HMLQCD

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Quenched gauge configurations were generated with the Wilson gauge action at beta 5.7, 5.85, 6 on lattices of size 84, 124, 164. These three lattices are therefore of approximately the same physical volume. For 300 configurations at each of the three lattice sizes, Wilson quark propagators were calculated for a single point source and all color—spin combinations. Propagators were calculated for five values of the hopping parameter: 0.138, 0.140, 0.142, 0.144, 0.147, corresponding to five lattice mass quarks.  The existing codes of FermiQCD are improved and new codes need for these calculations are written. Some of the results taken are presented in the figure 5.
Quenched gauge configurations were generated with the Wilson gauge action at beta 5.7, 5.85, 6 on lattices of size 84, 124, 164. These three lattices are therefore of approximately the same physical volume. For 300 configurations at each of the three lattice sizes, Wilson quark propagators were calculated for a single point source and all color—spin combinations. Propagators were calculated for five values of the hopping parameter: 0.138, 0.140, 0.142, 0.144, 0.147, corresponding to five lattice mass quarks.  The existing codes of FermiQCD are improved and new codes need for these calculations are written. Some of the results taken are presented in the figure 5.
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[[File:spectrum.jpg]] [[File:Spectrum2.jpg]]
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[[File:spectrum.JPEG]] [[File:Spectrum2.JPEG]]
Fig. 5. Results of the light hadrons spectrum in the continuum limit
Fig. 5. Results of the light hadrons spectrum in the continuum limit

Revision as of 18:54, 12 March 2013

Contents

General Information

  • Application's name: Hadron Masses from Lattice QCD
  • Application's acronym: HMLQCD
  • Virtual Research Community: Computational Physics
  • Scientific contact: Artan Boriçi
  • Technical contact: Dafina Xhako, dafinaxhako@yahoo.com, Rudina Zeqirllari, rudina_mj@hotmail.com
  • Developers: MSc. Dafina Xhako, MSc.Rudina Zeqirllari, Department of Physics,Faculty of Natural Science, University of Tirana, Albania
  • Web site: http://wiki.hp-see.eu/index.php/HMLQCD

Short Description

Lattice Quantum Chromodynamics (QCD) is the theory of strong interactions defined on four dimensional space-time hypercubic lattice. Its correlation functions are given by expectation values over path integrals. At present, the only direct tool to compute such integrals is the Markov Chain Monte Carlo method, which gives large autocorrelation times for certain observables. At any Markov step several huge and sparse linear systems have to be solved. Hence, the whole procedure results in a very expensive computational problem especially as the continuum limit is approached. The mass spectrum analysis involves computation of quark propagators, which are the solutions of huge linear systems of Dirac operators defined on the lattice. In order to converge, a typical Krylov subspace solver needs several hundreds or even thousands of multiplications by the lattice Dirac operator. The project idea is computation of basic properties of matter simulating the theory of strong interactions, Quantum Chromodynamic on the Lattice on massively parallel computers.

Our project aims to test for the first time local chiral actions for the calculation of the hadron masses. On the algorithmic side the project will test new solvers for overlap and domain wall fermions.

Problems Solved

Lattice QCD has become an indispensable tool both for particle and nuclear physics. The problems solved by the project are:

  • Hadron spectrum computation
  • Decay constants and comparison with chiral perturbation theory


Scientific and Social Impact

Solution of QCD has not been yet achieved. Our lattice study would like to complement other studies at different parameters and different lattice actions. Usage of local chiral fermions saves two orders of magnitude of computing resources. It gives physical results with unprecedented accuracy close to the chiral limit. Increased social support for scientific communities.

Collaborations

  • TIRLatt (Tirana lattice QCD group)
  • CaSToRC Institute, Cyprus, Greece

Beneficiaries

Main beneficiaries are research groups in Computational Physics. International lattice groups may benefit from expanded libraries of QCDLAB and of fermiQCD.

Number of users

2

Development Plan

  • Concept: The concept was done before the project started
  • Start of alpha stage: M01. Construction of an algorithm. Creating of the program.
  • Start of beta stage: M6. Parallelization and Debugging of the application.
  • Start of testing stage: M8. Testing on multiprocessor platforms.
  • Start of deployment stage: M10. Performing calculations.
  • Start of production stage: Calculation of quark-antiquark potential and hadron spectroscopy

Resource Requirements

  • Number of cores required: Limited to available number of CPUs
  • Minimum RAM/core required: 1GB
  • Storage space during a single run: 1-500GB
  • Long-term data storage: 1TB
  • Total core hours required: 2 000 000 hour

Technical Features and HP-SEE Implementation

  • Primary programming language: C/C++
  • Parallel programming paradigm: MPI/Open MP
  • Main parallel code: MPI
  • Pre/post processing code: Own developer
  • Application tools and libraries: FermiQCD, OpenMP

Usage Example

Calculation of quark-antiquark potential for 8^4 lattice volume, coupling constant beta=5.7, and number of configuration 100, using 4-processors.

Infrastructure Usage

  • Home system: HPC-Bulgaria
    • Applied for access on: 09.2010
    • Access granted on: 10.2010
    • Achieved scalability: 512 cores
  • Accessed production systems:
  1. .
    • Applied for access on: 10.2010
    • Access granted on: 10.2010
    • Achieved scalability: Scalabable for 4 processors for for 8^4 lattice volume
  • Porting activities: None
  • Scalability studies: Further studies for larger lattice volume'

Running on Several HP-SEE Centres

  • Benchmarking activities and results: .
  • Other issues: .

Achieved Results

•Scalability test of FermiQCD

The computation time fall exponentially (for example for lattice volumes 16^4)

P1.jpg

Fig. 1. The computation time from number of processors for lattice 16^4

•Speedup and Efficiency test

Let T(n,1) be the run-time of the fastest known sequential algorithm and let T(n,p) be the run-time of the parallel algorithm executed on p processors, where n is the size of the input (lattice volume). The speedup is then defined as


Ideally, one would like S(p)=p, which is called perfect speedup

P2.jpg

Fig. 2. Speedup form number of processors for different lattice volumes

The ideal speed up will be S(p) = p, so if we double for example the number of processors will double the time of execution. Another metric to measure the performance of a parallel algorithm is efficiency, E(p), defined as:

P3.jpg

Fig. 3. Efficiency (in percentage) form the number of processors for different lattice

P4.jpg

Fig. 4. Quark-anti-quark potential (lattice 8^4) in lattice unit from planar Wilson loops


Quenched gauge configurations were generated with the Wilson gauge action at beta 5.7, 5.85, 6 on lattices of size 84, 124, 164. These three lattices are therefore of approximately the same physical volume. For 300 configurations at each of the three lattice sizes, Wilson quark propagators were calculated for a single point source and all color—spin combinations. Propagators were calculated for five values of the hopping parameter: 0.138, 0.140, 0.142, 0.144, 0.147, corresponding to five lattice mass quarks. The existing codes of FermiQCD are improved and new codes need for these calculations are written. Some of the results taken are presented in the figure 5.

File:Spectrum.JPEG File:Spectrum2.JPEG

Fig. 5. Results of the light hadrons spectrum in the continuum limit

Publications

November 2012 “Fakulteti i Shkencave Natyrore ne 100 vjetorin e pavaresise”, Tirane, Albania

1. Zeqirllari, R., Xhako, D., Boriçi, A. “Light hadron spectrum for Wilson action”

2.Xhako, D., Zeqirllari, R., Boriçi, A, “Static quark-antiquark potential calculation”


October 2012 - HP-SEE User Forum 2012, Belgrade, Serbia

1.Zeqirllari, R., Xhako, D., Boriçi, A., “Quenched Hadron Spectroscopy Using FermiQCD”,

2.Xhako, D., Zeqirllari, R., Boriçi, A, “Using Parallel Computing to Calculate Static Interquark Potential in LQCD”

Foreseen Activities

We are trying to restore the broken hybercubic symmetry of the Borici – Creutz action and then test it for the calculation of the hadron masses. The codes for the calculation of specific hadrons are already written and tested for Wilson action. What we aim to achive soon is a perfect restoration of the broken symmetry in this action.

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