Understanding the performance of interactive applications

Many if not most computer systems are used by human users. The performance of such interactive systems ultimately affects those users. Thus, when measuring, understanding, and improving system performance, it makes sense to consider the human user's perspective. Essentially, the performance of interactive applications is determined by the perceptible lag in handling user requests. So, when characterizing the runtime of an interactive application we need a new approach that focuses on the perceptible lags rather than on overall and general performance characteristics. Such a new characterization approach should enable a new way to profile and improve the performance of interactive applications. Imagine a way that would seek out these perceptible lags and then investigate the causes of these lags. Performance analysts could simply optimize responsible parts of the software, thus eliminating perceptible lag for interactive applications. Unfortunately, existing profiling approaches either incur significant overhead that makes them impractical for an interactive scenario, or they lack the ability to provide insight into the causes of long latencies. An effective approach for interactive applications has to fulfill several requirements such as an accurate view of the causes of performance problems and insignificant perturbation of the interactive application. We propose a new profiling approach that helps developers to understand and improve the perceptible performance of interactive applications and satisfies the above needs

Automated GUI performance testing

A significant body of prior work has devised approaches for automating the functional testing of interactive applications. However, little work exists for automatically testing their performance. Performance testing imposes additional requirements upon GUI test automation tools: the tools have to be able to replay complex interactive sessions, and they have to avoid perturbing the application's performance. We study the feasibility of using five Java GUI capture and replay tools for GUI performance test automation. Besides confirming the severity of the previously known GUI element identification problem, we also describe a related problem, the temporal synchronization problem, which is of increasing importance for GUI applications that use timer-driven activity. We find that most of the tools we study have severe limitations when used for recording and replaying realistic sessions of real-world Java applications and that all of them suffer from the temporal synchronization problem. However, we find that the most reliable tool, Pounder, causes only limited perturbation and thus can be used to automate performance testing. Based on an investigation of Pounder's approach, we further improve its robustness and reduce its perturbation. Finally, we demonstrate in a set of case studies that the conclusions about perceptible performance drawn from manual tests still hold when using automated tests driven by Pounder. Besides the significance of our findings to GUI performance testing, the results are also relevant to capture and replay-based functional GUI test automation approache

Enhancing predictive accuracy of the cardiac risk score in open abdominal aortic surgery: the role of left ventricular wall motion abnormalities

BackgroundOpen abdominal aortic surgery carries many potential complications, with cardiac adverse events being the most significant concern. The Vascular Study Group Cardiac Risk Index (VSG-CRI) is a commonly used tool for predicting severe cardiac complications and guiding clinical decision-making. However, despite the potential prognostic significance of left ventricular wall motion abnormalities (LVWMAs) and reduced LV ejection fraction (LVEF) for adverse outcomes, the VSG-CRI model has not accounted for them. Hence, the main objective of this study was to analyze the added value of LV wall motion on the discriminatory power of the modified VSG-CRI in predicting major postoperative cardiac complications.MethodsA prospective study was conducted involving 271 patients who underwent elective abdominal aortic surgery between 2019 and 2021. VSG-CRI scores were calculated, and preoperative transthoracic echocardiography was conducted for all patients. Subsequently, a modified version of the VSG-CRI, accounting for reduced LVEF and LVWMAs, was developed and incorporated into the dataset. The postoperative incidence of the composite endpoint of major adverse cardiac events (MACEs), including myocardial infarction, clinically relevant arrhythmias treated with medicaments or by cardioversion, or congestive heart failure, was assessed at discharge from the index hospitalization, with adjudicators blinded to events. The predictive accuracy of both the original and modified VSG-CRI was assessed using C-Statistics.ResultsIn total, 61 patients (22.5%) experienced MACEs. Among these patients, a significantly higher proportion had preoperative LVWMAs compared to those without (62.3% vs. 32.9%, p < 0.001). Multivariable regression analysis revealed the VSG-CRI [odds ratio (OR) 1.46, 95% confidence interval (CI) 1.21–1.77; p < 0.001] and LVWMA (OR 2.76; 95% CI 1.46–5.23; p = 0.002) as independent predictors of MACEs. Additionally, the modified VSG-CRI model demonstrated superior predictability compared to the baseline VSG-CRI model, suggesting an improved predictive performance for anticipating MACEs following abdominal aortic surgery [area under the curve (AUC) 0.74; 95% CI 0.68–0.81 vs. AUC 0.70; 95% CI 0.63–0.77; respectively].ConclusionThe findings of this study suggest that incorporating preoperative echocardiography can enhance the predictive accuracy of the VSG-CRI for predicting MACEs after open abdominal aortic surgery. Before its implementation in clinical settings, external validation is necessary to confirm the generalizability of this newly developed predictive model across different populations

Accuracy of performance counter measurements

Many workload characterization studies depend on accurate measurements of the cost of executing a piece of code. Often these measurements are conducted using infrastructures to access hardware performance counters. Most modern processors provide such counters to count micro-architectural events such as retired instructions or clock cycles. These counters can be diffocult to configure, may not be programmable or readable from user-level code, and can not discriminate between events caused by different software threads. Various software infrastructures address this problem, providing access to per-thread counters from application code. This paper constitutes the first comparative study of the accuracy of three commonly used measurement infrastructures (perfctr, perfmon2, and PAPI) on three common processors (Pentium D, Core 2 Duo, and AMD ATHLON 64 X2). We find significant differences in accuracy of various usage patterns for the different infrastructures and processors. Based on these results we provide guidelines for finding the best measurement approach

SOCIAL STATUS OF THE SCHOOLCHILDREN FAMILIES

The paper gives an analyzes of the indicators of the social-economic situationof the schoolchildren families. The data are gathered by means of a questionnairefilled up by 262 families of the elementary schoolchildren in Niš as a results of thescientific project entitled "Health and Diseases of Schoolchildren". The research hasshown that the schoolchildren live in a nucleus family; regarding the parents'education, the dominant is high school level; the mothers are more often unemployedthan the fathers; the majority of the parents consider Yugoslav society as a "poor" oneand an important part of the family members are forced to turn to additional incomealso counting upon the help of relatives and friends. Regardless of the parents' level ofeducation, the majority of the examined do not go to the cinema, theater or any othercultural program. The majority of the parents think that the school programs have apositive effect upon appropriate childrens behavior

Counterpropagating optical vortices in photorefractive crystals

info:eu-repo/semantics/publishe