CaTS: Integration of Geant4 and Opticks Wenzel, Hans; Yung Jun, Soon; Genser, Krzysztof ...
EPJ Web of Conferences,
2024, Volume:
295
Journal Article, Conference Proceeding
Peer reviewed
Open access
CaTS 6is an advanced example that is part of Geant4 since version 11.0. It demonstrates the use of Opticks to offload the simulation of optical photons to GPUs. Opticks interfaces with the Geant4 ...toolkit to collect all the necessary information to generate and trace optical photons, re-implements the optical physics processes to be run on the GPU, and automatically translates the Geant4 geometry into a GPU appropriate format. To trace the photons, Opticks uses NVIDIA OptiX®. In this report, we describe CaTS and the integration of Opticks with Geant4. We demonstrate that the generation and tracing of optical photons represents an ideal application to be offloaded to GPUs, fully utilizing the high degree of available parallelism. In a typical liquid argon TPC simulation, a speedup of several hundred times is observed compared to an equivalent simulation using single threaded Geant4.
Celeritas: Accelerating Geant4 with GPUs Johnson, Seth R.; Esseiva, Julien; Biondo, Elliott ...
EPJ Web of Conferences,
01/2024, Volume:
295
Journal Article, Conference Proceeding
Peer reviewed
Open access
Celeritas 1 is a new Monte Carlo (MC) detector simulation code designed for computationally intensive applications (specifically, High Lumi- nosity Large Hadron Collider (HL-LHC) simulation) on ...high-performance heterogeneous architectures. In the past two years Celeritas has advanced from prototyping a GPU-based single physics model in infinite medium to implementing a full set of electromagnetic (EM) physics processes in complex geometries. The current release of Celeritas, version 0.3, has incorporated full device-based navigation, an event loop in the presence of magnetic fields, and detector hit scoring. New functionality incorporates a scheduler to offload electromagnetic physics to the GPU within a Geant4-driven simulation, enabling integration of Celeritas into high energy physics (HEP) experimental frameworks such as CMSSW. On the Summit supercomputer, Celeritas performs EM physics between 6 and 32 faster using the machine’s Nvidia GPUs compared to using only CPUs. When running a multithreaded Geant4 ATLAS test beam application with full hadronic physics, using Celeritas to accelerate the EM physics results in an overall simulation speedup of 1.8–2.3× on GPU and 1.2× on CPU.
Optimizing Geant4 Hadronic Models Genser, Krzysztof; Jun, Soon Yung; Ribon, Alberto ...
EPJ Web of Conferences,
2024, Volume:
295
Journal Article, Conference Proceeding
Peer reviewed
Open access
Geant4, the leading detector simulation toolkit used in high energy physics, employs a set of physics models to simulate interactions of particles with matter across a wide range of energies. These ...models, especially the hadronic ones, rely largely on directly measured cross-sections and inclusive characteristics, and use physically motivated parameters. However, they generally aim to cover a broad range of possible simulation tasks and may not always be optimized for a particular process or a given material. The Geant4 collaboration recently made many parameters of the models accessible via a configuration interface. This opens a possibility to fit simulated distributions to the thin target experimental datasets and extract optimal values of the model parameters and the associated uncertainties. Such efforts are currently undertaken by the Geant4 collaboration with the goal of offering alternative sets of model parameters, also known as "tunes", for certain applications. The effort should subsequently lead to more accurate estimates of the systematic errors in physics measurements given the detector simulation role in performing the physics measurements. Results of the study are presented to illustrate how Geant4 model parameters can be optimized through applying fitting techniques, to improve the agreement between the Geant4 and the experimental data.
Probability distribution functions (PDFs) are very used in modeling random processes and physics simulations. Improving the performance of algorithms that generate many random numbers under complex ...PDFs is often a very challenging task when methods as direct functions are not available. In this work we present general strategies on how to vectorize some PDFs using VecCore library. We show the results for the Exponential, Gaussian, discrete Poisson and Gamma probability distributions.
Celeritas is a new computational transport code designed for high-performance simulation of high-energy physics detectors. This work describes some of its current capabilities and the design choices ...that enable the rapid development of efficient on-device physics. The abstractions that underpin the code design facilitate low-level performance tweaks that require no changes to the higher-level physics code. We evaluate a set of independent changes that together yield an almost 40% speedup over the original GPU code for a net performance increase of 220× for a single GPU over a single CPU running 8.4M tracks on a small demonstration physics app.
We report on developments of the Geant4 electromagnetic physics sub-libraries of Geant4 release 10.4 and beyond. Modifications are introduced to the models of photoelectric effect, bremsstrahlung, ...gamma conversion, single and multiple scattering. The theory-based Goudsmit-Saunderson model of electron/positron multiple scattering has been recently reviewed and a new improved version, providing the most accurate results for scattering of electrons and positrons, was made available. The updated interfaces, models and configurations have already been integrated into LHC applications and may be useful for any type of simulations.
Geant Exascale Pilot Project Canal, Philippe; Sexton-Kennedy, Elizabeth; Madsen, Jonathan ...
EPJ Web of Conferences,
2020, Volume:
245
Journal Article, Conference Proceeding
Peer reviewed
Open access
The upcoming generation of exascale HPC machines will all have most of their computing power provided by GPGPU accelerators. In order to be able to take advantage of this class of machines for HEP ...Monte Carlo simulations, we started to develop a Geant pilot application as a collaboration between HEP and the Exascale Computing Project. We will use this pilot to study and characterize how the machines’ architecture affects performance. The pilot will encapsulate the minimum set of physics and software framework processes necessary to describe a representative HEP simulation problem. The pilot will then be used to exercise communication, computation, and data access patterns. The project’s main objective is to identify re-engineering opportunities that will increase event throughput by improving single node performance and being able to make efficient use of the next generation of accelerators available in Exascale facilities.
Objective: Amlodipine is the most widely prescribed calcium channel blocker (CCB) for hypertension. Lercanidipine, a newer CCB, is reported to exhibit fewer side effects, such as peripheral edema, ...and is believed to have beneficial effects on myocardial ischemia and congestive heart failure. However, its impact on major adverse cardiovascular events (MACE) has not been comprehensively explored. This study aims to elucidate the clinical efficacy of Lercanidipine in the prevention of major adverse cardiovascular events to that of Amlodipine. Design and method: A retrospective cohort study was conducted by analyzing electronic health records from three tertiary hospitals in Korea. We identified patients who were administered Lercanidipine (n = 2,182) or Amlodipine (n = 45,458) for a minimum of 30 days from January 1, 2017, to November 30, 2021. The incidence of MACE, including cardiovascular death, myocardial infarction, stroke, heart failure hospitalization, and coronary revascularization, was assessed over a three-year follow-up period. A total of 4,680 Amlodipine and 1,570 Lercanidipine patients were evaluated, with propensity score matching at a ratio of 1:3 after excluding those with end-stage renal disease. Results: Patients in the Lercanidipine cohort had a higher prevalence of low socioeconomic status, diabetes, hyperlipidemia, and chronic kidney disease. The usage of more than three antihypertensive drugs was more common in this group. The cardiovascular risk estimated by SCORE2/SCORE2-OP was also higher in the Lercanidipine cohort. After the propensity score matching, the incidence of MACE was numerically lower in the Lercanidipine group (2.8%) compared to the Amlodipine group (4.1%), but the difference was not statistically significant (p = 0.11). No differences in blood pressure control were observed over the follow-up period. Conclusions: In patients with higher cardiovascular risk profiles, Lercanidipine was preferred to Amlodipine. The study found that Lercanidipine had comparable efficacy to Amlodipine in preventing cardiovascular events.
SIMD acceleration can potentially boost by factors the application throughput. Achieving efficient SIMD vectorization for scalar code with complex data flow and branching logic, goes however way ...beyond breaking some loop dependencies and relying on the compiler. Since the refactoring effort scales with the number of lines of code, it is important to understand what kind of performance gains can be expected in such complex cases. We started to investigate a couple of years ago a top to bottom vectorization approach to particle transport simulation. Percolating vector data to algorithms was mandatory since not all the components can internally vectorize. Vectorizing low-level algorithms is certainly necessary, but not sufficient to achieve relevant SIMD gains. In addition, the overheads for maintaining the concurrent vector data flow and copy data have to be minimized. In the context of a vectorization R&D for simulation we developed a framework to allow different categories of scalar and vectorized components to co-exist, dealing with data flow management and real-time heuristic optimizations. The paper describes our approach on coordinating SIMD vectorization at framework level, making a detailed quantitative analysis of the SIMD gain versus overheads, with a breakdown by components in terms of geometry, physics and magnetic field propagation. We also present the more general context of this R&D work and goals for 2018.
Simulations in high energy physics (HEP) often require the numerical solution of ordinary differential equations (ODE) to determine the trajectories of charged particles in a magnetic field when ...particles move throughout detector volumes. Each crossing of a volume interrupts the underlying numerical method that solves the equations of motion, triggering iterative algorithms to estimate the intersection point within a given accuracy. The computational cost of this procedure can grow significantly depending on the application at hand. Quantized State System (QSS) is a recent family of discrete-event driven numerical methods exhibiting attractive features for this type of problems, such as native dense output (sequences of polynomial segments updated only by accuracy-driven events) and lightweight detection and handling of volume crossings. In this work we present GQLink, a proof-of-concept integration of QSS with the Geant4 simulation toolkit which stands as an interface for co-simulation that orchestrates robustly and transparently the interaction between the QSS simulation engine and aspects such as geometry definition and physics processes controlled by Geant4. We validate the accuracy and study the performance of the method in simple geometries (subject to intense volume crossing activity) and then in a realistic HEP application using a full CMS detector configuration.
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