The MVA Priority Approximation

A Mean Value Analysis (MVA) approximation is presented for computing the average performance measures of closed-, open-, and mixed-type multiclass queuing networks containing Preemptive Resume (PR) and nonpreemptive Head-Of-Line (HOL) priority service centers. The approximation has essentially the same storage and computational requirements as MVA, thus allowing computationally efficient solutions of large priority queuing networks. The accuracy of the MVA approximation is systematically investigated and presented. It is shown that the approximation can compute the average performance measures of priority networks to within an accuracy of 5 percent for a large range of network parameter values. Accuracy of the method is shown to be superior to that of Sevcik's shadow approximation

UC: a language for the connection machine

n designing parallel languages, the concern for defining a simple virtual machine must be balanced against the need to efficiently map a program on a specific architecture. UC addresses this problem by separating the programming task from efficiency considerations. UC programs are designed using a small set of constructs that include reduction, parallel assignment, and fixed-point computation. The language also provides a map section that may optionally be used by a programmer to specify data mappings for the program. The authors describe the UC constructs and their implementation on the Connection Machine. They also present measurements of the compiler for simple benchmarks

A parallel algorithm for correlating event streams

This paper describes a parallel algorithm for correlating or “fusing” streams of data from sensors and other sources of information. The algorithm is useful for applications where composite conditions over multiple data streams must be detected rapidly, such as intrusion detection or crisis management. The implementation of this algorithm on a multithreaded system and the performance of this implementation are also briefly described

Who shares and who doesn't? Results of the UK Sharing Economy Consumer Survey 2017

The survey, which was conducted in July 2017, captures 1220 responses, and is based on a representative sample of UK population based on gender, income level, education level, and place of residence in the UK. It was structured to ask questions about informants’ current usage of, opinions about, and future intentions to use the following sharing categories: places to stay (e.g. Airbnb, Beds on Board), rides (e.g. Uber, Liftshare), rental cars (e.g. Easycar, Zipcar), parking (e.g. JustPark, Your Parking Space), services (e.g. Parcelly, TaskRabbit), meals (e.g. MealSharing, Eatwith), pre-owned goods (e.g. eBay, Gumtree) and funding (e.g. Justgiving, Crowdcube)

Snapshot Processing in Streaming Environments

Computational issues related to streaming data, and in particular the monitoring and rapid correlation of multiple sources of streaming data, are becoming increasingly important in contexts ranging from business processes to crisis detection. For example, a government system to detect bioterror attacks must correlate multiple streams of possibly low-confidence data from sensors and local and national public health information networks with cues from indicators such as news and government sources indicating geographical locations, tactics and timing of possible attacks. The results of this correlation trigger appropriate responses, such as flagging information for more in-depth analysis or sending alerts to public health officials. Monitoring and correlation applications of this type are ideal for deployment on distributed computing grids, because they have high transaction throughput, require low latency, and can be partitioned into sets of small communicating computations with regular communication patterns. An important consideration in these applications is the need to ensure that, at any given time, computations are carried out on an accurate - or at least close to accurate - picture of the environment being monitored. One way of doing this, which we call snapshot processing, is to treat collections of events that occur at approximately the same time as representing a global snapshot - a valid state - of the environment. Computation on the resulting series of snapshots is much like computation on a real-time video of the entire environment. We briefly describe our model for these stream processing computations and introduce the concept of snapshot processin

Space Efficient Breadth-First and Level Traversals of Consistent Global States of Parallel Programs

Enumerating consistent global states of a computation is a fundamental problem in parallel computing with applications to debug- ging, testing and runtime verification of parallel programs. Breadth-first search (BFS) enumeration is especially useful for these applications as it finds an erroneous consistent global state with the least number of events possible. The total number of executed events in a global state is called its rank. BFS also allows enumeration of all global states of a given rank or within a range of ranks. If a computation on n processes has m events per process on average, then the traditional BFS (Cooper-Marzullo and its variants) requires $\mathcal{O}(\frac{m^{n-1}}{n})$ space in the worst case, whereas ou r algorithm performs the BFS requires $\mathcal{O}(m^2n^2)$ space. Thus, we reduce the space complexity for BFS enumeration of consistent global states exponentially. and give the first polynomial space algorithm for this task. In our experimental evaluation of seven benchmarks, traditional BFS fails in many cases by exhausting the 2 GB heap space allowed to the JVM. In contrast, our implementation uses less than 60 MB memory and is also faster in many cases

Enterprise Computing Systems as Information Factories

The analysis, and eventual approval or rejection, of new enterprise information technology (IT) initiatives often proceeds on the basis of informal estimates of return on investment. Investment in new IT initiatives includes the costs of hardware, software licenses, application development tailored to the enterprise, and maintenance. Returns are typically estimated informally in terms of cost savings or revenue increases. This paper makes the case for evaluating certain IT investments in the same way as investments in factories and other resources have been evaluated for decades. Just as industrial factories create value by transforming raw materials into finished products, some IT investments, which we call “information factories”, create value by transforming raw information (events) into structured data (and possibly actions based on that data). The return on investment is estimated by the difference between the economic value of the structured data and concomitant actions (the “finished product”) and that of the data available within the enterprise, from its partners and customers, and from the Internet (the “raw materials”). This paper introduces the concept of the information factory, and explores design considerations for maximizing the economic efficiency of information factories

Novel use Of Hydroxyurea in an African Region with Malaria (NOHARM): a trial for children with sickle cell anemia

Hydroxyurea treatment is recommended for children with sickle cell anemia (SCA) living in high-resource malaria-free regions, but its safety and efficacy in malaria-endemic sub-Saharan Africa, where the greatest sickle-cell burden exists, remain unknown. In vitro studies suggest hydroxyurea could increase malaria severity, and hydroxyurea-associated neutropenia could worsen infections. NOHARM (Novel use Of Hydroxyurea in an African Region with Malaria) was a randomized, double-blinded, placebo-controlled trial conducted in malaria-endemic Uganda, comparing hydroxyurea to placebo at 20 ± 2.5 mg/kg per day for 12 months. The primary outcome was incidence of clinical malaria. Secondary outcomes included SCA-related adverse events (AEs), clinical and laboratory effects, and hematological toxicities. Children received either hydroxyurea (N = 104) or placebo (N = 103). Malaria incidence did not differ between children on hydroxyurea (0.05 episodes per child per year; 95% confidence interval [0.02, 0.13]) vs placebo (0.07 episodes per child per year [0.03, 0.16]); the hydroxyurea/placebo malaria incidence rate ratio was 0.7 ([0.2, 2.7]; P = .61). Time to infection also did not differ significantly between treatment arms. A composite SCA-related clinical outcome (vaso-occlusive painful crisis, dactylitis, acute chest syndrome, splenic sequestration, or blood transfusion) was less frequent with hydroxyurea (45%) than placebo (69%; P = .001). Children receiving hydroxyurea had significantly increased hemoglobin concentration and fetal hemoglobin, with decreased leukocytes and reticulocytes. Serious AEs, sepsis episodes, and dose-limiting toxicities were similar between treatment arms. Three deaths occurred (2 hydroxyurea, 1 placebo, and none from malaria). Hydroxyurea treatment appears safe for children with SCA living in malaria-endemic sub-Saharan Africa, without increased severe malaria, infections, or AEs. Hydroxyurea provides SCA-related laboratory and clinical efficacy, but optimal dosing and monitoring regimens for Africa remain undefined. This trial was registered at www.clinicaltrials.gov as #NCT01976416

Roughening of the (1+1) interfaces in two-component surface growth with an admixture of random deposition

We simulate competitive two-component growth on a one dimensional substrate of $L$ sites. One component is a Poisson-type deposition that generates Kardar-Parisi-Zhang (KPZ) correlations. The other is random deposition (RD). We derive the universal scaling function of the interface width for this model and show that the RD admixture acts as a dilatation mechanism to the fundamental time and height scales, but leaves the KPZ correlations intact. This observation is generalized to other growth models. It is shown that the flat-substrate initial condition is responsible for the existence of an early non-scaling phase in the interface evolution. The length of this initial phase is a non-universal parameter, but its presence is universal. In application to parallel and distributed computations, the important consequence of the derived scaling is the existence of the upper bound for the desynchronization in a conservative update algorithm for parallel discrete-event simulations. It is shown that such algorithms are generally scalable in a ring communication topology.Comment: 16 pages, 16 figures, 77 reference