Tuning compilations by multi-objective optimization: Application to Apache web server

Modern compilers present a great and ever increasing number of options which can modify the features and behavior of a compiled program. Many of these options are often wasted due to the required comprehensive knowledge about both the underlying architecture and the internal processes of the compiler. In this context, it is usual, not having a single design goal but a more complex set of objectives. In addition, the dependencies between different goals are difficult to be a priori inferred. This paper proposes a strategy for tuning the compilation of any given application. This is accomplished by using an automatic variation of the compilation options by means of multi-objective optimization and evolutionary computation commanded by the NSGA-II algorithm. This allows finding compilation options that simultaneously optimize different objectives. The advantages of our proposal are illustrated by means of a case study based on the well-known Apache web server. Our strategy has demonstrated an ability to find improvements up to 7.5% and up to 27% in context switches and L2 cache misses, respectively, and also discovers the most important bottlenecks involved in the application performance.

Way of scoring by Spanish First Division volleyball teams in relation to winning/losing, home/away, final classification, and type of confrontation

The aim of this study was to assess the way volleyball teams score with regard to: whether or not they won the game, whether they were the home or away team, the level of the opposing teams, and the type of confrontation. The sample was composed of 118,083 plays from 794 men’s volleyball matches and 125,751 plays from 719 women’s matches of Spain’s first division clubs (from the 2002-2003 season to the 2006-2007 season). The variables studied were: the way points were obtained in each play, being the home or away team, the level of the teams, the result of the match, and the type of confrontation between the teams with regard to their level. The results demonstrate that for both men’s and women’s teams, the majority of the points were obtained in attack and by opponent errors. Differences were found with regard to the way points were obtained when winning or losing the match was taken into account as well as when considering the level of the teams. This paper discusses the differences found with regard to whether the team is home or visiting and the type of confrontation.

Performance of TerraSAR-X for urban subsidence monitoring: Murcia case study

This paper presents an analysis of the performance of TerraSAR-X for subsidence monitoring in urban areas. The city of Murcia has been selected as a test-site due to its high deformation rate and the set of extensometers deployed along the city that provide validation data. The obtained results have been compared with those obtained from ERS/ENVISAT data belonging to the same period and validated with the in-situ measurements.

Third-party complaints and firm performance: an application in Spanish banking

This article focuses on the impact of third-party complaints on firm performance. We propose two research hypotheses, which are developed from the literature of dissatisfaction, emotions, and economics. The methodology is based on an event study to estimate variation in firm share returns in the stock market due to the publication of the Annual Complaints Service Report by the Bank of Spain; as well as a regression analysis to examine the impact of the number of complaints per branch on the variation obtained. The empirical focus is on a sample of eleven banks to which complaints were made and which were quoted on the Spanish Stock Exchange between 1992 and 2001. The results show a negative impact of the publication of these annual complaint reports on the share returns of the banks concerned. Additionally, these returns have a negative relationship with the number of complaints per branch.