L'invention concerne un systeme reparti utilise pour creer un point de controle pour une plur... more L'invention concerne un systeme reparti utilise pour creer un point de controle pour une pluralite de processus executes dans le systeme reparti. Le systeme reparti comprend plusieurs noeuds de calcul, un systeme d'exploitation s'executant dans chaque noeud de calcul. Une bibliotheque de points de controle residant au niveau de l'utilisateur, dans chaque noeud de calcul, est transparente pour le systeme d'exploitation residant dans le meme noeud de calcul et pour les autres noeuds de calcul. Chaque bibliotheque de points de controle utilise un protocole d'entree en session de messagerie par fenetrage pour la creation des points de controle du systeme reparti. Des processus participant a un calcul distribue dans le systeme reparti peuvent etre migres d'un noeud de calcul a un autre noeud de calcul du systeme reparti, par remappage d'adresses de materiel a l'aide de la bibliotheque de points de controle.
Uncovering the metrics and procedures employed by an autonomous networking system is an important... more Uncovering the metrics and procedures employed by an autonomous networking system is an important problem with applications in instrumentation, traffic engineering, and game-theoretic studies of multi-agent environments. This thesis presents a method for utilizing inverse reinforcement learning (IRL) techniques for the purpose of discovering a composite metric used by a dynamic routing algorithm on an Internet Protocol (IP) network. The network and routing algorithm are modeled as a reinforcement learning (RL) agent and a Markov decision process (MDP). The problem of routing metric discovery is then posed as a problem of recovering the reward function, given observed optimal behavior. We show that this approach is empirically suited for determining the relative contributions of factors that constitute a composite metric. Experimental results for many classes of randomly generated networks are presented. Acknowledgments I would like to thank my advisers Dr. Naren Ramakrishnan and Dr....
This paper studies the evaluation of routing algorithms from the perspective of reachability rout... more This paper studies the evaluation of routing algorithms from the perspective of reachability routing, where the goal is to determine all paths between a sender and a receiver. Reachability routing is becoming relevant with the changing dynamics of the Internet and the emergence of low-bandwidth wireless/ad-hoc networks. We make the case for reinforcement learning as the framework of choice to realize reachability routing, within the confines of the current Internet infrastructure. The setting of the reinforcement learning problem offers several advantages, including loop resolution, multi-path forwarding capability, cost-sensitive routing, and minimizing state overhead, while maintaining the incremental spirit of current backbone routing algorithms. We identify research issues in reinforcement learning applied to the reachability routing problem to achieve a fluid and robust backbone routing framework. The paper is targeted toward practitioners seeking to implement a reachability ro...
As supercomputers continue to grow in scale and capabilities, it is becoming increasingly difficu... more As supercomputers continue to grow in scale and capabilities, it is becoming increasingly difficult to isolate processor and system level causes of performance degradation. Over the last several years, a significant number of performance analysis and monitoring tools have been built/proposed. However, these tools suffer from several important shortcomings, particularly in distributed environments. In this paper we present ScALPEL, a Scalable Adaptive Lightweight Performance Evaluation Library for application performance monitoring at the functional level. Our approach provides several distinct advantages. First, ScALPEL is portable across a wide variety of architectures, and its ability to selectively monitor functions presents low run-time overhead, enabling its use for large-scale production applications. Second, it is run-time configurable, enabling both dynamic selection of functions to profile as well as events of interest on a per function basis. Third, our approach is transpa...
Keyword-based text retrieval engines have been and will continue to be essential to text-based in... more Keyword-based text retrieval engines have been and will continue to be essential to text-based information access systems because they serve as the basic building blocks to high-level text analysis systems. Traditionally, text compression and text retrieval are teated as independent problems. Text les are compressed and indexed separately. To answer a keyword-based query, text les are rst uncompressed, and then searched sequentially or via an inverted index. This paper describes the design, implementation and evaluation of a novel integrated text compression and indexing scheme called ITCI, which combines the dictionary data structures for compression and indexing, and allows direct search through compressed text. The performance results show that ITCI's compression eeciency is within 7% to 17% of GZIP, which is among the best lossless data compression algorithms, The sum of the compressed text and the inverted index is only between 55% to 76% of the original text size, while th...
Keyword based search engines are the basic building block of text retrieval systems. Higher level... more Keyword based search engines are the basic building block of text retrieval systems. Higher level systems like content sensitive search engines and knowledge-based systems still rely on keyword search as the underlying text retrieval mechanism. With the explosive growth in content, Internet and Intranet information repositories require efficient mechanisms to store as well as index data. In this paper we discuss the implementation of the Shrink and Search Engine (SASE) framework which unites text compression and indexing to maximize keyword search performance while reducing storage cost. SASE features the novel capability of being able to directly search through compressed text without explicit decompression. The implementation includes a search server architecture, which can be accessed from a Java front-end to perform keyword search on the Internet. The performance results show that the compression efficiency of SASE is within 7-17% of GZIP one of the best lossless compression sch...
We recommend a programming construct - availability check - for programs that need to automatical... more We recommend a programming construct - availability check - for programs that need to automatically adjust to presence or absence of segments of code. The idea is to check the existence of a valid definition before a function call is invoked. The syntax is that of a simple 'if' statement. The vision is to enable customization of application functionality through addition or removal of optional components, but without requiring complete re-building. Focus is on C-like compiled procedural languages and UNIX-based systems. Essentially, our approach attempts to combine the flexibility of dynamic libraries with the usability of utility (dependency) libraries. We outline the benefits over prevalent strategies mainly in terms of development complexity, crudely measured as lesser lines of code. We also allude to performance and flexibility facets. A Preliminary implementation and figures from early experimental evaluation are presented.
Current directions in network routing research have not kept pace with the latest developments in... more Current directions in network routing research have not kept pace with the latest developments in network architectures, such as peer-to-peer networks, sensor networks, ad-hoc wireless networks, and overlay networks. A common characteristic among all of these new technologies is the presence of highly dynamic network topologies. Currently deployed single-path routing protocols cannot adequately cope with this dynamism, and existing multi-path algorithms make trade-offs which lead to less than optimal performance on these networks. This drives the need for routing protocols designed with the unique characteristics of these networks in mind. In this paper we propose the notion of reachability routing as a solution to the challenges posed by routing on such dynamic networks. In particular, our formulation of reachability routing provides cost-sensitive multi-path forwarding along with loop avoidance within the confines of the Internet Protocol (IP) architecture. This is achieved throug...
Grid infrastructures and computing environments have progressed significantly in the past few yea... more Grid infrastructures and computing environments have progressed significantly in the past few years. The vision of truly seamless Grid usage relies on runtime systems support that is cognizant of the operational issues underlying grid computations and, at the same time, is flexible enough to accommodate diverse application scenarios. This paper addresses the twin aspects of Grid infrastructure and application support through a novel combination of two computational technologies – Weaves, a source-language independent parallel runtime compositional framework that operates through reverse-analysis of compiled object files, and runtime recommender systems that aid in dynamic knowledge-based application composition. Domain-specific adaptivity is exploited through a novel compositional system that supports runtime recommendation of code modules and a sophisticated checkpointing and runtime migration solution that can be transparently deployed over Grid infrastructures. A core set of “ada...
L'invention concerne un systeme reparti utilise pour creer un point de controle pour une plur... more L'invention concerne un systeme reparti utilise pour creer un point de controle pour une pluralite de processus executes dans le systeme reparti. Le systeme reparti comprend plusieurs noeuds de calcul, un systeme d'exploitation s'executant dans chaque noeud de calcul. Une bibliotheque de points de controle residant au niveau de l'utilisateur, dans chaque noeud de calcul, est transparente pour le systeme d'exploitation residant dans le meme noeud de calcul et pour les autres noeuds de calcul. Chaque bibliotheque de points de controle utilise un protocole d'entree en session de messagerie par fenetrage pour la creation des points de controle du systeme reparti. Des processus participant a un calcul distribue dans le systeme reparti peuvent etre migres d'un noeud de calcul a un autre noeud de calcul du systeme reparti, par remappage d'adresses de materiel a l'aide de la bibliotheque de points de controle.
Uncovering the metrics and procedures employed by an autonomous networking system is an important... more Uncovering the metrics and procedures employed by an autonomous networking system is an important problem with applications in instrumentation, traffic engineering, and game-theoretic studies of multi-agent environments. This thesis presents a method for utilizing inverse reinforcement learning (IRL) techniques for the purpose of discovering a composite metric used by a dynamic routing algorithm on an Internet Protocol (IP) network. The network and routing algorithm are modeled as a reinforcement learning (RL) agent and a Markov decision process (MDP). The problem of routing metric discovery is then posed as a problem of recovering the reward function, given observed optimal behavior. We show that this approach is empirically suited for determining the relative contributions of factors that constitute a composite metric. Experimental results for many classes of randomly generated networks are presented. Acknowledgments I would like to thank my advisers Dr. Naren Ramakrishnan and Dr....
This paper studies the evaluation of routing algorithms from the perspective of reachability rout... more This paper studies the evaluation of routing algorithms from the perspective of reachability routing, where the goal is to determine all paths between a sender and a receiver. Reachability routing is becoming relevant with the changing dynamics of the Internet and the emergence of low-bandwidth wireless/ad-hoc networks. We make the case for reinforcement learning as the framework of choice to realize reachability routing, within the confines of the current Internet infrastructure. The setting of the reinforcement learning problem offers several advantages, including loop resolution, multi-path forwarding capability, cost-sensitive routing, and minimizing state overhead, while maintaining the incremental spirit of current backbone routing algorithms. We identify research issues in reinforcement learning applied to the reachability routing problem to achieve a fluid and robust backbone routing framework. The paper is targeted toward practitioners seeking to implement a reachability ro...
As supercomputers continue to grow in scale and capabilities, it is becoming increasingly difficu... more As supercomputers continue to grow in scale and capabilities, it is becoming increasingly difficult to isolate processor and system level causes of performance degradation. Over the last several years, a significant number of performance analysis and monitoring tools have been built/proposed. However, these tools suffer from several important shortcomings, particularly in distributed environments. In this paper we present ScALPEL, a Scalable Adaptive Lightweight Performance Evaluation Library for application performance monitoring at the functional level. Our approach provides several distinct advantages. First, ScALPEL is portable across a wide variety of architectures, and its ability to selectively monitor functions presents low run-time overhead, enabling its use for large-scale production applications. Second, it is run-time configurable, enabling both dynamic selection of functions to profile as well as events of interest on a per function basis. Third, our approach is transpa...
Keyword-based text retrieval engines have been and will continue to be essential to text-based in... more Keyword-based text retrieval engines have been and will continue to be essential to text-based information access systems because they serve as the basic building blocks to high-level text analysis systems. Traditionally, text compression and text retrieval are teated as independent problems. Text les are compressed and indexed separately. To answer a keyword-based query, text les are rst uncompressed, and then searched sequentially or via an inverted index. This paper describes the design, implementation and evaluation of a novel integrated text compression and indexing scheme called ITCI, which combines the dictionary data structures for compression and indexing, and allows direct search through compressed text. The performance results show that ITCI's compression eeciency is within 7% to 17% of GZIP, which is among the best lossless data compression algorithms, The sum of the compressed text and the inverted index is only between 55% to 76% of the original text size, while th...
Keyword based search engines are the basic building block of text retrieval systems. Higher level... more Keyword based search engines are the basic building block of text retrieval systems. Higher level systems like content sensitive search engines and knowledge-based systems still rely on keyword search as the underlying text retrieval mechanism. With the explosive growth in content, Internet and Intranet information repositories require efficient mechanisms to store as well as index data. In this paper we discuss the implementation of the Shrink and Search Engine (SASE) framework which unites text compression and indexing to maximize keyword search performance while reducing storage cost. SASE features the novel capability of being able to directly search through compressed text without explicit decompression. The implementation includes a search server architecture, which can be accessed from a Java front-end to perform keyword search on the Internet. The performance results show that the compression efficiency of SASE is within 7-17% of GZIP one of the best lossless compression sch...
We recommend a programming construct - availability check - for programs that need to automatical... more We recommend a programming construct - availability check - for programs that need to automatically adjust to presence or absence of segments of code. The idea is to check the existence of a valid definition before a function call is invoked. The syntax is that of a simple 'if' statement. The vision is to enable customization of application functionality through addition or removal of optional components, but without requiring complete re-building. Focus is on C-like compiled procedural languages and UNIX-based systems. Essentially, our approach attempts to combine the flexibility of dynamic libraries with the usability of utility (dependency) libraries. We outline the benefits over prevalent strategies mainly in terms of development complexity, crudely measured as lesser lines of code. We also allude to performance and flexibility facets. A Preliminary implementation and figures from early experimental evaluation are presented.
Current directions in network routing research have not kept pace with the latest developments in... more Current directions in network routing research have not kept pace with the latest developments in network architectures, such as peer-to-peer networks, sensor networks, ad-hoc wireless networks, and overlay networks. A common characteristic among all of these new technologies is the presence of highly dynamic network topologies. Currently deployed single-path routing protocols cannot adequately cope with this dynamism, and existing multi-path algorithms make trade-offs which lead to less than optimal performance on these networks. This drives the need for routing protocols designed with the unique characteristics of these networks in mind. In this paper we propose the notion of reachability routing as a solution to the challenges posed by routing on such dynamic networks. In particular, our formulation of reachability routing provides cost-sensitive multi-path forwarding along with loop avoidance within the confines of the Internet Protocol (IP) architecture. This is achieved throug...
Grid infrastructures and computing environments have progressed significantly in the past few yea... more Grid infrastructures and computing environments have progressed significantly in the past few years. The vision of truly seamless Grid usage relies on runtime systems support that is cognizant of the operational issues underlying grid computations and, at the same time, is flexible enough to accommodate diverse application scenarios. This paper addresses the twin aspects of Grid infrastructure and application support through a novel combination of two computational technologies – Weaves, a source-language independent parallel runtime compositional framework that operates through reverse-analysis of compiled object files, and runtime recommender systems that aid in dynamic knowledge-based application composition. Domain-specific adaptivity is exploited through a novel compositional system that supports runtime recommendation of code modules and a sophisticated checkpointing and runtime migration solution that can be transparently deployed over Grid infrastructures. A core set of “ada...
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Papers by Srinidhi Varadarajan