Sourav Chakraborty  Ignacio Laguna  Murali Emani  Kathryn Mohror  Dhabaleswar K. Panda  Martin Schulz  Hari Subramoni 《Concurrency and Computation》2020,32(3)

Scientists from many different fields have been developing Bulk‐Synchronous MPI applications to simulate and study a wide variety of scientific phenomena. Since failure rates are expected to increase in larger‐scale future HPC systems, providing efficient fault‐tolerance mechanisms for this class of applications is paramount. The global‐restart model has been proposed to decrease the time of failure recovery in Bulk‐Synchronous applications by allowing a fast reinitialization of MPI. However, the current implementations of this model have several drawbacks: they lack efficiency; their scalability have not been shown; and they require the use of the MPI profiling interface, which precludes the use of tools. In this paper, we present EReinit , an implementation of the global‐restart model that addresses these problems. Our key idea and optimization is the co‐design of basic fault‐tolerance mechanisms such as failure detection, notification, and recovery between MPI and the resource manager in contrast to current approaches on which these mechanisms are implemented in MPI only. We demonstrate EReinit in three HPC programs and show that it is up to four times more efficient than existing solutions at 4,096 processes.  相似文献   

    

Scott Levy  Kurt B. Ferreira  Patrick Widener 《Concurrency and Computation》2020,32(3)

Coordinated checkpoint/restart is currently the dominant approach to mitigating the impact of failures on important scientific applications running on large‐scale distributed systems. However, there is widespread evidence that coordinated checkpointing may no longer be viable on next‐generation systems. Uncoordinated checkpoint/restart attempts to address the shortcomings of coordinated checkpoint/restart by allowing application processes to checkpoint their state independently. However, eliminating coordination may significantly degrade application performance. In this paper, we propose an approach that leverages existing coordination in important scientific applications to approximately coordinate checkpoints. Specifically, we propose to extend MPI implementations to force checkpoints to occur immediately after the completion of a collective operation. We evaluate the performance implications of this approach using an existing validated simulation framework. Our results demonstrate that approximately coordinated checkpointing can significantly improve application performance relative to totally uncoordinated checkpointing. We also show that forcing checkpoints to occur following a collective operation has a small impact on the nominal checkpoint interval for several important workloads. As a whole, the results presented in this paper demonstrate that approximately coordinated checkpointing may provide significant performance benefits without significantly increasing the cost of failure recovery.  相似文献   

    

Weibei Fan  Jing He  Zhijie Han  Peng Li  Ruchuan Wang 《Concurrency and Computation》2020,32(11)

Network‐on‐chip (NoC) is a new design method of system‐on‐chip used in very large scale integrated circuit (VLSI) systems. It is an important issue for choosing the appropriate topology for NoC. Wirelength and layout area are significant parameters affecting NoC due to the restriction of chip area. In this paper, we propose a new interconnection network called the incomplete ternary n‐cube for parallel computing systems. Then, a linear algorithm is proposed to layout incomplete ternary n‐cube network onto torus NoC. Furthermore, the failure of interconnection network is also taken into account, and a fault‐tolerant layout of incomplete ternary n‐cube with faulty edges into torus NoC is verified. Theoretical analysis demonstrates that the proposed algorithm can reduce the network cost and wirelength, which be conducive to estimate the wire length and chip area.  相似文献   

    

Hrek Haugerud  Noha Xue  Anis Yazidi 《Concurrency and Computation》2020,32(17)

Hybrid cloud technology is becoming increasingly popular as it merges private and public clouds to bring the best of two worlds together. However, due to the heterogeneous cloud installation, facilitating a hybrid cloud setup is not simple. Despite some commercial solutions being available to build a hybrid cloud, an open‐source implementation is still unavailable. In this paper, we try to bridge the gap by providing an open‐source implementation using the power of Apache Mesos. We build a hybrid cloud on top of multiple cloud platforms, private and public. Through comprehensive experimental results, we show that our solution is able to ensure resource bursting by leveraging the power of the public cloud.  相似文献   

    

《Technology in Society》2020

China, despite its rapid economic modernization and the lack of powerful conservative institutions, is not known for embracing diverse sexual orientation. The present study investigates whether and how Internet use, a increasingly important part of contemporary people's daily life, leads to changes in people's attitudes toward homosexuality in China, and relevant policy implications. Analyzing the Chinese General Social Survey data from 2010 to 2015, this paper develops an ordered probit model to quantify the influence of Internet use on homosexuality tolerance, adopts a substitution variable method to conduct the robustness check, and utilizes instrument variables to address the potential endogeneity in the regressions. The results show that Internet use has a significant positive impact on Chinese people's homosexuality tolerance. Further studies have found that the influence of Internet use on homosexuality tolerance is also heterogeneous to different populations. Besides, compared with traditional media, the Internet has a more significant impact on homosexuality tolerance. This paper provides some explanations for the rise in China's homosexuality tolerance from 2010 to 2015, and additional impetus for the international community to push for a liberal Internet policy in China.  相似文献   

    

Yunxia Han  Yizhong Ma  Linhan Ouyang  Jianjun Wang  Yiliu Tu 《Quality and Reliability Engineering International》2020,36(1):414-433

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Ryan Murphy  Yucun Zhou  Lei Zhang  Luke Soule  Weilin Zhang  Yu Chen  Meilin Liu 《Advanced functional materials》2020,30(35)

Reversible solid oxide cells based on ceramic proton conductors have potential to be the most efficient system for large‐scale energy storage. The performance and long‐term durability of these systems, however, are often limited by the ionic conductivity or stability of the proton‐conducting electrolyte. Here new family of solid oxide electrolytes, BaHf_xCe_0.8?xY_0.1Yb_0.1O_3?δ (BHCYYb), which demonstrate a superior ionic conductivity to stability trade‐off than the state‐of‐the‐art proton conductors, BaZr_xCe_0.8?xY_0.1Yb_0.1O_3?δ (BZCYYb), at similar Zr/Hf concentrations, as confirmed by thermogravimetric analysis, Raman, and X‐ray diffraction analysis of samples over 500 h of testing are reported. The increase in performance is revealed through thermodynamic arguments and first‐principle calculations. In addition, lab scale full cells are fabricated, demonstrating high peak power densities of 1.1, 1.4, and 1.6 W cm^?2 at 600, 650, and 700 °C, respectively. Round‐trip efficiencies for steam electrolysis at 1 A cm^?2 are 78%, 72%, and 62% at 700, 650, and 600 °C, respectively. Finally, CO₂? H₂O electrolysis is carried out for over 700 h with no degradation.  相似文献   

    

Ting Wang  Qun-Li Lei  Ming Wang  Guoying Deng  Le Yang  Xijian Liu  Chunlin Li  Qi Wang  Zhihua Liu  Jianwu Wang  Zequn Cui  Kevin Goldio Utama  Ran Ni  Xiaodong Chen 《Advanced materials (Deerfield Beach, Fla.)》2020,32(22):2000991

Epidermal bioelectronics that can monitor human health status non-invasively and in real time are core to wearable healthcare equipment. Achieving mechanically tolerant surface bioreactions that convert biochemical information to detectable signals is crucial for obtaining high sensing fidelity. In this work, by combining simulations and experiments, a typical epidermal biosensor system is investigated based on a redox enzyme cascade reaction (RECR) comprising glucose oxidase/lactate oxidase enzymes and Prussian blue nanoparticles. Simulations reveal that strain-induced change in surface reactant flux is the key to the performance drop in traditional flat bioelectrodes. In contrast, wavy bioelectrodes capable of curvature adaptation maintain the reactant flux under strain, which preserves sensing fidelity. This rationale is experimentally proven by bioelectrodes with flat/wavy geometry under both static strain and dynamic stretching. When exposed to 50% strain, the signal fluctuations for wavy bioelectrodes are only 7.0% (4.9%) in detecting glucose (lactate), which are significantly lower than the 40.3% (51.8%) in flat bioelectrodes. Based on this wavy bioelectrode, a stable human epidermal metabolite biosensor insensitive to human gestures is further demonstrated. This mechanically tolerant biosensor based on adaptive curvature engineering provides a reliable bio/chemical-information monitoring platform for soft healthcare bioelectronics.  相似文献   

    

Xiaohan Wang  Shengnan Zhan  Zhongyuan Lu  Jian Li  Xiao Yang  Yongna Qiao  Yongfeng Men  Junqi Sun 《Advanced materials (Deerfield Beach, Fla.)》2020,32(50):2005759

There is a huge requirement of elastomers for use in tires, seals, and shock absorbers every year worldwide. In view of a sustainable society, the next generation of elastomers is expected to combine outstanding healing, recycling, and damage-tolerant capacities with high strength, elasticity, and toughness. However, it remains challenging to fabricate such elastomers because the mechanisms for the properties mentioned above are mutually exclusive. Herein, the fabrication of healable, recyclable, and mechanically tough polyurethane (PU) elastomers with outstanding damage tolerance by coordination of multiblock polymers of poly(dimethylsiloxane) (PDMS)/polycaprolactone (PCL) containing hydrogen and coordination bonding motifs with Zn²⁺ ions is reported. The organization of bipyridine groups coordinated with Zn²⁺ ions, carbamate groups cross-linked with hydrogen bonds, and crystallized PCL segments generates phase-separated dynamic hierarchical domains. Serving as rigid nanofillers capable of deformation and disintegration under an external force, the dynamic hierarchical domains can strengthen the elastomers and significantly enhance their toughness and fracture energy. As a result, the elastomers exhibit a tensile strength of ≈52.4 MPa, a toughness of ≈363.8 MJ m⁻³, and an exceptional fracture energy of ≈192.9 kJ m⁻². Furthermore, the elastomers can be conveniently healed and recycled to regain their original mechanical properties and integrity under heating.  相似文献   

    

Tahmida N. Huq  Lana C. Lee  Lissa Eyre  Weiwei Li  Robert A. Jagt  Chaewon Kim  Sarah Fearn  Vincenzo Pecunia  Felix Deschler  Judith L. MacManus‐Driscoll  Robert L. Z. Hoye 《Advanced functional materials》2020,30(13)

In the search for nontoxic alternatives to lead‐halide perovskites, bismuth oxyiodide (BiOI) has emerged as a promising contender. BiOI is air‐stable for over three months, demonstrates promising early‐stage photovoltaic performance and, importantly, is predicted from calculations to tolerate vacancy and antisite defects. Here, whether BiOI tolerates point defects is experimentally investigated. BiOI thin films are annealed at a low temperature of 100 °C under vacuum (25 Pa absolute pressure). There is a relative reduction in the surface atomic fraction of iodine by over 40%, reduction in the surface bismuth fraction by over 5%, and an increase in the surface oxygen fraction by over 45%. Unexpectedly, the Bi 4f_7/2 core level position, Fermi level position, and valence band density of states of BiOI are not significantly changed. Further, the charge‐carrier lifetime, photoluminescence intensity, and the performance of the vacuum‐annealed BiOI films in solar cells remain unchanged. The results show BiOI to be electronically and optoelectronically robust to percent‐level changes in surface composition. However, from photoinduced current transient spectroscopy measurements, it is found that the as‐grown BiOI films have deep traps located ≈0.3 and 0.6 eV from the band edge. These traps limit the charge‐carrier lifetimes of BiOI, and future improvements in the performance of BiOI photovoltaics will need to focus on identifying their origin. Nevertheless, these deep traps are three to four orders of magnitude less concentrated than the surface point defects induced through vacuum annealing. The charge‐carrier lifetimes of the BiOI films are also orders of magnitude longer than if these surface defects were recombination active. This work therefore shows BiOI to be robust against processing conditions that lead to percent‐level iodine‐, bismuth‐, and oxygen‐related surface defects. This will simplify and reduce the cost of fabricating BiOI‐based electronic devices, and stands in contrast to the defect‐sensitivity of traditional covalent semiconductors.  相似文献