An Experimental Evaluation of the HP V-Class and SGI Origin 2000 Multiprocessors using Microbenchmarks and Scientific Applications

As processor technology continues to advance at a rapid pace, the principal performance bottleneck of shared memory systems has become the memory access latency. In order to understand the effects of cache and memory hierarchy on system latencies, performance analysts perform benchmark analysis on existing multiprocessors. In this study, we present a detailed comparison of two architectures, the HP V-Class and the SGI Origin 2000. Our goal is to compare and contrast design techniques used in these multiprocessors. We present the impact of processor design, cache/memory hierarchies and coherence protocol optimizations on the memory system performance of these multiprocessors. We also study the effect of parallelism overheads such as process creation and synchronization on the user-level performance of these multiprocessors. Our experimental methodology uses microbenchmarks as well as scientific applications to characterize the user-level performance. Our microbenchmark results show the impact of Ll/L2 cache size and TLB size on uniprocessor load/store latencies, the effect of coherence protocol design/optimizations and data sharing patterns on multiprocessor memory access latencies and finally the overhead of parallelism. Our application-based evaluation shows the impact of problem size, dominant sharing patterns and number of Processors used on speedup and raw execution time. Finally, we use hardware counter measurements to study the correlation of system-level performance metrics and the application’s execution time performance.preliminary version of this paper appeared in the 13th ACM International Conference on Supercomputing (ICS’99).⁽¹³⁾ This work was done while Iyer and Bhuyan were at Texas A&M. It was supported in part by a Hewlett-Packard Equipment Grant. Amato and Rauchwerger supported in part by NSF Grants ACI-9872126, EIA-9975018, EIA-0103742, EIA-9805823, ACR-0081510, ACR-0113971, CCR-0113974, EIA-9810937, EIA-0079874, by the DOE ASCI ASAP program, and by the Texas Higher Education Coordinating Board grant ATP-000512-0261-2001. Perdue supported in part by a Dept. of Education Graduate Fellowship (GAANN)     

Althesin in cesarean section

The indications for the employment of Althesin in caesarean section are explained and a substantially favourable opinion is expressed on its clinical effects. Absence of neonatal depression is attributed both to the distribution and metabolism of the drug, and to the features of foetal circulation at term.     

Extended lymphadenectomy in carcinoma of the right colon

The Authors report on a retrospective study concerning 49 patients treated for a modified Dukes' stage B, C or D right colon cancer. A potentially curative right hemicolectomy with extended lymphadenectomy was performed. Locally advanced disease was treated by "en bloc" resection. Two (4.1%) patients died after surgery, in other 2 (4.1%) cases major postoperative complications were registered. Microscopic examination of the surgical specimens showed lymph node metastases in 44.9% of the cases: in this subgroup a metastatic involvement of the main (III level) nodal groups was detected in 22.7% of the patients. The Authors conclude that extended lymph node dissection does not increase postoperative complications and may play a role in the treatment of right colon cancer. A not negligible group of patients may be understaged or receive inadequate surgical treatment when submitted to traditional right colectomy.     

Application-driven,energy-efficient communication in wireless sensor networks

Several sensor network applications based on data diffusion and data management can determine the communication transfer rate between two sensors beforehand. In this framework, we consider the problem of energy efficient communication among nodes of a wireless sensor network and propose an application-driven approach that minimizes radio activity intervals and prolongs network lifetime. On the basis of possible communication delays we estimate packet arrival intervals at any intermediate hop of a fixed-rate data path. We study a generic strategy of radio activity minimization wherein each node maintains the radio switched on just in the expected packet arrival intervals and guarantees low communication latency. We define a probabilistic model that allows the evaluation of the packet loss probability that results from the reduced radio activity. The model can be used to optimally choose the radio activity intervals that achieve a certain probability of successful packet delivery for a specific radio activity strategy. Relying on the probabilistic model we also define a cost model that estimates the energy consumption of the proposed strategies, under specific settings. We propose three specific strategies and numerically evaluate the associated costs. We finally validate our work with a simulation made with TOSSIM (the Berkeley motes’ simulator). The simulation results confirm the validity of the approach and the accuracy of the analytic models.     

Finite‐time control of switching linear systems: The uncertain resetting times case

In recent years, a number of papers have treated the problem of the finite‐time stability and stabilization of impulsive (or, more in general, switching) dynamical linear systems. Generally, these works assume that the sequence of switching (in the following resetting) times is a priori known. In this paper, we remove such (strong) assumption, so making the technique more appealing from the practical control engineering point of view. A first result provided in this work is a sufficient condition for finite‐time stability when the resetting times are known with a certain degree of uncertainty. Such condition requires the solution of a suitable feasibility problem based on coupled difference/differential LMIs. We show that as the uncertainty intervals reduce in size, our condition becomes less conservative, becoming necessary and sufficient in the certain case (i.e., the resetting instants are perfectly known). Eventually, we consider the conceptually different situation in which the resetting times are totally unknown, namely, the arbitrary switching case. The analysis results are then used to derive sufficient conditions for the existence of state‐feedback controllers that finite time stabilizes the closed‐loop system in the three cases mentioned earlier. A nontrivial example, considering the finite‐time control of the liquid levels into three interconnected reservoirs, shows the effectiveness of the proposed approach. Copyright © 2014 John Wiley & Sons, Ltd.     

MI-File: using inverted files for scalable approximate similarity search

We propose a new efficient and accurate technique for generic approximate similarity searching, based on the use of inverted files. We represent each object of a dataset by the ordering of a number of reference objects according to their distance from the object itself. In order to compare two objects in the dataset, we compare the two corresponding orderings of the reference objects. We show that this representation enables us to use inverted files to obtain very efficiently a very small set of good candidates for the query result. The candidate set is then reordered using the original similarity function to obtain the approximate similarity search result. The proposed technique performs several orders of magnitude better than exact similarity searches, still guaranteeing high accuracy. To also demonstrate the scalability of the proposed approach, tests were executed with various dataset sizes, ranging from 200,000 to 100 million objects.     

3-D reconstruction by extended depth-of-field in failure analysis – Case study I: Qualitative fractographic investigation of fractured bolts in a partial valve

Extended depth-of-field 3-D reconstruction is an image processing based technique associated to optical microscopy for qualitative or quantitative analysis of surfaces topographies. It is proposed here as a low-cost alternative to scanning electron microscopy or confocal laser scanning microscopy methods in some cases in failure analysis. A case study of fractured bolts in a partial valve from a petrochemical plant is presented in this paper to illustrate a qualitative fractographic investigation using this technique.     

Microstructures and high temperature oxidation resistance of alloys from Nb–Cr–Si system

Oxidation behavior of Nb–30Si–(10,20)Cr alloys have been evaluated in air from 700 to 1400 °C by heating for 24 h and furnace cooling them. The lower weight gain per unit area has been observed for 20Cr alloy at 1200, 1300, and 1400 °C. Pesting has been observed at lower temperatures (700, 800, 900 °C). Analysis indicates that the powder formation at 900, 100, 1100 °C may be associated with β form of Nb₂O₅ (base centered monoclinic form). However the m-monoclinic form of Nb₂O₅ evolves at temperatures above 900 °C while o-orthorhombic Nb₂O₅ forms at below this temperature. The phases in the alloys have been calculated using the Pandat^TM software program at different temperatures using calculated Nb–Cr–Si phase diagrams.     

Fractal Nanotechnology

Self-similar patterns are frequently observed in Nature. Their reproduction is possible on a length scale 10²–10⁵ nm with lithographic methods, but seems impossible on the nanometer length scale. It is shown that this goal may be achieved via a multiplicative variant of the multi-spacer patterning technology, in this way permitting the controlled preparation of fractal surfaces.