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(2006)Conference PaperOn-going improvements in the scaling of FPGA device sizes and time-to-market pressures encourage the use of module-oriented design flows [3], while economic factors favour the reuse of smaller devices for high performance computational tasks. One of the core problems in proposing dynamic modular reconfiguration approaches is supporting the differing communications needs of the sequence of modules configured over time [2]. Proposals to date have not focussed on communications issues. Moreover, they have advocated the use of specific protocols [4], or they cannot be readily implemented [1], or they suffer from high overheads [5], or rely upon deprecated features such as tri-state lines [7]. In contrast, we propose a methodology for the rapid deployment of a communications infrastructure that provides the wires required by dynamic modules and allows users to implement the protocols they want. Our aim is to support new tiled dynamically reconfigurable architectures such as Virtex-4, as well as mature device families.
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(2006)Conference PaperIn line with Shannon's ideas, we define the entropy of FPGA reconfiguration to be the amount of information needed to configure a given circuit onto a given device. We propose using entropy as a gauge of the maximum configuration compression that can be achieved and determine the entropy of a set of 24 benchmark circuits for the Virtex device family. We demonstrate that simple off-the-shelf compression techniques such as Golomb encoding and hierarchical vector compression achieve compression results that are within 1-10% of the theoretical bound. We present an enhanced configuration memory system based on the hierarchical vector compression technique that accelerates reconfiguration in proportion to the amount of compression achieved. The proposed system demands little additional chip area and can be clocked at the same rate as the Virtex configuration clock.
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(2006)Conference PaperBypass delays are expected to grow beyond 1ns as technology scales. These delays necessitate pipelining of bypass paths at processor frequencies above 1GHz and thus affect the performance of sequential code sequences. We propose dealing with these delays through a dynamic functional unit chaining approach. We study the performance benefits of a superscalar, out-of-order processor augmented with a two-by-two array of ALUs interconnected by a fast, partial bypass network. An online profiler guides the automatic configuration of the network to accelerate specific patterns of dependent instructions. A detailed study of benchmark simulations demonstrates these first steps towards mapping binaries to a small coarse-grained array at runtime can improve instruction throughput by over 18% and 25% when the microarchitecure includes bypass delays of one cycle and two cycles, respectively.
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(2006)Conference Paper
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(2006)Conference PaperTo support reliable multicast routing in wireless mesh networks, it is important to protect multicast sessions against link or node failures. The issue of protecting multicast sessions in wireless mesh networks is a new problem to the best of our knowledge. In this paper, we propose a resilient forwarding mesh approach for protecting a multicast session in wireless mesh networks. Utilizing the wireless broadcast advantage, a resilient forwarding mesh effectively establishes two node disjoint paths for each source destination pair. This allows a multicast session to be immune from any single link or intermediate node failure. We introduce four heuristic algorithms to obtain approximate solutions that seek to minimize the number of required broadcast transmissions. We evaluate the performance of these heuristic algorithms against the optimal resilient forwarding mesh (ORFM) obtained by solving an integer linear programming (ILP) formulation of the problem. Experimental results demonstrate that one of these heuristic algorithms, which we call the minimal disjoint mesh algorithm (MDM), performs sufficiently close to ORFM. Besides, we find that the resilient forwarding mesh approach provides efficient 1+1 protection [8] to the multicast session without incurring much additional overhead on a single minimal cost multicast tree.
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(2006)Conference PaperTo support reliable multicast routing in wireless mesh networks, it is important to protect multicast sessions against link or node failures. In this paper, we propose a resilient forwarding mesh approach for protecting a multicast session. Utilizing the wireless broadcast advantage, a resilient forwarding mesh effectively establishes two node disjoint paths for each source-destination pair. This allows a multicast session to be immune from any single link or intermediate node failure. An integer linear programming (ILP) formulation is presented to find the optimal resilient forwarding mesh (ORFM) that minimizes the number of broadcast transmissions. In comparison with the existing optimal path-pair (OPP) approach proposed in [1] for wired mesh networks, our experimental results demonstrate that ORFM outperforms OPP in wireless scenarios.
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(2006)Conference PaperModern embedded system execute a single application or a class of applications repeatedly. A new emerging methodology of designing embedded system utilizes configurable processors where the cache size, associativity, and line size can be chosen by the designer. In this paper, a method is given to rapidly find the L1 cache miss rate of an application. An energy model and an execution time model are developed to find the best cache configuration for the given embedded application. Using benchmarks from Mediabench, we find that our method is on average 45 times faster to explore the design space, compared to Dinero IV while still having 100% accuracy.
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(2006)Conference PaperScratchpad memory has been introduced as a replacement for cache memory as it improves the performance of certain embedded systems. Additionally, it has also been demonstrated that scratchpad memory can significantly reduce the energy consumption of the memory hierarchy of embedded systems. This is significant, as the memory hierarchy consumes a substantial proportion of the total energy of an embedded system. This paper deals with optimization of the instruction memory scratchpad based on a novel methodology that uses a metric which we call the concomitance. This metric is used to find basic blocks which are executed frequently and in close proximity in time. Once such blocks are found, they are copied into the scratchpad memory at appropriate times; this is achieved using a special instruction inserted into the code at appropriate places. For a set of benchmarks taken from Mediabench, our scratchpad system consumed just 59% (avg) of the energy of the cache system, and 73% (avg) of the energy of the state of the art scratchpad system, while improving the overall performance. Compared to the state of the art method, the number of instructions copied into the scratchpad memory from the main memory is reduced by 88%.
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(2006)Conference PaperAudio Nomad comprises a series of cross-disciplinary art/science projects working on the concept of GPS-driven location-based audio applications. Project outcomes in the form of artworks enable a user or audience to experience a virtual audio world situated within the real world, as a spatial composition of sounds seeming to originate from real objects. Two-dimensional audio spatialization simulates realistic sound sources, and non-spatialized sounds may also be used as location-based content. Conceptually, sound is used to reveal information or create an aesthetic, often composed of a combination of oral histories, archival audio, site-specific historical information, field recordings, and music. The outcome is a culturally significant public sound artwork utilizing this new location-based audio medium – an application of global positioning, audio technologies, and software engineering. As GNSS technologies become more ubiquitous, Audio Nomad can take advantage of new platforms such as mobile phones. This unique multidisciplinary collaboration has driven the design of tools with great creative potential to provide new alternative location-based services poised to engage and appeal to the imagination of future GNSS users.
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(2006)Conference PaperImpossible futures equivalence is the semantic equivalence on labelled transition systems that identifies systems iff they have the same `AGEF` properties: temporal logic properties saying that reaching a desired outcome is not doomed to fail. We show that this equivalence, with an added root condition, is the coarsest congruence containing weak bisimilarity with explicit divergence that respects deadlock/livelock traces (or fair testing, or any liveness property under a global fairness assumption) and assigns unique solutions to recursive equations.