Comparing Small Programs for Equivalence: A Code Comprehension Task for Novice Programmers

Novice programmers should develop program comprehension skills as they learn to code so that they are able both to read and reason about code created by others, and to reflect on their code when writing, debugging or extending it. This work takes a little-explored perspective on the comprehension of small programs by asking students to decide if two code segments are equivalent or not in terms of carrying out the same computation. A variation of Euclid's algorithm, that extends the greatest common divisor calculation to more than two numbers, was chosen for this work, as it has an adequate level of complexity and its semantics are not obvious. Four program transformations of the original code were developed: two transformations were equivalent and two were not. 73.5% of students were able to identify correctly the four options and 75.5% provided good insights on the equivalent program flow to justify their choices. The overall task has a SOLO mean of 3.19, which indicates code equivalence is a suitable and approachable task to analyse program execution at novice level. In addition, the data analysis suggests that students' code-reading abilities beyond basic tracing may be generally underestimated and we should investigate how to bridge the potential gap between reasoning about program execution and extracting its purpose

Learning Transfer in Novice Programmers: A Preliminary Study

Learning transfer refers to the ability to correctly apply learned skills, knowledge and behaviors to new situations or contexts. This paper explores novice programmers' transfer through the analysis of two related coding tasks completed by CS1 students as part of their assessment. The first task was a take-home practical and the second task was a lab practical exam; both tasks requested the implementation of a C function with an integer parameter from which the digits are to be extracted and operated on. The solution set generated from each task by a cohort of 255 CS1 students has been explored and classified in order to determine the extent of transfer from the practice task to the later assessment task. This classification shows 36.5% of students consolidated or extended the acquired skills and 13% at least partly; 38%, on the other hand, failed to recall their previous valid strategy or to devise a better one, and were unsuccessful in the second task. On the positive side, 9% of students devised a different and improved strategy in the exam, indicating additional learning had occurred in between the two tasks. Peer review of key coding tasks could improve transfer by forcing weaker students to compare and evaluate different design strategies

Coupling Poisson and Jacobi structures on foliated manifolds

Let M be a differentiable manifold endowed with a foliation F. A Poisson structure P on M is F-coupling if the image of the annihilator of TF by the sharp-morphism defined by P is a normal bundle of the foliation F. This notion extends Sternberg's coupling symplectic form of a particle in a Yang-Mills field. In the present paper we extend Vorobiev's theory of coupling Poisson structures from fiber bundles to foliations and give simpler proofs of Vorobiev's existence and equivalence theorems of coupling Poisson structures on duals of kernels of transitive Lie algebroids over symplectic manifolds. Then we discuss the extension of the coupling condition to Jacobi structures on foliated manifolds.Comment: LateX, 38 page

Distance-hereditary embeddings of circulant graphs

©2003 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.In this paper we present a distance-hereditary decomposition of optimal chordal rings of 2k2 nodes into a set of rings of 2k nodes, where k is the diameter. All the rings belonging to this set have the same length and their diameter corresponds to the diameter of the chordal ring in which they are embedded. The members of this embedded set of rings are non-disjoint and preserve the minimal routing of the original circulant graph. Besides its practical consequences, our research allows the presentation of these optimal circulant graphs as a particular evolution of the traditional ring topology.Carmen Martinez, Beivide Beivide, Jaime Gutierrez, [Maria] Cruz Iz

An Implementation of K-NN Classification Algorithm for Detecting Impersonators in Online Examination Environment

The online examination platforms also known as computer-based testing (CBT) platforms for conducting mass-driven examinations over computer networks to eliminate certain issues such as delay in marking, misplacement of scripts, monitoring, etc., associated with the conventional Pen and Paper Type (PPT) of examination have also been bedeviled with the issue of impersonation commonly associated with the PPT system. The existing online examination platforms rely on passive mechanisms such as the CCTV system and the human invigilators for monitoring the examination halls against cheating and impersonation. The proposed model integrates some level of intelligence into existing online examination prototype by designing and developing an intelligent agent service that could assess students against impersonation threat in an online examination environment using the K-Nearest Neighbor (K-NN) machine learning classification technique considering the level of accuracy and response time in answering the questions. A total of 3,083 dataset was downloaded from an online repository; 80% (2,466) of the dataset was used for training the model, while 20% (617) dataset was used in testing the model to enable the model detect unseen data correctly. Results showed that the developed model has a 99.99% accuracy rate, precision, recall and f-score

Maternal and neonatal vitamin D status at birth in black South Africans

Background. Vitamin D deficiency (VDD) in pregnant women has been associated with adverse pregnancy and neonatal outcomes. 25-hydroxyvitamin D (25(OH)D) levels are affected by numerous factors, including vitamin D intake, skin pigmentation, latitude and season of the year; they therefore vary by race and country. Vitamin D status in pregnant women and their offspring in South Africa (SA) is not well established.Objectives. To assess vitamin D status by measuring serum 25(OH)D in pregnant black SA women and their offspring in Johannesburg (latitude 26°S) and to assess whether vitamin D status is affected by maternal HIV infection.Methods. We prospectively enrolled pregnant women and their healthy neonates, and measured 25(OH)D in maternal and cord blood at delivery. Pregnant women were stratified by their HIV status. Predictors of maternal and neonatal VDD (levels <30 nmol/L) were assessed using multiple logistic regression analysis.Results. A total of 291 pregnant women and their healthy neonates were enrolled over a 21-month period. Mean (standard deviation) maternal and cord blood 25(OH)D levels were 57.0 (29.7) and 41.9 (21.0) nmol/L and the prevalence of VDD was 15.9% and 32.8%, respectively. On average, concentrations of 25(OH)D in cord blood were ~80% of those in the mother. There was no association between cord 25(OH)D and gestational age, but levels were associated with birth weight (p<0.001). There were no differences in maternal or cord blood 25(OH)D levels between those HIV-infected or uninfected. The predictor of VDD in mothers was giving birth in winter (odds ratio (OR) 2.87, 95% confidence interval (CI) 1.47 - 5.61), and in neonates the predictors were maternal age (OR 16.5, 95% CI 1.82 - 149), being born in winter (OR 3.68, 95% CI 2.05 - 6.61), being born by caesarean section (OR 4.92, 95% CI 1.56 - 15.57) and being of low birth weight (OR 1.99, 95% CI 1.13 - 3.50).Conclusions. Among black SA women delivering in Johannesburg, about one in six mothers and one in three neonates have 25(OH)D levels indicative of VDD. Maternal HIV status appears not to affect levels of 25(OH)D in either the mother or her neonate. Research on the effects of VDD on the outcomes of pregnancy and the best methods to combat the high prevalence of VDD in women of childbearing age in the SA context is required

Analysis of network-on-chip topologies for cost-efficient chip multiprocessors

Abstract not availableMarta Ortín-Obón, Darío Suárez-Gracia, María Villarroya-Gaudó, Cruz Izu, Víctor Viñals-Yúfer

Evaluation of Interconnection Network Performance under Heavy Nonuniform Loads

Abstract. Many simulation-based performance studies of interconnection networks are carried out using synthetic workloads under the assumption of independent traffic sources. We show that this assumption, although may be useful for some traffic patterns, can lead to deceptive performance results for loads beyond saturation. Network throughput varies so much amongst the network nodes that average throughput does not reflect anymore network performance as a whole. We propose the utilization of burst synchronized traffic sources that better reflect the behavior of parallel applications at high loads. A performance study of a restrictive injection mechanism is used to illustrate the different results obtained using independent and non-independent traffic sources

Program Comprehension: Identifying Learning Trajectories for Novice Programmers

This working group asserts that Program Comprehension (PC) plays a critical part in the writing process. For example, this abstract is written from a basic draft that we have edited and revised until it clearly presents our idea. Similarly, a program is written in an incremental manner, with each step being tested, debugged and extended until the program achieves its goal. Novice programmers should develop their program comprehen- sion as they learn to code, so that they are able to read and reason about code while they are writing it. To foster such competencies our group has identified two main goals: (1) to collect and define learning activities that explicitly cover key components of program comprehension and (2) to define possible learning trajectories that will guide teachers using those learning activities in their CS0/CS1 or K-12 courses. [...