Task allocation and migration on a star-network

Modern day applications require computational power which cannot be satisfied with uniprocessor systems. So the use of multiprocessor systems in such jobs becomes necessary. This thesis presents an approach of allocating the tasks to a multiprocessor system called the star network. Generally, an incoming task requires only a part of the star network, and not the whole network, for its execution. So, we need a task allocation strategy which can identify the free processors forming a substar and allocate tasks to these substars. The task executes for a time equal to task residence time and then relinquishes the substar. Sometimes there might be enough free processors forming a substar in the network which can host the next incoming task. But the allocation strategy may not recognize the free processors as a substar. To create a substar of free processors to host the next task, task migration has to be performed such that the free processors are grouped into a substar. In this work, three processor allocation strategies: static, dynamic and dynamic work task migration are presented. Using simulations, a comparison of these strategies is done to obtain the percentage improvement of one strategy over the other. Also a comparative study of the working of these strategies in star-networks and hypercubes is done. A saving of 5-11% is achieved by for both the networks incorporating task-migration in dynamic allocation over simple dynamic allocation

Processor allocation strategies for modified hypercubes

Parallel processing has been widely accepted to be the future in high speed computing. Among the various parallel architectures proposed/implemented, the hypercube has shown a lot of promise because of its poweful properties, like regular topology, fault tolerance, low diameter, simple routing, and ability to efficiently emulate other architectures. The major drawback of the hypercube network is that it can not be expanded in practice because the number of communication ports for each processor grows as the logarithm of the total number of processors in the system. Therefore, once a hypercube supercomputer of a certain dimensionality has been built, any future expansions can be accomplished only by replacing the VLSI chips. This is an undesirable feature and a lot of work has been under progress to eliminate this stymie, thus providing a platform for easier expansion. Modified hypercubes (MHs) have been proposed as the building blocks of hypercube-based systems supporting incremental growth techniques without introducing extra resources for individual hypercubes. However, processor allocation on MHs proves to be a challenge due to a slight deviation in their topology from that of the standard hypercube network. This thesis addresses the issue of processor allocation on MHs and proposes various strategies which are based, partially or entirely, on table look-up approaches. A study of the various task allocation strategies for standard hypercubes is conducted and their suitability for MHs is evaluated. It is shown that the proposed strategies have a perfect subcube recognition ability and a superior performance. Existing processor allocation strategies for pure hypercube networks are demonstrated to be ineffective for MHs, in the light of their inability to recognize all available subcubes. A comparative analysis that involves the buddy strategy and the new strategies is carried out using simulation results

Efficient processor management strategies for multicomputer systems

Multicomputers are cost-effective alternatives to the conventional supercomputers. Contemporary processor management schemes tend to underutilize the processors and leave many of the processors in the system idle while jobs are waiting for execution;Instead of designing faster processors or interconnection networks, a substantial performance improvement can be obtained by implementing better processor management strategies. This dissertation studies the performance issues related to the processor management schemes and proposes several ways to enhance the multicomputer systems by means of processor management. The proposed schemes incorporate the concepts of size-reduction, non-contiguous allocation, as well as job migration. Job scheduling using a bypass-queue is also studied. All the proposed schemes are proven effective in improving the system performance via extensive simulations. Each proposed scheme has different implementation cost and constraints. In order to take advantage of these schemes, judicious selection of system parameters is important and is discussed