A. Natrajan - Academia.edu (original) (raw)
Papers by A. Natrajan
Google, Inc. (search). ...
Google, Inc. (search). ...
Wiley Series in Communications Networking & Distributed Systems, 2003
Multi-representation models are an attractive design solution for layered autonomous agent archit... more Multi-representation models are an attractive design solution for layered autonomous agent architectures in terms of man- aging complexity of internal representations and separation of design concerns. However, the representations maintained by the multiple layers can become inconsistent with one another due to the nature of the layers' concerns and capabil- ities. Consistency maintenance in multi-representation mod- els is an emerging
Lecture Notes in Computer Science, 2001
Computational Scientists often cannot easily access the large amounts of resources their applicat... more Computational Scientists often cannot easily access the large amounts of resources their applications require. Legion is a collection of software services that facilitate the secure and easy use of local and non-local resources by providing the illusion of a single virtual machine from heterogeneous, geographically-distributed resources. This paper describes the newest additions to Legion that enable high-performance (capacity) computing as well as secure, fault-tolerant and collaborative (capability) computing.
High Performance Computing Systems and Applications, 2003
Grids are becoming ubiquitous platforms for high-performance computing and distributed collaborat... more Grids are becoming ubiquitous platforms for high-performance computing and distributed collaboration. A grid benefits users by permitting them to access heterogeneous resources, such as machines, data, people and devices, that are distributed geographically and organisationally. It benefits organisations by permitting them to offer unused resources on existing hardware and thus reclaim otherwise lost costs. Although worldwide grids can be constructed today, issues regarding heterogeneity, security and failures must be resolved especially if the participating resources are controlled by different organisations. A grid infrastructure that harnesses the power of distributed resources for computing and collaboration must respect the autonomy of organisations to choose policies for using their resources.
International Series in Operations Research & Management Science, 2004
Grid resource management is not just about scheduling jobs on the fastest machines, but rather ab... more Grid resource management is not just about scheduling jobs on the fastest machines, but rather about scheduling all compute objects and all data objects on machines whose capabilities match the requirements, while preserving site autonomy, recognizing usage policies and respecting conditions for use. In this chapter, we present the Grid resource management of Legion, an object-based Grid infrastructure system. We argue that Grid resource management requires not a one-size-fits-all scheduler but an architectural framework that can accommodate different schedulers for different classes of problems.
Proceedings 11th Workshop on Parallel and Distributed Simulation, 1997
Multi-resolution representation of simulated entities is considered essential for a growing porti... more Multi-resolution representation of simulated entities is considered essential for a growing portion of distributed simulations. Heretofore, modelers have represented entites at just one level of resolution, or have represented concurrent representations in an inconsistent manner. We address the question of the cost of maintaining multiple, concurrent representations. We present a brief overview of our concept of a Multiple Resolution Entity (MRE) and Attribute Dependency Graph (ADG) both originally described elsewhere, and then compare simulation and consistency costs of some approaches, including our own MRE/ADG-based approach, to multi-resolution modeling. The cost analysis presented here is the first known analysis of its type, and will provide a basis for simulation designers to determine the best, and most cost-effective approach to supporting simulation of entities at different levels of resolution concurrently.
Proceedings of the IEEE, 2005
Proceedings 3rd IEEE International Workshop on Distributed Interactive Simulation and Real-Time Applications, 1999
Serialization, the traditional method of resolving concurrent interactions, is often inappropriat... more Serialization, the traditional method of resolving concurrent interactions, is often inappropriate; when interactions are dependent on each other, other policies for resolving them may be more suitable. We use semantic information to help categorize common interactions encountered in the modeling and simulation domain. This categorization enables us to suggest reasonable policies for resolving the effects of concurrent interactions.
IBM Journal of Research and Development, 2000
Grids are collections of interconnected resources harnessed to satisfy various needs of users. Le... more Grids are collections of interconnected resources harnessed to satisfy various needs of users. Legion and Globus are pioneering grid technologies. Several of the aims and goals of both projects are similar, yet their underlying architectures and philosophies differ substantially. The scope of both projects is the creation of worldwide grids; in that respect, they subsume several distributed systems technologies. However, Legion has been designed as a virtual operating system (OS) for distributed resources with OS-like support for current and expected future interactions among resources, whereas Globus has long been designed as a "sum of services" infrastructure, in which tools are developed independently in response to current needs of users. We compare and contrast Legion and Globus in terms of their underlying philosophy and the resulting architectures, and we discuss how these projects converge in the context of the new standards being formulated for grids.
Concurrency and Computation: Practice and Experience, 2002
The Legion Grid Portal is an interface to a grid system. Users interact with the portal, and henc... more The Legion Grid Portal is an interface to a grid system. Users interact with the portal, and hence a grid through an intuitive interface from which they can view files, submit and monitor runs, and view accounting information. The architecture of the portal is designed to accommodate multiple diverse grid infrastructures, legacy systems and application-specific interfaces. The current implementation of the Legion Grid Portal is with familiar web technologies over the Legion grid infrastructure. The portal can be extended in a number of directionsadditional support for grid administrators, greater number of application-specific interfaces, interoperability between grid infrastructures, and interfaces for programming support. The portal has been in operation since February 2000 on npacinet, a worldwide grid managed by Legion on NPACI resources.
Concurrency and Computation: Practice and Experience, 2004
One benefit of a computational Grid is the ability to run high-performance applications over dist... more One benefit of a computational Grid is the ability to run high-performance applications over distributed resources simply and securely. We demonstrated this benefit with an experiment in which we studied the protein-folding process with the CHARMM molecular simulation package over a Grid managed by Legion, a Grid operating system. High-performance applications can take advantage of Grid resources if the Grid operating system provides both low-level functionality as well as high-level services. We describe the nature of services provided by Legion for high-performance applications. Our experiences indicate that human factors continue to play a crucial role in the configuration of Grid resources, underlying resources can be problematic, Grid services must tolerate underlying problems or inform the user, and high-level services must continue to evolve to meet user requirements. Our experiment not only helped a scientist perform an important study, but also showed the viability of an integrated approach such as Legion's for managing a Grid.
Google, Inc. (search). ...
Google, Inc. (search). ...
Wiley Series in Communications Networking & Distributed Systems, 2003
Multi-representation models are an attractive design solution for layered autonomous agent archit... more Multi-representation models are an attractive design solution for layered autonomous agent architectures in terms of man- aging complexity of internal representations and separation of design concerns. However, the representations maintained by the multiple layers can become inconsistent with one another due to the nature of the layers' concerns and capabil- ities. Consistency maintenance in multi-representation mod- els is an emerging
Lecture Notes in Computer Science, 2001
Computational Scientists often cannot easily access the large amounts of resources their applicat... more Computational Scientists often cannot easily access the large amounts of resources their applications require. Legion is a collection of software services that facilitate the secure and easy use of local and non-local resources by providing the illusion of a single virtual machine from heterogeneous, geographically-distributed resources. This paper describes the newest additions to Legion that enable high-performance (capacity) computing as well as secure, fault-tolerant and collaborative (capability) computing.
High Performance Computing Systems and Applications, 2003
Grids are becoming ubiquitous platforms for high-performance computing and distributed collaborat... more Grids are becoming ubiquitous platforms for high-performance computing and distributed collaboration. A grid benefits users by permitting them to access heterogeneous resources, such as machines, data, people and devices, that are distributed geographically and organisationally. It benefits organisations by permitting them to offer unused resources on existing hardware and thus reclaim otherwise lost costs. Although worldwide grids can be constructed today, issues regarding heterogeneity, security and failures must be resolved especially if the participating resources are controlled by different organisations. A grid infrastructure that harnesses the power of distributed resources for computing and collaboration must respect the autonomy of organisations to choose policies for using their resources.
International Series in Operations Research & Management Science, 2004
Grid resource management is not just about scheduling jobs on the fastest machines, but rather ab... more Grid resource management is not just about scheduling jobs on the fastest machines, but rather about scheduling all compute objects and all data objects on machines whose capabilities match the requirements, while preserving site autonomy, recognizing usage policies and respecting conditions for use. In this chapter, we present the Grid resource management of Legion, an object-based Grid infrastructure system. We argue that Grid resource management requires not a one-size-fits-all scheduler but an architectural framework that can accommodate different schedulers for different classes of problems.
Proceedings 11th Workshop on Parallel and Distributed Simulation, 1997
Multi-resolution representation of simulated entities is considered essential for a growing porti... more Multi-resolution representation of simulated entities is considered essential for a growing portion of distributed simulations. Heretofore, modelers have represented entites at just one level of resolution, or have represented concurrent representations in an inconsistent manner. We address the question of the cost of maintaining multiple, concurrent representations. We present a brief overview of our concept of a Multiple Resolution Entity (MRE) and Attribute Dependency Graph (ADG) both originally described elsewhere, and then compare simulation and consistency costs of some approaches, including our own MRE/ADG-based approach, to multi-resolution modeling. The cost analysis presented here is the first known analysis of its type, and will provide a basis for simulation designers to determine the best, and most cost-effective approach to supporting simulation of entities at different levels of resolution concurrently.
Proceedings of the IEEE, 2005
Proceedings 3rd IEEE International Workshop on Distributed Interactive Simulation and Real-Time Applications, 1999
Serialization, the traditional method of resolving concurrent interactions, is often inappropriat... more Serialization, the traditional method of resolving concurrent interactions, is often inappropriate; when interactions are dependent on each other, other policies for resolving them may be more suitable. We use semantic information to help categorize common interactions encountered in the modeling and simulation domain. This categorization enables us to suggest reasonable policies for resolving the effects of concurrent interactions.
IBM Journal of Research and Development, 2000
Grids are collections of interconnected resources harnessed to satisfy various needs of users. Le... more Grids are collections of interconnected resources harnessed to satisfy various needs of users. Legion and Globus are pioneering grid technologies. Several of the aims and goals of both projects are similar, yet their underlying architectures and philosophies differ substantially. The scope of both projects is the creation of worldwide grids; in that respect, they subsume several distributed systems technologies. However, Legion has been designed as a virtual operating system (OS) for distributed resources with OS-like support for current and expected future interactions among resources, whereas Globus has long been designed as a "sum of services" infrastructure, in which tools are developed independently in response to current needs of users. We compare and contrast Legion and Globus in terms of their underlying philosophy and the resulting architectures, and we discuss how these projects converge in the context of the new standards being formulated for grids.
Concurrency and Computation: Practice and Experience, 2002
The Legion Grid Portal is an interface to a grid system. Users interact with the portal, and henc... more The Legion Grid Portal is an interface to a grid system. Users interact with the portal, and hence a grid through an intuitive interface from which they can view files, submit and monitor runs, and view accounting information. The architecture of the portal is designed to accommodate multiple diverse grid infrastructures, legacy systems and application-specific interfaces. The current implementation of the Legion Grid Portal is with familiar web technologies over the Legion grid infrastructure. The portal can be extended in a number of directionsadditional support for grid administrators, greater number of application-specific interfaces, interoperability between grid infrastructures, and interfaces for programming support. The portal has been in operation since February 2000 on npacinet, a worldwide grid managed by Legion on NPACI resources.
Concurrency and Computation: Practice and Experience, 2004
One benefit of a computational Grid is the ability to run high-performance applications over dist... more One benefit of a computational Grid is the ability to run high-performance applications over distributed resources simply and securely. We demonstrated this benefit with an experiment in which we studied the protein-folding process with the CHARMM molecular simulation package over a Grid managed by Legion, a Grid operating system. High-performance applications can take advantage of Grid resources if the Grid operating system provides both low-level functionality as well as high-level services. We describe the nature of services provided by Legion for high-performance applications. Our experiences indicate that human factors continue to play a crucial role in the configuration of Grid resources, underlying resources can be problematic, Grid services must tolerate underlying problems or inform the user, and high-level services must continue to evolve to meet user requirements. Our experiment not only helped a scientist perform an important study, but also showed the viability of an integrated approach such as Legion's for managing a Grid.