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Topic: Worst-case performance

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Best, worst and average case - Wikipedia, the free encyclopedia Less widely found is best-case performance, but it does have uses, for example knowing the best cases of individual tasks can be used to improve accuracy of an overall worst case analysis. Average performance and worst-case performance are the most used in algorithm analysis. Worst case analysis has similar problems, typically it is impossible to determine the exact worst case scenario. en.wikipedia.org /wiki/Worst-case_performance   (510 words)

Best-case performance - Wikipedia, the free encyclopedia Development and choice of algorithms is rarely based on best-case performance: most academic and commercial enterprises are more interested in improving average performance and worst-case performance. The term best-case performance is used in computer science to describe the way an algorithm behaves under optimal conditions. This page was last modified 02:52, 5 March 2005. en.wikipedia.org /wiki/Best-case_performance   (71 words)

sort worst case comparisons are merely ceil(lg n) n - 2^(ceil(lg n)) + 1, which for powers of 2 becomes 1-n+n lg n, which beats quicksort's average cases for bigger n. It's O(n log n) in comparisons as well (worst case), best case of about half of that for basically presorted data, no data needs to be copied (only pointer changes) and you can combine sorting one sublist with scanning for the head of the next sublist, making the stuff pretty efficient. Counting Sort (average and worst case behavior O(n)) Considerations: If you have a long key or a small data set, ACM 347 will probably be fastest. www.math.niu.edu /~rusin/papers/known-math/96/sort   (1008 words)

Search Background The worst case performance is no better than a breadth-first algorithm, but on average a depth-first algorithm will find a feasible solution quicker. In the limiting case, the priority function could be simply that all next steps have the same priority and the algorithm becomes a breadth-first algorithm. On the average, this algorithm is an order-of-magnitude less than N in complexity where N is the number of nodes in the tree. www-db.stanford.edu /~burback/watersluice/node84.html   (710 words)

Sequential Software Engineering Methodology Corollary 2.2 (Sequential: Worst Case) The worst case performance of the sequential software engineering methodology is O(N) where N is the size of the space. If a solution exists, and the sequential software engineering methodology finds the solution, the best case performance is O(N), the worst case performance is O(N), while the average case performance is O(N) where N is the total number of steps in the environment. Corollary 2.3 (Sequential: Average Case) The average case performance of the sequential software engineering methodology is O(N) where N is the size of the space. www-db.stanford.edu /~burback/watersluice/node78.html   (659 words)

Dr. Rina Dechter @ UCI This project provides a statistical analysis of an average case performance of five different CSP algorithms for some classes of CSP problems where the worst case analysis provides guarantees, which are far behind of any computational resources available nowadays. In the non-uniform case the distribution function is polynomial with randomly chosen power between 1 and 2, so its derivative (the probability density function) is polynomial with randomly chosen power between 0 and 1. The second explanation is that the pairwise correlation between each particular parameter and performance is not enough and one should statistically analyze the performance vs. the whole set of graph parameters simultaneously. www.ics.uci.edu /~dechter/ics-275a/fall-99/sazhin-275a-project.html   (1899 words)

DMTCS vol 3 no 4 (1999), pp. 155-166 Algorithm H_m has a moderate asymptotic worst-case performance ratio in the range [1{2/3}..1{13/18}] for all m>=6; but the algorithm has a small asymptotic worst-case performance ratio in the range [1+1/(r+1)..1+1/r], when task sizes do not exceed 1/r of the total available processors, where r>1 is an integer. If this is not the case, you should contact your system administrator to install your browser correctly. The problem is NP-hard, since it includes the bin packing problem as a special case when all tasks have unit execution time. dmtcs.loria.fr /volumes/abstracts/dm030403.abs.html   (310 words)

Linux as a RTOS LG #96 In order to deliver the tight worst-case timing performance needed by hard real-time, the RTOS needs to be simple, small, predictable, and optimized to minimize the worst-case performance. However, performance becomes a weak point since microkernel architecture places heavy load on interprocess communication and context switching. Linux kernel developers have realized this fact that bare Linux kernel cannot give real time performance which is like oxygen to any embedded real life system. www.linuxgazette.com /issue96/bhargava.html   (932 words)

RTOS Selection Guide - real-time operating system, criteria, latency Given these characteristics and the relative priorities of the tasks and interrupts in your system, it is possible to analyze the worst-case performance of the software using a technique such as rate monotonic analysis. In the ideal case, their worst-case performance is well understood and documented. An operating system is said to be deterministic if the worst-case execution time of each of its system calls is calculable. www.netrino.com /Articles/RTOSes   (1185 words)

Discrete Loops And Worst Case Performance - Blieberger (ResearchIndex) Although discrete loops can be used for applications that would otherwise require general loops, discrete loops are known to complete in any case. Furthermore it is possible to determine the number of iterations of a discrete loop, while this is trivial to do for for-loops and extremely difficult for general loops. In this paper so-called discrete loops are introduced which narrow the gap between general loops (e.g. citeseer.ist.psu.edu /259013.html   (606 words)

How to Achieve Worst-Case Performance (ResearchIndex) The intuitive argument is that this should lead to systems whose performance reflects the average-case performance of their components. The intuitive assumption that self-timed designs leads to average case performance is wrong. Abstract: Average case performance" is an oft-cited motivation for self-timed design. citeseer.ist.psu.edu /greenstreet01how.html   (383 words)

LS98.txt The algorithm has been implemented in a router prototype, which has a worst-case performance of one million packets/s for up to 512 rules. If the classification is more subtle, including perhaps the pathological case of a simple list of addresses (arguably relevant for an ISP with many customers with a single point of ingress), the number of actual rules required increases with the number of individual ranges in the classification. The authors offer an incremental modification to this algorithm which reduces memory usage, and a further specialization of the algorithm for the case of two-attribute rules: those matching both a prefix-based source address range and an arbitrary destination address range. www.cs.rice.edu /~animesh/comp620/reviews/LS98.txt   (766 words)

Assessment of True Worst Case Circuit Performance Under Interconnect Parameter Variations Unlike device variations, which can be captured by worst/best case corner points, the effects of interconnect variations are context-dependent, which makes it difficult to capture the true worst-case timing performance. @inproceedings{AcarNassifLiuPileggi2000, author = {Emrah Acar, Sani R. Nassif, Ying Liu and Lawrence T. Pileggi}, title = {Assessment of True Worst Case Circuit Performance Under Interconnect Parameter Variations}, booktitle = {TAU 2000}, month = {December}, year = {2000}, URL = {http://www.gigascale.org/pubs/22.html} } This paper discusses an efficient method to explore the extreme values of performance metrics and the specific parameters that will cause these extreme performances. www.gigascale.org /pubs/22.html   (306 words)

A Method to Improve the Estimated Worst-Case Performance of Data Caching Remarkably, we find that all data structures in five out of the seven programs are predictable and will lead to a worst-case cache performance which is as high as the real performance. This paper presents a method for tight prediction of worst-case performance of data caches in high-performance real-time systems. Cache performance of accesses to predictable data structures can be automatically and accurately determined by our method whereas we let accesses to unpredictable data structures bypass the cache to simplify and improve the analysis. www.ce.chalmers.se /~thomasl/publications/data-rtcsa99.html   (224 words)

CS 321 -- Lab 11 - Fall 2003 Based on the previous question, what is the worst case performance of performing n merges that require finding the appropriate sets first? Improve the algorithm and discuss its worst-case performance Today, you will implement disjoint sets in various ways, improving on its performance as we go. www.snc.edu /compsci/CS321/lab11/lab11.html   (565 words)

Approximability and Nonapproximability Results for Minimizing Total Flow Time on a Single Machine The performance guarantee of our approximation algorithm is not far from best possible, as our second, negative result demonstrates: Unless P=NP, no polynomial-time approximation algorithm for minimum total flow time can have a worst-case performance guarantee of $O(n^{1/2-\eps})$ for any $\eps>0$. In this paper, we present one positive and one negative result on polynomial-time approximations for the minimum total flow time problem: The positive result is the first approximation algorithm with a sublinear worst-case performance guarantee of $O(\sqrt{n})$. This problem is well known to be NP-complete, and the best polynomial-time approximation algorithms constructed so far had (more or less trivial) worst-case performance guarantees of O(n). epubs.siam.org /sam-bin/dbq/article/30577   (234 words)

Variable-Sized Bin Packing: Tight Absolute Worst-Case Performance Ratios for Four Approximation Algorithms The worst case bounds are 2 for LFLAW and LFLRW, 3 for LAW, and 2+ln 2 for LRW. In this paper we consider a one-dimensional bin packing problem where the bins do not have identical sizes, or a variable-sized bin packing problem, to minimize the bin consumption, i.e., the total size of the opened bins. Four greedy approximation algorithms based on a construction approach called largest object first with least absolute waste (LFLAW), largest object first with least relative waste (LFLRW), least absolute waste (LAW), and least relative waste (LRW) are examined. epubs.siam.org /sam-bin/dbq/article/34669   (219 words)

Pattern Matching For a text of length n and a fixed pattern of length m the best performance of the algorithm is n/m and the worst case is n*m. For text of length n and pattern of length m, its average and best case running time is O(n) (meaning proportional to n), but the worst case scenario is O(n*m), which is one of the reasons why it is not widely used. The word 'suffix' is used in this case to refer to the fact that the trie contains all of the suffixes of a given block of text (perhaps a viral genome.) www.softpanorama.org /Algorithms/pattern_matching.shtml   (5525 words)

Philadelphia: Muni Wi-Fi's Worst-Case Scenario The problem with the Philadelphia project is that it stands to become the Terri Shiavo case of municipal wireless: a high-profile project that doesn't particularly resemble any others but, nevertheless, will be used to drive political agendas. That's why Philadelphia is the worst test of municipal wireless that anyone could find. Perform remote support and management on multiple systems simultaneously over a LAN, WAN and the Internet with this PC remote... www.eweek.com /article2/0,1759,1784105,00.asp?kc=EWNKT0209KTX1K0100440   (981 words)

Open Directory - Computers: Algorithms: Sorting and Searching This variation addresses those problems and bounds worst case performance. An Improved Comb Sort with Pre-defined Gap Table - The original comb sort is vulnerable to seriously degraded performance with certain repetitive input sequences. GNU libavl - Details of this collection of binary search tree and balanced tree library routines by Ben Pfaff. dmoz.org /Computers/Algorithms/Sorting_and_Searching   (391 words)

Average case performance vs. Worst-case guarantee Re: Average case performance vs. Worst-case guarantee sthaug Or will it buy a router which can give better performance in the average case (it may drop some packets if the traffic pattern changes suddenly)? When an ISP buys a router does it want a worst-case guarantee about the router's capabilities? www.merit.edu /mail.archives/nanog/2003-09/msg01406.html   (98 words)

Find in a Library: Optimal control with a worst-case performance criterion and applications Optimal control with a worst-case performance criterion and applications Find in a Library: Optimal control with a worst-case performance criterion and applications WorldCat is provided by OCLC Online Computer Library Center, Inc. on behalf of its member libraries. worldcatlibraries.org /wcpa/ow/adece4ca97527267a19afeb4da09e526.html   (59 words)

Political Calculations: Best and Worst Case Stock Market Investing that shows the general trend between investment holding period and the best and worst case performance of the stock market between 1926 and 1992. I used Siegel's data to create the best and worst case, inflation-adjusted, stock market performance formulas below, using various regression techniques available in Microsoft Excel (and some other mathematical manipulation) to come up with the equations: Compared to determining the effective return that an average "investor" can expect to earn from their "investment" in Social Security, working out the best and worst case investment returns from investing in the stock market turned out to be a breeze! politicalcalculations.blogspot.com /2005/01/best-and-worst-case-stock-market.html   (515 words)

Best, worst and average case - Wikipedia, the free encyclopedia Average performance and worst-case performance are the most used in algorithm analysis. In real-time systems, the worst case execution time is often of particular concern since it important to know how much time might be needed in the worst case to guarantee the algorithm would always finish on time. In computer science, best, worst and average cases of a given algorithm express what the resource usage is at least, at most and on average, respectively. en.wikipedia.org /wiki/Worst-case_performance   (652 words)

Rustem, B. and Howe, M.: Algorithms for Worst-Case Design and Applications to Risk Management. The main tool used is minimax, which ensures robust policies with guaranteed optimal performance that will improve further if the worst case is not realized. Conversely, the cost of the assured performance provided by robust worst-case decision making needs to be evaluated relative to optimal expected values. Indeed, the determination of the worst case becomes nontrivial when faced with numerous--possibly infinite--and reasonably likely rival scenarios. pup.princeton.edu /titles/7321.html   (652 words)

Cache structure and method for improving worst case execution time - Patent 6272599 The addressing pattern causing the worse case cache conflicts is identified, and some of the cached data causing this conflict is not cached thereby reducing the conflict. An apparatus and method for improving the WCET performance of applications run on computers having cache-based architectures by setting cache/no-cache bits to selectively control the caching of different regions of address space thereby reducing thrashing in the cache memory and improving the real-time performance of such applications. The cache structure according to claim 1, wherein the structure improves the WCET of an N-way set associative cache in which the size of a sequential address stream is greater than the total cache memory available. www.freepatentsonline.com /6272599.html   (2095 words)

Best and worst cases - Wikipedia, the free encyclopedia Worst case performance analysis is often easier to do than "average case" performance. Linear search on an array has a worst-case performance O(n), when the algorithm has to check every element, but the average running time is O(n/2), when the item to be found is around the middle of an array. In computer science, best and worst cases in a given algorithm express what the resource usage is at least and at most, respectively. en.wikipedia.org /wiki/Worst-case_performance   (2095 words)

Rustem, B. and Howe, M.: Algorithms for Worst-Case Design and Applications to Risk Management. The main tool used is minimax, which ensures robust policies with guaranteed optimal performance that will improve further if the worst case is not realized. Indeed, the determination of the worst case becomes nontrivial when faced with numerous--possibly infinite--and reasonably likely rival scenarios. Recognizing that robust decision making is vital in risk management, this book provides concepts and algorithms for computing the best decision in view of the worst-case scenario. www.pupress.princeton.edu /titles/7321.html   (508 words)

RISC Processor Worst-Case Execution Time Penalties This report presents analytical results of performance penalties due to worst-case execution time (WCET) estimates for RISC processors in real-time systems. The results clearly indicate where efforts should be made to reduce variability in processor designs. www.cs.umass.edu /Dienst/UI/2.0/Describe/ncstrl.umassa_cs/UM-CS-1995-110   (105 words)

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