Modeling multi-threaded programs execution time in the many-core era

Multi-core have become ubiquitous and industry is already moving towards the many-core era. Many open-ended questions remain unanswered for the upcoming many-core era. From the software perspective, it is unclear which applications will benefit from many cores. From the hardware perspective, the tradeoff between implementing many simple cores, fewer medium aggressive cores or even only a moderate number of aggressive cores is still to debate. Estimating the potential performance of future parallel applications on the yet-to-be-designed future many cores is very speculative. The simple models proposed by Amdahl's law or Gustafson's law are not sufficient and may lead to overly optimistic conclusions. In this paper, we propose a more refined but still tractable execution time model for parallel applications, the SNAS model. % (\textbf{ManyCore Performance model (MCP model????)}). As previous models, the SNAS model evaluates the execution time of both the serial part and the parallel part of the application, but takes into account the scaling of both these execution times with the input problem size and the number of processors. For a given application, a few parameters are collected on the effective execution of the application with a few threads and small input sets. SNAS allows to extrapolate the behavior of a future application exhibiting similar scaling characteristics on a manycore and/or a large input set. Our study shows that the execution time of the serial part of many parallel applications tends to increase along with the problem size, and in some cases with the number of processors. It also shows that the efficiency of the execution of the parallel part decreases dramatically with the number of processors for some applications. Our model also indicates that since several different application scaling trends will be encountered, heterogeneous architectures featuring a few aggressive cores and many simple cores should be privileged

Predicting Hemiwicking Dynamics on Textured Substrates

The ability to predict liquid transport rates on textured surfaces is key to the design and optimization of devices and processes such as oil recovery, coatings, reaction-separation, high-throughput screening, and thermal management. In this work we develop a fully analytical model to predict the propagation coefficients for liquids hemiwicking through micropillar arrays. This is carried out by balancing the capillary driving force and a viscous resistive force and solving the Navier–Stokes equation for representative channels. The model is validated against a large data set of experimental hemiwicking coefficients harvested from the literature and measured in-house using high-speed imaging. The theoretical predictions show excellent agreement with the measured values and improved accuracy compared to previously proposed models. Furthermore, using lattice Boltzmann (LB) simulations, we demonstrate that the present model is applicable over a broad range of geometries. The scaling of velocity with texture geometry, implicit in our model, is compared against experimental data, where good agreement is observed for most practical systems. The analytical expression presented here offers a tool for developing design guidelines for surface chemistry and microstructure selection for liquid propagation on textured surfaces

Carbon nanotube-rich domain effects on bulk electrical properties of nanocomposites

Carbon nanotube (CNT)/epoxy composites are intriguing materials that enable materials scientists and engineers to tailor structural and electrical properties for applications in the automotive and aerospace industries. Recent insights into CNT-rich domain formation and its influence on electrical properties raise questions about which processing variables can be used to tune the overall electrical conductivity. Here, we investigate how mass fraction and curing temperature influence these electrical properties. CNT nanocomposites were fabricated varying the mass fraction of CNT and the epoxy curing temperature. First, scanning lithium ion microscopy coupled with transmission electron microscopy were employed to investigate the morphology of CNT-rich domains that formed more readily at elevated curing temperatures than during room temperature curing. Then, oscillatory shear rheology measurements of the unfilled curing epoxy informed a simple kinetic argument to explain the CNT-rich domain formation. Finally, the electrical conductivity (both alternating and direct current) was characterized with a novel microwave cavity perturbation spectroscopy technique (alternating current conductivity) and a standard four-point probe station (direct current conductivity). The overarching conclusion of the work was that the CNT-rich domains formed a secondary percolated network surrounded by an almost completely unfilled epoxy matrix that allowed for higher conductivities at lower loadings. This work demonstrates that perfect dispersion of the nanoparticulate is, at least in this instance, not necessarily the preferred morphology

A Panorama on Multiscale Geometric Representations, Intertwining Spatial, Directional and Frequency Selectivity

The richness of natural images makes the quest for optimal representations in image processing and computer vision challenging. The latter observation has not prevented the design of image representations, which trade off between efficiency and complexity, while achieving accurate rendering of smooth regions as well as reproducing faithful contours and textures. The most recent ones, proposed in the past decade, share an hybrid heritage highlighting the multiscale and oriented nature of edges and patterns in images. This paper presents a panorama of the aforementioned literature on decompositions in multiscale, multi-orientation bases or dictionaries. They typically exhibit redundancy to improve sparsity in the transformed domain and sometimes its invariance with respect to simple geometric deformations (translation, rotation). Oriented multiscale dictionaries extend traditional wavelet processing and may offer rotation invariance. Highly redundant dictionaries require specific algorithms to simplify the search for an efficient (sparse) representation. We also discuss the extension of multiscale geometric decompositions to non-Euclidean domains such as the sphere or arbitrary meshed surfaces. The etymology of panorama suggests an overview, based on a choice of partially overlapping "pictures". We hope that this paper will contribute to the appreciation and apprehension of a stream of current research directions in image understanding.Comment: 65 pages, 33 figures, 303 reference

Area Access Control Systems: Zone Management And Personnel Tracking

Area access control is defined as the process of mediating requests to enter a physical area through one or more entry points. Area access control database systems are the collections of information required for an access control system to access, query, retrieve and match real time user inputs with persistent data to ensure the integrity of the resources it protects. This thesis presents an object oriented approach to the design and implementation of a centralized area access control database system and focuses on two features, zone management and personnel tracking. Zone management is defined as the process of hierarchically relating a zone to other immediately adjacent zone(s) that a user is required to have prior access to. This feature will automatically generate all zones that a user requires prior access to in order to approach a target zone. To implement zone management, the database system is required to support recursive relationships and recursive querying. The personnel-tracking feature allows the administrator to obtain information such as the movement of persons of interest and their interactions with others in the installation at any particular time. The results of this thesis contribute to the implementation of a sophisticated area access control database system capable of handling multiple installations, and generating the access rules and paths for each new user automatically. In addition, the object oriented area access control database system is able to support unconventional data types such as images and sound which are essential for emerging biometric security systems

An Empirical High Level Performance Model For FutureMany-cores

International audienceEstimating the potential performance of parallel applicationson the yet-to-be-designed future many cores is veryspeculative. The simple models proposed by Amdahl's law(xed input problem size) or Gustafson's law (xed numberof cores) do not completely capture the scaling behaviourof a multi-threaded (MT) application leading to over estimationof performance in the many-core era. On the otherhand, modeling many-core by simulation is too slow to studythe applications performance.In this paper, we propose a more rened but still tractable,high level empirical performance model for multi-threadedapplications, the Serial/Parallel Scaling (SPS)Model to studythe scalability and performance of application in many-coreera. SPS model learns the application behavior on a givenarchitecture and provides realistic estimates of the performancein future many-cores. Considering both input problemsize and the number of cores in modeling, SPS model canhelp in making high level decisions on the design choice of futuremany-core applications and architecture. We validatethe model on the Many-Integrated Cores (MIC) xeon-phiwith 240 logical cores

Sensitivity of RP Surface Finish to Process Parameter Variation 251

In the rapid prototyping process, surface finish is critical as it can affect the part accuracy, reduce the post processing costs and improve the functionality of the parts. This paper presents an experimental design technique for determining the optimal surface finish of a part built by the Fused Deposition Modeling (FDM) process. The design investigates the effect of the parameters; build orientation, layer thickness, road width, air gap and model temperature on the surface finish. Experiments were conducted using a fractional factorial design with two levels for each factor. The results are statistically analyzed to determine the significant factors and their interactions. The significant factors, their interactions and the optimum settings are proposed.Mechanical Engineerin