Enhancing the power of two choices load balancing algorithm using round robin policy

This paper proposes a new version of the power of two choices, SQ(d), load balancing algorithm. This new algorithm improves the performance of the classical model based on the power of two choices randomized load balancing. This model considers jobs that arrive at a dispatcher as a Poisson stream of rate lambdan,lambda<1, at a set of n servers. Using the power of two choices, the dispatcher chooses some d constant for each job independently and uniformly from the n servers in a random way and sends the job to the server with the fewest number of jobs. This algorithm offers an advantage over the load balancing based on shortest queue discipline, because it provides good performance and reduces the overhead in the servers and the communication network. In this paper, we propose a new version, shortest queue of d with randomization and round robin policies, SQ-RR(d). This new algorithm combines randomization techniques and static local balancing based on a round-robin policy. In this new version, the dispatcher chooses the d servers as follows: one is selected using a round-robin policy, and the d&#8722;1 servers are chosen independently and uniformly from the n servers in a random way. Then, the dispatcher sends the job to the server with the fewest number of jobs. We demonstrate with a theoretical approximation of this approach that this new version improves the performance obtained with the classical solution in all situations, including systems at 99% capacity. Furthermore, we provide simulations that demonstrate the theoretical approximation developed.This work was partially supported by the Project ‘‘CABAHLA-CM: Convergencia Big data-Hpc: de los sensores a las Aplicaciones’’ S2018/TCS-4423 from Madrid Regional Government

Boosting Multi-Core Reachability Performance with Shared Hash Tables

This paper focuses on data structures for multi-core reachability, which is a key component in model checking algorithms and other verification methods. A cornerstone of an efficient solution is the storage of visited states. In related work, static partitioning of the state space was combined with thread-local storage and resulted in reasonable speedups, but left open whether improvements are possible. In this paper, we present a scaling solution for shared state storage which is based on a lockless hash table implementation. The solution is specifically designed for the cache architecture of modern CPUs. Because model checking algorithms impose loose requirements on the hash table operations, their design can be streamlined substantially compared to related work on lockless hash tables. Still, an implementation of the hash table presented here has dozens of sensitive performance parameters (bucket size, cache line size, data layout, probing sequence, etc.). We analyzed their impact and compared the resulting speedups with related tools. Our implementation outperforms two state-of-the-art multi-core model checkers (SPIN and DiVinE) by a substantial margin, while placing fewer constraints on the load balancing and search algorithms.Comment: preliminary repor

Distributed Online Modified Greedy Algorithm for Networked Storage Operation under Uncertainty

The integration of intermittent and stochastic renewable energy resources requires increased flexibility in the operation of the electric grid. Storage, broadly speaking, provides the flexibility of shifting energy over time; network, on the other hand, provides the flexibility of shifting energy over geographical locations. The optimal control of storage networks in stochastic environments is an important open problem. The key challenge is that, even in small networks, the corresponding constrained stochastic control problems on continuous spaces suffer from curses of dimensionality, and are intractable in general settings. For large networks, no efficient algorithm is known to give optimal or provably near-optimal performance for this problem. This paper provides an efficient algorithm to solve this problem with performance guarantees. We study the operation of storage networks, i.e., a storage system interconnected via a power network. An online algorithm, termed Online Modified Greedy algorithm, is developed for the corresponding constrained stochastic control problem. A sub-optimality bound for the algorithm is derived, and a semidefinite program is constructed to minimize the bound. In many cases, the bound approaches zero so that the algorithm is near-optimal. A task-based distributed implementation of the online algorithm relying only on local information and neighbor communication is then developed based on the alternating direction method of multipliers. Numerical examples verify the established theoretical performance bounds, and demonstrate the scalability of the algorithm.Comment: arXiv admin note: text overlap with arXiv:1405.778

FatPaths: Routing in Supercomputers and Data Centers when Shortest Paths Fall Short

We introduce FatPaths: a simple, generic, and robust routing architecture that enables state-of-the-art low-diameter topologies such as Slim Fly to achieve unprecedented performance. FatPaths targets Ethernet stacks in both HPC supercomputers as well as cloud data centers and clusters. FatPaths exposes and exploits the rich ("fat") diversity of both minimal and non-minimal paths for high-performance multi-pathing. Moreover, FatPaths uses a redesigned "purified" transport layer that removes virtually all TCP performance issues (e.g., the slow start), and incorporates flowlet switching, a technique used to prevent packet reordering in TCP networks, to enable very simple and effective load balancing. Our design enables recent low-diameter topologies to outperform powerful Clos designs, achieving 15% higher net throughput at 2x lower latency for comparable cost. FatPaths will significantly accelerate Ethernet clusters that form more than 50% of the Top500 list and it may become a standard routing scheme for modern topologies

Policy-based power consumption management in smart energy community using single agent and multi agent Q learning algorithms

Power consumption in residential sector has increased due to growing population, economic growth, invention of many electrical appliances and therefore is becoming a growing concern in the power industry. Managing power consumption in residential sector without sacrificing user comfort has become one of the main research areas recently. The complexity of the power system keeps growing due to the penetration of alternative sources of electric energy such as solar plant, Hydro, Biomass, Geothermal and wind farm to meet the growing demand for electricity. To overcome the challenges due to complexity, the power grid needs to be intelligent in all aspects. As the grid gets smarter and smarter, considerable efforts are being undertaken to make the houses and businesses smarter in consuming the electrical energy to minimize and level the electricity demand which is also known as Demand Side Management (DSM). It also necessitates that the conventional way of modelling, control and energy management in all sectors needs to be enhanced or replaced by intelligent information processing techniques. In our research work, it has been done in several stages. (Purpose of Study and Results) We proposed a policy-based framework which allows intelligent and flexible energy management of home appliances in a smart home which is complex and dynamic in ways that saves energy automatically. We considered the challenges in formalizing the behaviour of the appliances using their states and managing the energy consumption using policies. Policies are rules which are created and edited by a house agent to deal with situations or power problems that are likely to occur. Each time the power problem arises the house agent will refer to policy and one or a set of rules will be executed to overcome that situation. Our policy-based smart home can manage energy efficiently and can significantly participate in reducing peak energy demand (thereby may reduce carbon emission). Our proposed policy-based framework achieves peak shaving so that power consumption adapts to available power, while ensuring the comfort level of the inhabitants and taking device characteristics in to account. Our simulation results on MATLAB indicate that the proposed Policy driven homes can effectively contribute to Demand side power management by decreasing the peak hour usage of the appliances and can efficiently manage energy in a smart home in a user-friendly way. We propounded and developed peak demand management algorithms for a Smart Energy Community using different types of coordination mechanisms for coordination of multiple house agents working in the same environment. These algorithms use centralized model, decentralized model, hybrid model and Pareto resource allocation model for resource allocation. We modelled user comfort for the appliance based on user preference, the power reduction capability and the important activities that run around the house associated with that appliance. Moreover, we compared these algorithms with respect to their peak reduction capability, overall comfort of the community, simplicity of the algorithm and community involvement and finally able to find the best performing algorithm among them. Our simulation results show that the proposed coordination algorithms can effectively reduce peak demand while maintaining user comfort. With the help of our proposed algorithms, the demand for electricity of a smart community can be managed intelligently and sustainably. This work is not only aiming for peak reduction management it aims for achieving it while keeping the comfort level of the inhabitants is minimum. It can learn user’s behaviour and establish the set of optimal rules dynamically. If the available power to a house is kept at a certain level the house agent will learn to use this notional power to operate all the appliances according to the requirements and comfort level of the household. This way the consumers are forced to use the power below the set level which can result in the over-all power consumption be maintained at a certain rate or level which means sustainability is possible or depletion of natural resources for electricity can be reduced. Temporal interactions of Energy Demand by local users and renewable energy sources can also be done more efficiently by having a set of new policy rules to switch between the utility and the renewable source of energy but it is beyond the scope of this thesis. We applied Q learning techniques to a home energy management agent where the agent learns to find the optimal sequence of turning off appliances so that the appliances with higher priority will not be switched off during peak demand period or power consumption management. The policy-based home energy management determines the optimal policy at every instant dynamically by learning through the interaction with the environment using one of the reinforcement learning approaches called Q-learning. The Q-learning home power consumption problem formulation consisting of state space, actions and reward function is presented. The implications of these simulation results are that the proposed Q- learning based power consumption management is very effective and enables the users to have minimum discomfort during participation in peak demand management or at the time when power consumption management is essential when the available power is rationale. This work is extended to a group of 10 houses and three multi agent Q- learning algorithms are proposed and developed for improving the individual and community comfort while at the same time keeping the power consumption below the available power level or electricity price below the set price. The proposed algorithms are weighted strategy sharing algorithm, concurrent Q learning algorithm and cooperative distributive learning algorithm. These proposed algorithms are coded and tested for managing power consumption of a group of 10 houses and the performance of all three algorithms with respect to power management and community comfort is studied and compared. Actual power consumption of a community and modified power consumption curves using Weighted Strategy Sharing algorithm, Concurrent learning and Distributive Q Learning and user comfort results are presented, and the results are analysed in this thesis

Physical Time-Varying Transfer Functions as Generic Low-Overhead Power-SCA Countermeasure

Mathematically-secure cryptographic algorithms leak significant side channel information through their power supplies when implemented on a physical platform. These side channel leakages can be exploited by an attacker to extract the secret key of an embedded device. The existing state-of-the-art countermeasures mainly focus on the power balancing, gate-level masking, or signal-to-noise (SNR) reduction using noise injection and signature attenuation, all of which suffer either from the limitations of high power/area overheads, performance degradation or are not synthesizable. In this article, we propose a generic low-overhead digital-friendly power SCA countermeasure utilizing physical Time-Varying Transfer Functions (TVTF) by randomly shuffling distributed switched capacitors to significantly obfuscate the traces in the time domain. System-level simulation results of the TVTF-AES implemented in TSMC 65nm CMOS technology show > 4000x MTD improvement over the unprotected implementation with nearly 1.25x power and 1.2x area overheads, and without any performance degradation