29097074
Analysis on the Session Life Time Distribution of Gnutella
7180182
Minimizing mean flow time with error constraint
In a new model of task systems studied by J.W.S. Liu et al. (1987) each task is logically decomposed into two subtasks, mandatory and optional. The authors discuss preemptively scheduling this kind of task system on p>or=1 identical processors so as to minimize the mean flow time. Given a task system and an error threshold K, the goal is to find a preemptive schedule such that each task is executed in the interval of its release time and deadline, the average error is no more than K, and the mean flow time of the schedule is minimized. Such a schedule is called an optimal schedule. It is shown that the problem of finding an optimal schedule is NP-hard for each p>or=1, even if all tasks have the same ready time and deadline. For a single processor, a pseudo-polynomial time algorithm and polynomial time algorithms for various special cases of the problem are given.<<ETX>>
26809229
Packing Squares into a Square
Abstract The problem of determining whether a set of rectangles can be orthogonally packed into a larger rectangle has been studied as a geometric packing problem and as a floor planning problem. Recently, there is some renewed interest in this problem, as it is related to a job scheduling problem in a partitionable mesh connected system. In this paper we show that the problem of deciding whether a set of squares can be packed into a larger square is strongly NP-complete, answering an open question posed by Li and Cheng.
8828112
Real-Time Rate Control Via Variable Frame Rate and Quantization Parameters
Most of existing rate control schemes in the literature focus on the bit allocation under the assumption of constant frame rate. As a result, the distortion of consecutive frames varies in a great extent, which may result in low temporal quality (e.g. flickering effect). In this work, we design rate control with two control parameters (i.e. quantization factor and frame rate) to achieve better tradeoff between spatial quality and temporal quality in low complexity. Our optimization gives two suggested quantization step sizes. One is used to change the frame rate in order to allocate how many bits used in the current frame. Another one is used to change the quantization factor in order to quantize MBs to achieve target bit rates. The experimental results suggest that our scheme can achieve more consistent quality while keeping high spatial quality.
31592050
Analysis of a General Mass Storage System
A model of a general mass storage system is presented and its performance analyzed. The system is composed of a square two-dimensional grid of storage cells over which a single read/write head moves freely. The head can contain at most some fixed number b of cell contents. Algorithms for realizing an arbitrary permutation of the memory contents are presented for all ranges of b, particularly the important case $b = 1$; in each case the algorithms’ performances are explicitly characterized. Open problems, especially regarding the development of good heuristics, are then discussed.
6074974
Vertex Ranking of Asteroidal Triple-Free Graphs
We present an efficient algorithm for computing the vertex ranking number of an asteroidal triple-free graph. Its running time is bounded by a polynomial in the number of vertices and the number of minimal separators of the input graph.
15727543
Securing Mobile Agents for Electronic Commerce: An Experiment
Mobile software agents are becoming a major trend of distributed systems in the next decade. Electronic commerce and information retrieval are two prospective applications of mobile agents. Nevertheless, security is a crucial concern for such systems. Attacks to agents by malicious hosts are the most challenging part of the problem unsolved. In this paper, a Shopping Information Agent System (SIAS) is built based on mobile agent technology. Possible security attacks by malicious hosts to agents in the system are discussed, and solutions to prevent these attacks are presented. Security of the solutions is analysed, and the performance overhead introduced is evaluated.
12009161
Dynamic Placement of Records in Linear Storage
This paper considers allocation of space in a hnear storage medium when space must be allocated dynamically as customers arrive A heuristic is proposed for this problem and for a simple model of the resultmg reference sequence, we show that the average distance between consecutive references is asymptotically 7n/30, where n is the size of the storage For optimal static placement where one waits for all arrivals before any space allocation, the average distance is shown to be asymptotically 7n/30 For random placement, the average distance is asymptotically n/3 Thus, the heuristic is asymptotically optimal in a strong sense For reasonable values of n, we demonstrate that the heuristic is nearly as good as optimal static placement and much better than random placement