32709902
Disk Cache Design and Performance as Evaluated in Large Timesharing and Database Systems
38568062
Multiprocessor memory reference generation using Cerberus
Presents Cerberus, an efficient system for simulating the execution of shared-memory, multiprocessor programs on a uniprocessor workstation. Using EDS (execution-driven simulation), it generates address traces which can be used to drive cache simulations on-the-fly, eliminating the large disk space requirements needed by trace files. It is fast because it links the program to be traced together with the cache or statistics gathering tool into a single executable, which eliminates the context switching needed by communicating processes. It is flexible because it has a simple interface which allows users to easily add any kind of module to use the generated trace information. It compares favorably to other existing tracers; it runs on a commonly available workstation and it is accurate, allowing cycle-by-cycle interactions between the simulated processors. The resulting slowdown from Cerberus is approximately 31 in uniprocessor mode and 45-50 in multiprocessor mode, relative to the workloads run natively on the same machines. We demonstrate that EDS uses only 5% of the total execution cycles when combined with a cache simulator, and we show that EDS is just as efficient as using trace-driven simulation.
14158820
Disk caching in large database and timeshared systems
We present the results of a variety of trace-driven simulations of disk cache designs using traces from a variety of mainframe timesharing and database systems in production use. We compute miss ratios, run lengths, traffic ratios, cache residency times, degree of memory pollution and other statistics for a variety of designs, varying lock size, prefetching algorithm and write algorithm. We find that for this workload, sequential prefetching produces a significant (about 20%) but still limited improvement in the miss ratio, even using a powerful technique for detecting sequentiality. Copy-back writing decreased write traffic relative to write-through by more than 50%; periodic flushing of the dirty blocks increased write traffic only slightly compared to pure write-back, and then only for large cache sizes. Write-allocate had little effect compared to no-write-allocate. Block sizes of over a track don't appear to be useful. Limiting cache occupancy by a single process or transaction appears to have little effect. This study is unique in the variety and quality of the data used in the studies.
13154758
Design and characterization of the Berkeley multimedia workload
Abstract. The last decade has seen the integration of audio, video, and 3D graphics into existing workloads as well as the emergence of new workloads dominated by the processing of these forms of media. Unfortunately, widely accepted benchmarks which capture these new workloads in a realistic way have not emerged. The goal of this paper is to present the Berkeley multimedia workload, which was developed to facilitate our own studies on architectural support for multimedia. Here we present a survey of existing multimedia benchmarking methods, a description of the Berkeley multimedia workload, as well as a full workload characterization. We also extract a set of computationally important multimedia kernels for future study.
42361348
Analysis of the Optimal, Look-Ahead Demand Paging Algorithms
We express the future behavior of programs that may be described by two common program behavior models, the independent reference model and the LRU stack model, by a discrete time Markov chain. Using this Markov chain model, we are able to calculate the theoretical minimum number of page faults for a program representable by either of these models in either a fixed or variable size memory. The behavior of optimal look-ahead and optimal realizable demand paging algorithms are compared, and it is seen that look-ahead paging demonstrates an inherent advantage sufficient to account for the differences observed between currently implemented demand paging algorithms and theoretically optimal algorithms.
5777300
Evaluating Associativity in CPU Caches
The authors present new and efficient algorithms for simulating alternative direct-mapped and set-associative caches and use them to quantify the effect of limited associativity on the cache miss ratio. They introduce an algorithm, forest simulation, for simulating alternative direct-mapped caches and generalize one, which they call all-associativity simulation, for simulating alternative direct-mapped, set-associative, and fully-associative caches. The authors find that although all-associativity simulation is theoretically less efficient than forest simulation or stack simulation (a commonly used simulation algorithm), in practice it is not much slower and allows the simulation of many more caches with a single pass through an address trace. The authors also provide data and insight into how varying associatively affects the miss ratio. >
6414828
Local Search Genetic Algorithm for Optimization of Highly Reliable Communications Networks
This paper presents a genetic algorithm (GA) with specialized encoding, initialization and local search genetic operators to optimize communication network topologies. This NPhard problem is often highly constrained so that random initialization and standard genetic operators usually generate infeasible network architectures. Compounding this infeasibility issue is that the fitness function involves calculating the all-terminal reliability of the network, a calculation which is computationally expensive. Therefore, it is imperative that the search balances the need to thoroughly explore the boundary between feasible and infeasible networks, along with calculating fitness on only the most promising candidate networks. The algorithm results are compared to optimum results found by branch and bound and also to GA results without local search operators on a suite of 79 test problems. This GA strategy of employing bounds, simple heuristic checks and problem specific repair and local search operators can be used on other highly constrained combinatorial applications where numerous fitness calculations are prohibitive.
7048039
Establishing Communication Systems without Explicit Meaning Transmission
This paper investigates the development of experience-based meaning creation and explores the problem of establishing successful communication systems in a population of agents. The aim of the work is to investigate how such systems can develop, without reliance on phenomena not found in actual human language learning, such as the explicit transmission of meaning or the provision of reliable error feedback to guide learning. Agents develop individual, distinct meaning structures, and although they can communicate despite this, communicative success is closely related to the proportion of shared lexicalised meaning, and the communicative systems have a large degree of redundant synonymy.
16044004
Intelligent Meaning Creation in a Clumpy World Helps Communication
This article investigates the problem of how language learners decipher what words mean. In many recent models of language evolution, agents are provided with innate meanings a priori and explicitly transfer them to each other as part of the communication process. By contrast, I investigate how successful communication systems can emerge without innate or transferable meanings, and show that this is dependent on the agents developing highly synchronized conceptual systems. I present experiments with various cognitive, communicative, and environmental factors which affect the likelihood of agents achieving meaning synchronization and demonstrate that an intelligent meaning creation strategy in a clumpy world leads to the highest level of meaning similarity between agents.
7234685
Mining ChIP-chip data for transcription factor and cofactor binding sites
MOTIVATION
Identification of single motifs and motif pairs that can be used to predict transcription factor localization in ChIP-chip data, and gene expression in tissue-specific microarray data.


RESULTS
We describe methodology to identify de novo individual and interacting pairs of binding site motifs from ChIP-chip data, using an algorithm that integrates localization data directly into the motif discovery process. We combine matrix-enumeration based motif discovery with multivariate regression to evaluate candidate motifs and identify motif interactions. When applied to the HNF localization data in liver and pancreatic islets, our methods produce motifs that are either novel or improved known motifs. All motif pairs identified to predict localization are further evaluated according to how well they predict expression in liver and islets and according to how conserved are the relative positions of their occurrences. We find that interaction models of HNF1 and CDP motifs provide excellent prediction of both HNF1 localization and gene expression in liver. Our results demonstrate that ChIP-chip data can be used to identify interacting binding site motifs.


AVAILABILITY
Motif discovery programs and analysis tools are available on request from the authors.
2002086
Exploration of heterogeneous reconfigurable architectures
In contrast to early reconfigurable hardware, modern reconfigurable devices consist of a mixture of heterogeneous components. The heterogeneous components introduced in recent devices are both line and coarse-grain in their nature, and are primarily aimed at improving the speed, power consumption and area metrics of target designs. The aim of this PhD project is to look at analytical ways of exploring the design space of modern reconfigurable hardware. By automatically generating architectures and estimating benchmark performance, linear programming can eliminate architectural possibilities in an efficient way, meaning that a large number of different architectures can be examined in a fast and optimal manner.