44449006
Online and semi-online scheduling of two machines under a grade of service provision
We consider the online scheduling of two machines under a grade of service (GoS) provision and its semi-online variant where the total processing time is known. Respectively for the online and semi-online problems, we develop algorithms with competitive ratios of 53 and 32 which are shown to be optimal.
16824799
A heuristic method for self‐healing ring design in a single‐homing cluster
In this paper, we consider a SONET (Synchronous Optical NETwork) USHR (Uni‐directional Self‐Healing Ring) design problem for a single‐homing cluster, i.e., a cluster with a single designated hub. The problem is formulated as a nonlinear integer programming problem and a branch and bound heuristic method based on the Lagrangian relaxation and subgradient optimization technique is proposed to handle the problem. In solving any ring design problem, we should deal with two different aspects of the ring design, namely, the ring routing aspect and the ring loading aspect. Both of these two aspects are well integrated and represented in our model. Such an integrated formulation has not been proposed in the existing literature mainly due to its computationally intractable complexity. In order to cope with such complexity, a preprocessing technique for reducing the complexity and several branch and bound strategies are proposed. The efficiency of the proposed method is tested through computational experiments. For the computational experiments, test problems are generated using the data obtained from the actual topologies in Seoul, Korea. The computational experiments show that the proposed method yields near‐optimum designs within reasonable computation time.
18088728
Order Consolidation for Batch Processing
We consider the batch processing of orders where either whole or part of a single order or a specific pair of different orders may be grouped in a batch with a fixed capacity. The problem can be modelled by a graph G = (V,E), where each node v$${\in}$$V corresponds to an order, its weight w(v) corresponds to the amount of ordered quantity and a pair of orders, say u and v may be grouped in a batch if there exists the edge (u,v) $${\in}$$E. The objective is to maximize the number of batches filled up to its capacity $$\lambda$$. In this paper, we prove that the problem is NP-hard and, moreover, that no PTAS exists unless P = NP. Then, an optimal algorithm is developed with running time O(|V|log |V|) for the special case when G is a tree.
7967901
The effect of machine availability on the worst-case performance of LPT
We consider the makespan minimization parallel machine scheduling problem where each machine may be unavailable for a known time interval. For this problem, we investigate how the worst-case behavior of the longest processing time first algorithm (LPT) is affected by the availability of machines. In particular, for given m machines, we analyze the cases where arbitrary number, λ, ranging from one to m - 1, machines are unavailable simultaneously. Then, we show that the makespan of the schedule generated by LPT is never more than the tight worst-case bound of 1 + ½ ⌊m/(m - λ)⌋ times the optimum makespan.
15655721
The Worst-case Analysis of the MULTIFIT Algorithm for Scheduling Nonsimultaneous Parallel Machines
Abstract In this paper we consider the nonsimultaneous multiprocessor scheduling problem, or NMSP for short. The NMSP is a makespan minimization scheduling problem which involves the nonpreemptive assignment of independent jobs on m parallel machines with different starting times. It is well known that the longest processing time (LPT) algorithm and the modified LPT(MLPT) algorithm yield schedules with makespans bounded by 3 2 − 1 2m and 4/3 times the optimum makespan, respectively. In this paper, we show that the best known worst-case performance bound, 4/3 of the MLPT, is tight by constructing a worst-case example. Then, we employ the bin-packing heuristic algorithm called the MULTIFIT to solve the NMSP and show that the makespan of the schedule generated by the MULTIFIT algorithm is bounded by 9/7+2−k times the optimum makespan, where k is the selected number of the major iterations in the MULTIFIT. This worst-case bound of the MULTIFIT algorithm is, so far, the best bound for the NMSP and the tightness of the bound is still an open question.
18938523
A two-dimensional vector packing model for the efficient use of coil cassettes
We consider the problem of efficiently packing steel products, known as coils, into special containers, called cassettes for shipping. The objective is to minimize the number of cassettes used for packing all the given coils where each cassette has capacity limits on both total payload weight and size. We model this problem as a two-dimensional vector packing problem and propose a heuristic. We also analyze the worst-case performance of the proposed algorithm under a special condition which, in fact, holds for the particular real-world case that we handled. Our computational experiment with real production data shows that the proposed algorithm performs quite satisfactorily in practice.
16993485
The reconstruction of binary patterns from their projections
Given the horizontal and vertical projections of a finite binary pattern <italic>f</italic>, can we reconstruct the original pattern <italic>f</italic>? In this paper we give a characterization of patterns that are reconstructable from their projections. Three algorithms are developed to reconstruct both unambiguous and ambiguous patterns. It is shown that an unambiguous pattern can be perfectly reconstructed in time <italic>m</italic> × <italic>n</italic> and that a pattern similar to an ambiguous pattern can also be constructed in time <italic>m</italic> × <italic>n</italic>, where <italic>m</italic>, <italic>n</italic> are the dimensions of the pattern frame.
428530
Scalable MPEG2 Video Servers with Heterogeneous QoS on Parallel Disk Arrays
In this paper we focus on the video storage unit of a video server. We present a new, flexible data placement strategy for independent parallel disk arrays. The trade-off between utilization efficiency and interactive delay is investigated for this data placement strategy. Based on this trade-off, we show the advantage of video servers supporting a range of interactivity QoS. For our data placement strategy, we show that using scalable video improves the utilization and interactivity performance of a video server. We use three-layer, scalable MPEG2 digital video to support resolution QoS at a video server. Finally, we show that the data placement strategy reduces the complexity of admission control at the video server to that of a single disk system.
23414354
An iconic query system with intensional feedback capabilities
In recent years the issue of the interaction between casual users and database systems has become increasingly important. Moreover, the introduction of multimedia and distributed databases has necessitated the design of querying systems capable of reducing unnecessary and costly accesses. The authors address these issues by proposing a visual query system based on (1) the extensive utilization of icons and natural language in order to facilitate the access and the understanding of the database and (2) the use of knowledge, or the intensional part of the database, in order to reduce the physical access to the actual data (extensional part). In their query system the perception of the database structure is made particularly easy by introducing the concept of generalized attribute.<<ETX>>
206416394
An Intelligent Image Database System
A prototype intelligent image database system (IIDS) that is based on a novel pictorial data structure is presented. This prototype system supports spatial reasoning, flexible image information retrieval, visualization, and traditional image database operations. A pictorial data structure, based on 2-D strings, provides an efficient means for iconic indexing in image database systems and spatial reasoning. The modular design of IIDS facilitates its implementation. Further extensions of the prototype system are discussed. >
16514620
SIMD architecture for job shop scheduling problem solving
Job shop is a typical environment for manufacturing high-variety and low-volume discrete parts. Good scheduling is critical and challenging to the competitiveness of job shops. The Lagrangian relaxation neural network (LRNN) provides an approach of quantifiable quality and successful industrial applications. To further speed up scheduling for large-scale problems, in this paper, the parallelism of the LRNN approach is exploited for hardware implementation. New designs include a SIMD architecture, its associated instruction set and detailed circuits. Logic level simulation of the circuit design shows consistent schedules with those obtained by a software implementation. The hardware implementation is expected to have a one to two orders speed-up over the software one.