2,456 research outputs found
Machine Learning Based Auto-tuning for Enhanced OpenCL Performance Portability
Heterogeneous computing, which combines devices with different architectures,
is rising in popularity, and promises increased performance combined with
reduced energy consumption. OpenCL has been proposed as a standard for
programing such systems, and offers functional portability. It does, however,
suffer from poor performance portability, code tuned for one device must be
re-tuned to achieve good performance on another device. In this paper, we use
machine learning-based auto-tuning to address this problem. Benchmarks are run
on a random subset of the entire tuning parameter configuration space, and the
results are used to build an artificial neural network based model. The model
can then be used to find interesting parts of the parameter space for further
search. We evaluate our method with different benchmarks, on several devices,
including an Intel i7 3770 CPU, an Nvidia K40 GPU and an AMD Radeon HD 7970
GPU. Our model achieves a mean relative error as low as 6.1%, and is able to
find configurations as little as 1.3% worse than the global minimum.Comment: This is a pre-print version an article to be published in the
Proceedings of the 2015 IEEE International Parallel and Distributed
Processing Symposium Workshops (IPDPSW). For personal use onl
Nuclear Reactions: A Challenge for Few- and Many-Body Theory
A current interest in nuclear reactions, specifically with rare isotopes
concentrates on their reaction with neutrons, in particular neutron capture. In
order to facilitate reactions with neutrons one must use indirect methods using
deuterons as beam or target of choice. For adding neutrons, the most common
reaction is the (d,p) reaction, in which the deuteron breaks up and the neutron
is captured by the nucleus. Those (d,p) reactions may be viewed as a three-body
problem in a many-body context. This contribution reports on a feasibility
study for describing phenomenological nucleon-nucleus optical potentials in
momentum space in a separable form, so that they may be used for Faddeev
calculations of (d,p) reactions.Comment: to appear in the Proceedings of HITES 2012: Conference on `Horizons
of Innovative Theories, Experiments, and Supercomputing in Nuclear Physics',
June 4-7, 2012, New Orleans, Louisian
Subtractive renormalization of the NN scattering amplitude at leading order in chiral effective theory
The leading-order nucleon-nucleon (NN) potential derived from chiral
perturbation theory consists of one-pion exchange plus a short-distance contact
interaction. We show that in the 1S0 and 3S1-3D1 channels renormalization of
the Lippmann-Schwinger equation for this potential can be achieved by
performing one subtraction. This subtraction requires as its only input
knowledge of the NN scattering lengths. This procedure leads to a set of
integral equations for the partial-wave NN t-matrix which give
cutoff-independent results for the corresponding NN phase shifts. This
reformulation of the NN scattering equation offers practical advantages,
because only observable quantities appear in the integral equation. The
scattering equation may then be analytically continued to negative energies,
where information on bound-state energies and wave functions can be extracted.Comment: 16 pages, 11 figure
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