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586
The Conversational Classroom
 In 34rd ACM Technical Symposium on Computer Science Education (SIGCSE
, 2003
"... Concepts taught in large, lowerdivision computer science courses are carefully explained in standard textbooks. Thus we hypothesized that the classroom experience should not consist primarily of a restatement of those explanations by the professor. Instead, it should provide an opportunity for the ..."
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Cited by 367 (5 self)
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Concepts taught in large, lowerdivision computer science courses are carefully explained in standard textbooks. Thus we hypothesized that the classroom experience should not consist primarily of a restatement of those explanations by the professor. Instead, it should provide an opportunity for the students to team through a process of conversation among themselves and with the professor. We were able to establish such a process in a sophomorelevel course with an enrollment of 116 students. This change led to a doubling of the percentage of A and A grades compared to historical values.
Robust Constrained Model Predictive Control using Linear Matrix Inequalities
, 1996
"... The primary disadvantage of current design techniques for model predictive control (MPC) is their inability to deal explicitly with plant model uncertainty. In this paper, we present a new approach for robust MPC synthesis which allows explicit incorporation of the description of plant uncertainty i ..."
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Cited by 140 (5 self)
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The primary disadvantage of current design techniques for model predictive control (MPC) is their inability to deal explicitly with plant model uncertainty. In this paper, we present a new approach for robust MPC synthesis which allows explicit incorporation of the description of plant uncertainty in the problem formulation. The uncertainty is expressed both in the time domain and the frequency domain. The goal is to design, at each time step, a statefeedback control law which minimizes a "worstcase" infinite horizon objective function, subject to constraints on the control input and plant output. Using standard techniques, the problem of minimizing an upper bound on the "worstcase" objective function, subject to input and output constraints, is reduced to a convex optimization involving linear matrix inequalities (LMIs). It is shown that the feasible receding horizon statefeedback control design robustly stabilizes the set of uncertain plants under consideration. Several extensions...
Leakage aware dynamic voltage scaling for realtime embedded systems
 In CECS
, 2003
"... A fivefold increase in leakage current is predicted with each technology generation. While Dynamic Voltage Scaling (DVS) is known to reduce dynamic power consumption, it also causes increased leakage energy drain by lengthening the interval over which a computation is carried out. Therefore, for mi ..."
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Cited by 139 (8 self)
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A fivefold increase in leakage current is predicted with each technology generation. While Dynamic Voltage Scaling (DVS) is known to reduce dynamic power consumption, it also causes increased leakage energy drain by lengthening the interval over which a computation is carried out. Therefore, for minimization of the total energy, one needs to determine an operating point, called the critical speed. We compute processor slowdown factors based on the critical speed for energy minimization. Procrastination scheduling attempts to maximize the duration of idle intervals by keeping the processor in a sleep/shutdown state even if there are pending tasks, within the constraints imposed by performance requirements. Our simulation experiments show that the critical speed slowdown results in up to 5 % energy gains over a leakage oblivious dynamic voltage scaling. Procrastination scheduling scheme extends the sleep intervals to up to 5 times, resulting in up to an additional 18 % energy gains, while meeting all timing requirements.
Energy Efficient FixedPriority Scheduling for RealTime Systems On Variable . . .
 DAC 2001
, 2001
"... Energy consumption has become an increasingly important consideration in designing many realtime embedded systems. Variable voltage processors, if used properly, can dramatically reduce such system energy consumption. In this paper, we present a technique to determine voltage settings for a variabl ..."
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Cited by 108 (7 self)
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Energy consumption has become an increasingly important consideration in designing many realtime embedded systems. Variable voltage processors, if used properly, can dramatically reduce such system energy consumption. In this paper, we present a technique to determine voltage settings for a variable voltage processor that utilizes a fixed priority assignment to schedule jobs. Our approach also produces the minimum constant voltage needed to feasibly schedule the entire job set. Our algorithms lead to significant energy saving compared with previously presented approaches.
Feedback Utilization Control in Distributed RealTime Systems with EndtoEnd Tasks
 IEEE Trans. Parallel and Distributed Systems
, 2005
"... Abstract—An increasing number of distributed realtime systems face the critical challenge of providing quality of service guarantees in open and unpredictable environments. In particular, such systems often need to enforce utilization bounds on multiple processors in order to avoid overload and mee ..."
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Cited by 79 (29 self)
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Abstract—An increasing number of distributed realtime systems face the critical challenge of providing quality of service guarantees in open and unpredictable environments. In particular, such systems often need to enforce utilization bounds on multiple processors in order to avoid overload and meet endtoend deadlines even when task execution times are unpredictable. While recent feedback control realtime scheduling algorithms have shown promise, they cannot handle the common endtoend task model where each task is comprised of a chain of subtasks distributed on multiple processors. This paper presents the Endtoend Utilization CONtrol (EUCON) algorithm that adaptively maintains desired CPU utilization through performance feedbacks loops. EUCON is based on a model predictive control approach that models utilization control on a distributed platform as a multivariable constrained optimization problem. A multiinputmultioutput model predictive controller is designed based on a difference equation model that describes the dynamic behavior of distributed realtime systems. Both control theoretic analysis and simulations demonstrate that EUCON can provide robust utilization guarantees when task execution times deviate from estimation or vary significantly at runtime. Index Terms—Realtime systems, embedded systems, distributed systems, feedback control realtime scheduling, endtoend task, quality of service, model predictive control. æ
Vsched: Mixing batch and interactive virtual machines using periodic realtime scheduling
 In Proceedings of ACM/IEEE SC 2005 (Supercomputing
, 2005
"... We are developing Virtuoso, a system for distributed computing using virtual machines (VMs). Virtuoso must be able to mix batch and interactive VMs on the same physical hardware, while satisfying constraints on responsiveness and compute rates for each workload. VSched is the component of Virtuoso t ..."
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Cited by 69 (16 self)
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We are developing Virtuoso, a system for distributed computing using virtual machines (VMs). Virtuoso must be able to mix batch and interactive VMs on the same physical hardware, while satisfying constraints on responsiveness and compute rates for each workload. VSched is the component of Virtuoso that provides this capability. VSched is an entirely userlevel tool that interacts with the stock Linux kernel running below any typeII virtual machine monitor to schedule all VMs (indeed, any process) using a periodic realtime scheduling model. This abstraction allows compute rate and responsiveness constraints to be straightforwardly described using a period and a slice within the period, and it allows for fast and simple admission control. This paper makes the case for periodic realtime scheduling for VMbased computing environments, and then describes and evaluates VSched. It also applies VSched to scheduling parallel workloads, showing that it can help a BSP application maintain a fixed stable performance despite externally caused load imbalance.
Schedulability Analysis of Periodic Fixed Priority Systems
 IEEE TRANSACTIONS ON COMPUTERS
, 2004
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Performance comparison of dynamic voltage scaling algorithms for hard realtime systems
 Proc. IEEE RealTime and
"... Dynamic voltage scaling (DVS) is an effective lowpower design technique for embedded realtime systems. In recent years, many DVS algorithms have been proposed for reducing the energy consumption of embedded hard realtime systems. However, the proposed DVS algorithms were not quantitatively eva ..."
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Cited by 57 (8 self)
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Dynamic voltage scaling (DVS) is an effective lowpower design technique for embedded realtime systems. In recent years, many DVS algorithms have been proposed for reducing the energy consumption of embedded hard realtime systems. However, the proposed DVS algorithms were not quantitatively evaluated under a unified framework, making it a difficult task to select an appropriate DVS algorithm for a given application/system. In this paper, we compare several key DVS algorithms recently proposed for hard realtime periodic task sets, analyze their energy efficiency, and discuss the performance differences quantitatively. Our evaluation results give quantitative answers to several important DVS questions. 1
Worstcase response time analysis of realtime tasks under fixedpriority scheduling with deferred preemption
 RealTime Systems
, 2009
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Scheduling and Feedback CoDesign for Networked Control Systems
 PROC. IEEE CONF. ON DECISION AND CONTROL, LAS VEGAS
, 2002
"... Feedback control systems wherein the control loops are closed through a realtime network are called networked control systems (NCSs). The insertion of the communication network in the feedback control loop makes the analysis and design of an NCS complex. Driving our research e#ort into NCSs is the ..."
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Cited by 55 (6 self)
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Feedback control systems wherein the control loops are closed through a realtime network are called networked control systems (NCSs). The insertion of the communication network in the feedback control loop makes the analysis and design of an NCS complex. Driving our research e#ort into NCSs is the point of view that the design of both the communication protocols and the interacting controlled system should not be treated as separate. In the codesign approach we propose, network issues such as bandwidth, quantization, survivability, reliability and message delay will be considered simultaneously with controlled system issues such as stability, performance, fault tolerance and adaptability. Thus, we study network scheduling when a set of NCSs are connected to the network and arbitrating for network bandwidth. We first define the basic concepts of network scheduling in NCSs. Then, we apply the rate monotonic scheduling algorithm to schedule a set of NCSs. We also formulate the optimal scheduling problem under both ratemonotonicschedulability constraints and NCSstability constraints, and give an example of how such optimization is carried out. Next, the assumptions of ideal transmission are relaxed: we study the above network scheduling problem with networkinduced delay, packet dropouts, and multiplepacket transmissions taken into account.