27580015
Register Multimapping: A technique for reducing register bank conflicts in processors with large register files
In this paper, we investigate Register Multimapping as a technique to reduce register bank conflicts for processors with large register files, but relatively slow clock speeds. Register multimapping involves mapping an architectural register to multiple physical registers belonging to different banks. Reads can proceed using any of the physical registers, thereby minimizing read bank conflicts. Write conflicts can be minimized by allowing delayed allocation of physical registers [5]. Our experiments show that register multimapping can result in performance improvements up to 15% (10% on average) over baseline processors that are port-constrained. Improvements are up to 13% (5.5% on average) over port-constrained processors that support delayed allocation of registers.
205912378
The architecture of Efficient Multi-Core Processors: A Holistic Approach
Abstract The most straightforward methodology for designing a multi-core architecture is to replicate an off-the-shelf core design multiple times, and then connect the cores together using an interconnect mechanism. However, this methodology is “multi-core oblivious” as subsystems are designed/optimized unaware of the overall chip-multiprocessing system they would become parts of. The chapter demonstrates that this methodology is inefficient in terms of area/power. It recommends a holistic approach where the subsystems are designed from the ground up to be effective components of a complete system. The inefficiency in “multi-core oblivious” designs comes from many sources. Having multiple replicated cores results in an inability to adapt to the demands of execution workloads, and results in either underutilization or overutilization of processor resources. Single-ISA (instruction-set architecture) heterogeneous multi-core architectures host cores of varying power/performance characteristics on the die, but all cores are capable of running the same ISA. Such a processor can result in significant power savings and performance improvements if the applications are mapped to cores judiciously. The paper also presents holistic design methodologies for such architectures. Another source of inefficiency is blind replication of over-provisioned hardware structures. Conjoined-core chip multiprocessing allows adjacent cores of a multi-core architecture to share some resources. This can result in significant area savings with little performance degradation. Yet another source of inefficiency is the interconnect. The interconnection overheads can be very significant for a “multi-core oblivious” multi-core design—especially as the number of cores increases and the pipelines get deeper. The paper demonstrates the need to co-design the cores, the memory and the interconnection to address the inefficiency problem, and also makes several suggestions regarding co-design.
113025
Distributed peak power management for many-core architectures
Recently proposed techniques for peak power management involve centralized decision-making and assume quick evaluation of the various power management states. These techniques do not prevent instantaneous power from exceeding the peak power budget, but instead trigger corrective action when the budget has been exceeded. Similarly, they are not suitable for many-core architectures (processors with tens or possibly hundreds of cores on the same die) due to an exponential explosion in the number of global power management states. In this paper, we look at a hierarchical and a gradient ascent-based technique for decentralized peak power management for many-core architectures. The proposed techniques prevent power from exceeding the peak power budget and enable the placement of several more cores on a die than what the power budget would normally allow. We show up to 47% (33% on average) improvements in throughput for a given power budget. Our techniques outperform the static oracle by 22%.
2789297
Dynamic depth recovery from multiple synchronized video streams
This paper addresses the problem of extracting depth information of non-rigid dynamic 3D scenes from multiple synchronized video streams. Three main issues are discussed in this context. (i) temporally consistent depth estimation, (ii) sharp depth discontinuity estimation around object boundaries, and (iii) enforcement of the global visibility constraint. We present a framework in which the scene is modeled as a collection of 3D piecewise planar surface patches induced by color based image segmentation. This representation is continuously estimated using an incremental formulation in which the 3D geometric, motion, and global visibility constraints are enforced over space and time. The proposed algorithm optimizes a cost function that incorporates the spatial color consistency constraint and a smooth scene motion model.
62589113
Linear model hashing and batch RANSAC for rapid and accurate object recognition
This paper proposes a joint feature-based model indexing and geometric constraint based alignment pipeline for efficient and accurate recognition of 3D objects from a large model database. Traditional approaches either first prune the model database using indexing without geometric alignment or directly perform recognition based alignment. The indexing based pruning methods without geometric constraints can miss the correct models under imperfections such as noise, clutter and obscurations. Alignment based verification methods have to linearly verify each model in the database and hence do not scale up. The proposed techniques use spin images as semi-local shape descriptors and locality-sensitive hashing (LSH) to index into a joint spin image database for all the models. The indexed models represented in the pruned set are further pruned using progressively complex geometric constraints. A simple geometric configuration of multiple spin images, for instance a doublet, is first used to check for geometric consistency. Subsequently, full Euclidean geometric constraints are applied using RANSAC-based techniques on the pruned spin images and the models to verify specific object identity. As a result, the combined indexing and geometric alignment based pipeline is able to focus on matching the most promising models, and generate far less pose hypotheses while maintaining the same level of performance as the sequential alignment based recognition. Furthermore, compared to geometric indexing techniques like geometric hashing, the construction time and storage complexity for the proposed technique remains linear in the number of features rather than higher order polynomial. Experiments on a 56 3D model database show promising results.
1111313
Resist pattern peeling assessment in DUV chemically amplified resist
As device size shrinks resist line peeling becomes more challenging. In this paper we studied the resist pattern peeling based on resist processing parameters and type of bottom antireflective coating (BARC), for patterning trench structures with different duty ratios, in copper and low k dual damascene process. To minimize resist poisoning in dual damascene process, acetal-based resist was used. Significant improvement in via poisoning was observed with this chemistry as compared to environmentally stable chemically amplified resist chemistry but at the cost of pattern peeling. In order to solve pattern peeling problem we tried to analyze key factors such as compatibility with BARC, post-exposure bake, BARC curing, adhesion and their effects. Pitch dependency on pattern peeling margin is observed.
14585589
Real-time wide area multi-camera stereo tracking
We present a fully integrated real-time system to track humans with a network of stereo sensors over a wide area. The processing includes single camera tracking and multi-camera fusion. Each single camera detects and tracks humans in its own view and a multi-camera fusion module combines all the local tracks of the same human into a global track. We propose stereo segmentation and tracking techniques to handle multiple humans moving in groups in cluttered environments. We have developed a ground-based fusion method for camera handoff using space-time constraint. We show results and performance evaluation on very challenging data from a 12-camera system.
10455339
Pollution in P2P file sharing systems
One way to combat P2P file sharing of copyrighted content is to deposit into the file sharing systems large volumes of polluted files. Without taking sides in the file sharing debate, in this paper we undertake a measurement study of the nature and magnitude of pollution in the FastTrack P2P network, currently the most popular P2P file sharing system. We develop a crawling platform which crawls the majority of the FastTrack Network's 20,000+ supernodes in less than 60 minutes. From the raw data gathered by the crawler for popular audio content, we obtain statistics on the number of unique versions and copies available in a 24-hour period. We develop an automated procedure to detect whether a given version is polluted or not, and we show that the probabilities of false positives and negatives of the detection procedure are very small. We use the data from the crawler and our pollution detection algorithm to determine the fraction of versions and fraction of copies that are polluted for several recent and old songs. We observe that pollution is pervasive for recent popular songs. We also identify and describe a number of anti-pollution mechanisms.