Emulating and evaluating hybrid memory for managed languages on NUMA hardware

Non-volatile memory (NVM) has the potential to become a mainstream memory technology and challenge DRAM. Researchers evaluating the speed, endurance, and abstractions of hybrid memories with DRAM and NVM typically use simulation, making it easy to evaluate the impact of different hardware technologies and parameters. Simulation is, however, extremely slow, limiting the applications and datasets in the evaluation. Simulation also precludes critical workloads, especially those written in managed languages such as Java and C#. Good methodology embraces a variety of techniques for evaluating new ideas, expanding the experimental scope, and uncovering new insights. This paper introduces a platform to emulate hybrid memory for managed languages using commodity NUMA servers. Emulation complements simulation but offers richer software experimentation. We use a thread-local socket to emulate DRAM and a remote socket to emulate NVM. We use standard C library routines to allocate heap memory on the DRAM and NVM sockets for use with explicit memory management or garbage collection. We evaluate the emulator using various configurations of write-rationing garbage collectors that improve NVM lifetimes by limiting writes to NVM, using 15 applications and various datasets and workload configurations. We show emulation and simulation confirm each other's trends in terms of writes to NVM for different software configurations, increasing our confidence in predicting future system effects. Emulation brings novel insights, such as the non-linear effects of multi-programmed workloads on NVM writes, and that Java applications write significantly more than their C++ equivalents. We make our software infrastructure publicly available to advance the evaluation of novel memory management schemes on hybrid memories

Dibbling Machine for ArborGen

ArborGen’s nursery, located in Tokoroa, supplies approximately 6 million seedlings per year to the forestry industry (figure 1). The vast majority of seedlings are Pine Radiata but they also supply Plug Plus and Douglas fir. In peak season, they plant up to 120,000 seedlings per day that each require a straight vertical hole of certain depth and spacing, (depending on seedling type). For example the most common seedling, Radiata pine, requires holes of approximately 10mm diameter x 40mm deep (figure 2). The process of making the holes is called dibbling. Dibbling has become a major problem that has resulted in an estimated 400,000 rejections per year. An investigation of the dibbling process identified the following problems: • Existing human dibbling methods too slow and unreliable • Machine methods produce low quality holes that lead to mis-planted seedlings • Lack of flexibility of existing, methods with regard to hole size and spacing • Current methods compact the soil hindering root growth so hole drilling is preferred • Currently, dibbling must be done on the day of planting due to the deterioration of the bed surfac

Incremental copying garbage collection for WAM-based Prolog systems

The design and implementation of an incremental copying heap garbage collector for WAM-based Prolog systems is presented. Its heap layout consists of a number of equal-sized blocks. Other changes to the standard WAM allow these blocks to be garbage collected independently. The independent collection of heap blocks forms the basis of an incremental collecting algorithm which employs copying without marking (contrary to the more frequently used mark&copy or mark&slide algorithms in the context of Prolog). Compared to standard semi-space copying collectors, this approach to heap garbage collection lowers in many cases the memory usage and reduces pause times. The algorithm also allows for a wide variety of garbage collection policies including generational ones. The algorithm is implemented and evaluated in the context of hProlog.Comment: 33 pages, 22 figures, 5 tables. To appear in Theory and Practice of Logic Programming (TPLP

Reviews

John Bowden and Ference Marton, The University of Learning: Beyond Quality and Competence in Higher Education, London: Kogan Page, 1998. ISBN: 0–7494–2292–0. Hardback, x310 pages, £35.00

Perceptions of gender in early years

This article presents an exploration of a group of Early Years Practitioners’ (EYPs) perceptions of gender that may provide some insight into the growing divide between boys’ and girls’ educational performance [Burusic, J., T. Babarovic, and M. Seric. 2012. “Differences in Elementary School Achievement between Girls and Boys: Does the Teacher’s Gender Play a Role?” European Journal of Psychology of Education 27 (4): 523–538]. I argue that the current media and educational interest in the gendered brain [Sax, L. 2005. Why Gender Matters: What Parents and Teachers Need to Know About the Emerging Science of Sex Differences. New York: Broadway Books] and the influences that surround the child [Eckert, P., and G. S. McConnell. 2013. Language and Gender. 2nd ed. Cambridge: Cambridge University Press], can result in children acquiring social expectations and attitudes to learning that are different for both sexes. The frequent dimorphic treatment of boys and girls is often based on assumed biological differences [Baron-Cohen, S., S. Lutchmaya, and R. Knickmeyer. 2004. Prenatal Testosterone in Mind: Amniotic Fluids Studies. Massachusetts Institute of Technology] that suggest that the sexes learn differently. This can result in the approaches to the care and education of children being established on their sex categories rather than their individual needs. My focus here is to explore practitioners’ expectations and understanding of children’s behaviour and learning in the nursery environment. The study is premised on the belief that practitioners’ perceptions of gender could, as argued by [Eliot, L. 2009. Pink Brain, Blue Brain: How Small Differences Grow into Troublesome Gaps – And what we can do About It. New York: Houghton Mifflin Harcourt Publishing Company], result in self-fulfilling prophecies being (re)produced and (re)created. The deployment of stereotypical assumptions and practices could, I suggest, limit children’s opportunities. The data used here are drawn from my doctoral study of the nature of gender as was understood by eight EYPs who took part in five discussion group sessions. An interpretative paradigm was adopted, where the EYPs’ discussed their experiences and understanding of gender from their practice. Following [Holloway, I., and S. Wheeler. 2013. Qualitative Research in Nursing and Healthcare. 3rd ed. West Sussex: John Wiley & Sons Limited], the study explored experiences and perceptions in order to illuminate meaning and understanding. The findings indicated that there is a belief amongst the group of practitioners with whom I worked that gender is either innate or learned and that EYPs play no role in its development. The tentative conclusions suggest that changes to the education and training of EYPs are required in order to raise awareness of gender issues in nurseries. I suggest that there is a need to place gender back on the education and training agenda for EYP in order to support changes to practice that could, in turn, provide children with more equitable teaching and learning experiences

Beltway: Getting Around Garbage Collection Gridlock

We present the design and implementation of a new garbage collection framework that significantly generalizes existing copying collectors. The Beltway framework exploits and separates object age and incrementality. It groups objects in one or more increments on queues called belts, collects belts independently, and collects increments on a belt in first-in-first-out order. We show that Beltway configurations, selected by command line options, act and perform the same as semi-space, generational, and older-first collectors, and encompass all previous copying collectors of which we are aware. The increasing reliance on garbage collected languages such as Java requires that the collector perform well. We show that the generality of Beltway enables us to design and implement new collectors that are robust to variations in heap size and improve total execution time over the best generational copying collectors of which we are aware by up to 40%, and on average by 5 to 10%, for small to moderate heap sizes. New garbage collection algorithms are rare, and yet we define not just one, but a new family of collectors that subsumes previous work. This generality enables us to explore a larger design space and build better collectors

Developing Virtual Field Trips for Agriculture

Field trips play an important role in teaching and learning, from stimulating students’ motivations to allowing students to connect in-class concepts and the real world. Including field trips within an agricultural curriculum is essential as concepts are highly interdisciplinary, and knowledge application to a range of production systems and environments is critical. Despite their importance, many factors, such as high enrolments, present challenges to its successful integration. Virtual field trips (VFT) allow universities to leverage the affordances of technology to mitigate some of the associated challenges while maintaining quality course delivery. In this pilot study, an experiential learning activity was designed around a VFT application, and the student experience and outcome were investigated. The student experience measures indicated satisfaction with multimedia elements, although it is noted that improvements to the user interface would enhance the experience. Students had positive reflections on the learning experience, including an increased interest in the field of study but did not see VFTs as replacing actual field trips. Paired t-tests showed students’ attainment of learning outcomes. This pilot implementation provides an activity design for other courses with similar challenges and highlights the value of VFTs to the curriculum for undergraduate agricultural courses

Using software to tell a trustworthy, convincing and useful story

This paper discusses the potential of specialist software to develop category construction in qualitative data analysis and considers how the uses of software may best be reported to substantiate researchers’ claims. Examples are examined from two recent projects: a consultation of pupil’s perceptions of assessment for learning strategies and an exploratory enquiry on employing music as a tool for inclusion in post-conflict Northern Ireland. From this experience, a number of suggestions on how to support the researchers’ claims are made and a model of knowledge generation is put forward. Some of the practical implications outlined are discussed within the context of social research, but it is acknowledged that the suggestions also apply to any field in which knowledge is generated from qualitative data