Akishina, V.

Kisel, I.

Kulakov, I.

Zyzak, M.

GSI Repository

FLES: Standalone First Level Event Selection Package for CBM∗V. Akishina1,2,3, I. Kisel1,2,4, I. Kulakov1,2,4, and M. Zyzak1,2,41Uni-Frankfurt, Germany; 2GSI, Darmstadt, Germany; 3JINR, Dubna, Russia; 4FIAS, Frankfurt, GermanyThe main focus of the CBM experiment is the measure-ment of very rare probes, that requires interaction ratesof up to 10 MHz. Together with the high multiplicity ofcharged particles (up to 1000) produced in heavy-ion col-lisions, this leads to huge data rates of up to 1 TB/s. Mosttrigger signatures are complex (short-lived particles, e.g.open charm decays) and require information from severaldetector sub-systems.Figure 1: Block diagram of the FLES package.The First Level Event Selection (FLES) package of theCBM experiment is intended to reconstruct the full eventtopology including tracks of charged long-lived particlesand short-lived particles. The FLES package consists ofseveral modules (see Figure 1): track finder, track fitter,particle finder and physics selection. As an input the FLESpackage receives the geometry of the tracking detectors andthe measurements, which are created by the charged parti-cles crossing the detectors — hits. Tracks of the chargedparticles are reconstructed by the Cellular Automaton trackfinder [1]. The Kalman filter based track fitter [2] is usedfor precise estimation of the track parameters. The KF Par-ticle Finder [3] is used to find short-lived particles. In ad-dition, a module for quality assurance is implemented, thatallows to monitor the quality of the reconstruction at allstages.The package provides the high reconstruction efficiencyand the high signal to background (S/B) ratio for the recon-structed decays. For instance, for 240 000 minimum bias∗This work was supported by the Hessian LOEWE initiative throughthe Helmholtz International Center for FAIR (HIC for FAIR) and EU-FP7 HadronPhysics2. Das Projekt wird vom Hessischen Ministerium fuerWissenschaft und Kunst gefoerdert.Au+Au UrQMD events at 25 AGeV the reconstruction effi-ciency (normalized on 4π) for the K 0s meson is 15.3% withthe S/B ratio 3.5 and for the Λ hyperon — 17.2% and 5.1respectively.Number of logical cores0 10 20 30 40 50 60 70 80Events/s0200400600800100012001400160018002000Intel E7-4860 2.27 GHzAMD 6164EH  1.70 GHzIntel L5640   2.27 GHzIntel X5550   2.67 GHzFigure 2: Scalability of the FLES package on many-coreservers.The first version of the FLES package is optimized withrespect to speed, intrinsically local and parallel. The im-plemenation is based on the SIMD instructions and havebeen parallelized between cores using the Intel ThreadingBuilding Blocks package [4], that provides scalable event-level parallelism with respect to the number of hardwarethreads and CPU cores. Four servers with Intel Xeon andAMD processors have been used for the scalability tests.The most powerful server has 4 processors with 10 physi-cal cores each, that gives 80 logical cores in total. Figure 2shows a strong scalability for all many-core systems. Theachieved reconstruction speed is 1700 events per second onthe 80-cores server.References[1] I. Kisel, “Event reconstruction in the CBM experiment,”Nucl. Instr. and Meth. A566 (2006) pp. 85–88.[2] S. Gorbunov, U. Kebschull, I. Kisel, V. Lindenstruth, andW.F.J. Mu¨ller, “Fast SIMDized Kalman filter based track fit,”Comp. Phys. Comm. 178 (2008) pp. 374–383.[3] M. Zyzak et al., “The KF Particle Finder package for short-lived particles reconstruction for the CBM experiment”, thisreport.[4] ITBB Reference Manual.Available at: http://threadingbuildingblocks.orgGSI SCIENTIFIC REPORT 2012 PHN-NQM-EXP-4777

FLES: Standalone First Level Event Selection Package for CBM

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FLES: Standalone First Level Event Selection Package for CBM

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