A scheduling algorithm for multi‐processor real‐time systems with relative timing constraints and resource restrictions

In this paper, a scheduling algorithm for multi-processor real-time systems with relative timing constraints and resource constraints is proposed. The proposed algorithm has the capability to satisfy any timing constraints expressed as inequalities in two variables and a constant. This implies that scheduling problems imposed on various timing constraints such as end-to-end timing constraints and/or relative timing constraints, which are known to be difficult to handle, can be solved. Since the problem addressed in this paper is a generalization of some NP-complete problems, it is difficult to solve efficiently. Thus, the goal of the authors is to derive a heuristic algorithm which performs well on many instances of the problem, although in some cases it will take enormous space and time. Experimental results show that the proposed algorithm achieves a success rate of 80% in 3 minutes of computation time.

Allocation problem has always been one of the fundamental issues of building the applications in real-time computing systems. For real-time applications, the allocation problem should directly address the issues of task and communication scheduling. In this context, the allocation of tasks has to fully utilize the available processors and the scheduling of tasks has to meet the specified timing constraints. Clearly, the execution of tasks under the allocation and schedule has to satisfy the precedence, resources, and other synchronization constraints among them. Recently, the timing requirements of the real-time systems emerge that the relative timing constraints are imposed on the consecutive executions of each task and the inter-task temporal relationships are specified across task periods. In this paper we consider the allocation and scheduling problem of the periodic tasks with such timing requirements. Given a set of periodic tasks, we consider the least common multiple (LCM) of the task periods. Each task is extended to several instances within the LCM. The scheduling window for each task instance is derived to satisfy the timing constraints. We develop a simulated annealing algorithm as the overall control algorithm. An example problem of the sanitized version of the Boeing 777 Aircraft Information Management System is solved by the algorithm. Experimental results show that the algorithm solves the problem in a reasonable time complexity.

Traditional scheduling models assume that the execution time of a job in a periodic job-set is constant in every instance of its execution. This assumption does not hold in real-time systems wherein job execution time is known to vary. A second feature of traditional models is their lack of expressiveness, in that constraints more complex than precedence constraints (for instance, relative timing constraints) cannot be modeled. Thirdly, the schedulability of a real-time system depends upon the degree of clairvoyance afforded to the dispatcher. In this paper, we shall discuss Totally Clairvoyant Scheduling, as modeled within the E-T-C scheduling framework [Sub05]. We show that this instantiation of the scheduling framework captures the central issues in a real-time flow-shop scheduling problem and devise a polynomial time sequential algorithm for the same. The design of the polynomial time algorithm involves the development of a new technique, which we term Mutable Dynamic Programming. We expect that this technique will find applications in other areas of system design, such as Validation and Software Verification.

This paper discusses a class of mission planning problems in which mission objectives and relative timing constraints are specified using the linear temporal logic language LTL-x. Among all mission plans that satisfy the LTL-x specifications, it is desired to find those minimizing a given cost functional. We show that such an optimization problem can be formulated as a mixed-integer linear program, and present an algorithm for this purpose. This algorithm mainly relies on a novel systematic procedure which converts a given LTL-x formula into a set of mixed-integer linear constraints. The approach presented here can be used for multiple-UAV mission planning purposes, allowing the operator to specify complex mission objectives in LTL-x in a very natural manner; the proposed algorithm constructs the optimal mission plan satisfying the given LTL-x specification. Examples for practical problem sizes are presented and discussed in the paper.

We present a tool that performs real time analysis and priority assignment for software tasks in a mixed hardware software system with a custom run time scheduler. The tasks in hardware and software have precedence constraints, resource constraints, relative timing constraints, and a rate constraint. A dynamic programming formulation assigns the static priorities such that a hard real time rate constraint can be predictably met. We describe the task control/data flow extraction, runtime scheduler implementation, real time analysis and priority scheduler template. We show how our approach fits into an overall tool flow and target architecture. Finally, we conclude with a sample application of the system to a design example.

We propose a novel technique for modeling and verifying timed circuits based on the notion of generalized relative timing. Generalized relative timing constraints can express not just a relative ordering between events, but also some forms of metric timing constraints. Circuits modeled using generalized relative timing constraints are formally encoded as timed automata. Novel fully symbolic verification algorithms for timed automata are then used to either verify a temporal logic property or to check conformance against an untimed specification. The combination of our new modeling technique with fully symbolic verification methods enables us to verify larger circuits than has been possible with other approaches. We present case studies to demonstrate our approach, including a self-timed circuit used in the integer unit of the Intel/sup /spl reg// Pentium/sup /spl reg//4 processor.

Planning effective English reading lessons is a complex task for teachers because of challenges such as variations in student ability levels, limited resources, and time constraints. This research aims to identify the main challenges teachers face in planning reading lessons, including improving students' reading comprehension, adjusting the level of support to students' abilities, and implementing reading strategies. The research method used is qualitative, with data collection through semi-structured interviews with teachers from various levels of education. Data were analyzed using thematic analysis to identify main patterns and themes. The research results show that teachers face challenges in managing the diversity of students' reading abilities, selecting reading materials that are interesting and culturally relevant, and integrating technology into learning. Additionally, appropriate assessments for English Language Learners (ELL) students and the need to provide emotional support to students are also challenges. Limited professional training and resources contribute to this situation. This research also concludes that successful learning to read English requires a multifaceted approach that includes learning adjustments, teacher training, collaboration, and access to a variety of reading materials. By providing adequate support for teachers, these obstacles can be overcome, so that reading learning becomes more effective and inclusive.

Water scarcity in semiarid environments provides a model system to evaluate the role of mesic resources in structuring the distribution and abundance of wildlife. We used remote sensing and point process analyses to evaluate spatio–temporal variability in limited mesic resources in relation to greater sage‐grouse (Centrocercus urophasianus) distributions in Oregon, California, and northwest Nevada,USA, 1984–2011. We then link population distribution to changes in resource availability over time, space, and land tenure. Despite encompassing only 2.4% of landscape area, mesic sites influenced sage‐grouse breeding distributions as evidenced by significantly shorter lek to mesic resource distances in observed (5.3 km) vs. predicted (8.2 km) values. Population abundance increased with proximity to mesic sites. Lag effects evident in abundance and proximity trends of mesic resources suggest a level of drought tolerance that moderated climatic variability. Mesic abundance and proximity remained relatively stable during the study period in comparison to more dynamic climatic patterns. Drought effects were most pronounced during multiyear events as evidenced by the 1987–1992 period that decreased mesic abundance >25% and approximately doubled mean lek to mesic resource distances (4.8–8.3 km). In our study area, 75% of all mesic resources were in private ownership, where the predominant land use is livestock ranching. Results suggest a holistic conservation strategy inclusive of private and public lands is needed to ensure sage‐grouse habitat requisites are met throughout the life cycle of this landscape species.

Parenting programmes in elementary schools play an important role in supporting students' character development but often face challenges in terms of parental involvement. Problems include low parental participation in school activities, limited resources and parents' lack of understanding of their role in their children's education. The purpose of this study was to identify the role of parents in students' character development, the challenges faced in implementing the parenting programme, as well as the strategies implemented by the school to increase parental participation in public school 2 Kemasan, Boyolali, Indonesia. This study used qualitative methods with direct observation techniques, structured interviews with parents, teachers, and principals, and document analysis related to the parenting programme. The results show that despite constraints such as limited time and resources, active parental involvement can improve students' attitudes, discipline and learning motivation. However, the level of parental participation in some activities is still low, which affects the effectiveness of the programme. Recommendations to improve the effectiveness of the parenting programme include providing parenting materials online to overcome time constraints and collaborating with external counsellors to provide more support to parents in educating their children. This research is expected to provide insights for other schools in optimising their existing parenting programmes.

As satellites grow both in number and in the fields involved, it has become an enormous challenge to allocate limited satellite resources against complicated constraints and confined working hours. In this paper, particle swarm optimization integrated with tabu search is introduced to solve the satellite-imaging task-planning issue. Based on the related constraints and construction of a satellite-imaging task-planning model, local search and tabu rules are added to the particle swarm algorithm to improve diversity and effective search. The works of this paper includes but not limited to developing task plans that feature quick convergence and global near-optimal solutions, designing groups of data containing different task loads, comparing the plans in terms of integrated assessment value, the number of tasks completed, task priority, and planning time consumed. The result of the experiment indicate that particle swarm optimization with Tabu search is effective in handling satellite imaging task planning.

A self-timed microarchitecture called KeyRing is presented, and a method for implementing KeyRing circuits compatible with a timing-driven electronic design automation (EDA) flow is discussed. The KeyRing microarchitecture is derived from the AnARM, a low-power self-timed ARM processor based on ad hoc design principles. First, the unorthodox design style and circuit structures are revisited. A theoretical model that can support the design of generic circuits and the elaboration of EDA methods is then presented. Also addressed are the compatibility issues between KeyRing circuits and timing-driven EDA flows. The proposed method leverages relative timing constraints to translate the timing relations in a KeyRing circuit into a set of timing constraints that enable timing-driven synthesis and static timing analysis. Finally, two 32-bit RISC-V processors are presented; called KeyV and based on KeyRing microarchitectures, they are synthesized in a 65 nm technology using the proposed EDA flow. Postsynthesis results demonstrate the effectiveness of the design methodology and allow comparisons with a synchronous alternative called SynV. Performance and power consumption evaluations show that KeyV has a power efficiency that lies between SynV with clock-gating and SynV without clock-gating.

BackgroundIndividuals with co-occurring mental health and substance use disorders (i.e., concurrent disorders) have complex healthcare needs, which can be challenging for nurses to manage. Providing optimal care for this subpopulation requires nurses to develop high-level competencies despite limited resources at their disposal and the isolated settings in which many of them work. The Extension for Healthcare Community Outcomes (ECHO®) is a promising collaborative learning and capacity building model that uses videoconference technology to support and train healthcare professionals in the management of complex and chronic health conditions. The aim of this study was to explore the experiences and perceptions of nurses participating in a Canadian ECHO programme on concurrent disorders about the competencies they developed and used in their clinical practice, and which factors have influenced this process.MethodsThe study was qualitative, guided by an interpretive description approach. Individual semi-structured interviews were held with ten nurses who had participated in the programme between 2018 and 2020. A thematic analysis was conducted iteratively using an inductive approach to progressive data coding and organization.ResultsFour themes and eighteen sub-themes were identified. During their participation in ECHO, the nurses perceived as having further developed eight clinical nursing competencies. Nurses viewed ECHO as a unique opportunity to open themselves to their peers’ experiences and reflect on their own knowledge. Learning from experts in the field of concurrent disorders helped them to build their confidence in managing complex clinical situations. The nurses’ sense of belonging to a community further enhanced their engagement in the programme, and learning was facilitated through the programme’s interprofessional environment. Nevertheless, the lack of contextualized educative content linked to local realities, the limited resources in concurrent disorders, and time constraints were experienced as factors limiting competency development.ConclusionsECHO is a promising alternative to conventional, in-person continuing education programmes to improve the development of advanced competencies among nurses providing care to individuals with chronic and complex health conditions. These findings can inform clinicians, educators, researchers, and decision makers who are developing, implementing, evaluating, and escalating future educational interventions in the field of CDs.

ABSTRACTStreet-involved (SI) youth represent a significant proportion of urban homeless populations. While previous research has identified SI youth as substantial users of emergency department (ED) services and has examined their experiences of ED care, little is known about the experiences and perceptions of the service providers who assist these youth with health care related issues. Using grounded theory, individual interviews and focus groups were conducted with 20 community agency staff serving SI youth, 17 health service providers, two hospital administrators, and two hospital security personnel regarding their experiences in providing or facilitating ED care for SI youth. Results identify differences in expectations between SI youth and hospital staff, along with service issues and gaps, including relational barriers and resource constraints. Implications for practice and policy development are offered.

In multimedia applications, media data such as audio and video are transmitted from server to clients via network according to some transmission schedules. Different from the conventional data streams, end-to-end quality-of-service (QoS) is necessary for media transmission to provide jitter-free playback. Therefore, each data packet has been assigned with related timing constraints for transmission. As network resources are allocated exclusively in fixed-size chunks to serve different data streams, it is simple to support constant-bit-rate (CBR) transmission. Grossglauser and Keshav (1996) have investigated the performance of CBR traffic in a large-scale network with many connections and switches. They concluded that the network queuing delay for CBR transmission is less than one cell time per switch even under heavy loading. Besides, resource allocation and admission control are simple as there are no variations in resource requirements. However, media streams are notably variable-bit-rate (VBR) in nature due to the coding and compression technologies applied (Garrett and Willinger, 1994). The average data rate of an MPEG-1 movie is usually less than 25% of its peak data rate. It is inherently at odds with the goals of designing efficient real-time network transmission and admission control mechanisms capable of achieving high resource utilization (Sen et al., 1997). The conventional CBR service model that allocates the peak data rate to transmit the VBR stream would be a waste of bandwidth. Furthermore, it requires a large size of client buffer. To ameliorate this problem, we need a good traffic shaping algorithm to transmit VBR video in a less bursty (i.e., smoother) manner by exploiting different performance measurements. In a multimedia system, we usually measure the performance of a transmission schedule by the following four indices: peak bandwidth, network utilization, initial delay and client buffer.

We propose a refinement-based technique to formally verify circuits of the GasP family. Verifying GasP circuits presents two main challenges: exploit their highly modular structure to reduce verification costs, and express formally their unconventional behavior at the low level, such as bidirectional signals, self-resetting logic, and fights. We propose a novel semi-automated technique for constructing specification models for interfaces of GasP circuit control units, which synchronize single-track handshake signals from different channels. These specifications are captured at a high level using abridged data transition events and transformed into intermediate specifications using low-level signal transition events. High-level verifications using data transition events are exact if each unit conforms to its intermediate specification. As a case study, we verify that a set of relative timing constraints inside the units and along channels between units, consistent with the original sizing of the circuits, is sufficient to guarantee correctness of a previously proposed square FIFO.