The Cache Complexity of Multithreaded Cache Oblivious Algorithms

We present a technique for analyzing the number of cache misses incurred by multithreaded cache oblivious algorithms on an idealized parallel machine in which each processor has a private cache. We specialize this technique to computations executed by the Cilk work-stealing scheduler on a machine with dag-consistent shared memory. We show that a multithreaded cache oblivious matrix multiplication incurs cache misses when executed by the Cilk scheduler on a machine with P processors, each with a cache of size Z, with high probability. This bound is tighter than previously published bounds. We also present a new multithreaded cache oblivious algorithm for 1D stencil computations incurring cache misses with high probability, one for Gaussian elimination and back substitution, and one for the length computation part of the longest common subsequence problem incurring cache misses with high probability. This work was supported in part by the Defense Advanced Research Projects Agency (DARPA) under contract No. NBCH30390004.     

Forest cover change and illegal logging in the Ukrainian Carpathians in the transition period from 1988 to 2007

Illegal logging is a major environmental and economic problem, and exceeds in some countries the amounts of legally harvested timber. In Eastern Europe and the former Soviet Union, illegal logging increased and reforestation on abandoned farmland was widespread after the breakdown of socialism, and the region's forest cover trends remain overall largely unclear. Our goal here was to map forest cover change and to assess the extent of illegal logging and reforestation in the Ukrainian Carpathians. We used Landsat TM/ETM+ images and Support Vector Machines (SVM) to derive forest change trajectories between 1988 and 2007 for the entire Ukrainian Carpathians. We calculated logging and reforestation rates, and compared Landsat-based forest trends to official statistics and inventory maps. Our classification resulted in reliable forest/non-forest maps (overall accuracies between 97.1%-98.01%) and high clear cut detection rates (on average 89.4%). Forest cover change was widespread in the Ukrainian Carpathians between 1988 and 2007. We found forest cover increase in peripheral areas, forest loss in the interior Carpathians, and increased logging in remote areas. Overall, our results suggest that unsustainable forest use from socialist times likely persisted in the post-socialist period, resulting in a continued loss of older forests and forest fragmentation. Landsat-based forest trends differed substantially from official forest resource statistics. Illegal logging appears to have been at least as extensive as documented logging during the early 1990s and so-called sanitary clear-cuts represent a major loophole for overharvesting and logging in restricted areas. Reforestation and illegal logging are frequently not accounted for in forest resource statistics, highlighting limitations of these data. Combating illegal logging and transitioning towards sustainable forestry requires better monitoring and up-to-date accounting of forest resources, in the Carpathians and elsewhere in Eastern Europe, and remote sensing can be a key technology to achieve these goals.     

iManual

This article describes the iManual-concept developed at Fraunhofer FIT which deals with the use of mobile devices as context-aware integrated control and help systems for in principal arbitrary wirelessly connected consumer or industrial products. Following the premise of designing the interface of various IT-based products in a way that facilitates learning and respects user expectations, we explore the design space that is created by combining control and help functions by way of mobile devices. On the way, we discuss various potentials of this approach to enhance the corresponding products and services. Based on a review of the state of the art on intelligent help systems and mobile interfaces we describe the iManual concept and a prototypical implementation for a PDA-based control and help system for the navigation system of the BMW 7. We conclude with a discussion of limitations and opportunities for extension of the approach and corresponding further work.     

Polyimide-based X-ray masks with advanced performance of pattern accuracy and thermal stability

Polyimide-based X-ray masks which are generated by optical lithography and electroplating of gold absorbers on a polyimide mask membrane gain attention as low cost masks. The organic membranes generally have problem of (1) pattern edge sharpness, (2) miniaturization of pattern and (3) thermal stability. To make the masks commodity in deep and accurate lithography area, Optnics Precision, Japan, has overcome the above difficulties and realized the masks with advanced performance of pattern accuracy and thermal stability by improving the making process and the material. Good results were obtained in the exposure experiment that used this mask. When this X-ray mask is combined with the electroforming technique and the material development technique that Optnics has, the application to various fields like an industrial field and medical field can be expected.     

Benchmarking urban six‐degree‐of‐freedom simultaneous localization and mapping

Quite a number of approaches for solving the simultaneous localization and mapping (SLAM) problem exist by now. Some of them have recently been extended to mapping environments with six‐degree‐of‐freedom poses, yielding 6D SLAM approaches. To demonstrate the capabilities of the respective algorithms, it is common practice to present generated maps and successful loop closings in large outdoor environments. Unfortunately, it is nontrivial to compare different 6D SLAM approaches objectively, because ground truth data about the outdoor environments used for demonstration are typically unavailable. We present a novel benchmarking method for generating the ground truth data based on reference maps. The method is then demonstrated by comparing the absolute performance of some previously existing 6D SLAM algorithms that build a large urban outdoor map. © 2008 Wiley Periodicals, Inc.     

Simulation of satellite water vapour lidar measurements: Performance assessment under real atmospheric conditions

A lidar simulator has been applied to assess the performances of a satellite water vapour differential absorption lidar (DIAL) system. Measurements performed by the airborne Deutsches Zentrum für Luft-und Raumfahrt (DLR) water vapour DIAL on 15 May 2002 during ESA's Water Vapour Lidar Experiment (WALEX), in combination with PSU/NCAR Mesoscale Model (MM5) output, were used to obtain backscatter and water vapour fields with high resolution and accuracy. These data and model output serve as input for the simulator, allowing for the performance of satellite DIAL under highly-inhomogeneous atmospheric conditions including clouds to be assessed. The airborne measurements show an intrusion of stratospheric air into the troposphere, and MM5 data used above the DLR Falcon airplane flight altitude are characterized by very high upper tropospheric humidity levels, comparable to those associated with strong mid-latitude transport events from the troposphere to the lowermost stratosphere. Results of the simulator reveal that the maximum systematic error does not exceed 5% up to 16 km, except in the presence of thick cirrus and mid level clouds with an optical thickness up to 2 and, occasionally, inside the dry stratospheric intrusion, while the random error is less than 20% up to 16 km when spatial measurement resolutions are applied that follow the World Meteorological Organization (WMO) threshold observational requirements for numerical weather prediction (NWP). The bias is even smaller if a drier upper troposphere/lower stratosphere (UTLS) region from a reference atmosphere is considered. The results confirm the capability of satellite water vapour DIAL systems to retrieve thin structures of the tropospheric water vapour and particle backscatter fields, as well as its capability to provide low bias and random error measurements even in the presence of clouds.     

A data decomposition method for stepwise migration of complex legacy data

Sooner or later, in almost every company, the maintenance and further development of large enterprise information technology (IT) applications reaches its limit. From the point of view of cost as well as technical capability, legacy applications must eventually be replaced by new enterprise IT applications. Data migration is an inevitable part of making this switch. While different data migration strategies can be applied, incremental data migration is one of the most popular strategies, due to its low level of risk: the entire data volume is split into several data tranches, which are then migrated in individual migration steps. The key to a successful migration is the strategy for decomposing the data into suitable tranches. This paper presents a method for data decomposition where the entire data volume of a monolithic enterprise IT application is split into independent data migration tranches. Each tranche comprises the data to be migrated in one migration step, which is usually executed during the application's downtime window. Unlike other methods, which describe data migration in a highly abstract way, we propose specific heuristics for data decomposition into independent data packages (tranches). The data migration approach described here is being applied in one of the largest migration projects currently underway in the European health care sector, comprising millions of customer records.     

Technologies for the Electronic Distribution of Information Services - A Value Proposition Analysis

Since the original design and deployment of the Internet architecture, the economical and technological requirements regarding the distribution quality of web-based information services have changed drastically. Business models have evolved that particularly address quality and cost aspects of information service distribution, e.g. content delivery networks and peer-to-peer distribution. In addition, network operators apply differentiated routing technologies in dedicated infrastructures to guarantee a superior quality of service (QoS). This article compares the value propositions of technologies for information service distribution. 103 information services were analyzed by means of discriminant analyses in order to identify the main aspects influencing delivery quality and costs. The results indicate that the value propositions differ with regard to the type of services they support rather than with regard to direct QoS criteria, such as latency and packet loss. The insights derived from this work support information service vendors in their choice of a distribution provider.     

A differentiated services implementation for high-performance TCP flows

The IETF’s recent differentiated services (DS) architecture, which specifies a scalable mechanism for treating packets differently, offers new opportunities for building end-to-end quality of service (QoS) systems. However, it also introduces new challenges. In particular, it is not clear whether TCP’s flow and congestion control mechanisms work well with the mechanisms used for end-to-end QoS. For that reason it is essential to analyze whether the existing DS mechanisms can be used with standard TCP implementations or whether it is necessary to wait for upcoming features introduced in future modified versions of TCP. The general-purpose architecture for reservation and allocation (GARA) supports flow-specific QoS specification, immediate and advance reservation, and online monitoring and control of both individual resources and heterogeneous resource ensembles. Using GARA, we evaluated actual DS mechanisms provided by Cisco routers. We present the results of this evaluation and discuss their impact on the performance of popular TCP implementations.