Last update: Apr 1, 2000
Speaker: MONARC CollaborationThe MONARC simulation and modelling of distributed computing systems needs realistic description of complex data access patterns and of very large of jobs running on large scale distributed systems and exchanging very large amounts of data.
A process oriented approach for discrete event simulation is well suited to describe various activities running concurrently as well the stochastic arrival patterns, specific for such type of simulation. Threaded objects or "Active Objects" (having an execution thread, program counter, stack...) provide a natural way to map the specific behaviour of distributed data processing into the simulation program.
Building the logical simulation model requires the abstraction from the real system all the components and their time dependent interaction. This logical model has to be equivalent to the simulated system in all important respects. An Object Oriented design, which allows an easy and direct mapping of the logical components into the simulation program and provides the interaction mechanism, offers the best solution for such a large scale system and also copes with systems which may change dynamically.
The simulation tool developed within MONARC is based on Java technology which provides adequate tools for developing a flexible and distributed process oriented simulation. Java has a build-in support for multi-threaded objects and for concurrent processing, which can be used for simulation purposes provided a dedicated scheduling mechanism is developed. Java also offers good support for graphics which can be easily interfaced with the simulation code. Proper graphics tools, and ways to analyse data interactively, are essential in any simulation project.
The design elements, status and features of the MONARC simulation tool are presented. The program allows realistic modelling of complex data access patterns by multiple concurrent users in large scale computing systems in a wide range of possible architectures, from centralized to highly distributed.
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