the open source community, and is already being used by over one hundred of companies and research institutions.
{"title":"Conquering big data with spark and BDAS","authors":"I. Stoica","doi":"10.1145/2637364.2611389","DOIUrl":"https://doi.org/10.1145/2637364.2611389","url":null,"abstract":"Today, big and small organizations alike collect huge amounts of data, and they do so with one goal in mind: extract \"value\" through sophisticated exploratory analysis, and use it as the basis to make decisions as varied as personalized treatment and ad targeting. Unfortunately, existing data analytics tools are slow in answering queries, as they typically require to sift through huge amounts of data stored on disk, and are even less suitable for complex computations, such as machine learning algorithms. These limitations leave the potential of extracting value of big data unfulfilled.\u0000 To address this challenge, we are developing Berkeley Data Analytics Stack (BDAS), an open source data analytics stack that provides interactive response times for complex computations on massive data. To achieve this goal, BDAS supports efficient, large-scale in-memory data processing, and allows users and applications to trade between query accuracy, time, and cost. In this talk, I'll present the architecture, challenges, results, and our experience with developing BDAS, with a focus on Apache Spark, an in-memory cluster computing engine that provides support for a variety of workloads, including batch, streaming, and iterative computations. In a relatively short time, Spark has become the most active big data project in the open source community, and is already being used by over one hundred of companies and research institutions.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116433011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With the growth in number and significance of the emerging applications that require extremely low latencies, network operators are facing increasing need to perform latency measurement on per-flow basis for network monitoring and troubleshooting. In this paper, we propose COLATE, the first per-flow latency measurement scheme that requires no probe packets and time stamping. Given a set of observation points, COLATE records packet timing information at each point so that later for any two points, it can accurately estimate the average and standard deviation of the latencies experienced by the packets of any flow in passing the two points. The key idea is that when recording packet timing information, COLATE purposely allows noise to be introduced for minimizing storage space, and when querying the latency of a target flow, COLATE uses statistical techniques to denoise and obtain an accurate latency estimate. COLATE is designed to be efficiently implementable on network middleboxes. In terms of processing overhead, COLATE performs only one hash and one memory update per packet. In terms of storage space, COLATE uses less than 0.1 bit per packet, which means that, on a backbone link with about half a million packets per second, using a 256GB drive, COLATE can accumulate time stamps of packets traversing the link for over 1.5 years. We evaluated COLATE using three real traffic traces that include a backbone traffic trace, an enterprise network traffic trace, and a data center traffic trace. Results show that COLATE always achieves the required reliability for any given confidence interval.
{"title":"Noise can help: accurate and efficient per-flow latency measurement without packet probing and time stamping","authors":"Muhammad Shahzad, A. Liu","doi":"10.1145/2591971.2591988","DOIUrl":"https://doi.org/10.1145/2591971.2591988","url":null,"abstract":"With the growth in number and significance of the emerging applications that require extremely low latencies, network operators are facing increasing need to perform latency measurement on per-flow basis for network monitoring and troubleshooting. In this paper, we propose COLATE, the first per-flow latency measurement scheme that requires no probe packets and time stamping. Given a set of observation points, COLATE records packet timing information at each point so that later for any two points, it can accurately estimate the average and standard deviation of the latencies experienced by the packets of any flow in passing the two points. The key idea is that when recording packet timing information, COLATE purposely allows noise to be introduced for minimizing storage space, and when querying the latency of a target flow, COLATE uses statistical techniques to denoise and obtain an accurate latency estimate. COLATE is designed to be efficiently implementable on network middleboxes. In terms of processing overhead, COLATE performs only one hash and one memory update per packet. In terms of storage space, COLATE uses less than 0.1 bit per packet, which means that, on a backbone link with about half a million packets per second, using a 256GB drive, COLATE can accumulate time stamps of packets traversing the link for over 1.5 years. We evaluated COLATE using three real traffic traces that include a backbone traffic trace, an enterprise network traffic trace, and a data center traffic trace. Results show that COLATE always achieves the required reliability for any given confidence interval.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117182843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The combination of loss-based TCP and drop-tail routers often results in full buffers, creating large queueing delays. The challenge with parameter tuning and the drastic consequence of improper tuning have discouraged network administrators from enabling AQM even when routers support it. To address this problem, we propose a novel design principle for AQM, called the pricing-link-by-time (PLT) principle. PLT increases the link price as the backlog stays above a threshold β, and resets the price once the backlog goes below β. We prove that such a system exhibits cyclic behavior that is robust against changes in network environment and protocol parameters. While β approximately controls the level of backlog, the backlog dynamics are invariant for β across a wide range of values. Therefore, β can be chosen to reduce delay without undermining system performance. We validate these analytical results using packet-level simulation.
{"title":"Pricing link by time","authors":"Chengdi Lai, S. Low, Ka-Cheong Leung, V. Li","doi":"10.1145/2591971.2591974","DOIUrl":"https://doi.org/10.1145/2591971.2591974","url":null,"abstract":"The combination of loss-based TCP and drop-tail routers often results in full buffers, creating large queueing delays. The challenge with parameter tuning and the drastic consequence of improper tuning have discouraged network administrators from enabling AQM even when routers support it. To address this problem, we propose a novel design principle for AQM, called the pricing-link-by-time (PLT) principle. PLT increases the link price as the backlog stays above a threshold β, and resets the price once the backlog goes below β. We prove that such a system exhibits cyclic behavior that is robust against changes in network environment and protocol parameters. While β approximately controls the level of backlog, the backlog dynamics are invariant for β across a wide range of values. Therefore, β can be chosen to reduce delay without undermining system performance. We validate these analytical results using packet-level simulation.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128858843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Computing a ranking over choices using consumer data gathered from a heterogenous population has become an indispensable module for any modern consumer information system, e.g. Yelp, Netflix, Amazon and app-stores like Google play. In such applications, a ranking or recommendation algorithm needs to extract meaningful information from noisy data accurately and in a scalable manner. A principled approach to resolve this challenge requires a model that connects observations to recommendation decisions and a tractable inference algorithm utilizing this model. To that end, we abstract the preference data generated by consumers as noisy, partial realizations of their innate preferences, i.e. orderings or permutations over choices. Inspired by the seminal works of Samuelson (cf. axiom of revealed preferences) and that of McFadden (cf. discrete choice models for transportation), we model the population's innate preferences as a mixture of the so called Multi-nomial Logit (MMNL) model. Under this model, the recommendation problem boils down to (a) learning the MMNL model from population data, (b) finding am MNL component within the mixture that closely represents the revealed preferences of the consumer at hand, and (c) recommending other choices to her/him that are ranked high according to thus found component. In this work, we address the problem of learning MMNL model from partial preferences. We identify fundamental limitations of any algorithm to learn such a model as well as provide conditions under which, a simple, data-driven (non-parametric) algorithm learns the model effectively. The proposed algorithm has a pleasant similarity to the standard collaborative filtering for scalar (or star) ratings, but in the domain of permutations. This work advances the state-of-art in the domain of learning distribution over permutations (cf. [2]) as well as in the context of learning mixture distributions (cf. [4]).
{"title":"What's your choice?: learning the mixed multi-nomial","authors":"A. Ammar, Sewoong Oh, D. Shah, L. Voloch","doi":"10.1145/2591971.2592020","DOIUrl":"https://doi.org/10.1145/2591971.2592020","url":null,"abstract":"Computing a ranking over choices using consumer data gathered from a heterogenous population has become an indispensable module for any modern consumer information system, e.g. Yelp, Netflix, Amazon and app-stores like Google play. In such applications, a ranking or recommendation algorithm needs to extract meaningful information from noisy data accurately and in a scalable manner. A principled approach to resolve this challenge requires a model that connects observations to recommendation decisions and a tractable inference algorithm utilizing this model. To that end, we abstract the preference data generated by consumers as noisy, partial realizations of their innate preferences, i.e. orderings or permutations over choices. Inspired by the seminal works of Samuelson (cf. axiom of revealed preferences) and that of McFadden (cf. discrete choice models for transportation), we model the population's innate preferences as a mixture of the so called Multi-nomial Logit (MMNL) model. Under this model, the recommendation problem boils down to (a) learning the MMNL model from population data, (b) finding am MNL component within the mixture that closely represents the revealed preferences of the consumer at hand, and (c) recommending other choices to her/him that are ranked high according to thus found component. In this work, we address the problem of learning MMNL model from partial preferences. We identify fundamental limitations of any algorithm to learn such a model as well as provide conditions under which, a simple, data-driven (non-parametric) algorithm learns the model effectively. The proposed algorithm has a pleasant similarity to the standard collaborative filtering for scalar (or star) ratings, but in the domain of permutations. This work advances the state-of-art in the domain of learning distribution over permutations (cf. [2]) as well as in the context of learning mixture distributions (cf. [4]).","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130910889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Gulur, M. Mehendale, R. Manikantan, Ramaswamy Govindarajan
Memory system design is increasingly influencing modern multi-core architectures from both performance and power perspectives. However predicting the performance of memory systems is complex, compounded by the myriad design choices and parameters along multiple dimensions, namely (i) technology, (ii) design and (iii) architectural choices. In this work, we construct an analytical model of the memory system to comprehend this diverse space and to study the impact of memory system parameters from latency and bandwidth perspectives. Our model, called ANATOMY, consists of two key components that are coupled with each other, to model the memory system accurately. The first component is a queuing model of memory which models in detail various design choices and captures the impact of technological choices in memory systems. The second component is an analytical model to summarize key workload characteristics, namely row buffer hit rate (RBH), bank-level parallelism (BLP), and request spread (S) which are used as inputs to the queuing model to estimate memory performance. We validate the model across a wide variety of memory configurations on 4, 8 and 16 cores using a total of 44 workloads. ANATOMY is able to predict memory latency with an average error of 8.1%, 4.1% and 9.7% over 4, 8 and 16 core configurations. We demonstrate the extensibility and applicability of our model by exploring a variety of memory design choices such as the impact of clock speed, benefit of multiple memory controllers, the role of banks and channel width, and so on. We also demonstrate ANATOMY's ability to capture architectural elements such as scheduling mechanisms (using FR_FCFS and PAR_BS) and impact of DRAM refresh cycles. In all of these studies, ANATOMY provides insight into sources of memory performance bottlenecks and is able to quantitatively predict the benefit of redressing them.
{"title":"ANATOMY: an analytical model of memory system performance","authors":"N. Gulur, M. Mehendale, R. Manikantan, Ramaswamy Govindarajan","doi":"10.1145/2591971.2591995","DOIUrl":"https://doi.org/10.1145/2591971.2591995","url":null,"abstract":"Memory system design is increasingly influencing modern multi-core architectures from both performance and power perspectives. However predicting the performance of memory systems is complex, compounded by the myriad design choices and parameters along multiple dimensions, namely (i) technology, (ii) design and (iii) architectural choices. In this work, we construct an analytical model of the memory system to comprehend this diverse space and to study the impact of memory system parameters from latency and bandwidth perspectives. Our model, called ANATOMY, consists of two key components that are coupled with each other, to model the memory system accurately. The first component is a queuing model of memory which models in detail various design choices and captures the impact of technological choices in memory systems. The second component is an analytical model to summarize key workload characteristics, namely row buffer hit rate (RBH), bank-level parallelism (BLP), and request spread (S) which are used as inputs to the queuing model to estimate memory performance. We validate the model across a wide variety of memory configurations on 4, 8 and 16 cores using a total of 44 workloads. ANATOMY is able to predict memory latency with an average error of 8.1%, 4.1% and 9.7% over 4, 8 and 16 core configurations. We demonstrate the extensibility and applicability of our model by exploring a variety of memory design choices such as the impact of clock speed, benefit of multiple memory controllers, the role of banks and channel width, and so on. We also demonstrate ANATOMY's ability to capture architectural elements such as scheduling mechanisms (using FR_FCFS and PAR_BS) and impact of DRAM refresh cycles. In all of these studies, ANATOMY provides insight into sources of memory performance bottlenecks and is able to quantitatively predict the benefit of redressing them.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125193047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose the correlated mobile k-hop clustered networks model to implement correlated node movements and scalable clusters. We divide network states into three categories, i.e., cluster-sparse state, cluster-dense state and cluster-inferior dense state, and achieve the critical transmission range for the last two states. Furthermore, we find that correlated mobility and cluster scalability are closely related with each other and the impact of these two properties on connectivity is mainly through influencing network state transition.
{"title":"Impact of correlated mobility and cluster scalability on connectivity of wireless networks","authors":"Qi Wang, Liang Liu, Jinbei Zhang, Xinyu Wang, Xinbing Wang, Songwu Lu","doi":"10.1145/2591971.2592012","DOIUrl":"https://doi.org/10.1145/2591971.2592012","url":null,"abstract":"We propose the correlated mobile k-hop clustered networks model to implement correlated node movements and scalable clusters. We divide network states into three categories, i.e., cluster-sparse state, cluster-dense state and cluster-inferior dense state, and achieve the critical transmission range for the last two states. Furthermore, we find that correlated mobility and cluster scalability are closely related with each other and the impact of these two properties on connectivity is mainly through influencing network state transition.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115647824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study the stochastic multi-armed bandit (MAB) problem in the presence of side-observations across actions. In our model, choosing an action provides additional side observations for a subset of the remaining actions. One example of this model occurs in the problem of targeting users in online social networks where users respond to their friends's activity, thus providing information about each other's preferences. Our contributions are as follows: 1) We derive an asymptotic (with respect to time) lower bound (as a function of the network structure) on the regret (loss) of any uniformly good policy that achieves the maximum long term average reward. 2) We propose two policies - a randomized policy and a policy based on the well-known upper confidence bound (UCB) policies, both of which explore each action at a rate that is a function of its network position. We show that these policies achieve the asymptotic lower bound on the regret up to a multiplicative factor independent of network structure. The upper bound guarantees on the regret of these policies are better than those of existing policies. Finally, we use numerical examples on a real-world social network to demonstrate the significant benefits obtained by our policies against other existing policies.
{"title":"Stochastic bandits with side observations on networks","authors":"Swapna Buccapatnam, A. Eryilmaz, N. Shroff","doi":"10.1145/2591971.2591989","DOIUrl":"https://doi.org/10.1145/2591971.2591989","url":null,"abstract":"We study the stochastic multi-armed bandit (MAB) problem in the presence of side-observations across actions. In our model, choosing an action provides additional side observations for a subset of the remaining actions. One example of this model occurs in the problem of targeting users in online social networks where users respond to their friends's activity, thus providing information about each other's preferences. Our contributions are as follows: 1) We derive an asymptotic (with respect to time) lower bound (as a function of the network structure) on the regret (loss) of any uniformly good policy that achieves the maximum long term average reward. 2) We propose two policies - a randomized policy and a policy based on the well-known upper confidence bound (UCB) policies, both of which explore each action at a rate that is a function of its network position. We show that these policies achieve the asymptotic lower bound on the regret up to a multiplicative factor independent of network structure. The upper bound guarantees on the regret of these policies are better than those of existing policies. Finally, we use numerical examples on a real-world social network to demonstrate the significant benefits obtained by our policies against other existing policies.","PeriodicalId":306456,"journal":{"name":"Measurement and Modeling of Computer Systems","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127188063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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