1,210 research outputs found
Performance Engineering for Real and Complex Tall & Skinny Matrix Multiplication Kernels on GPUs
General matrix-matrix multiplications with double-precision real and complex
entries (DGEMM and ZGEMM) in vendor-supplied BLAS libraries are best optimized
for square matrices but often show bad performance for tall & skinny matrices,
which are much taller than wide. NVIDIA's current CUBLAS implementation
delivers only a fraction of the potential performance as indicated by the
roofline model in this case. We describe the challenges and key characteristics
of an implementation that can achieve close to optimal performance. We further
evaluate different strategies of parallelization and thread distribution, and
devise a flexible, configurable mapping scheme. To ensure flexibility and allow
for highly tailored implementations we use code generation combined with
autotuning. For a large range of matrix sizes in the domain of interest we
achieve at least 2/3 of the roofline performance and often substantially
outperform state-of-the art CUBLAS results on an NVIDIA Volta GPGPU.Comment: 12 pages, 22 figures. Extended version of arXiv:1905.03136v1 for
journal submissio
A Spectroscopic and Photometric Investigation of the Mercury-Manganese Star KIC 6128830
The advent of space-based photometry provides the opportunity for the first
precise characterizations of variability in Mercury-Manganese (HgMn/CP3) stars,
which might advance our understanding of their internal structure. We have
carried out a spectroscopic and photometric investigation of the candidate CP3
star KIC 6128830. A detailed abundance analysis based on newly-acquired
high-resolution spectra was performed, which confirms that the star's abundance
pattern is fully consistent with its proposed classification. Photometric
variability was investigated using four years of archival Kepler data. In
agreement with results from the literature, we have identified a single
significant and independent frequency =0.2065424 d with a
peak-to-peak amplitude of 3.4 mmag and harmonic frequencies up to .
Drawing on the predictions of state-of-the-art pulsation models and information
on evolutionary status, we discuss the origin of the observed light changes.
Our calculations predict the occurrence of g-mode pulsations at the observed
variability frequency. On the other hand, the strictly mono-periodic nature of
the variability strongly suggests a rotational origin. While we prefer the
rotational explanation, the present data leave some uncertainty.Comment: 13 pages, 13 figures, accepted for publication in MNRA
Plenary Agenda Report for Research Group B-II-1
Political authority over extensive territories is a well-known phenomenon of
the ancient world, and one conceptualized already in antiquity through the
image of the succession of empires. Each such politico-spatial order was based
on the successful interrelationship of heterogeneous symbolic and concrete
forms of governance in the context of contingent structural conditions. While
each major empire must be regarded as a singular historical case, the question
nonetheless presents itself of how an awareness of such structures of
political administration were constituted in premodern states. In the
framework of Area B »Mechanisms of Control and Social Spaces« large-scale
phenomena of governance were examined particularly with regard to the forms of
knowledge associated with the organizational implementation of these of
hegemonic structures. This research group investigates the interdependency of
spatial structures and the organization of authority with reference to four
major empires. Brought to light through the analysis of contrasting
interventions into these territories are continuities and discontinuities of
practice within which the spectrum of forms of knowledge as well as the object
of knowledge itself become discernible. The geographic region of investigation
is the Near East. Three ancient Near Eastern case studies, namely the Hittite
and Mittani Kingdoms and the Middle Assyrian Empire, illustrate the region of
Anatolia-Upper Mesopotamia in a dense chronological stratification which
traverses a period lasting circa 500 years. Emerging within this chronotope
both geographically and chronologically are intersections through which
commonalities and differences in the organization of governance are revealed,
not least of all in their spatial conditionality. In contrast, the subproject
in Ancient History dealing with the system of rule of the Imperium Romanum in
the Ancient Near East focuses on the early period of the Principate, with a
special focus on the Palestinian-Syrian realm. In terms of systematics and
chronology, two detailed studies contrast the relatively homogeneous
perspectives of the four above-named empires: the first examines »trade
relations« in the Neo-Babylonian empire of the 1st millennium BCE, and the
second »multiethnicity« in the formation of the ancient Near Eastern empires
of the later 1st millennium BCE. The analysis proceeds via archaeological,
philological, and historical methods and focuses on concrete forms of
political authority as exercised in interdependency with the governed regions
on various scales. Settlement structures, artifacts, and border formations
have been investigated along with a multiplicity of textual genres, including
historical documents such as treaties, but also epigraphic materials, legal,
and commercial documents. Some of the sources are being made accessible and
published for the first time in the framework of these investigations. A web-
supported map project will permit links to be created between geographically
defined discursive horizons and object data such as settlement patterns, areas
of settlement, and texts
A Diffusion Model Predicts 3D Shapes from 2D Microscopy Images
Diffusion models are a special type of generative model, capable of
synthesising new data from a learnt distribution. We introduce DISPR, a
diffusion-based model for solving the inverse problem of three-dimensional (3D)
cell shape prediction from two-dimensional (2D) single cell microscopy images.
Using the 2D microscopy image as a prior, DISPR is conditioned to predict
realistic 3D shape reconstructions. To showcase the applicability of DISPR as a
data augmentation tool in a feature-based single cell classification task, we
extract morphological features from the red blood cells grouped into six highly
imbalanced classes. Adding features from the DISPR predictions to the three
minority classes improved the macro F1 score from to . We thus demonstrate that
diffusion models can be successfully applied to inverse biomedical problems,
and that they learn to reconstruct 3D shapes with realistic morphological
features from 2D microscopy images
Thickness dependence of the anomalous Hall effect in thin films of the topological semimetal CoMnGa
Topological magnetic semimetals promise large Berry curvature through the
distribution of the topological Weyl nodes or nodal lines and further novel
physics with exotic transport phenomena. We present a systematic study of the
structural and magnetotransport properties of CoMnGa films from thin (20
nm) to bulk like behavior (80 nm), in order to understand the underlying
mechanisms and the role on the topology. The magnetron sputtered CoMnGa
films are -ordered showing very good heteroepitaxy and a
strain-induced tetragonal distortion. The anomalous Hall conductivity was found
to be maximum at a value of 1138 S/cm, with a corresponding anomalous Hall
angle of 13 %, which is comparatively larger than topologically trivial metals.
There is a good agreement between the theoretical calculations and the Hall
conductivity observed for the 80 nm film, which suggest that the effect is
intrinsic. Thus, the CoMnGa compound manifests as a promising material
towards topologically-driven spintronic applications.Comment: 7 pages, 5 figures, 1 tabl
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