Dan C. Marinescu

Agent-based resource discovery

Presents a distributed discovery method allowing individual nodes to gather information about resources in a wide-area distributed system made up of autonomous systems linked together by a network technology substrate. We introduce an algorithm and a model for distributed awareness and a framework for the dynamic assembly of agents monitoring network resources. Whenever an agent needs detailed information about the individual components of another system, it uses the information gathered by the distributed awareness mechanism to identify the target system, then creates a description of a monitoring agent that is capable of providing the information about remote resources, and sends this description to the remote site. There, an agent factory dynamically assembles the monitoring agent. This solution is scalable and is suitable for heterogeneous environments where the architecture and the hardware resources of individual nodes differ, where the services provided by the system are diverse, and where the bandwidth and latency of the communication links cover a broad range.

Models for monitoring and debugging tools for parallel and distributed software

Several aspects of the multidimensional problem of providing monitoring support tools for the debugging and performance analysis of software for distributed and parallel systems are presented. A formal event-action model at the process level and a layered architectural model are introduced. The application of the event-action model to the development of the layered architectural model is shown. This effort was motivated by the need to understand the ways in which a monitoring system may intrude upon a monitored system. An understanding of the fundamental ideas underlying the relationship between monitoring and monitored systems is necessary to build practical tools for software development. These models are currently being used in the development of monitoring tools for the PASM parallel processing system prototype.

Models and algorithms for coscheduling compute-intensive taks on a network of workstations

The problem of using the idle cycles of a number of high performance workstations, interconnected by a high speed network, for solving computationally intensive tasks is discussed. The classes of distributed applications examined require some form of synchronization among the subtasks, hence the need for coscheduling to guarantee that subtasks start at the same time and execute at the same pace on a group of workstations. A model of the system is presented that allows the definition of an objective function to be maximized. Then a quadratic time and linear space algorithm is derived for computing the optimal coschedule, for the given model and class of applications addressed

Logical inference of Horn clauses in Petri net models

Petri net models for the Horn clause form of propositional logic and of first-order predicate logic are studied. A net model for logical inconsistency check is proposed. Algorithms for computing T-invariants of Petri net models of logical inference systems are investigated. The algorithms are based on the idea of resolution and exploit the presence of one-literal, pure-literal, and splitting clauses to lead to faster computation. Algorithms for computing T-invariants of high-level Petri net (HLPN) models of predicate logic are presented. >

Ad hoc grids: communication and computing in a power constrained environment

We introduce ad hoc grids as a hierarchy of mobile devices with different computing and communication capabilities. An ad hoc grid allows a group of individuals to accomplish a mission, often in a hostile environment; examples of applications of ad hoc grids are disaster management, wild-fire prevention, and peacekeeping operations. We are concerned with the interplay between computing and communication in the power-constrained environment of an ad hoc grid.

Modeling and performance analysis of QoS-aware load balancing of web-server clusters

This paper introduces mechanisms to correlate contents and priorities of incoming HTTP requests used for server process scheduling with the load balancing policies for Web-server clusters. This approach enables both load balancing and Web quality of service (QoS). Another contribution is a modeling and analysis technique based on stochastic high-level Petri net methods for QoS-aware load balancing. We propose an approximate analysis technique to reduce the complexity of the model.

Specification and identification of events for debugging and performance monitoring of distributed multiprocessor systems

The design of a debugging and performance analysis system that includes a specification language for process-level events and hardware for nonintrusive identification of these events during the execution of parallel and distributed application for a nonshared memory system is presented. The design is based on a formal event/action model and a layered architecture model that have been previously presented. Background, related work, and specification, and identification of events are discussed.<<ETX>>

Performance Equivalent Analysis of Workflow Systems Based on Stochastic Petri Net Models

Performance analysis is one of the most important aspects in workflow management system. In this paper, we propose the stochastic Petri nets workflow model (WF-SPN), which is the extension of WF-net. Based on our model, we give four performance equivalent formulae for four basic routing pattern of workflow system. Then, we put forward an approximate performance analysis method on the base of our performance equivalent formulae. An example illustrates our method can solve real-world problems efficiently.

An object-oriented framework for building collaborative network agents

We are primarily interested in the design of software agents supporting interoperability in a heterogeneous computing system. We view an agent as a composite object consisting of several other objects including a finite state machine, a model of the world, strategies associated with every state and an agenda. We introduced an object- oriented framework for building collaborative network agents. Moreover, we introduce an agent definition language and describe a mechanism to create agents dynamically.

A computational framework for the 3D structure determination of viruses with unknown symmetry

The protein shell of all virus structures resolved to this date exhibit some form of symmetry, most of them are spherical viruses with icosahedral symmetry; the study of viruses whose symmetry is not known, of structures which do not exhibit any symmetry, as well as the study of the genetic material of a virus are considerably more challenging. Increasing the resolution of the structure determination and solving structures with no symmetry represents a quantum leap in virus structure determination based upon electron microscopy. Computing is a major component of the structure determination process. Nowadays it is not feasible to increase the resolution of the structure determination of large macromolecules like viruses or to solve structures with no symmetry without novel parallel algorithms and environments enabling structural biologists to use parallel systems, clusters of workstations, or providing access to grid computing.