Real-Time Simulation and Prognosis of Smoke Propagation in Compartments Using a GPU

The evaluation of life safety in buildings in case of fire is often based on smoke spread calculations. However, recent simulation models – in general, based on computational fluid dynamics – often require long execution times or high-performance computers to achieve simulation results in or faster than real-time. Therefore, the objective of this study is the development of a concept for the real-time and prognosis simulation of smoke propagation in compartments using a graphics processing unit (GPU). The developed concept is summarized in an expandable open source software basis, called JuROr (Jülich's Real-time simulation within ORPHEUS). JuROr simulates buoyancy-driven, turbulent smoke spread based on a reduced modeling approach using finite differences and a Large Eddy Simulation turbulence model to solve the incompressible Navier-Stokes and energy equations. This reduced model is fully adapted to match the target hardware of highly parallel computer architectures. Thereby, the code is written in the object-oriented programming language C++ and the pragma-based programming model OpenACC. This model ensures to maintain a single source code, which can be executed in serial and parallel on various architectures. Further, the study provides a proof of JuROr's concept to balance sufficient accuracy and practicality. First, the code was successfully verified using unit and (semi-) analytical tests. Then, the underlying model was validated by comparing the numerical results to the experimental results of scenarios relevant for fire protection. Thereby, verification and validation showed acceptable accuracy for JuROr's application. Lastly, the performance criteria of JuROr – being real-time and prognosis capable with comparable performance across various architectures – was successfully evaluated. Here, JuROr also showed high speedup results on a GPU and faster time-to-solution compared to the established Fire Dynamics Simulator. These results show JuROr's practicality.Die Bewertung der Personensicherheit bei Feuer in Gebäuden basiert häufig auf Berechnungen zur Rauchausbreitung. Bisherige Simulationsmodelle – im Allgemeinen basierend auf numerischer Strömungsdynamik – erfordern jedoch lange Ausführungszeiten oder Hochleistungsrechner, um Simulationsergebnisse in und schneller als Echtzeit liefern zu können. Daher ist das Ziel dieser Arbeit die Entwicklung eines Konzeptes für die Echtzeit- und Prognosesimulation der Rauchausbreitung in Gebäuden mit Hilfe eines Grafikprozessors (GPU). Zusammengefasst ist das entwickelte Konzept in einer erweiterbaren Open-Source-Software, genannt JuROr (Jülich's Real-time Simulation in ORPHEUS). JuROr simuliert die Ausbreitung von auftriebsgetriebenem, turbulentem Rauch basierend auf einem reduzierten Modellierungsansatz mit finiten Differenzen und einem Large Eddy Simulation Turbulenzmodell, um inkompressible Navier- Stokes und Energiegleichungen zu lösen. Das reduzierte Modell ist voll- ständig angepasst an hochparallele Computerarchitekturen. Dabei ist der Code implementiert mit C++ und OpenACC. Dies hat den Vorteil mit nur einem Quellcode verschiedenste serielle und parallele Ausführungen des Programms für unterschiedliche Architekturen erstellen zu können. Die Studie liefert weiterhin einen Konzeptnachweis dafür, ausreichende Genauigkeit und Praktikabilität im Gleichgewicht zu halten. Zunächst wurde der Code erfolgreich mit Modul- und (semi-) analytischen Tests verifiziert. Dann wurde das zugrundeliegende Modell durch einen Vergleich der numerischen mit den experimentellen Ergebnissen für den Brandschutz relevanter Szenarien validiert. Die Verifizierung und Validierung zeigten dabei ausreichende Genauigkeit für JuROr. Zuletzt, wurden die Kriterien von JuROr – echtzeit- und prognosefähig zu sein mit vergleichbarer Leistung auf unterschiedlichsten Architekturen – erfolgreich geprüft. Zudem zeigte JuROr hohe Beschleunigungseffekte auf einer GPU und schnellere Lösungszeiten im Vergleich zum etablierten Fire Dynamics Simulator. Diese Ergebnisse zeigen JuROr's Praktikabilität

Use of multi-GPU systems for large FFTs: with applications in ultrasound simulations

Ultrasound simulations are a type of application that are both computationally and communicatively intensive. With better performance, implementations of these can be used in designing new ultrasound probes, developing better signal processing techniques, training new ultrasonographers, in treatment planning and many other uses [11]. The pseudo-spectral technique can be used effectively to express the wave-propagation model used in these simulations, and is characterised by its use of the Fast Fourier Transform (FFT). The FFT can account for over half of the time spent by ultrasound simulations, with the remaining consisting of embarrassingly parallel arithmetic [28]. The use of a Graphics Processing Unit (GPU) for general computations like the FFT has become ubiquitous with favourable performance. The current trend in the design of the Central Processing Unit (CPU) of most systems has seen a shift from single-core to multi-core processing with these now being assembled into multi-socket configurations. GPUs are already massively multi-core processors typically with three or four times as many cores the question remains: will GPUs follow a similar trend and incorporate multiple devices in individual sockets when implemented? The purpose of the work in this thesis is to assess the viability of multi-GPU systems for ultrasound simulations in terms of cost and performance compared to other system designs that offer similar computational resources. Current machine hardware is capable of supporting multiple GPU through peripheral devices and offers a glimpse of the potential of future machines however, relatively little work has been reported on the use of such systems for ultrasound simulations and the FFT algorithm. In this thesis, to address this issue, we benchmark and model the device-to-device communication potential of an existing multi-GPU system. Four different methods are considered, namely: via CPU, pointer swapping, hybrid-staged, and kernel. The results reveal that the pointer swapping and kernel based methods of managing communication can be up to twice as efficient as other methods. The methods for communication identified in the benchmarks are then used as the basis for a number of important generic communication functions, which are in turn used to implement a distributed 3D FFT algorithm as required by the ultrasound simulation. The multi-GPU distributed 3D FFT with four GPUs was found to be up to 18% faster than an existing FFT implementation on a six core CPU. This multi-GPU distributed 3D FFT implementation is then used in an ultra- sound simulation as a proof-of-concept case study of the thesis. By overlapping communication and computation between the CPU and GPU resources a speed up of 8% is observed

CIRA annual report FY 2014/2015

Reporting period July 1, 2014-March 31, 2015

Gaze-Based Human-Robot Interaction by the Brunswick Model

We present a new paradigm for human-robot interaction based on social signal processing, and in particular on the Brunswick model. Originally, the Brunswick model copes with face-to-face dyadic interaction, assuming that the interactants are communicating through a continuous exchange of non verbal social signals, in addition to the spoken messages. Social signals have to be interpreted, thanks to a proper recognition phase that considers visual and audio information. The Brunswick model allows to quantitatively evaluate the quality of the interaction using statistical tools which measure how effective is the recognition phase. In this paper we cast this theory when one of the interactants is a robot; in this case, the recognition phase performed by the robot and the human have to be revised w.r.t. the original model. The model is applied to Berrick, a recent open-source low-cost robotic head platform, where the gazing is the social signal to be considered

CIRA annual report FY 2015/2016

Reporting period April 1, 2015-March 31, 2016

Performance Portability Analysis for Real-Time Simulations of Smoke Propagation Using OpenACC

Real-time simulations of smoke propagation during fires in complex geometries challenge engineers, physicists, mathematicians and computer scientists due to the complexity of fluid dynamics and the large number of involved physical and chemical processes. Recently, several application scenarios emerged that require real-time predictions during an incident to support the rescue teams. Therefore, we develop the CFD-based simulation software JuROr aiming to run in real-time by leveraging parallel computer architectures like CPUs and GPUs. For that, we parallelize the code with OpenACC directives that promise maintenance of a single source base by delegating some architecture-agnostic optimizations to the compiler. We investigate the performance portability of JuROr using PGI’s OpenACC implementation across four Intel CPUs and three NVIDIA GPUs. We present the achieved performance shares as part of a roofline model where we focus on traditionally-computed arithmetic code intensities, as well as on a measurement approach based on performance counters

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described