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Title: Evaluating Placement Algorithms with the DREAM Framework for Reconfigurable Hardware Devices
Authors: Eatmon, Dedra
Advisors: Clay S. Gloster, Jr., Chair
Winser A. Alexander, Member
Edward Davis, Member
Issue Date: 9-Aug-2000
Degree: MS
Discipline: Computer Engineering
Abstract: The field programmable gate array (FPGA) has become one of the most utilized configurable devices in the area of reconfigurable computing. FPGAs have alarge amount of flexibility and provide a high degree of parallel computing capability. Since their introduction in the 1980's, these configurable logicdevices have experienced a dramatic increase in programming capabilities and performance. Both factors have been significant in the changing roles ofconfigurable devices in custom-computing machines. However, the improvements in capability and performance have not eliminated the issues related toefficient placement of applications on these devices. This thesis presents a tool that evaluates placement algorithms for configurable logic devices. Written in Java, the tool is a framework in whichvarious placement algorithms can be executed and the performance and quality ofeach placement evaluated using a cost function. Based on devices thatsupport relocatable hardware modules (RHMs), the tool places modules with user-specified placement algorithms and provides feedback that can be usedfor a comparative analysis. The framework manages module mappings to the logicdevice that are both independent of each other and do not requirepin-to-pin routing connections. Such a tool is valuable for the identification of effective placement algorithms for real-time placement of RHMs in run-time reconfigurable systems. The Dynamic Resource Allocation and Management (DREAM) framework, has been designed and developed to evaluate FPGA placement algorithms/heuristics. Aportion of the evaluation is based on a simplistic cost function that calculates the amount of contiguous unused space remaining on the device intwo dimensions. In our experiments, we use an FPGA logic core generator to produce several rectangular RHMs. In addition to the rectangular RHMs producedby the logic core generation tool, our framework can handle arbitrary circuit profiles. Several scenarios consisting of approximately 500insertions/deletions of both rectangular and non-rectangular RHMs are used as test data sets for placement. Three placement algorithms are presented todemonstrate the flexibility of the framework. The first algorithm tested in the DREAM framework is a random placement algorithm. The second algorithm isan adaptation of a traditional best-fit algorithm that we call exhaustivesearch. The third algorithm is a modified version of first-fit.Future work will involve the development of additional placement algorithms andthe incorporation ofplacement issues that relate to requests for central reconfigurable computing resources originating from a remote site. The DREAM framework answers the call for a tool that is sorely needed to identify placement algorithms that can be effectively used for real-timeplacement. In addition to providing results that can be used to benchmark the performance of placement algorithms in real-time on a configurablesystem, this tool also allows the end-user methods to store and load placementsfor future optimization. By taking full advantage of the partial andfull dynamic reconfiguration capabilities of logic devices currently used in run-time reconfigurable systems, the goal of DREAM is to provide a tool with whichthe quality of placement algorithms can be quantified and compared.
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