In this paper, we present a new algorithm for aperiodic clustered-dot halftoning based on direct binary search (DBS). The DBS optimization framework has been modified for designing clustered-dot texture, by using filters with different sizes in the initialization and update steps of the algorithm. Following an intuitive explanation of how the clustered-dot texture results from this modified framework, we derive a closed-form cost metric which, when minimized, equivalently generates stochastic clustered-dot texture. An analysis of the cost metric and its influence on the texture quality is presented, which is followed by a modification to the cost metric to reduce computational cost and to make it more suitable for screen design.

Many relational operations are best performed when the relations are stored sorted over the relevant attributes (e.g. the common attributes in a natural join operation). However, generally relations are not stored sorted because it is expensive to maintain them this way (and impossible whenever there is more than one relevant sort key). Still, many times relations turn out to be nearly-sorted, where most tuples are close to their place in the order. This state can result from "leftover sortedness", where originally sorted relations were updated, or were combined into interim results when evaluating a complex query. It can also result from weak correlations between attribute values. Currently, nearly-sorted relations are treated the same as unsorted relations, and when relational operations are evaluated for them, a generic algorithm is used. Yet, many operations can be computed more efficiently by an algorithm that exploits this near-ordering.

Most electrophotographic printers use periodic, clustered-dot screening for rendering smooth and stable prints. However, when used for color printing, this approach suffers from the problem of periodic moire resulting from interference between the periodic halftones of individual color planes. There has been proposed an approach, called CLU-DBS for stochastic, clustered-dot halftoning and screen design based on direct binary search. We propose a methodology to embed a printer model within this halftoning algorithm to account for dot-gain and dot-loss effects. Without accounting for these effects, the printed image will not have the appearance predicted by the halftoning algorithm. We incorporate a measurement-based stochastic model for dot interactions of an electro-photographic printer within the iterative CLU-DBS binary halftoning algorithm. The stochastic model developed is based on microscopic absorptance and variance measurements. The experimental results show that electrophotography-model based stochastic clustered dot halftoning improves the homogeneity and reduces the graininess of printed halftone images.

Periodic clustered-dot screens are widely used for electrophotographic printers due to their homogeneous halftone texture and their robustness to dot gain. However, when applied to color printing, there are two important phenomena that limit the quality of printed color halftones generated using a screening technology: (1) moire´ due to the superposition halftone patterns corresponding to different periodicity matrices, and (2) appearance changes due to misregistration between different colorant planes. This paper focuses on analyzing the registration sensitivity of periodic, clustered-dot screens. To quantitatively measure the effect of registration errors, we introduce two new functions: (1) cost, and (2) risk of registration errors. We propose the notion of “visual equivalence”, and derive three propositions under which visual equivalence can be achieved, even when registration errors occur.

We present a document processing method that addresses some of the practical challenges in image enhancement for digital photo album in PDF documents. With the advent of digital offset presses, consumer photo books are becoming increasingly popular, and most such workflows convert the consumer's photos and layout into PDF documents. In order to produce appealing photo albums from consumer photographs, some form of automatic enhancement is usually required, and this enhancement is often done late in the workflow just before printing, and therefore it is done on the PDF file. If each and every PDF generation tool simply inserted a single complete image each time an image appeared in the document, then the process of opening a PDF document, iterating through the document, extracting, enhancing, and replacing images, and then saving the enhanced document would be relatively easy. Unfortunately, PDF generation tools often violate that assumption in two ways. Firstly, large images are often written as a set of small images in strips or tiles, which visually appear to be a single image. Secondly, an image in a PDF document may be reused in the document on different position and pages; directly enhancing images without the consideration of the reuse model could result in great increase in the document size and poor system performance. Therefore, image reconstruction and document optimization were performed in our PDF photo album enhancement solution.

lmbench is a powerful and extensible suite of micro-benchmarks that measures a variety of important aspects of system performance. It has a powerful timing harness that manages most of the ‘housekeeping’ chores associated with benchmarking, making it easy to create new benchmarks that analyze systems or components of specific interest to the user. In many ways lmbench is a Swiss army knife for performance analysis. It includes an extensive suite of micro-benchmarks that give powerful insights into system performance. For those aspects of system or application performance not covered by the suite, it is generally a simple task to create new benchmarks using the timing harness. lmbench is written in ANSI-C and uses POSIX interfaces, so it is portable across a wide variety of systems and architectures. It also includes powerful new tools that measure performance under scalable loads to analyze SMP and clustered system performance. Copyright © 2005 John Wiley & Sons, Ltd.

The Mariposa distributed data manager uses an economic model for managing the allocation of both storage objects and queries to servers. In this paper, we present extensions to the economic model which support replica management, as well as our mechanisms for propagating updates among replicas. We show how our replicacontrol mechanism can be used to provide consistent, although potentially stale, views of data across many machines without expensive pertransaction synchronization. We present a rule-based con#ict resolution mechanism, which can be usedto enhancetraditional time-stamp serialization. We discuss the e#ects of our replica system on query processing for both read-only and read-write queries. We further demonstrate how the replication model and mechanisms naturally support name service in Mariposa. 1 Introduction In this paper we describe replica managementin the Mariposa distributed data base management system #STON94a#. There has been considerable research devoted to stu...

Configuring redundant disk arrays is a black art. To configure an array properly, a system administrator must understand the details of both the array and the workload it will support. Incorrect understanding of either, or changes in the workload over time, can lead to poor performance. We present a solution to this problem: a two-level storage hierarchy implemented inside a single disk-array controller. In the upper level of this hierarchy, two copies of active data are stored to provide full redundancy and excellent performance. In the lower level, RAID 5 parity protection is used to provide excellent storage cost for inactive data, at somewhat lower performance. The technology we describe in this article, know as HP AutoRAID, automatically and transparently manages migration of data blocks between these two levels as access patterns change. The result is a fully redundant storage system that is extremely easy to use, is suitable for a wide variety of workloads, is largely insensitive to dynamic workload changes, and performs much better than disk arrays with comparable numbers of spindles and much larger amounts of front-end RAM cache. Because the implementation of the HP AutoRAID technology is almost entirely in software, the additional hardware cost for these benefits is very small. We describe the HP AutoRAID technology in detail, provide performance data for an embodiment of it in a storage array, and summarize the results of simulation studies used to choose algorithms implemented in the array.

article Free Access Share on The HP AutoRAID hierarchical storage system Authors: J. Wilkes Hewlett-Packard Laboratories, Palo Alto, CA Hewlett-Packard Laboratories, Palo Alto, CAView Profile , R. Golding Hewlett-Packard Laboratories, Palo Alto, CA Hewlett-Packard Laboratories, Palo Alto, CAView Profile , C. Staelin Hewlett-Packard Laboratories, Palo Alto, CA Hewlett-Packard Laboratories, Palo Alto, CAView Profile , T. Sullivan Hewlett-Packard Laboratories, Palo Alto, CA Hewlett-Packard Laboratories, Palo Alto, CAView Profile Authors Info & Claims ACM SIGOPS Operating Systems ReviewVolume 29Issue 5Dec. 3, 1995 pp 96–108https://doi.org/10.1145/224057.224065Published:03 December 1995Publication History 95citation648DownloadsMetricsTotal Citations95Total Downloads648Last 12 Months37Last 6 weeks7 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF