4,231 research outputs found
Characteristics of unification: exploring the tension between quantum and gravitational physics
Natural Compression for Distributed Deep Learning
Modern deep learning models are often trained in parallel over a collection
of distributed machines to reduce training time. In such settings,
communication of model updates among machines becomes a significant performance
bottleneck and various lossy update compression techniques have been proposed
to alleviate this problem. In this work, we introduce a new, simple yet
theoretically and practically effective compression technique: {\em natural
compression (NC)}. Our technique is applied individually to all entries of the
to-be-compressed update vector and works by randomized rounding to the nearest
(negative or positive) power of two, which can be computed in a "natural" way
by ignoring the mantissa. We show that compared to no compression, NC increases
the second moment of the compressed vector by not more than the tiny factor
\nicefrac{9}{8}, which means that the effect of NC on the convergence speed
of popular training algorithms, such as distributed SGD, is negligible.
However, the communications savings enabled by NC are substantial, leading to
{\em - improvement in overall theoretical running time}. For
applications requiring more aggressive compression, we generalize NC to {\em
natural dithering}, which we prove is {\em exponentially better} than the
common random dithering technique. Our compression operators can be used on
their own or in combination with existing operators for a more aggressive
combined effect, and offer new state-of-the-art both in theory and practice.Comment: 8 pages, 20 pages of Appendix, 6 Tables, 14 Figure
Updated analysis of the dynamical relation between asteroid 2003 EH1 and comets C/1490 Y1 and C/1385 U1
The asteroid 2003 EH1, proposed as the parent body of the Quadrantid meteor
shower, is thought to be the remnant of a past cometary object, tentatively
identified with the historical comets C/1490 Y1 and C/1385 U1. In the present
work we use recovery astrometry to extend the observed arc of 2003 EH1 from 10
months to about 5 years, enough to exclude the proposed direct relationship of
the asteroid with both of the comets.Comment: Submitted to Monthly Notices of the RAS Letters Updated with a new
table and other minor change
Binding of the Allosteric Effector Inositol Hexaphosphate (IHP) Modulates the Dynamics of Carbonmonoxyhemoglobin on Multiple Length Scales
Optimization of a dual ring antenna by means of artifcial neural network
In literature, heuristic algorithms have been successfully applied to a number of electromagnetic problems. The associated cost functions are commonly linked to full-wave analysis, leading to complexity and high computational expense. Arti-cial Neural Network is one of the most eŸective biological inspired techniques. In this article, an e±cient surrogate model is trained to replace the full-wave analysis in optimizing the bandwidth of microstrip antenna. The numerical comparison between ANN substitution model and full-wave characterization shows signi-cant improvements in time convergence and computational cost. To verify the robustness of this approach, all these concepts are integrated into a case study represented by a rectangular ring antenna with proximity-coupled feed antenna
A Survey for Planetary Nebulae in M31 Globular Clusters
We report the results of an [O III] 5007 spectroscopic survey for planetary
nebulae (PNe) located within the star clusters of M31. By examining R ~ 5000
spectra taken with the WIYN+Hydra spectrograph, we identify 3 PN candidates in
a sample of 274 likely globular clusters, 2 candidates in objects which may be
globular clusters, and 5 candidates in a set of 85 younger systems. The
possible PNe are all faint, between ~2.5 and ~6.8 mag down the PN luminosity
function, and, partly as a consequence of our selection criteria, have high
excitation, with [O III] 5007 to H-beta ratios ranging from 2 to ~12. We
discuss the individual candidates, their likelihood of cluster membership, and
the possibility that they were formed via binary interactions within the
clusters. Our data are consistent with the suggestion that PN formation within
globular clusters correlates with binary encounter frequency, though, due to
the small numbers and large uncertainties in the candidate list, this study
does not provide sufficient evidence to confirm the hypothesis.Comment: Accepted for publication in the Astrophysical Journal. 54 pages,
including 9 figures and 4 table
An assessment of financial sector rescue programmes
We analyse the wide array of rescue programmes adopted in several countries, following Lehman Brothersâ default in September 2008, in order to support banks and other financial institutions. We first provide an overview of the programmes, comparing their characteristics, magnitudes and participation rates across countries. We then consider the effects of the programmes on banksâ risk and valuation, looking at the behaviour of CDS premia and stock prices. We then proceed to analyse the issuance of government guaranteed bonds by banks, examining their impact on banksâ funding and highlighting undesired effects and distortions. Finally, we briefly review the recent evolution of bank lending to the private sector. We draw policy implications, in particular as regards the way of mitigating the distortions implied by such programmes and the need for an exit strategy.bank asset guarantees, capital injection, banks, financial sector, financial crisis, bank consolidation, bank mergers and acquisitions, event studies, government guaranteed bonds, credit crunch, exit strategy
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