437 research outputs found
Tight Load Balancing via Randomized Local Search
We consider the following balls-into-bins process with bins and
balls: each ball is equipped with a mutually independent exponential clock of
rate 1. Whenever a ball's clock rings, the ball samples a random bin and moves
there if the number of balls in the sampled bin is smaller than in its current
bin. This simple process models a typical load balancing problem where users
(balls) seek a selfish improvement of their assignment to resources (bins).
From a game theoretic perspective, this is a randomized approach to the
well-known Koutsoupias-Papadimitriou model, while it is known as randomized
local search (RLS) in load balancing literature. Up to now, the best bound on
the expected time to reach perfect balance was due to Ganesh, Lilienthal, Manjunath, Proutiere, and Simatos
(Load balancing via random local search in closed and open systems, Queueing
Systems, 2012). We improve this to an asymptotically tight
. Our analysis is based on the crucial observation
that performing "destructive moves" (reversals of RLS moves) cannot decrease
the balancing time. This allows us to simplify problem instances and to ignore
"inconvenient moves" in the analysis.Comment: 24 pages, 3 figures, preliminary version appeared in proceedings of
2017 IEEE International Parallel and Distributed Processing Symposium
(IPDPS'17
Multiphoton processes and higher resonances in the quantum regime of the free-electron laser
Despite exhibiting novel radiation features, the operation of the proposed
quantum free-electron laser would have the drawback that the number of emitted
photons is limited by one per electron, significantly reducing the output power
of such a device. We show that relying on different resonances of the initial
momentum of the electrons increases the number of emitted photons, but also
increases the required length of the undulator impeding an experimetal
realization. Moreover, we investigate how multiphoton processes influence the
dynamics in the deep quantum regime
A high-gain Quantum free-electron laser: emergence & exponential gain
We derive an effective Dicke model in momentum space to describe collective
effects in the quantum regime of a free-electron laser (FEL). The resulting
exponential gain from a single passage of electrons allows the operation of a
Quantum FEL in the high-gain mode and avoids the experimental challenges of an
X-ray FEL oscillator. Moreover, we study the intensity fluctuations of the
emitted radiation which turn out to be super-Poissonian
Improved Scheduling with a Shared Resource
We consider the following shared-resource scheduling problem: Given a set of
jobs , for each we must schedule a job-specific processing volume
of . A total resource of is available at any time. Jobs have a
resource requirement , and the resources assigned to them may vary
over time. However, assigning them less will cause a proportional slowdown.
We consider two settings. In the first, we seek to minimize the makespan in
an online setting: The resource assignment of a job must be fixed before the
next job arrives. Here we give an optimal -competitive algorithm with
runtime . In the second, we aim to minimize the
total completion time. We use a continuous linear programming (CLP) formulation
for the fractional total completion time and combine it with a previously known
dominance property from malleable job scheduling to obtain a lower bound on the
total completion time. We extract structural properties by considering a
geometrical representation of a CLP's primal-dual pair. We combine the CLP
schedule with a greedy schedule to obtain a -approximation
for this setting. This improves upon the so far best-known approximation factor
of .Comment: Submitted to COCOA 2023, Full Versio
Kindness or Hypocrisy : Political Mindset and Corporate Social Responsibility Decoupling in Chinese firms
This work was supported by National Natural Science Foundation of China: [Grant Number grant number 72202184]; Guanghua Talent Project of Southwestern University of Finance and Economics: [Grant Number NA].Peer reviewe
Simple and Efficient Leader Election
We provide a simple and efficient population protocol for leader election that uses O(log n) states and elects exactly one leader in O(n (log n)^2) interactions with high probability and in expectation. Our analysis is simple and based on fundamental stochastic arguments. Our protocol combines the tournament based leader elimination by Alistarh and Gelashvili, ICALP\u2715, with the synthetic coin introduced by Alistarh et al., SODA\u2717
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