一种新的面向对象程序的内存管理器

设计并实现一种新的面向对象程序的内存管理器。使用混合数据结构分别处理小对象、中等对象和大对象,减少内存碎片。通过分布适合和位图适合算法,降低内存分配和释放的时间复杂度。采用边界标识技术加快相邻空闲块的合并,利用缓存技术和程序局部性原理提高内存请求的响应速度。实验结果表明,该管理器具有较快的响应速度以及较高的内存使用率。     

A Geometric Modeller Based on the Exact Octtree Representation of Polyhedra

Geometric Modellers based on a Boundary Representation scheme are well suited for display operations, but boolean operations require algorithms with quadratic complexity. Using a class of extended octtrees which is presented here, boolean operations become linear, while exact recomputation of the boundary model in the case of polyhedral objects is possible, and memory requirements are less than in classical octtree encodings. Some bounds on the memory savings are given and discussed. The DMI system, a Geometric Modeller based on a hybrid model Boundary - Extended Octtrees, is presented, discussing the main operations and the interface between both models. Some modelling examples are shown. Finally, a generalization of the extended octtree encoding which allows the exact representation of objects limited by sculptured surfaces is presented.     

Colour induction on computer displays-adjacency and shape effects

The perceived interactions, induction and assimilation between colours presented on a computer screen were investigated for seven participants who gave estimates on the perceived colours. A method based on memory estimation was used. In one experiment, a red - green scale was used, while in a second experiment a white - green scale was used. The distance between objects, shape of objects and colour of objects was varied. A distance effect of colour interaction was found in both experiments, but stronger for the red - green scale. For objects adjacent to each other the interaction effects were statistically significant. For objects not adjacent to each other some smaller effects occurred. No shape effects were found. Assimilation effects were shown for the red - green colour combinations. The participants seemed to use their own internal memory scale for their judgements. A theoretical model for distance effects of colour interaction is also presented.     

Memory leak detection in Plumbr

Platforms with automatic memory management, such as the JVM, are usually considered free of memory leaks. However, memory leaks can happen in such environments, as the garbage collector cannot free objects, which are not used by the application anymore, but are still referenced. Such unused objects can eventually fill up the heap and crash the application. Although this problem has been studied extensively, nevertheless, there are still many rooms for improvement in this area. This paper describes the statistical approach for memory leak detection, as an alternative, along with a commercial tool, Plumbr, which is based on the method. The tool is later analyzed with three case studies of real applications and in the process also analyzes strengths and weaknesses of the statistical approach for memory leak detection. Copyright © 2014 John Wiley & Sons, Ltd.     

Colour induction on computer displays – adjacency and shape effects

The perceived interactions, induction and assimilation between colours presented on a computer screen were investigated for seven participants who gave estimates on the perceived colours. A method based on memory estimation was used. In one experiment, a red – green scale was used, while in a second experiment a white – green scale was used. The distance between objects, shape of objects and colour of objects was varied. A distance effect of colour interaction was found in both experiments, but stronger for the red – green scale. For objects adjacent to each other the interaction effects were statistically significant. For objects not adjacent to each other some smaller effects occurred. No shape effects were found. Assimilation effects were shown for the red – green colour combinations. The participants seemed to use their own internal memory scale for their judgements. A theoretical model for distance effects of colour interaction is also presented.     

Participatory ergonomics in design processes: the role of boundary objects

The aim of this paper is to introduce the concept of boundary objects in order to better understand the role of objects in participatory ergonomics (PE) design processes. The research question is: What characterizes boundary objects in PE processes? Based on two case studies, we identify eight characteristics of boundary objects and their use, which make them particularly useful in PE design processes. These characteristics go beyond the object itself and extend into the context of their use. We argue that the selection of boundary objects in PE processes is of great importance, since different objects enable workers’ participation and collaborative design in different ways. The framework developed may serve to provide criteria to guide practitioners and intervention researchers in the selection of objects to facilitate a PE process. The paper concludes with a list of recommendations for ergonomic practitioners that are based on the framework.     

The Dynamics of Material Artifacts in Collaborative Research Teams

Boundary objects are material artifacts that mediate the relationship between two or more disparate perspectives. The concept of boundary objects has been demonstrably useful in a variety of research areas; however, the meaning and function of boundary objects is contested. At issue is the relationship between boundary objects that negotiate between perspectives and those that specify across perspectives. In this study the changing nature of boundary objects in cooperative work is related to the dynamics of evolving problem conceptualization, system design, and enactment within cooperative work settings. Design based research on material artifacts produced by an incipient cross-disciplinary research team during their efforts towards negotiating integrated conceptualizations and specifying shared research agendas is used to generate a more comprehensive model of boundary objects through the life of a project.     

基于内存映射文件的复杂对象快速读取方法

当前内存数据库(NoSQL)、嵌入式数据库技术在高并发高性能系统中得到了广泛的应用,但对于复杂对象数据的读取效率仍然低下,研究发现主要性能瓶颈有两个:一是内核态与用户态间的内存拷贝,拷贝消耗时间与复杂对象的数据量成线性增长;二是从数据库数据到运行时数据对象的格式转化操作,不但需要开辟新的内存空间存储运行时数据对象,而且还需要解析原始数据并拷贝至新对象之中。为此,提出了一种基于内存映射(memory mapping)文件的复杂对象共享读取方法。借助内存映射文件与自定义内存分配器,实现了结构复杂的C++标准模板库容器对象跨进程无拷贝、无格式转化的共享,有效降低了数据读取延时。通过性能的分析比较表明,与NoSQL内存数据库、嵌入式数据库比,读取性能效率提升10倍以上。再加上底层技术成熟稳定,复用了标准模板库,具有开发成本低、可维护性强、实用性高等优点,因此,适用于高并发高性能的高可用后台服务系统。     

ASN_EZE: An Analgesic for Writers of ASN.1 Applications

Many programmers find that the logical structure of data defined in ASA.1 is simple enough, but the physical representation requires painfully careful attention to lots of detail. ASN.1 'compilers' which we had used required a programmer ot know the intricacies of both ASN.1 and the generated code. Furthermore those which generated 'C' code were prone to 'memory leaks' and produced bulky code. Two features of object orientiation led us to develop a code generator that procues 'C++'. First Class inheritance permits a small number of functions to operate on objects of any derived class. Second, the destructors of such objects can be designed to prevent memory leaks automatically. Our own use of the system shows that within a few days programmers withh no pair exposure to ASN.1 can start writing applications using only the ASN.1 specification for reference. The generated code is compact and well protected anainst memory leaks. This paper describes the capabilies of the code generator, the library of functions for handling all ASN.1 objects so generated, and the interior structure of these objects which allows the library functions to navigate any hierarchy. The las section discusses our experience in using the system.     

Replication techniques for speeding up parallel applications on distributed systems

Most methods for programming loosely coupled systems are based on message-passing. Recently, however, methods have emerged based on ‘virtually’ sharing data. These methods simplify distributed programming, but are hard to implement efficiently, as loosely coupled systems do not contain physical shared memory. We introduce a new model, the shared data-object model, that eases the implementation of parallel applications on loosely coupled systems, but can still be implemented efficiently. In our model, shared data are encapsulated in passive data-objects, which are variables of user-defined abstract data types. To speed up access to shared data, data-objects are replicated. This ability to replicate objects is a significant difference with other object-based models (e.g. Emerald and Amber). Also, by replicating logical objects rather than physical pages, our model has many advantages over shared virtual memory systems. This paper discusses the design choices involved in replicating objects and their effect on performance. Important issues are: how to maintain consistency among different copies of an object; how to implement changes to objects; which strategy for object replication to use. We have implemented several options to determine which ones are the most efficient.     

基于边界区域局部模糊增强的uppiRKM 聚类算法

如何对交叉边界区域的数据对象进行度量与处理一直是粗糙k-means(RKM)及其衍生算法的主要出发点.uppiRKM算法通过引入Laplace无差别原则,较好地解决了传统RKM算法对权重系数的选择比较敏感等相关问题,但没有考虑边界区域多个类簇的交叉程度以及边界区域数据对象的空间位置分布对聚类结果的影响.鉴于此,设计一种对边界区域的数据对象进行局部模糊度量的方法,并提出基于边界区域局部模糊增强的uppiRKM聚类改进算法,通过多组实例分析验证了所提出算法的有效性.     

Towards an optimum language data model

Maximizing the satisfaction of a value in an engineering design is usually limited by tradeoffs in which other values become unacceptably sacrificed. In a few cases, however, the maximization is limited by a boundary between what is mathematically possible and what is not. Round wheels, vertical pillars, and binary memory elements are examples of optimum engineering structures which result from such mathematical limits. It is proposed that optimum characteristics of a language data model result similarly by minimizing the variety of primitive data objects, the complexity of those objects, and the number of objects needed to represent data states. Reducing these measures is needed to combine both rich data structure and powerful operations in one language. The minimizations lead to a narrow range of designs for language semantics in which the potential advantages of specialization is small compared with the advantages of commonality. Universal language for support of technical literacy appears to be an appropriate scope of generality in language design.     

Convexity Rule for Shape Decomposition Based on Discrete Contour Evolution

We concentrate here on decomposition of 2D objects into meaningfulparts of visual form, orvisual parts. It is a simple observation that convex parts of objects determine visual parts. However, the problem is that many significant visual parts are not convex, since a visual part may have concavities. We solve this problem by identifying convex parts at different stages of a proposed contour evolution method in which significant visual parts will become convex object parts at higher stages of the evolution. We obtain a novel rule for decomposition of 2D objects into visual parts, called the hierarchical convexity rule, which states that visual parts are enclosed by maximal convex (with respect to the object) boundary arcs at different stages of the contour evolution. This rule determines not only parts of boundary curves but directly the visual parts of objects. Moreover, the stages of the evolution hierarchy induce a hierarchical structure of the visual parts. The more advanced the stage of contour evolution, the more significant is the shape contribution of the obtained visual parts.     

The dynamics of IT boundary objects,information infrastructures,and organisational identities: the introduction of 3D modelling technologies into the architecture,engineering, and construction industry

In recent years, more companies engage in collaborative cross-organisational practices to achieve their business objectives. To cooperate effectively across boundaries requires organisations to overcome the tension between their distinct backgrounds and the need to create shared understandings with their partners for collaboration. This requires the creation of shared artefacts such as boundary objects. Whereas the past work on boundary objects has highlighted their role as translation devices, we examine them in relation to the information infrastructures within which they are embedded, and the identities of the organisations that use them. We propose a model that outlines the relationships among the three concepts and illustrate its dynamics by presenting two case studies that describe the introduction of three-dimensional modelling technologies into the architecture, engineering, and construction industry. Based on the case studies we suggest that boundary objects, in addition to facilitating cross-organisational communication, also help to form organisational identities. We further suggest the occurrence of a process whereby changes in boundary objects enable changes in information infrastructures and identities in one organisation. These changes, in turn, create the conditions for change in bordering organisations through shared boundary objects and boundary practices.     

Cold object identification in the Java virtual machine

Many Java applications instantiate objects within the Java heap that are persistent but seldom if ever referenced by the application. Examples include strings, such as error messages, and collections of value objects that are preloaded for fast access. This paper describes a stack‐based framework for detecting these ‘cold’ objects at runtime, with a view to marshaling and sequestering them in designated regions of the heap where they may be preferentially paged out to a backing store, thereby freeing physical memory pages for occupation by more active objects. Furthermore, we evaluate the correctness and efficiency of stack‐based approach with an access barrier. The experimental results from a series of SPECjvm2008 benchmarks are presented. Copyright © 2016 John Wiley & Sons, Ltd.     

全卷积语义分割与物体检测网络

目的 目前主流物体检测算法需要预先划定默认框,通过对默认框的筛选剔除得到物体框。为了保证足够的召回率,就必须要预设足够密集和多尺度的默认框,这就导致了图像中各个区域被重复检测,造成了极大的计算浪费。提出一种不需要划定默认框,实现完全端到端深度学习语义分割及物体检测的多任务深度学习模型（FCDN）,使得检测模型能够在保证精度的同时提高检测速度。方法 首先分析了被检测物体数量不可预知是目前主流物体检测算法需要预先划定默认框的原因,由于目前深度学习物体检测算法都是由图像分类模型拓展而来,被检测数量的无法预知导致无法设置检测模型的输出,为了保证召回率,必须要对足够密集和多尺度的默认框进行分类识别;物体检测任务需要物体的类别信息以实现对不同类物体的识别,也需要物体的边界信息以实现对各个物体的区分、定位;语义分割提取了丰富的物体类别信息,可以根据语义分割图识别物体的种类,同时采用语义分割的思想,设计模块提取图像中物体的边界关键点,结合语义分割图和边界关键点分布图,从而完成物体的识别和定位。结果 为了验证基于语义分割思想的物体检测方法的可行性,训练模型并在VOC（visual object classes）2007 test数据集上进行测试,与目前主流物体检测算法进行性能对比,结果表明,利用新模型可以同时实现语义分割和物体检测任务,在训练样本相同的条件下训练后,其物体检测精度优于经典的物体检测模型;在算法的运行速度上,相比于FCN,减少了8 ms,比较接近于YOLO（you only look once）等快速检测算法。结论 本文提出了一种新的物体检测思路,不再以图像分类为检测基础,不需要对预设的密集且多尺度的默认框进行分类识别;实验结果表明充分利用语义分割提取的丰富信息,根据语义分割图和边界关键点完成物体检测的方法是可行的,该方法避免了对图像的重复检测和计算浪费;同时通过减少语义分割预测的像素点数量来提高检测效率,并通过实验验证简化后的语义分割结果仍足够进行物体检测任务。     

Expectations and memory in link search

Strategies in searching a link from a web page can rely either on expectations of prototypical locations or on memories of earlier visits to the page. What is the nature of these expectations, how are locations of web objects remembered, and how do the expectations and memories control search? These questions were investigated in an experiment where, in the experimental group, nine experienced users searched links. To obtain information about expectations, users' eye movements were recorded. Memory for locations of web objects was tested immediately afterwards. In the control group, nine matched users had to guess the locations of web objects without seeing the page. Eye-movement data and control group's guesses both indicated a robust expectation of links residing on the left side of the page. Only the location of task-relevant web objects could be recollected, indicating that deep processing is required for memories to become consciously accessible. A comparison between the experimental group and the control group revealed that what was represented in memory was not an individual link's location but the approximate locations of link panels. We argue that practice-related decreases in reaction time were caused by semantic priming. Roles for the different types of memory in link search are discussed.     

改进的基于遗传算法的粗糙聚类方法

传统的聚类算法都是使用硬计算来对数据对象进行划分,然而现实中不同类之间对象通常没有明确的界限。粗糙集理论提供了一种处理边界对象不确定的方法。因此将粗糙理论与k-均值方法相结合。同时,传统的k-均值聚类方法必须事先给定聚类数k,但实际情况下k很难确定;另外虽然传统k-均值算法局部搜索能力强,但容易陷入局部最优。遗传算法能得到全局最优解,但收敛过快。鉴于此,提出了一种改进的基于遗传算法的的粗糙聚类方法。该算法能动态地生成k-均值聚类数,采用最大最小原则生成初始聚类中心,同时结合粗糙集理论的上近似和下近似处理边界对象。最后,用UCI的Iris数据集分别对算法进行实际验证。实验结果表明,该算法具有较高的正确率,综合性能更加稳定。     

灰度级信息的目标边界精确周长估算

目的 针对图像目标边界不连续或具有模糊性导致的目标周长无法精确估算这一问题,结合边界跟踪,提出一种基于灰度级信息的目标边界精确周长估算方法。方法 该方法利用目标边界的灰度级信息,同时结合边界跟踪得到的内外边界来估计目标图像的边界周长,从而提高边界周长估计的精确性和鲁棒性。为了获得目标物体真实周长,实验采用人工合成图像。结果 实验应用所提方法和3种传统周长估算方法分别计算合成目标对象的周长,并与真实周长比较。为了验证所提方法的有效性和鲁棒性,实验中对目标对象的边界进行不同程度的加厚模糊化;并在边界加入噪声,使边界不连续。当边界变得复杂时,本文所提方法的优势得到极大体现。结论 实验结果表明,在边界模糊和边界不连续的情况下,本文所提的算法具有更好的适应性和稳定性。