Online OVSF code assignment has an important application to wireless communications. Recently, this problem was formally modeled as an online problem, and performances of online algorithms have been analyzed by the competitive analysis. The previous best upper and lower bounds on the competitive ratio were 10 and 5/3, respectively. In this paper, we improve them to 7 and 2, respectively. We als...

We consider the problem of nonclairvoyantly scheduling jobs, which arrive over time and have varying sizes and degrees of parallelizability, with the objective of minimizing the maximum flow. We give essentially tight bounds on the achievable competitiveness. More specifically we show that the competitive ratio of every deterministic nonclairvoyant algorithm is high, namely Ω( √ n). But there i...

In this paper, based on the Position Maintaining Strategy (PMS for short), on-line scheduling of k-truck problem, which is a generalization of the famous k-server problem, is originally presented by our team. We proposed several competitive algorithms applicable under different conditions for solving the on-line k-truck problem. First, a competitive algorithm with competitive ratio 2k + 1/θ is ...

Group scheduling in flexible flow shops: a hybridised approach of imperialist competitive algorithm and electromagnetic-like mechanism N. Karimi a , M. Zandieh b & A.A. Najafi c a Faculty of Industrial and Mechanical Engineering, Qazvin Islamic Azad University, Qazvin, Iran b Department of Industrial Management, Management and Accounting Faculty, Shahid Beheshti University, G.C., Tehran, Iran c...

We provide new competitive upper bounds on the performance of the memoryless, randomized caching algorithm RAND. Our bounds are expressed in terms of the inherent hit rate α of the sequence of memory references, which is the highest possible hit rate that any algorithm can achieve on the sequence for a cache of a given size. Our results show that RAND is (1−αe−1/α)/(1−α)-competitive on any refe...

We consider the class of balancing algorithms for two servers. Such algorithms have appeared in a number of the early papers on this problem; they are so named because they seek to \balance" the distance traveled evenly among the servers. In this paper, we show a universal lower bound on the competitive ratio of any balancing algorithm for two servers. The lower bound is equal to (5 + p 7)=2 (3...

The paging algorithm LRU-2 was proposed for use in database disk buffering and shown experimentally to perform better than LRU [O’Neil, O’Neil, and Weikum, 1993]. We compare LRU-2 and LRU theoretically, using both the standard competitive analysis and the newer relative worst order analysis. The competitive ratio for LRU-2 is shown to be 2k for cache size k, which is worse than LRU’s competitiv...

We study the extremal competitive ratio of Boolean function evaluation. We provide the first non-trivial lower and upper bounds for classes of Boolean functions which are not included in the class of monotone Boolean functions. For the particular case of symmetric functions our bounds are matching and we exactly characterize the best possible competitiveness achievable by a deterministic algori...

Following Mettu and Plaxton [15, 16], we study online algorithms for the k-medians problem. Such an algorithm must produce an incremental sequence F1 ⊆ F2 ⊆ · · · ⊆ Fn ⊆ F of sets of facilities. Mettu and Plaxton show that online metric medians has a (roughly) 40-competitive deterministic polynomial-time algorithm. We give improved algorithms, including a (24 + ǫ)competitive deterministic polyn...

We investigate the problem of on-line scheduling open shops of two and three machines with an objective of minimizing the schedule makespan. We 1rst propose a 1.848-competitive permutation algorithm for the non-preemptive scheduling problem of two machines and show that no permutation algorithm can be better than 1.754-competitive. Secondly, we develop a (27=19)-competitive algorithm for the pr...