DIPLOMA: Consistent and coherent shared memory over mobile phones

No doubt, the usages of mobile agent and mobile phone technologies are rapidly increased. The mobile agent has a promising room in the industry area. Unfortunately, this technology faces some security problems from mobile agents and hosts sides. Two of the fundamental issues in designing protocols for message passing between mobile agents (MAs) are tracking the migration of the target agent and forwarding messages to it. Even with an ideal fault-free network-transport mechanism, messages can be dropped during MA migration. Therefore, in order to provide reliable message delivery, protocols need to overcome message loss caused by asynchronous operations of agent migration and message forwarding. As mobile devices and third generation mobile networks have become a reality, location based services are thought to be a major growing area. Mobile devices are given context sensitiveness so that they can be aware of the users/services surrounding physical environment and state. In this paper we propose message forwarding approaches, namely push and pull, are explored to design adaptive and reliable message delivery protocols.Also location aware services scheme by using an agency, which helps in discovering the required services for the mobile users. The agency consists of five agents: Manager Agent (MA), Route Monitoring Agent (RMA), Local Service Management Agent (LSMA), Global Service Management Agent (GSMA) and Area Monitoring Agent (AMA).

The currently dominant programming models to write software for multicore processors use threads that run over shared memory. However, as the core count increases, cache coherency protocols get very complex and ineffective, and maintaining a shared memory abstraction becomes expensive and impractical. Moreover, writing multithreaded programs is notoriously difficult, as the programmer needs to reason about all the possible thread interleavings and interactions, including the myriad of implicit, non-obvious, and often unpredictable thread interactions through shared memory. Overall, as processors get more cores and parallel software becomes mainstream, the shared memory model reaches its limits regarding ease of programming and efficiency.This position paper presents two ideas aiming to solve the problem. First, we restrict the way the programmer expresses parallelism: The program is a collection of possibly recursive tasks, where each task is atomic and cannot communicate with any other task during its execution. Second, we relax the requirement for coherent shared memory: Each task defines its memory footprint, and is guaranteed to have exclusive access to that memory during its execution. Using this model, we can then define a runtime system that transparently performs the data transfers required among cores without cache coherency, and also produces a deterministic execution of the program, provably equivalent to its sequential elision.

Current credit card authorization was developed on single-threaded model whereby authentication process takes longer time to respond due to sequential process of card's risk management profile and its limitation of handling huge number of simultaneous transactions at single point of time. As a result, the performance of the authorization system was affected during peak hours. This study presented an architectural framework and prototype of credit card authorization system using multi-threading and shared memory pool techniques in order to improve the response time during authorization process. Through multi-threading technique, each worker thread will be assigned with several child threads to perform online fraud validation concurrently, depending on numbers of cryptographic elements presented in transaction message. Meanwhile, the worker threads itself performed card restriction validation based on the information stored in card's shared memory pool. This approach was implemented to reduce the idle time while waiting for slow cryptographic operation in each I/O operations that is performed through external device and to accelerate the authorization process through memory operation instead of accessing similar information from database. The implementation of these techniques, were then measured in terms of response time. The results showed that the performance of multi-threaded authentication engine was almost double of single-threaded authentication engine and the number of credit card authorization that can be processed using shared memory was ten percent higher than the number of credit card authorization that can be processed using database at single point of time.

Parallel programming has been widely used in many scientific and technical areas to solve large problems. While general-purpose processors have rich infrastructure to support parallel programming on shared memory, such as coherent caches and synchronization libraries, parallel programming infrastructure for FPGAs is limited. Thus, development of FPGA-based parallel algorithms remains difficult. In this work, we seek to simplify parallel programming on FPGAs. We provide a set of easy-to-use declarative primitives to maintain coherency and consistency of accesses to shared memory resources. We propose a shared-memory service that automatically manages coherent caches on multiple FPGAs. Experimental results of a 2-dimensional heat transfer equation show that the shared memory service with our distributed coherent caches outperforms a centralized cache by 2.6x. To handle synchronization, we provide new lock and barrier primitives that leverage native FPGA communication capabilities and outperform traditional through-memory primitives by 1.8x.

Simulation Training to Improve Competency and Confidence at the University of California San Diego, Women and Infants Services

The effects of radiofrequency exposure on cognition: A systematic review and meta-analysis of human observational studies

Goal: Load balancing policies often map workloads on virtual machines, and are being sought to achieve their goals by creating an almost equal level of workload on any virtual machine. In this research, a hybrid load balancing algorithm is proposed with the aim of reducing response time and processing time.
 Design / Methodology / Approach: The proposed algorithm performs load balancing using a table including the status indicators of virtual machines and the task list allocated to each virtual machine. The evaluation results of response time and processing time in data centers from four algorithms, ESCE, Throttled, Round Robin and the proposed algorithm is done.
 Results: The overall response time and data processing time in the proposed algorithm data center are shorter than other algorithms and improve the response time and data processing time in the data center. The results of the overall response time for all algorithms show that the response time of the proposed algorithm is 12.28%, compared to the Round Robin algorithm, 9.1% compared to the Throttled algorithm, and 4.86% of the ESCE algorithm.
 Limitations of the investigation: Due to time and technical limitations, load balancing has not been achieved with more goals, such as lowering costs and increasing productivity.
 Practical implications: The implementation of a hybrid load factor policy can improve the response time and processing time. The use of load balancing will cause the traffic load between virtual machines to be properly distributed and prevent bottlenecks. This will be effective in increasing customer responsiveness. And finally, improving response time increases the satisfaction of cloud users and increases the productivity of computing resources.
 Originality/Value: This research can be effective in optimizing the existing algorithms and will take a step towards further research in this regard.

Multicore chips are expected to rely on coherent shared memory. Albeit the coherence hardware can scale gracefully, the protocol state space grows exponentially with core count. That is why design verification requires directed test generation (DTG) for dynamic coverage control under the tight time constraints resulting from slow simulation and short verification budgets. Next generation EDA tools are expected to exploit Machine Learning for reaching high coverage in less time. We propose a technique that addresses DTG as a decision process and tries to find a decision-making policy for maximizing the cumulative coverage, as a result of successive actions taken by an agent. Instead of simply relying on learning, our technique builds upon the legacy from constrained random test generation (RTG). It casts DTG as coverage-driven RTG, and it explores distinct RTG engines subject to progressively tighter constraints. We compared three Reinforcement Learning generators with a state-of-the-art generator based on Genetic Programming. The experimental results show that the proper enforcement of constraints is more efficient for guiding learning towards higher coverage than simply letting the generator learn how to select the most promising memory events for increasing coverage. For a 3-level MESI 32-core design, the proposed approach led to the highest observed coverage (95.81%), and it was 2.4 times faster than the baseline generator to reach the latter’s maximal coverage.

This paper evaluates the tradeoffs involved in the design of the software-extended memory system of Alewife, a multiprocessor architecture that implements coherent shared memory through a combination of hardware and software mechanisms. For each block of memory, Alewife implements between zero and five coherence directory pointers in hardware and allows software to handle requests when the pointers are exhausted. The software includes a flexible coherence interface that facilitates protocol software implementation. This interface is indispensable for conducting experiments and has proven important for implementing enhancements to the basic system.Simulations of a number of applications running on a complete system (with up to 256 processors) demonstrate that the hybrid architecture with five pointers achieves between 71% and 100% of full-map directory performance at a constant cost per processing element. Our experience in designing the software protocol interfaces and experiments with a variety of system configurations lead to a detailed understanding of the interaction of the hardware and software components of the system. The results show that a small amount of shared memory hardware provides adequate performance: One-pointer systems reach between 42% and 100% of full-map performance on our parallel benchmarks. A software-only directory architecture with no hardware pointers has lower performance but minimal cost.

Due to modern technology trends such as decreasing feature sizes and lower voltage levels, fault tolerance is becoming increasingly important in computing systems. Shared memory in modern multiprocessor systems is supported by cache coherence mechanisms. The correctness of cache coherence of the system is crucial for the data integrity. This work proposes an error detection scheme for snooping-based cache coherence protocols. For the widely used MESI coherence protocol, the proposed method does not introduce any performance overhead. Only a limited amount of additional hardware is required. Existing systems can be easily extended to support the proposed technique. Almost all single faults that are able to affect data integrity in the system are covered, with the exception of a few very rare cases. Experimental results involving fault injection do not encounter any undetected faults leading to corrupted application output.

In a preliminary study a film was designed to shorten the time necessary to perceive the direction of a tennis return. Ss showed significant improvement in response time. Since the training was conducted with individual Ss, the use of the training film in a classroom situation was examined. Results indicated significant improvement in response time; thus the training device appears to be useful in classroom situations.

The ambulance service in Victoria, Australia implemented a revised clinical response model (CRM) in 2016 which was designed to increase the diversion of low-acuity Triple Zero (000) calls to secondary telephone triage and reduce emergency ambulance dispatches. The present study evaluates the influence of the revised CRM on emergency ambulance response times and ED presentations. A retrospective study of emergency calls for ambulance between 1 January 2015 and 31 December 2018. Ambulance data were linked with ED presentations occurring up to 48 h after contact. Interrupted time series analyses were used to evaluate the impact of the revised CRM. A total of 2 365 529 calls were included. The proportion allocated a Code 1 (time-critical, lights/sirens) dispatch decreased from 56.6 to 41.0% after implementation of the revised CRM. The proportion of calls not receiving an emergency ambulance increased from 10.4 to 19.6%. Interrupted time series analyses demonstrated an improvement in Code 1 cases attended within 15 min (Key Performance Indicator). However, for patients with out-of-hospital cardiac arrest or requiring lights and sirens transport to hospital, there was no improvement in response time performance. By the end of the study period, there was also no difference in the proportion of callers presenting to ED when compared with the estimated proportion assuming the revised CRM had not been implemented. The revised CRM was associated with improved Code 1 response time performance. However, there was no improvement in response times for high acuity patients, and no change in the proportion of callers presenting to ED.

Understanding the Design of Mobile Social Networking

<p dir="ltr"><b>Background</b></p><p dir="ltr">A credible public health survey or surveillance program is judged by its ability to measure intended outcomes accurately and cost effectively. However, in the pursuit of operational efficiency, such programs risk introducing bias in their estimates. This thesis examines several key potential sources of bias in public health surveys, focusing on three main domains: the characteristics and selection of respondents paying attention to the hard-to-reach late respondents, the use of mobile phone technology for data collection, and the adaptation of standardized measurement tools-specifically the Framingham Risk Score (FRS) and the Finnish Diabetes Risk Score (FINDRISC). The tools are internationally recognized for estimating the 10-year risk of cardiovascular disease and type 2 diabetes, respectively. By exploring these domains, this work aims to highlight critical methodological considerations that survey designers and implementers must consider minimizing measurement bias and enhance data validity.</p><p dir="ltr"><b>Methods</b></p><p dir="ltr">The study was conducted within the Rakai Community Cohort Study (RCCS), a long-standing surveillance program in south-central Uganda. Covering 34 diverse communities, the RCCS focuses on HIV and other health priorities. In each round, 70-80% respond on time, while late respondents require extra effort from the researchers to track them. Study I examined whether late respondents differ from early ones and if their (late respondents) exclusion could bias results. We conducted descriptive analyses and compared these groups using Chi-square tests. Multivariable logistic regression was used to adjust for confounders, reporting adjusted odds ratios (AORs) with 95% confidence intervals. We also modelled interactions with age to estimate marginal predictive means (MPMs), illustrating how the likelihood of late response varies across age groups. The results are reported in constituent manuscript I. The use of mobile phones for population-based surveys is an ongoing global discussion, particularly in resource-limited settings. We leveraged RCCS Rounds 19 and 18 data, collected around the COVID-19 period, and data from a concurrent mobile phone-based surveillance in the same population to compare participation rates by survey modality (face-to-face vs. mobile phone surveys), we assessed phone access, and characterized the differences between respondents reached and missed by each method. The primary independent variable was interviewing modality, with adjustments made for sex, age, community type, HIV status, and other covariates. Robust standard errors accounted for clustering at the individual level. We also examined longitudinal trends in mobile phone ownership, including the frequency of mobile phone number change, the time to change of numbers and multiple SIM ownership. Phone number change was defined as the complete replacement of previously recorded numbers between survey rounds, excluding partial changes. Rates and associated factors were estimated using Poisson regression with generalized estimating equations (GEE), while time to number change was assessed using the Andersen-Gill Cox model to account for repeated measurements. The results are reported in studies II (face-to-face vs mobile phone surveys) and study III (mobile phone ownership, numbers change and time to change analyses) We conducted qualitative exit interviews to assess participants' experiences with the FRS and FINDRISC risk score tools. Interviews were held on the same day, immediately after participants completed the questionnaires and measurement procedures. The analysis, based on 15 interviews, followed an iterative approach. Thematic coding was used to identify and summarize key themes that we report in constituent study IV.</p><p dir="ltr"><b>Results</b></p><p dir="ltr">Overall, 68,263 participants were included in the late respondent analysis. Men were 22% times more likely to be late respondents than women (23% vs. 19%, respectively). This was true for younger participants 15-19 years old relative to 40+years old participants. Compared to the unemployed, participants engaged in formal employment followed by those engaged in fishing were more likely to be late respondents (28% and 27% respectively). When comparing response times between people living with HIV and those who are HIV-negative, no significant difference was observed (AOR=1.06; 95% C.I .: 0.99, 1.13). In women, HIV status had no effect on the marginal predictive mean (MPM) of being late, which declined with age in both groups. Among young men, MPM of being a late respondent was significantly higher in those with HIV but decreased with age. Conversely, in HIV- negative men, the MPM increased with age. In study II, we observed 90% access to mobile phones, with lower access among older people, and people living with HIV. When including only individuals who participated in the previous RCCS survey round, participation in the face-to-face survey (82%) was higher than participation in the mobile phone survey (75%, p < . 001). Survey participation was higher among people living with HIV compared to HIV-negative individuals (84% vs 82%, p< . 001) in the face-to-face survey. In study III we assessed mobile phone ownership. A total of 97,034 participants were included in this analysis. Overall, 61.8% reported owning a phone. Mobile phone ownership increased by 33% over the study period, from 51% in 2010 to 68% in 2020 (p<0.001). Ownership was higher among men. There was no difference in phone ownership by HIV status (adjPR=1.01, 95% CI 0.97-1.05). About 75% of participants who reported more than one sexual partner in the past 12 months owned a mobile phone, compared to 58% who reported zero or one partner in the same period (p<0.001). Phone number change is as high as 15-19/100 person years and consistent across the ten years of observation.</p><p dir="ltr">When we examined participants' experiences with FRS and FINDRISC, we found that overall, the tools were clear and acceptable in this setting. Participants were comfortable with having their weights, waists, heights and other measurements taken if it was by a health worker. There were a few challenges with interpretation and measurement of physical activity, and dietary practice questions given the seasonal variations in their availability in the community.</p><p dir="ltr"><b>Conclusion</b></p><p dir="ltr">The studies reveal that late respondents are different and cannot be ignored therefore means to speed up their participation should be devised. The use of mobile phones is feasible, there are some differentials in those who are missed by phone surveys (especially men). Meanwhile, mobile phone ownership is on a rapid rise across both sexes with men slightly higher and women rapidly catching up (by 2020). However, the rate of phone number change is quite high and this needs to be considered. The FRS and the FINDRISC scores are generally acceptable, however, some adaptation to match local practices and the seasonal dietary practices need to be addressed during survey planning, data analysis and interpretation.</p><p dir="ltr">Key terms: Late respondents, Mobile phones, Bias, Framingham, Finnish Diabetes Risk Score.</p><h3>List of scientific papers</h3><p dir="ltr">Paper I: Characterizing late respondents in the Rakai Community Cohort Study, 2012-2020, Uganda<b>. </b><b>Robert Ssekubugu</b>, Zangin Zeebari, Hadija Nakawooya, Ping Teresa Yeh, Anthony Ndyanabo, Fredrick Edward Makumbi, Anna Mia Ekström, Grace Nalwoga Kigozi, Eli. M Binder, Kate Grabowski, David Serwadda, Victor Ssempijja, Larry W Chang, Godfrey Kigozi, Helena Nordenstedt [Manuscript]</p><p dir="ltr">Paper II: Use of Mobile Phone to collect data on COVID-19; phone access and participation rates in Rakai, Uganda. <b>Robert Ssekubugu</b>, Anthony Ndyanabo, Fredrick Edward Makumbi, Anna Mia Ekström, Laura Bere, Grace Nalwoga Kigozi, Hadijja Nakawooya, Joseph Ssekasanvu, Maria J. Wawer, Fred Nalugoda, Nelson Sewankambo, Victor Ssempijja, Betty Nantume, David Serwadda, Godfrey Kigozi, Ronald H. Gray, Larry W Chang, M. Kate Grabowski, Helena Nordenstedt & Joseph Kagaayi Glob Health Action. 2024 Dec 31;17(1):2419160. <a href="https://doi.org/10.1080/16549716.2024.2419160" rel="noreferrer" target="_blank">https://doi.org/10.1080/16549716.2024.2419160</a></p><p dir="ltr">Paper III: Mobile phone ownership, number change, time to change and the implications to public health services delivery in Uganda, 2010-2020<b>. </b><b>Robert Ssekubugu</b>, Ping Teresa Yeh, Hadija Nakawooya, Victor Ssempijja, Godfrey Kigozi, Joseph Kagaayi, Fred Nalugoda, Anna Mia Ekström, Betty Nantume, David Serwadda, Philip Kreniske, Zangin Zeebari, Michelle A. Moffa, Larry W. Chang, Kate M. Grabowski, Fredrick Makumbi and Helena Nordenstedt [Manuscript]</p><p dir="ltr">Paper IV: Cardiovascular (Framingham) and type II diabetes (Finnish Diabetes) risk scores: a qualitative study of local knowledge of diet, physical activity and body measurements in rural Rakai, Uganda<b>. </b><b>Robert Ssekubugu</b>, Fredrick Makumbi1, Rocio Enriquez, Susanne Rautiainen Lagerstrom, Ping Teresa Yeh, Caitlin E. Kennedy, Ronald H. Gray, Lilian Negesa, David M. Serwadda, Godfrey Kigozi, Anna Mia Ekström and Helena Nordenstedt BMC Public Health. 2022 Nov 29;22(1):2214. <a href="https://doi.org/10.1186/s12889-022-14620-9" rel="noreferrer" target="_blank">https://doi.org/10.1186/s12889-022-14620-9</a></p>

Redundancy is an important strategy for reducing response time in multi-server distributed queueing systems. This strategy has been used in a variety of settings, but only recently have researchers begun analytical studies. The idea behind redundancy is that customers can greatly reduce response time by waiting in multiple queues at the same time, thereby experiencing the minimum time across queues. Redundancy has been shown to produce significant response time improvements in applications ranging from organ transplant waitlists to Google’s BigTable service. However, despite the growing body of theoretical and empirical work on the benefits of redundancy, there is little work addressing the questions of how many copies one needs to make to achieve a response time benefit, and the magnitude of the potential gains. In this paper we propose a theoretical model and dispatching policy to evaluate these questions. Our system consists of k servers, each with its own queue. We introduce the Redundancy-d policy, under which each incoming job makes copies at a constant number of servers, d, chosen at random. Under the assumption that a job’s service times are exponential and independent across servers, we derive the first exact expressions for mean response time in Redundancy-d systems with any finite number of servers, as well as expressions for the distribution of response time which are exact as the number of servers approaches infinity. Using our analysis, we show that mean response time decreases as d increases, and that the biggest marginal response time improvement comes from having each job wait in only d = 2 queues. The e-companion is available at https://doi.org/10.1287/opre.2016.1582 .