Analyzing and improving MPI communication performance in overcommitted virtualized systems

Nowadays, it is an important trend in the system domain to use the software-based virtualization technology to build the execution environments (e.g., Clouds) and serve high performance computing extra virtualization layer, the application performance may be (HPC) applications. However, with the extra virtualization layer, the application performance may be negatively affected. Studies revealed that the communication performance of the MPI library, which is widely used by the HPC applications, would suffer a high penalty when a physical host machine becomes overcommitted by virtual processors (VCPU). Unfortunately, the problem has not received enough attention and has not been solved yet in literature. In this paper, we investigate the reasons behind the performance penalty, and propose a solution to improve the communication performance of running MPI applications in the overcommitted virtualized systems. The experimental results show that by our proposal, most HPC applications can gain performance improvement to different extents among the overcommitted systems, depending on their communication patterns and the overcommitting level

Is Export Spillover Localized in China

The hypothesis of localized export spillover has been widely supported by the previous studies. Based on Chinese firm-level data of more than 47,000 firms from 2000 to 2006, this paper investigates whether export spillover is localized in China. Drawing on the idea of revealed comparative advantage, six export spillover indicators are constructed to capture both the within- and between- provinces, cities as well as industries spillover effects. The multinomial logit model estimation results show that there is no sign of localized spillover effects despite the fact that domestic firms gain from export spillovers due to geographic and industrial agglomeration effects. This is especially true for those new entrants to export markets. The finding indicates that there may be export congestions resulting from over-agglomeration of local exporters due to the rapid export expansion in China

VSA : an offline scheduling analyzer for Xen virtual machine monitor

Nowadays, it is an important trend in the system domain to use the software-based virtualization technology to build the execution environments (e.g., the Clouds). After introducing the virtualization layer, there exist two schedulers: One in the hypervisor and the other inside the Guest Operating System (GOS). To fully understand the virtualized system and identify the possible reasons for performance problems incurred by the virtualization technology, it is very important for the system administrators and engineers to know the scheduling behavior of the hypervisor, in addition to understanding the scheduler inside the GOS. In this paper, we develop a virtualization scheduling analyzer, called VSA, to analyze the trace data of the Xen virtual machine monitor. With VSA, one can easily obtain the scheduling data associated with virtual processors (i.e., VCPUs) and physical processors (i.e., PCPUs), and further conduct the scheduling analysis for a group of interacting VCPUs running in the same domain

Active Intra-Abdominal Drainage Following Abdominal Digestive System Surgery: A Meta-Analysis and Systematic Review

Background Our objective is to compare the early outcomes associated with passive (gravity) drainage (PG) and active drainage (AD) after surgery. Methods Studies published until April 28, 2022 were retrieved from the PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, Web of Science databases. Results Nine studies with 14,169 patients were identified. Two groups had the same intra-abdominal infection rate (RR: 0.55; P = 0.13); In subgroup analysis of pancreaticoduodenectomy, active drainage had no significant effect on postoperative pancreatic fistula (POPF) rate (RR: 1.21; P = 0.26) and clinically relevant POPF (CR-POPF) (RR: 1.05; P = 0.72); Active drainage was not associated with lower percutaneous drainage rate (RR: 1.00; P = 0.96), incidence of sepsis (RR: 1.00; P = 0.99) and overall morbidity (RR: 1.02; P = 0.73). Both groups had the same POPF rate (RR: 1.20; P = 0.18) and CR-POPF rate (RR: 1.20; P = 0.18) after distal pancreatectomy. There was no difference between two groups on the day of drain removal after pancreaticoduodenectomy (Mean difference: −0.16; P = 0.81) and liver surgery (Mean difference: 0.03; P = 0.99). Conclusions Active drainage is not superior to passive drainage and both drainage methods can be considered

Effect of carbon material on Pd catalyst for formic acid electrooxidation reaction

Effect of several usually used carbon materials on Pd catalyst for formic acid electrooxidation reaction is studied by physical characterization and electrochemical measurements. New active sites are formed due to the Pd and carbon interaction which is confirmed by the XPS measurements, and electrochemical impedance spectroscopy confirms that the presence of the carbon material reduced the charge transfer resistance. Further, an improved fuel cell performance is observed when integrating the carbon-modified Pd catalyst in to a direct formic acid fuel cell. The results reveal that the carbon material is not only used as support, but also involves the new active sites formation. (C) 2014 Elsevier B.V. All rights reserved

Simultaneous Sensitive Determination of δ13C, δ18O, and δ17O in Human Breath CO2 Based on ICL Direct Absorption Spectroscopy

Previous research revealed that isotopes 13C and 18O of exhaled CO2 have the potential link with Helicobacter pylori; however, the 17O isotope has received very little attention. We developed a sensitive spectroscopic sensor for simultaneous δ13C, δ18O, and δ17O analysis of human breath CO2 based on mid-infrared laser direct absorption spectroscopy with an interband cascade laser (ICL) at 4.33 μm. There was a gas cell with a small volume of less than 5 mL, and the pressure in the gas cell was precisely controlled with a standard deviation of 0.0035 Torr. Moreover, real-time breath sampling and batch operation were achieved in gas inlets. The theoretical drifts for δ13C, δ18O, and δ17O measurement caused by temperature were minimized to 0.017‰, 0.024‰, and 0.021‰, respectively, thanks to the precise temperature control with a standard deviation of 0.0013 °C. After absolute temperature correction, the error between the system responded δ-value and the reference is less than 0.3‰. According to Allan variance analysis, the system precisions for δ13C, δ18O, and δ17O were 0.12‰, 0.18‰, and 0.47‰, respectively, at 1 s integration time, which were close to the real-time measurement errors of six repeated exhalations

Active Intra-Abdominal Drainage Following Abdominal Digestive System Surgery: A Meta-Analysis and Systematic Review

Our objective is to compare the early outcomes associated with passive (gravity) drainage (PG) and active drainage (AD) after surgery. Studies published until April 28, 2022 were retrieved from the PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, Web of Science databases. Nine studies with 14,169 patients were identified. Two groups had the same intra-abdominal infection rate (RR: 0.55; P = 0.13); In subgroup analysis of pancreaticoduodenectomy, active drainage had no significant effect on postoperative pancreatic fistula (POPF) rate (RR: 1.21; P = 0.26) and clinically relevant POPF (CR-POPF) (RR: 1.05; P = 0.72); Active drainage was not associated with lower percutaneous drainage rate (RR: 1.00; P = 0.96), incidence of sepsis (RR: 1.00; P = 0.99) and overall morbidity (RR: 1.02; P = 0.73). Both groups had the same POPF rate (RR: 1.20; P = 0.18) and CR-POPF rate (RR: 1.20; P = 0.18) after distal pancreatectomy. There was no difference between two groups on the day of drain removal after pancreaticoduodenectomy (Mean difference: −0.16; P = 0.81) and liver surgery (Mean difference: 0.03; P = 0.99). Active drainage is not superior to passive drainage and both drainage methods can be considered.</p

Direct Trajectory Optimization of Free-Floating Space Manipulator for Reducing Spacecraft Variation

This letter investigates the direct trajectory optimization of the free-floating space manipulator (FFSM). The main purpose is to plan the joint space trajectories to reduce the spacecraft motion due to the joint rotation during the FFSM performing tasks. To improve the calculation efficiency, the adaptive Radau pseudospectral method (A-RPM) is applied to discretize the system dynamics and transform the formulated optimal problem into a nonlinear programming problem (NLP). By adaptively subdividing the current segment and assigning collocation points according to the solution error, high-degree interpolation polynomials are avoided. To verify the effectiveness of the proposed method, a ground micro-gravity platform of the FFSM system is designed by using the air-bearing technique, on which experiments are carried out. The results show that the variation of the base spacecraft is dramatically reduced if the joints rotate along the optimized trajectories. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Learning & Autonomous Contro

Model-Based Control for Soft Robots With System Uncertainties and Input Saturation

Model-based strategies are a promising solution to the grand challenge of equipping continuum soft robots with motor intelligence. However, finite-dimensional models of these systems are inherently inaccurate, thus posing pressing robustness concerns. Moreover, the actuation space of soft robots is usually limited. This article aims at solving both these challenges by proposing a robust model-based strategy for the shape control of soft robots with system uncertainty and input saturation. The proposed architecture is composed of two key components. First, we propose an observer that estimates deviations between the theoretical model and the soft robot, ensuring that the estimation error converges to zero within finite time. Second, we introduce a sliding mode controller to regulate the soft robot shape while fulfilling saturation constraints. This controller uses the observer's output to compensate for the deviations between the real system and the established model. We prove the convergence of the closed-loop with theoretical analysis and the method's effectiveness with simulations and experiments