QPACE 2 and Domain Decomposition on the Intel Xeon Phi

We give an overview of QPACE 2, which is a custom-designed supercomputer based on Intel Xeon Phi processors, developed in a collaboration of Regensburg University and Eurotech. We give some general recommendations for how to write high-performance code for the Xeon Phi and then discuss our implementation of a domain-decomposition-based solver and present a number of benchmarks.Comment: plenary talk at Lattice 2014, to appear in the conference proceedings PoS(LATTICE2014), 15 pages, 9 figure

Energy Concerns with HPC Systems and Applications

For various reasons including those related to climate changes, {\em energy} has become a critical concern in all relevant activities and technical designs. For the specific case of computer activities, the problem is exacerbated with the emergence and pervasiveness of the so called {\em intelligent devices}. From the application side, we point out the special topic of {\em Artificial Intelligence}, who clearly needs an efficient computing support in order to succeed in its purpose of being a {\em ubiquitous assistant}. There are mainly two contexts where {\em energy} is one of the top priority concerns: {\em embedded computing} and {\em supercomputing}. For the former, power consumption is critical because the amount of energy that is available for the devices is limited. For the latter, the heat dissipated is a serious source of failure and the financial cost related to energy is likely to be a significant part of the maintenance budget. On a single computer, the problem is commonly considered through the electrical power consumption. This paper, written in the form of a survey, we depict the landscape of energy concerns in computer activities, both from the hardware and the software standpoints.Comment: 20 page

Strategies for improving the sustainability of data centers via energy mix, energy conservation, and circular energy

Information and communication technologies (ICT) are increasingly permeating our daily life and we ever more commit our data to the cloud. Events like the COVID-19 pandemic put an exceptional burden upon ICT. This involves increasing implementation and use of data centers, which increased energy use and environmental impact. The scope of this work is to summarize the present situation on data centers as to environmental impact and opportunities for improvement. First, we introduce the topic, presenting estimated energy use and emissions. Then, we review proposed strategies for energy efficiency and conservation in data centers. Energy uses pertain to power distribution, ICT, and non-ICT equipment (e.g., cooling). Existing and prospected strategies and initiatives in these sectors are identified. Among key elements are innovative cooling techniques, natural resources, automation, low-power electronics, and equipment with extended thermal limits. Research perspectives are identified and estimates of improvement opportunities are mentioned. Finally, we present an overview on existing metrics, regulatory framework, and bodies concerned

Experimental Design and Comparative Testing of a Hybrid-Cooled Computer Cluster

With water cooling becoming an affordable option both at home and at scale, it is important to consider the possible benefits over air cooling. There are several methods of liquid cooling, notables include: immersion, cold water cooling, and warm water cooling. The total cost of ownership is difficult to determine with these options as each has a different impact on the data center. Considering retrofit, over a new data center, introduces unforeseen variables that make cost analysis a challenge. Besides the added costs of additional infrastructure, and the cost to remove old, the upfront costs could be daunting. Therefore a cost analysis would be a study of its won. This study however hopes to reveal the resulting tradeoffs in temperature, performance, and power usage presented in the case between classical airflow based heat sink mechanisms to water provided directly at the heatsink. Having control over a discrete chiller will provide answers to the CPU temperatures, power usage, and performance at various inlet water temperatures. To water or to air

The Mpemba effect in spin glasses is a persistent memory effect

The Mpemba effect occurs when a hot system cools faster than an initially colder one, when both are refrigerated in the same thermal reservoir. Using the custom built supercomputer Janus II, we study the Mpemba effect in spin glasses and show that it is a non-equilibrium process, governed by the coherence length \xi of the system. The effect occurs when the bath temperature lies in the glassy phase, but it is not necessary for the thermal protocol to cross the critical temperature. In fact, the Mpemba effect follows from a strong relationship between the internal energy and \xi that turns out to be a sure-tell sign of being in the glassy phase. Thus, the Mpemba effect presents itself as an intriguing new avenue for the experimental study of the coherence length in supercooled liquids and other glass formers.Comment: Version accepted for publication in PNAS. 6 pages, 7 figure

Towards Thermally-Aware Design of 3D MPSoCs with Inter-Tier Cooling

Abstract—New tendencies envisage 3D Multi-Processor System-On-Chip (MPSoC) design as a promising solution to keep increasing the performance of the next-generation highperformance computing (HPC) systems. However, as the power density of HPC systems increases with the arrival of 3D MPSoCs, supplying electrical power to the computing equipment and constantly removing the generated heat is rapidly becoming the dominant cost in any HPC facility. Thus, both power and thermal/cooling implications play a major role in the design of new HPC systems, given the energy constraints in our society. Therefore, EPFL, IBM and ETHZ have been working within the CMOSAIC Nano-Tera.ch program project in the last three years on the development of a holistic thermally-aware design. This paper presents the exploration in CMOSAIC of novel cooling technologies, as well as suitable thermal modeling and system-level design methods, which are all necessary to develop 3D MPSoCs with inter-tier liquid cooling systems. As a result, we develop energy-efficient run-time thermal control strategies to achieve energy-efficient cooling mechanisms to compress almost 1 Tera nano sized functional units into one cubic centimeter with a 10 to 100 fold higher connectivity than otherwise possible. The proposed thermally-aware design paradigm includes exploring the synergies of hardware-, software- and mechanical-based thermal control techniques as a fundamental step to design 3D MPSoCs for HPC systems. More precisely, we target the use of inter-tier coolants ranging from liquid water and twophase refrigerants to novel engineered environmentally friendly nano-fluids, as well as using specifically designed micro-channel arrangements, in combination with the use of dynamic thermal management at system-level to tune the flow rate of the coolant in each micro-channel to achieve thermally-balanced 3D-ICs. Our management strategy prevents the system from surpassing the given threshold temperature while achieving up to 67% reduction in cooling energy and up to 30% reduction in system-level energy in comparison to setting the flow rate at the maximum value to handle the worst-case temperature

Electronics Thermal Management in Information and Communications Technologies: Challenges and Future Directions

This paper reviews thermal management challenges encountered in a wide range of electronics cooling applications from large-scale (data center and telecommunication) to smallscale systems (personal, portable/wearable, and automotive). This paper identifies drivers for progress and immediate and future challenges based on discussions at the 3rd Workshop on Thermal Management in Telecommunication Systems and Data Centers held in Redwood City, CA, USA, on November 4–5, 2015. Participants in this workshop represented industry and academia, with backgrounds ranging from data center thermal management and energy efficiency to high-performance computing and liquid cooling, thermal management in wearable and mobile devices, and acoustic noise management. By considering a wide range of electronics cooling applications with different lengths and time scales, this paper identifies both common themes and diverging views in the thermal management community

Working Papers: Astronomy and Astrophysics Panel Reports

The papers of the panels appointed by the Astronomy and Astrophysics survey Committee are compiled. These papers were advisory to the survey committee and represent the opinions of the members of each panel in the context of their individual charges. The following subject areas are covered: radio astronomy, infrared astronomy, optical/IR from ground, UV-optical from space, interferometry, high energy from space, particle astrophysics, theory and laboratory astrophysics, solar astronomy, planetary astronomy, computing and data processing, policy opportunities, benefits to the nation from astronomy and astrophysics, status of the profession, and science opportunities

Incentives to Apply Green Cloud Computing

Abstract In recent years, there have been two major trends in the ICT industry: green computing and cloud computing. Green computing implies that the ICT industry has become a significant energy consumer and consequently, a major source of CO2 emissions. Cloud computing makes it possible to purchase IT resources as a service without upfront costs. In this paper, the combination of these two trends, green cloud computing, will first be evaluated based on existing research findings, which indicate that private clouds are the most green option to offer services. Hosting of private clouds can be outsourced, which allows companies to focus on their core competences. Furthermore, three case studies of state-of-the-art companies offering green hosting services are presented and incentives affecting their energy-efficiency development are analyzed. The results reveal that currently there is no demand in the market for green hosting services, because the only incentive for companies is low costs. Service providers should illustrate their greenness with transparent efficiency metrics, draw up green service level agreements and compete with greenness. Then it is up to end users to require more green web services and create derived demand for green cloud services and green hosting services