Speculative Staging for Interpreter Optimization

Interpreters have a bad reputation for having lower performance than just-in-time compilers. We present a new way of building high performance interpreters that is particularly effective for executing dynamically typed programming languages. The key idea is to combine speculative staging of optimized interpreter instructions with a novel technique of incrementally and iteratively concerting them at run-time. This paper introduces the concepts behind deriving optimized instructions from existing interpreter instructions---incrementally peeling off layers of complexity. When compiling the interpreter, these optimized derivatives will be compiled along with the original interpreter instructions. Therefore, our technique is portable by construction since it leverages the existing compiler's backend. At run-time we use instruction substitution from the interpreter's original and expensive instructions to optimized instruction derivatives to speed up execution. Our technique unites high performance with the simplicity and portability of interpreters---we report that our optimization makes the CPython interpreter up to more than four times faster, where our interpreter closes the gap between and sometimes even outperforms PyPy's just-in-time compiler.Comment: 16 pages, 4 figures, 3 tables. Uses CPython 3.2.3 and PyPy 1.

Accurate Extra-Galactic Distances and Dark Energy: Anchoring the Distance Scale with Rotational Parallaxes

We investigate how the uncertainty on the Hubble constant (H_0) affects the uncertainty in the Equation of State (EOS) of Dark Energy and the total density of the Universe (Omega_tot). We use the approximate relations between the cosmological parameters [Spergel etal (2007)] and use error-propagation to estimate the effects of improving the CMB parameters and H_0 on the EOS of Dark Energy (DE). First we assume that the additional data does not improve significantly, but decrease the error on H_0 by a factor <~10. Second, we allow improved additional data but current H_0 errors (i.e., the DE Task Force case). In the 1st scenario, improvements of the CMB parameters hardly change the accuracy of the EOS and Omega_tot, unless H_0 can be measured with an accuracy of a few %. We find that a combination of moderate improvements for both H_0 and other data significantly constrains the evolution of dark energy, but at a reduced cost. We review several methods (and their strengths and weaknesses) that might yield extra-galactic distances with errors of about 1%. We review: the Velocity Field method, two Maser methods, two Light Echo techniques, the Binary Star method, and the Rotational Parallax (RP) technique. Because these methods substantially rely on geometry rather than astrophysics or cosmology, their results are quite robust. We focus on the advantages of the RP technique which can provide single-step, bias-free distances to nearby spirals. These distances can be used to improve the zero-point for other methods which in turn allow for a much improved H_0 errors. Achieving an accuracy of ~2% in the distances to M31, M33 and the LMC by the RP method requires proper motions from future astrometric missions (SIM, GAIA and OBSS, or the SKA).Comment: 20 pages, 2 figures. Minor changes. Now includes a review of methods capable of achieving unbiased 1% extra-galactic distances. MNRAS: Accepted for publicatio

Radio Linear and Circular Polarization from M81*

We present results from archival Very Large Array (VLA) data and new VLA observations to investigate the long term behavior of the circular polarization of M81*, the nuclear radio source in the nearby galaxy M81. We also used the Berkeley-Illinois-Maryland Association (BIMA) array to observe M81* at 86 and 230 GHz. M81* is unpolarized in the linear sense at a frequency as high as 86 GHz and shows variable circular polarization at a frequency as high as 15 GHz. The spectrum of the fractional circular polarization is inverted in most of our observations. The sign of circular polarization is constant over frequency and time. The absence of linear polarization sets a lower limit to the accretion rate of $10^{-7} M_\odot y^{-1}$. The polarization properties are strikingly similar to the properties of Sgr A*, the central radio source in the Milky Way. This supports the hypothesis that M81* is a scaled up version of Sgr A*. On the other hand, the broad band total intensity spectrum declines towards milimeter wavelengths which differs from previous observations of M81* and also from Sgr A*.Comment: Astronomy & Astrophysics, minor changes, matching the published version, also available at http://www.mpifr-bonn.mpg.de/staff/abrunthaler/pub.shtm

Proper Motions in the Andromeda Subgroup

This article presents results of VLBI observations of regions of H2O maser activity in the Local Group galaxies M33 and IC10. Since all position measurements were made relative to extragalactic background sources, the proper motions of the two galaxies could be measured. For M33, this provides this galaxy's three dimensional velocity, showing that this galaxy is moving with a velocity of 190 +/- 59 km\s relative to the Milky Way. For IC10, we obtain a motion of 215 +/- 42 km/s relative to the Milky Way. These measurements promise a new handle on dynamical models for the Local Group and the mass and dark matter halo of Andromeda and the Milky Way.Comment: 4 pages 1 figures, to appear in the proceedings of "Galaxies in the Local Volume", Astrophysics and Space Science, editors B. Koribalski and H. Jerjen also available at http://www.mpifr-bonn.mpg.de/staff/abrunthaler/pub.shtm

Discovery of a bright radio transient in M82: a new radio supernova?

In this Letter, we report the discovery of a new bright radio transient in M82. Using the Very Large Array, we observed the nuclear region of M82 at several epochs at 22 GHz and detected a new bright radio source in this galaxy's central region. We find a flux density for this flaring source that is ~300 times larger than upper limits determined in previous observations. The flare must have started between 2007 October 29 and 2008 March 24. Over the last year, the flux density of this new source has decreased from ~100 mJy to ~11 mJy. The lightcurve (based on only three data points) can be fitted better with an exponential decay than with a power law. Based on the current data we cannot identify the nature of this transient source. However, a new radio supernova seems to be the most natural explanation. With it's flux density of more than 100 mJy, it is at least 1.5 times brighter than SN1993J in M81 at the peak of its lightcurve at 22 GHz.Comment: accepted Astronomy & Astrophysics, 4 pages, 3 figures, final version & corrected abstract, also available at http://www.mpifr-bonn.mpg.de/staff/abrunthaler/pub.shtm

IT-Strukturen für die Lebensmittel-Rückverfolgbarkeit mit RFID im Mittelstand der Transportindustrie

Rückverfolgbarkeit ist eine durch EU-Richtlinien (z. B. 178/ 2002) und nationale Gesetze vorgeschriebene Eigenschaft, die Logistikketten (Supply Chains) für Lebensmittel seit Anfang 2005 haben müssen. Dies bedeutet kurz gefasst, dass jedes Produkt in allen seinen Komponenten lückenlos durch die gesamte Logistikkette rückverfolgbar sein muss. Der typische Anwendungsfall (und die Motivation der Politik für diese Gesetzgebung) ist die Aussonderung verdorbener Chargen eines Produktes, bevor die Bevölkerung in großem Maße betroffen ist. Um diese Anwendung tatsächlich in Echtzeit umsetzen zu können, werden informationsverarbeitende Systeme benötigt, die für alle Teilnehmer an der Logistikkette sowie auch für weitere Interessengruppen wie Verbraucherverbände oder öffentliche Einrichtungen einfach, preisgünstig, sicher und mit jeweils individuellen Berechtigungen zugänglich sind. Ein solches System wird in diesem Beitrag vorgeschlagen.Traceability is a feature for food supply chains which must be implemented and is regulated in EU standards (e. g. 178/200) and national laws. Participants in supply chains must co-operate to fulfill these standards, but small or medium companies often do not have the IT infrastructure to do that on a regular and cost effective basis. This article gives an outline for an open IT system structure (»DOTS«) to help participants in supply chains to communicate with respect to traceability of food products and transport units

Jet precession in the active nucleus of M81. Ongoing VLBI monitoring

In a recent publication, we reported results of a multi-frequency VLBI campaign of observations of the Active Galactic Nucleus (AGN) in galaxy M\,81, phase-referenced to the supernova SN\,1993J. We were able to extract precise information on the relative astrometry of the AGN radio emission at different epochs and frequencies. We found strong evidence of precession in the AGN jet (i.e., a systematic evolution in the jet inclination at each frequency) coupled to changes in the overall flux density at the different frequencies. In these proceedings, we summarise the main contents of our previous publication and we report on (preliminary) new results from our follow-up VLBI observations, now phase-referenced to the young supernova SN2008iz. We also briefly discuss how these results match the picture of our previously-reported precession model.Comment: 6 pages, 3 figures. Proceedings of EVN meeting 201

Constraints on the Proper Motion of the Andromeda Galaxy Based on the Survival of Its Satellite M33

A major uncertainty in the dynamical history of the local group of galaxies originates from the unknown transverse speed of the Andromeda galaxy (M31) relative to the Milky Way. We show that the recent VLBA measurement of the proper motion of Andromeda's satellite, M33, severely constrains the possible values of M31's proper motion. The condition that M33's stellar disk will not be tidally disrupted by either M31 or the Milky Way over the past 10 billion years, favors a proper motion amplitude of 100+-20km/s for M31 with the quadrant of a negative velocity component along Right Ascension and a positive component along Declination strongly ruled-out. This inference can be tested by future astrometric measurements with SIM, GAIA, or the SKA. Our results imply that the dark halos of Andromeda and the Milky Way will pass through each other within the next 5-10 billion years.Comment: Accepted for publication in Ap