We consider a model for interacting objects, where the evolution of each object is given by a finite state Markov chain, whose transition matrix depends on the present and the past of the distribution of states of all objects. This is a general model of wide applicability; we mention as examples: TCP connections, HTTP flows, robot swarms, reputation systems. We show that when the number of objects is large, the occupancy measure of the system converges to a deterministic dynamical system (the "mean field") with dimension the number of states of an individual object. We also prove a fast simulation result, which allows to simulate the evolution of a few particular objects imbedded in a large system. We illustrate how this can be used to model the determination of reputation in large populations, with various liar strategies.
{"title":"A Generic Mean Field Convergence Result for Systems of Interacting Objects","authors":"J. Boudec, D. McDonald, Jochen Mundinger","doi":"10.1109/QEST.2007.3","DOIUrl":"https://doi.org/10.1109/QEST.2007.3","url":null,"abstract":"We consider a model for interacting objects, where the evolution of each object is given by a finite state Markov chain, whose transition matrix depends on the present and the past of the distribution of states of all objects. This is a general model of wide applicability; we mention as examples: TCP connections, HTTP flows, robot swarms, reputation systems. We show that when the number of objects is large, the occupancy measure of the system converges to a deterministic dynamical system (the \"mean field\") with dimension the number of states of an individual object. We also prove a fast simulation result, which allows to simulate the evolution of a few particular objects imbedded in a large system. We illustrate how this can be used to model the determination of reputation in large populations, with various liar strategies.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115051148","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}
A new algorithm to assess transient performance measures for every possible initial configuration of a quasi-birth-and-death (QBD) Markov chain is introduced. We make use of the framework termed QBDs with marked time epochs that transforms the transient problem into a stationary one by applying a discrete Erlangization and constructing a reset Markov chain. To avoid the need to repeat ail computations for each initial configuration, we propose a level based recursive algorithm that uses intermediate results obtained for initial states belonging to levels 0,hellip, tau - 1 to compute the transient measure when the initial state is part of level tau. Also, the computations for all states belonging to level tau are performed simultaneously. A key property of our approach lies in the exploitation of the internal structure of the block matrices involved, avoiding any need to store large matrices. A flexible Matlab implementation of the proposed algorithm is available online.
提出了一种评估准生-死(QBD)马尔可夫链各种可能初始构型的暂态性能度量的新算法。我们利用带有标记时间点的qbd框架，通过应用离散埃尔朗化和构造重置马尔可夫链，将瞬态问题转化为平稳问题。为了避免对每个初始配置重复所有计算的需要，我们提出了一种基于级别的递归算法，该算法使用属于级别0,hellip, tau - 1的初始状态获得的中间结果来计算初始状态为级别tau的一部分时的瞬态度量。同时，对属于tau层的所有状态进行计算。我们的方法的一个关键特性在于利用了所涉及的块矩阵的内部结构，避免了任何存储大矩阵的需要。该算法的一个灵活的Matlab实现可以在网上找到。
{"title":"Simultaneous Transient Analysis of QBD Markov Chains for all Initial Configurations using a Level Based Recursion","authors":"J. V. Velthoven, B. V. Houdt, C. Blondia","doi":"10.1109/QEST.2007.21","DOIUrl":"https://doi.org/10.1109/QEST.2007.21","url":null,"abstract":"A new algorithm to assess transient performance measures for every possible initial configuration of a quasi-birth-and-death (QBD) Markov chain is introduced. We make use of the framework termed QBDs with marked time epochs that transforms the transient problem into a stationary one by applying a discrete Erlangization and constructing a reset Markov chain. To avoid the need to repeat ail computations for each initial configuration, we propose a level based recursive algorithm that uses intermediate results obtained for initial states belonging to levels 0,hellip, tau - 1 to compute the transient measure when the initial state is part of level tau. Also, the computations for all states belonging to level tau are performed simultaneously. A key property of our approach lies in the exploitation of the internal structure of the block matrices involved, avoiding any need to store large matrices. A flexible Matlab implementation of the proposed algorithm is available online.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122117545","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}
H. Wen, S. Sbaraglia, Seetharami R. Seelam, I. Chung, Guojing Cong, D. Klepacki
Our productivity centered performance tuning framework for HPC applications comprises of three main components: (1) a versatile source code, performance metrics, and performance data visualization and analysis graphical user interface, (2) a unique source code and binary instrumentation engine, and (3) an array of data collection facilities to gather performance data across various dimensions including CPU, message passing, threads, memory and I/O. We believe that the ability to decipher performance impacts at the source level and the ability to probe the application with different tools at the same time at varying granularities, while hiding the complications of binary instrumentation, leads to higher productivity of scientists in understanding and tuning the performance of associated computing systems and applications.
{"title":"A Productivity Centered Tools Framework for Application Performance Tuning","authors":"H. Wen, S. Sbaraglia, Seetharami R. Seelam, I. Chung, Guojing Cong, D. Klepacki","doi":"10.1109/QEST.2007.14","DOIUrl":"https://doi.org/10.1109/QEST.2007.14","url":null,"abstract":"Our productivity centered performance tuning framework for HPC applications comprises of three main components: (1) a versatile source code, performance metrics, and performance data visualization and analysis graphical user interface, (2) a unique source code and binary instrumentation engine, and (3) an array of data collection facilities to gather performance data across various dimensions including CPU, message passing, threads, memory and I/O. We believe that the ability to decipher performance impacts at the source level and the ability to probe the application with different tools at the same time at varying granularities, while hiding the complications of binary instrumentation, leads to higher productivity of scientists in understanding and tuning the performance of associated computing systems and applications.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"258 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115496305","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 present a GUI-based tool supporting the stochastic process algebra PEPA with modules for performance evaluation through Markovian steady-state analysis, fluid flow analysis, and stochastic simulation.
{"title":"The PEPA Plug-in Project","authors":"Lars Grunske, R. Colvin, Kirsten Winter","doi":"10.1109/QEST.2007.34","DOIUrl":"https://doi.org/10.1109/QEST.2007.34","url":null,"abstract":"We present a GUI-based tool supporting the stochastic process algebra PEPA with modules for performance evaluation through Markovian steady-state analysis, fluid flow analysis, and stochastic simulation.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115186717","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}
Puppetnets are created when a web server hosts a page that when loaded simultaneously by many users causes malicious behavior; there are a wide variety of means by which puppetnets can cause mischief. This paper analyzes the behavior and effectiveness of puppetnets for Internet reconnaissance-methodical means of discovering live IP addresses-as a prelude to another attack. We consider local reconnaissance, in which the client reconnoiters addresses in its local IP neighborhood. We focus on mod eling critical facets that impact coverag-the fraction of addresses analyzed-as a function of time. We prove that certain scanning strategies are superior to others, and de velop formulae that describe the inefficiencies due to lack of coordination. Finally we use the model to estimate how global Internet coverage grows as a function of time, under generous assumptions about the size of puppetnet and length of script execution. We see that even a strategy that focuses on exploring blocks of adjacent live addresses may take days to map a significant fraction of the Internet address space.
{"title":"Analysis of Local Address Scanning by Puppetnets","authors":"D. Nicol","doi":"10.1109/QEST.2007.45","DOIUrl":"https://doi.org/10.1109/QEST.2007.45","url":null,"abstract":"Puppetnets are created when a web server hosts a page that when loaded simultaneously by many users causes malicious behavior; there are a wide variety of means by which puppetnets can cause mischief. This paper analyzes the behavior and effectiveness of puppetnets for Internet reconnaissance-methodical means of discovering live IP addresses-as a prelude to another attack. We consider local reconnaissance, in which the client reconnoiters addresses in its local IP neighborhood. We focus on mod eling critical facets that impact coverag-the fraction of addresses analyzed-as a function of time. We prove that certain scanning strategies are superior to others, and de velop formulae that describe the inefficiencies due to lack of coordination. Finally we use the model to estimate how global Internet coverage grows as a function of time, under generous assumptions about the size of puppetnet and length of script execution. We see that even a strategy that focuses on exploring blocks of adjacent live addresses may take days to map a significant fraction of the Internet address space.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130289719","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}
Performance trees are a recently-proposed mechanism for the specification of performance properties and measures. They represent an attractive alternative to stochastic logics, since they support traditional stochastic model checking queries, while also allowing for the direct extraction of a wide range of quantitative measures. In this paper we illustrate differences in expressiveness between performance trees and continuous stochastic logic (CSL), and present quantitative semantics showing the mathematical basis underlying performance tree operators. As a running example, we demonstrate performance query specification with performance trees on a stochastic Petri net model of a healthcare system.
{"title":"Performance Trees: Expressiveness and Quantitative Semantics","authors":"T. Suto, J. Bradley, W. Knottenbelt","doi":"10.1109/QEST.2007.9","DOIUrl":"https://doi.org/10.1109/QEST.2007.9","url":null,"abstract":"Performance trees are a recently-proposed mechanism for the specification of performance properties and measures. They represent an attractive alternative to stochastic logics, since they support traditional stochastic model checking queries, while also allowing for the direct extraction of a wide range of quantitative measures. In this paper we illustrate differences in expressiveness between performance trees and continuous stochastic logic (CSL), and present quantitative semantics showing the mathematical basis underlying performance tree operators. As a running example, we demonstrate performance query specification with performance trees on a stochastic Petri net model of a healthcare system.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116625216","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}
L. Brenner, Paulo Fernandes, B. Plateau, Ihab Sbeity
PEPS is a tool package for modeling and solving models expressed in Stochastic Automata Networks fS AN J. The SAN formalism defines a compact storage scheme for the transition matrix of the Markov chain and it uses tensor algebra to handle the basic vector matrix multiplications. This paper presents a short timeline of PEPS previous versions and the new features included in version 2007.
{"title":"PEPS2007 - Stochastic Automata Networks Software Tool","authors":"L. Brenner, Paulo Fernandes, B. Plateau, Ihab Sbeity","doi":"10.1109/QEST.2007.33","DOIUrl":"https://doi.org/10.1109/QEST.2007.33","url":null,"abstract":"PEPS is a tool package for modeling and solving models expressed in Stochastic Automata Networks fS AN J. The SAN formalism defines a compact storage scheme for the transition matrix of the Markov chain and it uses tensor algebra to handle the basic vector matrix multiplications. This paper presents a short timeline of PEPS previous versions and the new features included in version 2007.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122387600","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}
Many approaches to tackle the state-space explosion problem of Markov chains are based on the notion of lumpability (a.k.a. probabilistic bisimulation), which allows computation of measures using the quotient Markov chain, which, in some cases, has much smaller state space than the original one. We present a new signature-based algorithm for computing the optimal (i.e., smallest possible) quotient Markov chain, prove its correctness, and implement it symbolically for Markov chains represented as Multi-Terminal BDDs (MTBDDs). The algorithm is very time-efficient because we translate the core operation of the algorithm, i.e., the computation of the signatures, into symbolic operations. Our experiments on various configurations of three example models with different levels of lump ability show that the algorithm (1) handles significantly larger state spaces than an explicit algorithm, (2) outperforms a very efficient explicit algorithm for significantly lump able Markov chains while it is not prohibitively slower in the worst case, and (3) outperforms our previous optimal symbolic algorithm [10] in terms of running time although it has higher space requirement for most of the configurations.
{"title":"Signature-based Symbolic Algorithm for Optimal Markov Chain Lumping","authors":"Salem Derisavi","doi":"10.1109/QEST.2007.27","DOIUrl":"https://doi.org/10.1109/QEST.2007.27","url":null,"abstract":"Many approaches to tackle the state-space explosion problem of Markov chains are based on the notion of lumpability (a.k.a. probabilistic bisimulation), which allows computation of measures using the quotient Markov chain, which, in some cases, has much smaller state space than the original one. We present a new signature-based algorithm for computing the optimal (i.e., smallest possible) quotient Markov chain, prove its correctness, and implement it symbolically for Markov chains represented as Multi-Terminal BDDs (MTBDDs). The algorithm is very time-efficient because we translate the core operation of the algorithm, i.e., the computation of the signatures, into symbolic operations. Our experiments on various configurations of three example models with different levels of lump ability show that the algorithm (1) handles significantly larger state spaces than an explicit algorithm, (2) outperforms a very efficient explicit algorithm for significantly lump able Markov chains while it is not prohibitively slower in the worst case, and (3) outperforms our previous optimal symbolic algorithm [10] in terms of running time although it has higher space requirement for most of the configurations.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133899637","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 definition of behavioural preorders over process terms as the maximal (pre-)congruences induced by basic observables has proven to be a useful technique to define various preorders and equivalences in the non-probabilistic setting. In this paper, we consider probabilistic observables to define an observational semantics for a probabilistic process calculus. The resulting pre-congruence is proven to coincide with a probabilistic may preorder, which, in turn, corresponds to a natural probabilistic extension of the may testing preorder of De Nicola and Hennessy.
{"title":"Basic Observables for Probabilistic May Testing","authors":"Maria Carla Palmeri, R. Nicola, M. Massink","doi":"10.1109/QEST.2007.19","DOIUrl":"https://doi.org/10.1109/QEST.2007.19","url":null,"abstract":"The definition of behavioural preorders over process terms as the maximal (pre-)congruences induced by basic observables has proven to be a useful technique to define various preorders and equivalences in the non-probabilistic setting. In this paper, we consider probabilistic observables to define an observational semantics for a probabilistic process calculus. The resulting pre-congruence is proven to coincide with a probabilistic may preorder, which, in turn, corresponds to a natural probabilistic extension of the may testing preorder of De Nicola and Hennessy.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117337691","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 present an implementation of model checking for the probabilistic pi-calculus-calculus, a process algebra which supports modelling of concurrency, mobility and discrete probabilistic behaviour. Formal verification techniques for this calculus have clear applications in several domains, including mobile ad-hoc network protocols and random security protocols. Despite this, no implementation of automated verification exists. Building upon the (non-probabilistic) pi-calculus model checker MMC, we first show an automated procedure for constructing the Markov decision process representing a probabilistic pi-calculus process. This can then be verified using existing probabilistic model checkers such as PRISM. Secondly, we demonstrate how for a large class of systems a more efficient, compositional approach can be applied, which uses our extension of MMC on each parallel component of the system and then translates the results into a high-level model description for the PRISM tool. The feasibility of our techniques is demonstrated through three case studies from the pi-calculus literature.
{"title":"Model checking the probabilistic pi-calculus","authors":"G. Norman, C. Palamidessi, D. Parker, Peng Wu","doi":"10.1109/QEST.2007.31","DOIUrl":"https://doi.org/10.1109/QEST.2007.31","url":null,"abstract":"We present an implementation of model checking for the probabilistic pi-calculus-calculus, a process algebra which supports modelling of concurrency, mobility and discrete probabilistic behaviour. Formal verification techniques for this calculus have clear applications in several domains, including mobile ad-hoc network protocols and random security protocols. Despite this, no implementation of automated verification exists. Building upon the (non-probabilistic) pi-calculus model checker MMC, we first show an automated procedure for constructing the Markov decision process representing a probabilistic pi-calculus process. This can then be verified using existing probabilistic model checkers such as PRISM. Secondly, we demonstrate how for a large class of systems a more efficient, compositional approach can be applied, which uses our extension of MMC on each parallel component of the system and then translates the results into a high-level model description for the PRISM tool. The feasibility of our techniques is demonstrated through three case studies from the pi-calculus literature.","PeriodicalId":249627,"journal":{"name":"Fourth International Conference on the Quantitative Evaluation of Systems (QEST 2007)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115541819","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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