53,426 research outputs found
Iconic store and partial report
The iconic store has recently been challenged on the grounds that data in its favor may have resulted from some procedural artifacts. The display-instruction compatibility and perceptual grouping hypotheses were reexamined in two experiments with the partial-report paradigm. When care was taken to rectify some procedural problems found in Merikle's (1980) study, it was established that the iconic store (as a hypothetical mechanism) can still be validly entertained. This report demonstrates one important procedural point in studying the iconic store with the partial-report task, namely, that subjects must be given more than token training on the partial-report task
goSLP: Globally Optimized Superword Level Parallelism Framework
Modern microprocessors are equipped with single instruction multiple data
(SIMD) or vector instruction sets which allow compilers to exploit superword
level parallelism (SLP), a type of fine-grained parallelism. Current SLP
auto-vectorization techniques use heuristics to discover vectorization
opportunities in high-level language code. These heuristics are fragile, local
and typically only present one vectorization strategy that is either accepted
or rejected by a cost model. We present goSLP, a novel SLP auto-vectorization
framework which solves the statement packing problem in a pairwise optimal
manner. Using an integer linear programming (ILP) solver, goSLP searches the
entire space of statement packing opportunities for a whole function at a time,
while limiting total compilation time to a few minutes. Furthermore, goSLP
optimally solves the vector permutation selection problem using dynamic
programming. We implemented goSLP in the LLVM compiler infrastructure,
achieving a geometric mean speedup of 7.58% on SPEC2017fp, 2.42% on SPEC2006fp
and 4.07% on NAS benchmarks compared to LLVM's existing SLP auto-vectorizer.Comment: Published at OOPSLA 201
Constraining the Symmetry Energy: A Journey in the Isospin Physics from Coulomb Barrier to Deconfinement
Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium
nuclear interaction in regions away from saturation. In this work we present a
selection of reaction observables in dissipative collisions particularly
sensitive to the isovector part of the interaction, i.e. to the symmetry term
of the nuclear Equation of State (EoS). At low energies the behavior of the
symmetry energy around saturation influences dissipation and fragment
production mechanisms. We will first discuss the recently observed Dynamical
Dipole Radiation, due to a collective neutron-proton oscillation during the
charge equilibration in fusion and deep-inelastic collisions. Important Iso-EOS
effects are stressed. Reactions induced by unstable 132Sn beams appear to be
very promising tools to test the sub-saturation Isovector EoS. New Isospin
sensitive observables are also presented for deep-inelastic, fragmentation
collisions and Isospin equilibration measurements (Imbalance Ratios). The high
density symmetry term can be derived from isospin effects on heavy ion
reactions at relativistic energies (few AGeV range), that can even allow a
``direct'' study of the covariant structure of the isovector interaction in the
hadron medium. Rather sensitive observables are proposed from collective flows
and from pion/kaon production. The possibility of the transition to a mixed
hadron-quark phase, at high baryon and isospin density, is finally suggested.
Some signatures could come from an expected ``neutron trapping'' effect. The
importance of studying violent collisions with radioactive beams from low to
relativistic energies is finally stressed.Comment: 15 pages, 5 figures, Int.Workshop on Nuclear Dynamics in Heavy Ion
Reactions and Neutron Stars, Beijing Normal Univ. July 07, to appear in
Int.Journ.Modern Physics E (2008
Light scalars as tetraquarks or two-meson states from large Nc and unitarized Chiral Perturbation Theory
By means of unitarized Chiral Perturbation Theory it is possible to obtain a
remarkable description of meson-meson scattering amplitudes up to 1.2 GeV, and
generate poles associated to scalar and vector resonances. Since Chiral
Perturbation Theory is the QCD low energy effective theory, it is possible then
to study its large Nc limit where qqbar states are easily identified. The
vectors thus generated follow closely a qqbar behavior, whereas the light
scalar poles follow the large Nc behavior expected for a dominant tetraquark or
two-meson structure.Comment: Invited Brief Report to appear in Modern Physcis Letters A. 15 page
Stream VByte: Faster Byte-Oriented Integer Compression
Arrays of integers are often compressed in search engines. Though there are
many ways to compress integers, we are interested in the popular byte-oriented
integer compression techniques (e.g., VByte or Google's Varint-GB). They are
appealing due to their simplicity and engineering convenience. Amazon's
varint-G8IU is one of the fastest byte-oriented compression technique published
so far. It makes judicious use of the powerful single-instruction-multiple-data
(SIMD) instructions available in commodity processors. To surpass varint-G8IU,
we present Stream VByte, a novel byte-oriented compression technique that
separates the control stream from the encoded data. Like varint-G8IU, Stream
VByte is well suited for SIMD instructions. We show that Stream VByte decoding
can be up to twice as fast as varint-G8IU decoding over real data sets. In this
sense, Stream VByte establishes new speed records for byte-oriented integer
compression, at times exceeding the speed of the memcpy function. On a 3.4GHz
Haswell processor, it decodes more than 4 billion differentially-coded integers
per second from RAM to L1 cache
Summary of Experimental Meson Physics
A summary of the present experimental status of meson physics is presented.
The presentation includes the new results presented at the MESON06 workshop, as
well as other recent experimental developments in the field.Comment: 15 pages, 6 figures, presented at 9th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, June 200
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EXTEND-L : an input language for extensible register transfer compilation
This report discusses the model and input language for EXTEND, a synthesis system that permits extensible register transfer synthesis. EXTEND-L fills the need for a language that bridges the gap between existing behavioral input descriptions, which are too abstract, and structural schematics, which cannot capture the high-level behavior. The report first discusses previous work in behavioral synthesis and summarizes the deficiencies of these behavioral specifications. The report then describes the proposed langauge in detail, and concludes with a few examples that show its utility
Location, correlation, radiation: where is the , what is its structure and what is its coupling to photons?
Scalar mesons are a key expression of the infrared regime of QCD. The
lightest of these is the . Now that its pole in the complex energy
plane has been precisely located, we can ask whether this state is transiently
or or a multi-meson molecule or largely glue? The
two photon decay of the can, in principle, discriminate between these
possibilities. We review here how the ,
cross-sections can be accurately computed. The result not only agrees with
experiment, but definitively fixes the radiative coupling of the . This
equates to a two photon width of keV, which accords with the
simple non-relativistic quark model expectation for a
scalar. Nevertheless, robust predictions from relativistic strong coupling QCD
are required for each of the possible compositions before we can be sure which
one really delivers the determined coupling.Comment: 18 pages, 11 figures. To be published in Modern Physics Letters A A
number of references updated and three sentences changed in the text to
reflect thes
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