Making an Embedded DBMS JIT-friendly

While database management systems (DBMSs) are highly optimized, interactions across the boundary between the programming language (PL) and the DBMS are costly, even for in-process embedded DBMSs. In this paper, we show that programs that interact with the popular embedded DBMS SQLite can be significantly optimized - by a factor of 3.4 in our benchmarks - by inlining across the PL / DBMS boundary. We achieved this speed-up by replacing parts of SQLite's C interpreter with RPython code and composing the resulting meta-tracing virtual machine (VM) - called SQPyte - with the PyPy VM. SQPyte does not compromise stand-alone SQL performance and is 2.2% faster than SQLite on the widely used TPC-H benchmark suite.Comment: 24 pages, 18 figure

Approaches to Interpreter Composition

In this paper, we compose six different Python and Prolog VMs into 4 pairwise compositions: one using C interpreters; one running on the JVM; one using meta-tracing interpreters; and one using a C interpreter and a meta-tracing interpreter. We show that programs that cross the language barrier frequently execute faster in a meta-tracing composition, and that meta-tracing imposes a significantly lower overhead on composed programs relative to mono-language programs.Comment: 33 pages, 1 figure, 9 table

Homology of the mapping class group for surfaces of genus 2 with boundary

We report on the computation of the integral homology of the mapping class group of genus g surfaces with one boundary curve and m punctures, when 2g + m is smaller than 6. In particular, it includes the genus 2 case with no or one puncture.Comment: This is the version published by Geometry & Topology Monographs on 29 April 200

Image gathering, coding, and processing: End-to-end optimization for efficient and robust acquisition of visual information

Researchers are concerned with the end-to-end performance of image gathering, coding, and processing. The applications range from high-resolution television to vision-based robotics, wherever the resolution, efficiency and robustness of visual information acquisition and processing are critical. For the presentation at this workshop, it is convenient to divide research activities into the following two overlapping areas: The first is the development of focal-plane processing techniques and technology to effectively combine image gathering with coding, with an emphasis on low-level vision processing akin to the retinal processing in human vision. The approach includes the familiar Laplacian pyramid, the new intensity-dependent spatial summation, and parallel sensing/processing networks. Three-dimensional image gathering is attained by combining laser ranging with sensor-array imaging. The second is the rigorous extension of information theory and optimal filtering to visual information acquisition and processing. The goal is to provide a comprehensive methodology for quantitatively assessing the end-to-end performance of image gathering, coding, and processing

Does the Introduction of IFRS Change the Timeliness of Loss Recognition? Evidence from German Firms

In this paper, we re-evaluate the hypothesis that the introduction of the IFRS has an impact on the timeliness of loss recognition. We test this hypothesis in a data set of public German firms that report according to German-GAAP and IFRS, respectively. The parallel use of the two accounting standards in Germany provides a unique opportunity to contribute to the academic discussion, as well as to the current policy debate on regulatory reform in Germany. Starting from the standard time series concept of conditional conservatism that was initially proposed by Basu (1997), we implement a wide range of test specifications, including (i) a threshold unit-root test specification; (ii) a multivariate approach to outlier detection and (iii) various forms of controlling for fixed effects. We do not find evidence that IFRS and German-GAAP firms differ with respect to their timeliness of loss recognition in any of these specifications - a result that appears surprising in light of the more prudent regulation in the German-GAAP, but is consistent with some earlier findings in the literature.IFRS, German-GAAP, Timely loss recognition, Conservatism

Genossenschaften: Zwischen Corporate und Cooperative Governance

Corporate Governance und ihre Verankerung in entsprechenden Codizes sind zu einem viel und kontrovers diskutierten Thema in der betriebswirtschaftlichen Theorie, in der unternehmerischen Praxis, aber auch in der Politik geworden. Die Anreize formeller Verhaltensregeln für die am Unternehmensgeschehen beteiligten Akteure sollen einzelwirtschaftlichen Fehlentwicklungen vorbeugen, die auch negative Wohlfahrtseffekte mit sich bringen können. Entsprechende Aktivitäten finden derzeit auf nationaler und supranationaler Ebene statt. Dieses IfG-Arbeitspapier enthält die schriftliche Fassung eines Vortrages, den Dr. Carl-Friedrich Leuschner, Vorstandsvorsitzender des DGRV, im Rahmen der Internationalen enossenschaftswissenschaftlichen Tagung im September 2004 in Münster präsentiert hat. Leuschner setzt sich mit der Frage auseinander, ob Genossenschaften mit ihrem spezifischen Geschäftsmodell einen Corporate Governance Kodex benötigen und welche genossenschaftsadäquaten Elemente ein solcher beinhalten müsste. Er stellt den Corporate Governance für Genossenschaften vor, der vom DGRV zur Anwendung auf freiwilliger Basis entwickelt wurde und vergleicht seine Inhalte mit dem Deutschen Corporate Governance Index. Genossenschaftsspezifische Argumente können in diesem Zusammenhang in die europäischen Erörterungen und in die Diskussion in Deutschland eingebracht werden. Mit diesem Arbeitspapier Nr. 47 setzt das IfG seine Berichterstattung über die IGT 2004 fort und lädt zur Diskussion der vorgestellten Überlegungen ein

Fine-grained Language Composition: A Case Study

Although run-time language composition is common, it normally takes the form of a crude Foreign Function Interface (FFI). While useful, such compositions tend to be coarse-grained and slow. In this paper we introduce a novel fine-grained syntactic composition of PHP and Python which allows users to embed each language inside the other, including referencing variables across languages. This composition raises novel design and implementation challenges. We show that good solutions can be found to the design challenges; and that the resulting implementation imposes an acceptable performance overhead of, at most, 2.6x.Comment: 27 pages, 4 tables, 5 figure