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UID:submissions.pasc-conference.org_PASC23_sess176_pap120@linklings.com
SUMMARY:Graph Contractions for Calculating Correlation Functions in Lattic
e QCD
DESCRIPTION:Paper\n\nJie Chen and Robert Edwards (Jefferson Lab) and Weizh
en Mao (William & Mary)\n\nComputing correlation functions for many-partic
le systems in Lattice QCD is vital to extract nuclear physics observables
like the energy spectrum of hadrons such as protons. However, this type of
calculation has long been considered to be very challenging because of th
e complex nature of a hadron composed of quarks with many degrees of freed
om. In particular, a correlation function can be calculated through a sum
of all possible pairs of quark contractions dictated by *Wick*'s th
eorem. Because the number of terms of this sum can be very large for any h
adronic system of interest, fast evaluation of the sum faces several chall
enges: an extremely large number of contractions, a huge memory footprint,
and the speed of contractions. In this paper, we present a Lattice QCD an
alysis software suite, *Redstar*, which addresses these challenges
by utilizing novel algorithmic and software engineering methods targeting
modern computing platforms such as many-core CPUs and GPUs. In particular,
*Redstar* represents every term in the sum of a correlation functi
on by a graph, applies efficient graph algorithms to reduce the number of
contractions, to lower the cost of the computations, and to minimize the t
otal memory footprint. Moreover, *Redstar* carries out the contract
ions on either CPUs or GPUs utilizing an internal and highly efficient *Hadron* contraction library. Specifically, we illustrate some importa
nt algorithmic optimizations of *Redstar*, show key design features
of *Hadron* library, and present the speedup values due to the opt
imizations along with performance figures for calculating six correlations
functions on four computing platforms.\n\nDomain: Physics\n\nSession Chai
r: Sinéad Ryan (Trinity College, Hamilton Mathematics Institute)
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