We introduce a system for near-duplicate detection and sub-image retrieval. Such a system is useful for finding copyright violations and detecting forged images. We define near-duplicates as images altered with common transformations such as changing contrast, saturation, scaling, cropping, framing, etc. Our system builds a parts-based representation of images using distinctive local descriptors which give high quality matches even under severe transformations. To cope with the large number of features extracted from the images, we employ locality-sensitive hashing to index the local descriptors. This allows us to make approximate similarity queries that only examine a small fraction of the database. Although locality-sensitive hashing has excellent theoretical performance properties, a standard implementation would still be unacceptably slow for this application. We show that, by optimizing layout and access to the index data on disk, we can efficiently query indices containing millions of keypoints. Our system achieves nearperfect accuracy (100% precision at 99.85% recall) on the tests presented in Meng et al. [16], and consistently strong results on our own, significantly more challenging experiments. Query times are interactive even for collections of thousands of images.

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We propose a new Bayesian approach to object-based image retrieval with relevance feedback.

Database management systems (DBMSs) do not take full advantage of modern microarchitectural resources, such as wide-issue out-of-order processor pipelines. Increases in processor clock rate and instruction-level parallelism have left memory accesses as the dominant bottleneck in DBMS execution. Prior research indicates that simultaneous multithreading (SMT) can hide memory access latency from a single thread and improve throughput by increasing the number of outstanding memory accesses. Rather than expend chip area and power on out-of-order execution, as in current SMT processors, we demonstrate the effectiveness of using many simple processor cores, each with hardware support for multiple thread contexts. This paper shows an existing hardware architecture-the network processor-already fits the model for multi-threaded, multi-core execution. Using an Intel IXP2400 network processor, we evaluate the performance of three key database operations and demonstrate improvements of 1.9X to 2.5X when compared to a generalpurpose processor.

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