Miguel Revilla

Correlations between Internal Software Metrics and Software Dependability in a Large Population of Small C/C++ Programs

Software metrics are often supposed to give valuable information for the development of software. In this paper we focus on several common internal metrics: Lines of Code, number of comments, Halstead Volume and McCabes Cyclomatic Complexity. We try to find relations between these internal software metrics and metrics of software dependability: Probability of Failure on Demand and number of defects. The research is done using 59 specifications from a programming competition---The Online Judge--on the internet. Each specification provides us between 111 and 11,495programs for our analysis; the total number of programs used is 71,917. We excluded those programs that consist of a look-up table. The results for the Online Judge programs are: (1) there is a very strong correlation between Lines of Code and Hal- stead Volume; (2) there is an even stronger correlation between Lines of Code and McCabes Cyclomatic Complexity; (3) none of the internal software metrics makes it possible to discern correct programs from incorrect ones; (4) given a specification, there is no correlation between any of the internal software metrics and the software dependability metrics.

The Effectiveness of Software Diversity in a Large Population of Programs

In this paper, we first present an exploratory analysis of the aspects of multiple-version software diversity using 36,123, programs written to the same specification. We do so within the framework of the theories of Eckhardt and Lee and Littlewood and Miller. We analyse programming faults made, explore failure regions and difficulty functions, show how effective 1-out-of-2 diversity is and how language diversity increases this effectiveness. The second part of the paper generalizes the findings about 1-out-of-2 diversity, and its special case language diversity by performing statistical analyses of 89,402 programs written to 60 specifications. Most observations in the exploratory analysis are confirmed; however, although the benefit of language diversity can be observed, its effectiveness appears to be low.

Heart Rate Biorhythm Changes during the First Three Months of Life

UNLABELLED Heart rate (HR) was recorded in healthy full-term newborns aged 1-90 days. The aim of this study was to study the existence of circadian and/or ultradian rhythms in HR to determine maturity. HR was recorded during 24 h, at 30-min intervals, at different postnatal ages. Six-groups were investigated: day 1 (group 1); day 7 (group 7); day 15 (group 15); day 30 (group 30); day 60 (group 60), and day 90 (group 90). The chronograms for HR showed peaks and nadirs along the 24-hour periods, and the cosinor analysis proved the existence of 3-hour ultradian rhythm in groups 1, 7 and 30, and a 12-hour ultradian rhythm in group 90 (p < 0.01 in all cases). The same type of analysis confirmed the existence of a circadian rhythm in group 30. Similar results were obtained for groups 60 and 90 (p < 0.05). IN CONCLUSION at birth, newborns have an endogenous ultradian period of 3 h. A circadian rhythm appears within 15-30 days of postnatal life.

The effectiveness of choice of programming language as a diversity seeking decision

Software reliability can be increased by using a diverse pair of programs (1-out-of-2 system), both written to the same specification. The improvement of the reliability of the pair versus the reliability of a single version depends on the degree of diversity of the programs. The choice of programming language has been suggested as an example of a diversity seeking decision. However, little is known about the validity of this recommendation. This paper assesses the effect of language on program diversity. We compare the effects of the choice of programming language as a diversity seeking decision by using programs written to three different specifications in the “UVa Online Judge”. Thousands of programs have been written to these specifications; this makes it possible to provide statistical evidence. The experiment shows that when the average probability of failure on demand (pfd) of the programs is high, the programs fail almost independently, and the choice of programming language does not make any difference. When the average pfd of the pools gets lower, the programs start to fail dependently, and the pfd of the pairs deviates more and more from the product of the pfds of the individual programs. Also, we observe that the diverse C/Pascal or C++/Pascal pairs perform as good as or better than the other possible pairs.

COIN EXCHANGE ALGORITHMS AND TORIC PROJECTIVE CURVES

We show how the availability of the greedy algorithm for finding the minimun number of coins in the money exchange problem is related to the Cohen–Macaulay property of the toric projective curves given by the coin values. *Partially supported by junta de Castilla y León VA 27/98 and DGES PB97-0370.

On the effectiveness of run-time checks

Run-time checks are often assumed to be a cost-effective way of improving the dependability of software components, by checking required properties of their outputs and flagging an output as incorrect if it fails the check. However, evaluating how effective they are going to be in a future application is difficult, since the effectiveness of a check depends on the unknown faults of the program to which it is applied. A programming contest, providing thousands of programs written to the same specifications, gives us the opportunity to systematically test run-time checks to observe statistics of their effects on actual programs. In these examples, run-time checks turn out to be most effective for unreliable programs. For more reliable programs, the benefit is relatively low as compared to the gain that can be achieved by other (more expensive) measures, most notably multiple-version diversity.

Circadian changes of heart rate in West syndrome.

Patterns of circadian and ultradian rhythms in the heart rate(HR) are described in a full-term baby with birth asphyxia and convulsions.A 24h HR recording was carried out at the age of 1, 15, 56, 289, and 295 days;West syndrome diagnosis was made when the patient was 3 months old. The HRshowed no circadian rhythm in the follow-up, whereas it is known that thecircadian rhythm appears in healthy infants at the age of 1 month and remainsthereafter. This observation may be an indirect indicator of the interferenceof West syndrome with centers of neurological maturity. (ChronobiologyInternational, 17(4), 591–595, 2000)

Having Your Own Automatic Judge: EEWS

In this poster we present the way to install any personal computer under linux, a shareware software developed by the University of Valladolid, into the frame of the European project EduJudge. It will facilitate the knowing and use of automated judging, probably the most powerful method to develop the programming skills of the students.