Abstract
The aim of this work is to compare the performance and ease of programming of the various data transfer strategies provided by SYCL 2020:
buffers/accessors
on one hand and the different ...storage types exposed by
Unified Shared Memory
(USM) on the other hand. We measured the relative performance of USM exclusively located either on the host (
USM host
) or on the device (
USM device
), or automatically managed and moved (
USM shared
). We also tried to quantify the impact of formatting data in a GPU-friendly manner as opposed to using a regular pointer-based structure in which the C++ allocator was replaced by the SYCL allocator sycl::malloc. We first made a PCIe-bound micro-benchmark to test the SYCL memory models with a simple access pattern. We then switched to a real use-case provided by Traccc, a research project associated to the ACTS particle tracking library. The algorithm of interest is SparseCCL, a clustering algorithm used on the first step of track reconstruction. For consistency, all tests were made on a single hardware architecture: a recent server having a discrete GPU with dedicated VRAM, representative of the hardware currently used by the ACTS team.
Lot of efforts have been devoted by ATLAS and CMS teams to improve the quality of LHC events analysis with the Matrix Element Method (MEM). Up to now, very few implementations try to face up the huge ...computing resources required by this method. We propose here a highly parallel version, combining MPI and OpenCL, which makes the MEM exploitation reachable for the whole CMS datasets with a moderate cost. In the article, we describe the status of two software projects under development, one focused on physics and one focused on computing. We also showcase their preliminary performance obtained with classical multi-core processors, CUDA accelerators and MIC co-processors. This let us extrapolate that with the help of 6 high-end accelerators, we should be able to reprocess the whole LHC run 1 within 10 days, and that we have a satisfying metric for the upcoming run 2. The future work will consist in finalizing a single merged system including all the physics and all the parallelism infrastructure, thus optimizing implementation for best hardware platforms.
The amplitude of the signal collected from the PbWO4 crystals of the CMS electromagnetic calorimeter is reconstructed by a digital filtering technique. The amplitude reconstruction has been studied ...with test beam data recorded from a fully equipped barrel supermodule. Issues specific to data taken in the test beam are investigated, and the implementation of the method for CMS data taking is discussed.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A measurement of the phase difference between the short- and long-distance contributions to the Formula: see text decay is performed by analysing the dimuon mass distribution. The analysis is based ...on
collision data corresponding to an integrated luminosity of 3Formula: see text collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the Formula: see text decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the Formula: see text and Formula: see text resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, Formula: see text and Formula: see text, and the branching fraction of the short-distance component is measured.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A search for the decays Bc+→J/ψD(*)0K+ and Bc+→J/ψD(*)+K*0 is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb−1. The decays Bc+→J/ψD0K+ and ...Bc+→J/ψD*0K+ are observed for the first time, while first evidence is reported for the Bc+→J/ψD*+K*0 and Bc+→J/ψD+K*0 decays. The branching fractions of these decays are determined relative to the Bc+→J/ψπ+ decay. The Bc+ mass is measured, using the J/ψD0K+ final state, to be 6274.28±1.40(stat)±0.32(syst) MeV/c2. This is the most precise single measurement of the Bc+ mass to date.
Decays of the Ξ_{b}^{-} and Ω_{b}^{-} baryons to the charmless final states ph^{-}h^{'-}, where h^{(')} denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a ...sample of proton-proton collision data collected at center-of-mass energies sqrts=7 and 8 TeV, corresponding to an integrated luminosity of 3 fb^{-1}. The decay Ξ_{b}^{-}→pK^{-}K^{-} is observed with a significance of 8.7 standard deviations, and evidence at the level of 3.4 standard deviations is found for the Ξ_{b}^{-}→pK^{-}π^{-} decay. Results are reported, relative to the B^{-}→K^{+}K^{-}K^{-} normalization channel, for the products of branching fractions and b-hadron production fractions. The branching fractions of Ξ_{b}^{-}→pK^{-}π^{-} and Ξ_{b}^{-}→pπ^{-}π^{-} relative to Ξ_{b}^{-}→pK^{-}K^{-} decays are also measured.
A search for Formula omitted violation in charmless four-body decays of Formula omitted and Formula omitted baryons with a proton and three charged mesons in the final state is performed. To cancel ...out production and detection charge-asymmetry effects, the search is carried out by measuring the difference between the Formula omitted asymmetries in a charmless decay and in a decay with an intermediate charmed baryon with the same particles in the final state. The data sample used was recorded in 2011 and 2012 with the LHCb detector and corresponds to an integrated luminosity of Formula omitted. A total of 18 Formula omitted asymmetries are considered, either accounting for the full phase space of the decays or exploring specific regions of the decay kinematics. No significant Formula omitted-violation effect is observed in any of the measurements.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The branching fraction and direct Formula omitted asymmetry of the decay Formula omitted are measured using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of ...7 and 8 TeV, corresponding to a total integrated luminosity of 3 Formula omitted. The following results are obtained: B(B+right arrowJ/psirho+)=(3.81-0.24+0.25±0.35)x10-5,ACP(B+right arrowJ/psirho+)=-0.045-0.057+0.056±0.008,where the first uncertainties are statistical and the second systematic. Both measurements are the most precise to date.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A Dalitz plot analysis of Formula omitted decays is performed using data samples of pp collisions collected with the Formula omitted detector at centre-of-mass energies of Formula omitted and Formula ...omitted, corresponding to a total integrated luminosity of Formula omitted. A satisfactory description of the data is obtained when including a contribution representing an exotic Formula omitted resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are Formula omitted and Formula omitted, respectively. The spin-parity assignments Formula omitted and Formula omitted are both consistent with the data. In addition, the first measurement of the Formula omitted branching fraction is performed and gives B(B0right arrowetac(1S)K+pi-)=(5.73±0.24±0.13±0.66)x10-4,where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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