Motivated by the problem of packing Virtual Machines on physical servers in the cloud, we study the problem of online stochastic bin packing under two settings-packing with permanent items, and packing under item departures. In the setting with permanent items, we present the first truly distribution-oblivious bin packing heuristic that achieves O(√ n) regret compared to OPT for all distributions. Our algorithm is essentially gradient descent on suitably defined Lagrangian relaxation of the bin packing Linear Program. We also prove guarantees of our heuristic against non i.i.d. input using a randomly delayed Lyapunov function to smoothen the input. For the setting where items eventually depart, we are interested in minimizing the steady-state number of bins. Our algorithm extends as is to the case of item departures. Further, leveraging the Lagrangian approach, we generalize our algorithm to a setting where the processing time of an item is inflated by a certain known factor depending on the configuration it is packed in.
We consider the problem of admission control in resource sharing systems, such as web servers and transaction processing systems, when the job size distribution has high variability, with the aim of minimizing the mean response time. It is well known that in such resource sharing systems, as the number of tasks concurrently sharing the resource is increased, the server throughput initially increases, due to more efficient utilization of resources, but starts falling beyond a certain point, due to resource contention and thrashing. Most admission control mechanisms solve this problem by imposing a fixed upper bound on the number of concurrent transactions allowed into the system, called the Multi-Programming-Limit (MPL), and making the arrivals which find the server full queue up. Almost always, the MPL is chosen to be the point that maximizes server efficiency.
In this paper we abstract such resource sharing systems as a Processor Sharing (PS) server with state-dependent service rate and a First-Come-First-Served (FCFS) queue, and we analyze the performance of this model from a queueing theoretic perspective. We start by showing that, counter to the common wisdom, the peak efficiency point is not always optimal for minimizing the mean response time. Instead, significant performance gains can be obtained by running the system at less than the peak efficiency. We provide a simple expression for the static MPL that achieves near-optimal mean response time for general distributions.
Next we present two traffic-oblivious dynamic admission control policies that adjust the MPL based on the instantaneous queue length while also taking into account the variability of the job size distribution. The structure of our admission control policies is a mixture of fluid control when the number of jobs in the system is high, with a stochastic component when the system is near-empty. We show via simulations that our dynamic policies are much more robust to unknown traffic intensities and burstiness in the arrival process than imposing a static MPL.
We present a control plane architecture to accelerate multicast and incast traffic delivery for data-intensive applications in cluster-computing interconnection networks. The architecture is experimentally examined by enabling physical layer optical multicasting on-demand for the application layer to achieve non-blocking performance.
Diversity is a great challenge for software engineers in the social sector context. The objective of this paper is to contribute to the identification of the RE processes and associated challenges in releasing the software in the social sector markets for which an exploratory case study is conducted. The outcome of the case study indicates that the diversity limits the ability to involve the representative samples of user populations using the same set of RE tools and techniques as one size fits all solution for all segments. The diverse user base must be partitioned into different segments, with each segment triggered using a suitable set of RE techniques i.e., traditional and crowd-based RE. The diverse perspectives learned as a result of the interaction with each segment, must be merged together into a single perspective about the software meant to be used in the social sector. There is a need for a new RE process specially designed for handling the complexities of the social sector, which this paper terms as
Social Sector Requirement Engineering (SSRE).
There is an increased need for collaboration between government social sector institutions and software engineers to get access to diverse customers to improve software quality.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.