We study the online maximum coverage problem on a target interval, in which, given an online sequence of sub-intervals (which may intersect among each other) to arrive, we aim to select at most k of the sub-intervals ...
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We study the online maximum coverage problem on a target interval, in which, given an online sequence of sub-intervals (which may intersect among each other) to arrive, we aim to select at most k of the sub-intervals such that the total covered length of the target interval is maximized. The decision to accept or reject each sub-interval is made immediately and irrevocably right at the release time of the sub-interval. We comprehensively study various settings of this problem regarding both the length of each released sub-interval and the total number of released sub-intervals. To begin with, we investigate the offline version of the problem where the sequence of all the released sub-intervals is known in advance to the decision-maker and propose two polynomial-time optimal solutions to different settings of our offline problem. For the online problem, lower bounds on the competitive ratio are first proposed on our well-designed release schemes of sub-intervals. Then, we propose a Single-threshOld-based deterministic algorithm (SOA), which adds a sub-interval if the added length without overlap exceeds a certain threshold, achieving competitive ratios close to the lower bounds. Further, we extend SOA to a Double-threshOlds-based deterministic algorithm (DOA) by using the first threshold for exploration and the second threshold (larger than the first one) for exploitation. With the two thresholds generated by our proposed program, we show that DOA outperforms SOA slightly in the worst-case scenario. Moreover, we show that more thresholds cannot induce better worst-case performance of an online deterministic algorithm as long as those thresholds are used in non-increasing order in accepting sub-intervals.
Idling, or running the engine when the vehicle is not moving, accounts for 13%-23% of vehicle driving time and costs billions of gallons of fuel each year. In this paper, we consider the problem of idling reduction un...
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Idling, or running the engine when the vehicle is not moving, accounts for 13%-23% of vehicle driving time and costs billions of gallons of fuel each year. In this paper, we consider the problem of idling reduction under the uncertainty of vehicle stop time. We abstract it as a classic ski rental problem, and propose a constrained version with two statistics mu(B)- and q(B+), the expected length of short stops and the probability of long stops. We develop two online algorithms, a suboptimal closed-form algorithm and an optimal numerical solution, that combine the best of the well-known deterministic and randomized schemes to minimize the worst case competitive ratio. We demonstrate the algorithms perform better than existing solutions in terms of both worst case guarantee and average case performance using simulation and real-world driving data.
Age of information (AoI) is recently proposed to measure the freshness of information, which provides a new performance metric for the real-time Internet of Things (IoT). In this letter, we investigate low complexity ...
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Age of information (AoI) is recently proposed to measure the freshness of information, which provides a new performance metric for the real-time Internet of Things (IoT). In this letter, we investigate low complexity online algorithms to minimize the average AoI in an IoT system where the nodes are scheduled to sample the status with multiple packets and send it to the destination through noisy channels. Three online policies are proposed: Greedy policy, Max-Ratio policy and Lyapunov drift policy. Simulation results show that our online algorithms outperform the existing suboptimal algorithm and the Lyapunov drift policy yields the best performance.
In this short note, we consider a graph process recently introduced by Frieze, Krivelevich and Michaeli. In their model, the edges of the complete graph K-n are ordered uniformly at random and are then revealed consec...
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In this short note, we consider a graph process recently introduced by Frieze, Krivelevich and Michaeli. In their model, the edges of the complete graph K-n are ordered uniformly at random and are then revealed consecutively to a player called Builder. At every round, Builder must decide if they accept the edge proposed at this round or not. We prove that, for every d >= 2, Builder can construct a spanning d-connected graph after (1 + o (1)) n log n/2 rounds by accepting (1 + o (1)) dn/2 edges with probability converging to 1 as n -> 8. This settles a conjecture of Frieze, Krivelevich and Michaeli.
This paper investigates the general k-search problem, in which a player is to sell totally k units of some asset within n periods, aiming at maximizing the total revenue. At each period, the player observes a quoted p...
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This paper investigates the general k-search problem, in which a player is to sell totally k units of some asset within n periods, aiming at maximizing the total revenue. At each period, the player observes a quoted price which expires before the next period, and decides irrecoverably the amount of the asset to be sold at the price. We present a deterministic online algorithm and prove it optimal for the case where k <= n - 1. For the other case where k >= n, we show by numerical illustration that the gap between the upper and the lower bound of competitive ratio is quite small for many situations. (C) 2011 Elsevier B.V. All rights reserved.
In this paper, we consider a variant of the classical parallel machine scheduling problem. For this problem, we are given m potential identical machines to non-preemptively process a sequence of independent jobs. Mach...
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In this paper, we consider a variant of the classical parallel machine scheduling problem. For this problem, we are given m potential identical machines to non-preemptively process a sequence of independent jobs. Machines need to be activated before starting to process, and each machine activated incurs a fixed machine activation cost. No machines are initially activated, and when a job is revealed the algorithm has the option to activate new machines. The objective is to minimize the sum of the makespan and activation cost of machines. We first present two optimal online algorithms with competitive ratios of 3/2 and 5/3 for m = 2, 3 cases, respectively. Then we present an online algorithm with a competitive ratio of at most 2 for general m >= 4, while the lower bound is 1.88.
In this paper, we study the Min-cost Perfect k-way Matching with Delays (k-MPMD), recently introduced by Melnyk et al. In the problem, m requests arrive one-by-one over time in a metric space. At any time, we can irre...
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In this paper, we study the Min-cost Perfect k-way Matching with Delays (k-MPMD), recently introduced by Melnyk et al. In the problem, m requests arrive one-by-one over time in a metric space. At any time, we can irrevocably make a group of k requests who arrived so far, that incurs the distance cost among the k requests in addition to the sum of the waiting cost for the k requests. The goal is to partition all the requests into groups of k requests, minimizing the total cost. The problem is a generalization of the min-cost perfect matching with delays (corresponding to 2- MPMD). It is known that no online algorithm for k-MPMD can achieve a bounded competitive ratio in general, where the competitive ratio is the worst-case ratio between its performance and the offline optimal value. On the other hand, k-MPMD is known to admit a randomized online algorithm with competitive ratio O(k5 log n) for a certain class of k-point metrics called the Hmetric, where n is the size of the metric space. In this paper, we propose a deterministic online algorithm with a competitive ratio of O(mk2) for the k-MPMD in H-metric space. Furthermore, we show that the competitive ratio can be improved to O(m + k2) if the metric is given as a diameter on a line.
The advent of Computing Power Network (CPN) has opened up vast opportunities for machine learning inference, yet the challenge of reducing high operational cost due to intensive computations and the sheer volume of in...
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The advent of Computing Power Network (CPN) has opened up vast opportunities for machine learning inference, yet the challenge of reducing high operational cost due to intensive computations and the sheer volume of inference tasks cannot be overlooked. Scheduling inference tasks for mitigating operational cost involves various challenges, such as migrating tasks under unpredictable CPN status, making time-coupled decisions for resource provisioning, and selecting computing sites based on dynamic electricity prices. To address these issues, we introduce CPN-Inference, a novel and flexible inference framework built upon CPN. Specifically, we formulate a time-varying integer program problem that aims to minimize long-term cost, involving switching cost, operational cost, communication cost, queuing cost, and accuracy loss. We also propose a group of polynomial-time online algorithms for supporting the formulated problem by solving delicately constructed subproblems based on the inputs predicted via online learning. Furthermore, our algorithms are proven for their competitive ratio, showcasing the performance gap between our approach and the offline optimum. A testbed is constructed to evaluate inference performance on real devices. Our comprehensive evaluations, based on datasets from real systems, demonstrate that our algorithms outperform multiple alternatives, by achieving an average cost reduction of 35%.
High computing power and large storage capacity are necessary for running big data tasks, which leads to high infrastructure costs. Infrastructure-as-a-Service (IaaS) clouds can provide configuration environments and ...
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High computing power and large storage capacity are necessary for running big data tasks, which leads to high infrastructure costs. Infrastructure-as-a-Service (IaaS) clouds can provide configuration environments and computing resources needed for running big data tasks, while saving users from expensive software and hardware infrastructure investments. Many studies show that the cost of computation can be reduced by caching intermediate results and reusing them instead of repeating computations. However, the storage cost incurred by caching a large number of intermediate results over along period of time may exceed the cost of computation, ultimately leading to an increase in total cost instead. For making optimal caching decisions, future usage profiles for big data tasks are needed, but it is generally very hard to predict them precisely. In this paper, to address this problem, we propose two practical online algorithms, one deterministic and the other randomized, which can determine whether to cache intermediate results to reduce the total cost of big data tasks without requiring any future information. We prove theoretically that the competitive ratio of the proposed deterministic (randomized) algorithm is min(2 - 1-eta, 2 - eta beta) (resp., e e-1 ). Using real-world Wikipedia data as well as synthetic datasets, we verify the effectiveness of our proposed algorithms through a large number of experiments based on the price of Alibaba's public IaaS cloud products.
We investigate and analyze the FFH algorithm proposed by Kinnersley and Langston [5]. We prove that the tight worst-case performance bound of FFH algorithm is 1.7, thereby answering a question in [5]. The case that bi...
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We investigate and analyze the FFH algorithm proposed by Kinnersley and Langston [5]. We prove that the tight worst-case performance bound of FFH algorithm is 1.7, thereby answering a question in [5]. The case that bin sizes can be chosen is also considered.
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