Storage Allocation Research Articles

Planning vehicle transhipment in a seaport automobile terminal using a multi-agent system

A multi-agent system (MAS) for supporting the planning of transhipments of imported finished vehicles via a seaport is presented. The focus is on storage allocation, i.e. the allocation of parking areas for the temporary storage of vehicles, and on deployment scheduling, i.e. the allocation of drivers to the vehicles that have to be moved in the terminal area. These planning tasks, which in practice are usually carried out by different operators, are assigned to two different agent types. A further agent, the coordinator agent, is responsible for combining the local sub-plans into an overall plan in such a way that the demand for drivers in the planning period is minimised and balanced. The MAS is tested using randomly generated problem instances with different distributions of the manufacturer shares in the vehicle streams. The tests verify a certain robustness of the MAS with regard to changes in the problem data, in particular to the number of permanently employed drivers and the cost surcharge for hired drivers. In addition, the results highlight that the minimum overall (relative) costs of the drivers depends on the number of permanently employed drivers and on the level of the cost surcharge for hired drivers.

OpenDHT

Large-scale distributed systems are hard to deploy, and distributed hash tables (DHTs) are no exception. To lower the barriers facing DHT-based applications, we have created a public DHT service called OpenDHT. Designing a DHT that can be widely shared, both among mutually untrusting clients and among a variety of applications, poses two distinct challenges. First, there must be adequate control over storage allocation so that greedy or malicious clients do not use more than their fair share. Second, the interface to the DHT should make it easy to write simple clients, yet be sufficiently general to meet a broad spectrum of application requirements. In this paper we describe our solutions to these design challenges. We also report our early deployment experience with OpenDHT and describe the variety of applications already using the system.

Upper bound for defragmenting buddy heaps

Knuth's buddy system is an attractive algorithm for managing storage allocation, and it can be made to operate in real-time. At some point, storage-management systems must either over-provide storage or else confront the issue of defragmentation. Because storage conservation is important to embedded systems, we investigate the issue of defragmentation for heaps that are managed by the buddy system. In this paper, we present tight bounds for the amount of storage necessary to avoid defragmentation. These bounds turn out to be too high for embedded systems, so defragmentation becomes necessary.We then present an algorithm for defragmenting buddy heaps and present experiments from applying that algorithm to real and synthetic benchmarks. Our algorithm relocates less than twice the space relocated by an optimal algorithm to defragment the heap so as to respond to a single allocation request. Our experiments show our algorithm to be much more efficient than extant defragmentation algorithms.

Minimizing the Buffer Size in Fault-Tolerant Video Servers for VBR Streams

To guarantee the high reliability of video services, video servers usually adopt parity-encoding techniques in which data blocks and their associated parity blocks form a parity group. For real-time video service, all the blocks in a parity group are prefetched in order to cope with a possible disk failure, thereby incurring a buffering overhead. In this paper, we propose a new scheme called Round-level Parity Grouping (RPG) to reduce the buffer overhead while restoring VBR video streams in the presence of a faulty disk. RPG allows variable parity group sizes so that the exact amount of data is retrieved during each round. Based on RPG, we have developed a storage allocation algorithm for effective buffer management. Experimental results show that our proposed scheme reduces the buffer requirement by 20% to 25%.

Design and control of an AS/RS

Automated storage/retrieval systems (AS/RSs) are a combination of equipment and controls which automatically handle, store and retrieve materials (components, tools, raw material and subassemblies) with great speed and accuracy. Consequently, they are widely used in industrial companies to manage products with cost-effective utilization of time, space and equipment. This paper presents a multi-parametric dynamic model of a product-to-picker storage system with class based storage allocation of products. Thousands of what-if scenarios are simulated in order to measure the impact of alternative design and operating configurations on the expected system performance and to identify the most critical factors and combinations of factors affecting the response of the system. Class based storage proves to be a very effective way of both reducing the picking cycle time and maximizing the throughput of the system. The rapid effectiveness of visual interactive simulation (VIS) in supporting the design (redesign) and control of new (existing) warehouses emerges, responding to the need for flexibility which modern companies need in order to adapt to strongly changing operating conditions quickly.

Periodic Streaming Data Reduction Using Flexible Adjustment of Time Section Size

Much of the research regarding streaming data has focused only on real time querying and analysis of recent data stream allowable in memory. However, as data stream mining, or tracking of past data streams, is often required, it becomes necessary to store large volumes of streaming data in stable storage. Moreover, as stable storage has restricted capacity, past data stream must be summarized. The summarization must be performed periodically because streaming data flows continuously, quickly, and endlessly. Therefore, in this paper, we propose an efficient periodic summarization method with a flexible storage allocation. It improves the overall estimation error by flexibly adjusting the size of the summarized data of each local time section. Additionally, as the processing overhead of compression and the disk I/O cost of decompression can be an important factor for quick summarization, we also consider setting the proper size of data stream to be summarized at a time. Some experimental results with artificial data sets as well as real life data show that our flexible approach is more efficient than the existing fixed approach.

Structural impacts on thallus and algal cell components of two lichen species in response to low-level air pollution in pacific northwest forests.

Lichens have long been regarded as bioindicators of air pollution, and structural studies typically have indicated negative impacts in highly polluted areas. In this research, Parmelia sulcata and Platismatia glauca were collected from one clean and two polluted sites in the Pacific Northwest forests of the United States to investigate the anatomical and ultrastructural responses of relatively resistant lichens to moderate air pollution. Light microscopy of polluted materials revealed only slight increases in the algal cell proportions of the thallus, and a decrease in the fungal cells of the medulla. Using transmission electron microscopy, increased lipid droplets in the cytoplasm and an increase in the cell wall thickness of the photobionts were found in the polluted lichens. These results were compared with physiological data in which the net carbon uptake did not show any significant differences; however, the total chlorophyll content was heightened in the polluted samples. The increased total chlorophyll content and the absence of any changes in the algal cell proportions of the polluted samples suggest that the photobionts possessed a higher chlorophyll content per unit volume of the photobiont at polluted sites. The results also indicate that lichens have altered their storage allocation in different cellular compartments. This may be a result of symbiotic readjustment(s) between the photobiont and the mycobiont. In comparison with the physiological results from these two species, these changes do not represent damaging effects by low-level air pollution.

Data Structures in Power System Reliability Estimation

In this paper a technique for the estimation of power system reliability using fault tree analysis (FTA) and the concept of data structures is presented. The proposed approach for representing the fault trees uses data structures concept and dynamic storage allocation which overcomes the dimensionality problem. This approach reduces the computational complexity and execution time. This method can efficiently handle systems having any number of cut-sets between the input-output nodes depending upon the available computer memory. Three sample power system networks are considered to test the efficiency of the algorithm developed and the computation times with different approaches are compared.

Building certified libraries for PCC: dynamic storage allocation

Proof-carrying code (PCC) allows a code producer to provide to a host a program along with its formal safety proof. The proof attests to a certain safety policy enforced by the code, and can be mechanically checked by the host. While this language-based approach to code certification is very general in principle, existing PCC systems have only focused on programs whose safety proofs can be automatically generated. As a result, many low-level system libraries (e.g., memory management) have not yet been handled. In this paper, we explore a complementary approach in which general properties and program correctness are semi-automatically certified. In particular, we introduce a low-level language, CAP, for building certified programs and present a certified library for dynamic storage allocation.

Scheduling intermediate storage multipurpose batch plants using the S‐graph

AbstractA graph theoretical approach is proposed for the optimal scheduling of multipurpose batch plants when constraints on intermediate storage allocation are met. The novel S‐graph representation is extended and combined with a set of rationales to consider intermediate storage policy in production scheduling. This set of rationales accelerates the optimization procedure, reducing the searching tree from the very beginning, without losing optimality. It is assumed that the storage units can be commonly used throughout the plant to achieve maximum plant flexibility. Therefore, the problem solved suggests the more general batch‐process transfer strategy, common intermediate storage policy (CIS). This policy is suggested for more flexible use of intermediate storage units. The accuracy of this proposed algorithm is tested with an exhaustive B&B search algorithm. The methodology is compared with other CIS algorithms and is applied to solve several case studies. The benefits of considering this kind of storage coupled with the use of the proposed algorithm are discussed through motivating examples. © 2004 American Institute of Chemical Engineers AIChE J, 50: 403–417, 2004

Mitigating the Effects of Climate Change on the Water Resources of the Columbia River Basin

The potential effects of climate change on the hydrology and water resources of the Columbia River Basin (CRB) were evaluated using simulations from the U.S. Department of Energy and National Center for Atmospheric Research Parallel Climate Model (DOE/NCAR PCM). This study focuses on three climate projections for the 21st century based on a `business as usual' (BAU) global emissions scenario, evaluated with respect to a control climate scenario based on static 1995 emissions. Time-varying monthly PCM temperature and precipitation changes were statistically downscaled and temporally disaggregated to produce daily forcings that drove a macro-scale hydrologic simulation model of the Columbia River basin at 1/4-degree spatial resolution. For comparison with the direct statistical downscaling approach, a dynamical downscaling approach using a regional climate model (RCM) was also used to derive hydrologic model forcings for 20-year subsets from the PCM control climate (1995–2015) scenario and from the three BAU climate(2040–2060) projections. The statistically downscaled PCM scenario results were assessed for three analysis periods (denoted Periods 1–3: 2010–2039,2040–2069, 2070–2098) in which changes in annual average temperature were +0.5,+1.3 and +2.1 °C, respectively, while critical winter season precipitation changes were –3, +5 and +1 percent. For RCM, the predicted temperature change for the 2040–2060 period was +1.2 °C and the average winter precipitation change was –3 percent, relative to the RCM controlclimate. Due to the modest changes in winter precipitation, temperature changes dominated the simulated hydrologic effects by reducing winter snow accumulation, thus shifting summer streamflow to the winter. The hydrologic changes caused increased competition for reservoir storage between firm hydropower and instream flow targets developed pursuant to the Endangered Species Act listing of Columbia River salmonids. We examined several alternative reservoir operating policies designed to mitigate reservoir system performance losses. In general, the combination of earlier reservoir refill with greater storage allocations for instream flow targets mitigated some of the negative impacts to flow, but only with significant losses in firm hydropower production (ranging from –9 percent in Period1 to –35 percent for RCM). Simulated hydropower revenue changes were lessthan 5 percent for all scenarios, however, primarily due to small changes inannual runoff.

An improvement of a beam search method for warehouse storage allocation planning problems minimizing the number of operations and the aggregated number of products for each customer

An improvement of a beam search method for warehouse storage allocation planning problems minimizing the number of operations and the aggregated number of products for each customer

OPTVersusLOADin Dynamic Storage Allocation

Dynamic storage allocation is the problem of packing given axis-aligned rectangles into a horizontal strip of minimum height by sliding the rectangles vertically but not horizontally. Where L= is the maximum sum of heights of rectangles that intersect any vertical line and OPT is the minimum height of the enclosing strip, it is obvious that $\ensuremath{\text{\it OPT}}\ge \ensuremath{\text{\it LOAD}}$; previous work showed that $\ensuremath{\text{\it OPT}}\le 3\cdot LOAD. We continue the study of the relationship between OPT and LOAD, proving that OPT=L+O((hmax/L)1/7)L, where hmax is the maximum job height. Conversely, we prove that for any $\epsilon>0$, there exists a c>0 such that for all sufficiently large integers $h_{\max}$, there is a dynamic storage allocation instance with maximum job height $h_{\max}$, maximum load at most L, and $\ensuremath{\text{\it OPT}}\geq L+c(h_{\max}/L)^{1/2+\epsilon}L$, for infinitely many integers L. En route, we construct several new polynomial-time approximation algorithms for dynamic storage allocation, including a $(2+\epsilon)$-approximation algorithm for the general case and polynomial-time approximation schemes for several natural special cases.

Finite-size scaling approach to dynamic storage allocation problem

It is demonstrated how dynamic storage allocation algorithms can be analyzed in terms of finite-size scaling. The method is illustrated in the three simple cases of the first-fit, next-fit and best-fit algorithms, and the system works at full capacity. The analysis is done from two different points of view—running speed and employed memory. In both cases, and for all algorithms, it is shown that a simple scaling function exists and the relevant exponents are calculated. The method can be applied on similar problems as well.

The Internet Backplane Protocol: a study in resource sharing

In this work we present the Internet Backplane Protocol (IBP), a middleware created to allow the sharing of storage resources, implemented as part of the network fabric. IBP allows an application to control intermediate data staging operations explicitly. As IBP follows a very simple philosophy, very similar to the Internet Protocol, and the resulting semantic might be too weak for some applications, we introduce the exNode, a data structure that aggregates storage allocations on the Internet.

Leaf area accumulation helps juvenile evergreen trees tolerate shade in a temperate rainforest.

Most knowledge of the physiological correlates of interspecific variation in shade tolerance derives from studies of first-year seedlings in artificial environments. The present study relates growth, allocation, foliage turnover, biomass distribution and gas exchange traits to low-light survival of large seedlings (20-100cm tall) of eight temperate rainforest evergreens under field conditions. Taxa for which natural mortality was not observed in low light during the 14-month study are referred to here as "shade-tolerant" species, and those which did die in the shade are referred to as "light-demanding" species. In low light (2-5% canopy openness), shade-tolerant species had slightly lower light compensation points than light-demanders. Light-demanding species had more plastic aboveground allocation patterns, generally allocating proportionally less aboveground biomass to foliage production than shade-tolerant associates in high light (>10% canopy openness), but more in low light. Foliage turnover was generally much slower in shade-tolerant species (10-40% year-1) than in light-demanding species (30-190%). As these differences in leaf retention outweighed variation in allocation, shade-tolerant species displayed higher leaf areas at all light levels. Furthermore, all shade-tolerant species gained leaf area in low light during the study period, whereas light-demanding taxa showed leaf area declines. Higher leaf area ratios, plus differences in light compensation points, indicate that large seedlings of shade-tolerant evergreens enjoy net carbon gain advantages over light-demanding associates in low light. However, minimal growth rate differences in low light imply higher storage allocation in shade-tolerant species. This study provides a rather different picture from that which has emerged from recent reviews of first-year seedling data, illustrating the long-term consequences of foliage turnover differences for biomass distribution, and suggesting that shade tolerance in juvenile evergreen trees is associated with a suite of traits which enhance net carbon gain, but not growth, in low light. Accumulation of a large foliage area through long leaf retention times is probably a key mechanism enhancing low-light carbon gain in evergreens.

Allocation of bandwidth and storage

We consider two allocation problems in this paper, namely, allocation of bandwidth and storage. In these problems, we face a number of independent requests, respectively, for reservation of bandwidth of a communication channel of fixed capacity and for storage of items into a space of fixed size. In both problems, a request is characterized by: (i) its required period of allocation; (ii) its required bandwidth (item width, respectively)and (iii)the profit of accepting the request. The problem is to decide which requests to accept so as to maximize the total profit. These problems in general are NP-hard. In this paper we provide polynomial-time algorithms for solving various special cases, and develop polynomial-time approximation algorithms for very general NP-hard cases with good performance guarantees.

Energy Storage and the Evolution of Population Dynamics

We explore the mutual dependence of life history evolution and population dynamics by modeling a structured rotifer population that preys on a dynamic food supply. We focus on the ecological role of energy storage. A physiologically based submodel describes how individual predators allocate assimilated energy among growth, reproduction, and storage. We use invasibility analyses to predict evolutionary stable strategies for energy allocation. Various proxy measures of fitness based on measurable biological quantities, such as average population size or average per-capita fecundity, fail to predict evolutionary stable strategies. The predicted strategies indicate that selection strongly favors storage allocation for juveniles, but only for adults when prey densities are high. With the evolution of energy storage, population dynamics can shift from aperiodic to stable cycles without any need to invoke group selection.

A Scalable and Efficient Storage Allocator on Shared-Memory Multiprocessors

An efficient dynamic storage allocator is important for time-critical parallel programs. In this paper, we present a fast and simple parallel allocator for fixed size blocks on shared-memory multiprocessors. We show both theoretically and empirically that the allocator incurs very low lock contention. The allocator is tested with parallel simulation applications with frequent allocation and release requests. The results confirm that our allocator is indeed very efficient.

A unified approach to approximating resource allocation and scheduling

We present a general framework for solving resource allocation and scheduling problems. Given a resource of fixed size, we present algorithms that approximate the maximum throughput or the minimum loss by a constant factor. Our approximation factors apply to many problems, among which are: (i) real-time scheduling of jobs on parallel machines, (ii) bandwidth allocation for sessions between two endpoints, (iii) general caching, (iv) dynamic storage allocation, and (v) bandwidth allocation on optical line and ring topologies. For some of these problems we provide the first constant factor approximation algorithm. Our algorithms are simple and efficient and are based on the local-ratio technique. We note that they can equivalently be interpreted within the primal-dual schema.