J. Spray, J. Hill, A. Trew
The implementation of a proof-of-concept Lattice Quantum Chromodynamics kernel on the Cell processor is described in detail, illustrating issues encountered in the porting process. The resulting code performs up to 45GFlop/s per socket, indicating that the Cell processor is likely to be a good platform for future Lattice QCD calculations.
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The QCDSP computer (Quantum Chromodynamics on Digital Signal Processors) is an inexpensive, massively parallel computer intended primarily for simulations in lattice gauge theory. Currently, two large QCDSP machines are in full-time use: an 8,192 processor, 0.4 Teraflops machine at Columbia University and an 12,288 processor, 0.6 Teraflops machine at the RIKEN-BNL Research Center at Brookhaven National Laboratory. We describe the design process, architecture, software and current physics projects of these computers.
We present a summary of the progress on QCDSP in the last year. QCDSP, Quantum Chromodynamics on Digital Signal Processors, is an inexpensive computer being built at Columbia that can achieve 0.8 teraflops for three million dollars.
We present results of the implementation of one MILC lattice QCD application-simulation with dynamical clover fermions using the hybrid-molecular dynamics R algorithm-on the Cell Broadband Engine processor. Fifty-four individual computational kernels responsible for 98.8% of the overall execution time were ported to the Cell's Synergistic Processing Elements (SPEs). The remaining application framework, including MPI-based distributed code execution, was left to the Cell's PowerPC processor. We observe that we only infrequently achieve more than 10 GFLOPS with any of the kernels, which is just …
Variational Quantum Simulation of the Interacting Schwinger Model on a Trapped-Ion Quantum Processor
本文在 trapped-ion 量子处理器上利用变分量子模拟探索一维多味 lattice Schwinger model，通过参数化量子电路识别基态并绘制量子相变，利用量子态层析分析相变过程中的性质变化并确定相边界。
The gap between the cost of moving data and the cost of computing continues to grow, making it ever harder to design iterative solvers on extreme-scale architectures. This problem can be alleviated by alternative algorithms that reduce the amount of data movement. We investigate this in the context of Lattice Quantum Chromodynamics and implement such an alternative solver algorithm, based on domain decomposition, on Intel Xeon Phi co-processor (KNC) clusters. We demonstrate close-to-linear on-chip scaling to all 60 cores of the KNC. With a mix of single- and half-precision the domain-decomposi…
We study microscopic processes responsible for chirality flips in the thermal bath of Quantum Chromodynamics at finite temperature and zero baryon chemical potential. We focus on the temperature range where the crossover from chirally broken phase to quark-gluon plasma takes place, namely $T \simeq (150, 200)$ MeV. The processes we consider are quark-quark scatterings mediated by collective excitations with the quantum number of pions and $σ$-meson, hence we refer to these processes simply as \sugg{to} one-pion (one-$σ$) exchange\sugg{s}. We use a Nambu-Jona-Lasinio model to compute equilibriu…
The Collins-Soper kernel relates transverse momentum-dependent parton distribution functions (TMDPDFs) at different energy scales. For small parton transverse momentum $q_T\sim Λ_\text{QCD}$, this kernel is non-perturbative and can only be determined with controlled uncertainties through experiment or first-principles calculations. This work presents the first exploratory determination of the Collins-Soper kernel using the lattice formulation of Quantum Chromodynamics. In a quenched calculation, the $N_f=0$ kernel is determined at scales in the range 250 MeV $< q_T < 2$ GeV, and an analysis of…
Determination of the Collins-Soper kernel from Lattice QCD
本文利用格点QCD首次系统控制质量、混合和离散化效应，通过次次领头阶对数匹配确定夸克Collins-Soper核，结果与部分现象学参数化一致并排除其他方案。
This work presents a lattice quantum chromodynamics (QCD) calculation of the nonperturbative Collins-Soper kernel, which describes the rapidity evolution of quark transverse-momentum-dependent parton distribution functions. The kernel is extracted at transverse momentum scales in the range 400 MeV $< q_T < 1.7$ GeV in a calculation with dynamical fermions and quark masses corresponding to a larger-than-physical pion mass, $m_π=538(1)$ MeV. It is found that different approaches to extract the Collins-Soper kernel from the same underlying lattice QCD matrix elements yield significantly different…
Three-qubit encoding in ytterbium-171 atoms for simulating 1+1D QCD
通过在ytterbium-171原子中编码三个量子比特，实现对1+1维QCD的高效模拟，展示了该方法在真空持续振荡和弦断裂模拟中的应用。
Collins-Soper kernel from lattice QCD at the physical pion mass
本文首次在接近物理π介子质量的格点QCD中确定夸克Collins-Soper核，通过次次领先对数匹配和完整系统不确定性分析，在240 MeV至1.6 GeV横动量范围内达到可区分非微扰区唯象模型的精度。
Implementations of measurement kernels in high-level Lattice QCD frameworks enable rapid prototyping, but can leave hardware capabilities significantly underutilized. This is an acceptable tradeoff if the time spent in unoptimized routines is generally small. The computational cost of modern spectroscopy projects however can be comparable to or even exceed the cost of generating gauge configurations and computing solutions of the Dirac equation. One such key kernel in the stochastic LapH method is the computation of baryon blocks; we discuss several implementation strategies and achieve a 7.2x…
Kernels and integration cycles in complex Langevin simulations
复数Langevin模拟有时会收敛到错误分布，本文证明仅靠边界项不足以判定正确性，并提出在复数Langevin方程中引入核以控制积分环路从而恢复正确收敛。
Mixed precision solvers with half-precision floating point numbers for Lattice QCD on A64FX processor
本文提出在A64FX处理器上使用半精度浮点数的混合精度求解器，通过重标定步骤提高稳定性，实验表明其在格点量子色动力学模拟中具有可行性。
The A64FX CPU is arguably the most powerful Arm-based processor design to date. Although it is a traditional cache-based multicore processor, its peak performance and memory bandwidth rival accelerator devices. A good understanding of its performance features is of paramount importance for developers who wish to leverage its full potential. We present an architectural analysis of the A64FX used in the Fujitsu FX1000 supercomputer at a level of detail that allows for the construction of Execution-Cache-Memory (ECM) performance models for steady-state loops. In the process we identify architectu…
String Breaking Dynamics and Glueball Formation in a $2+1$D Lattice Gauge Theory
本文利用张量网络方法研究$2+1$维$\mathbb{Z}_2$晶格规范理论中电通量弦的淬火动力学，揭示了共振条件下的弦断裂过程及远离共振时的禁闭行为，并发现最大长度弦可演化为类似QCD胶球的圈结构。
Transverse-momentum-dependent pion structures from lattice QCD: Collins-Soper kernel, soft factor, TMDWF, and TMDPDF
本文首次在LaMET框架内用格点QCD计算π介子价夸克TMDPDF，提取软函数和CS核，并与微扰论及文献结果一致，所得TMDPDF与唯象参数化相符，同时给出较重π介子的TMDWF。
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