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Topic: Time-space tradeoff

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Space-time tradeoff - Wikipedia, the free encyclopedia In the case of the sorting problem, a space-time tradeoff can be made by using a different algorithm such as binary tree sort. A space-time tradeoff can be applied to the simple problem of data storage. If data is stored uncompressed, it takes more space but less time than if the data were stored compressed (since compressing the data reduces the amount of space it takes, but it takes time to run the compression algorithm). en.wikipedia.org /wiki/Space-time_tradeoff   (423 words)

Space-Time Tradeoffs This is an example of a space-versus-time tradeoff. Time is the length of the longest path in a multigraph and space is the logarithm of its number of vertices. If the space is increased, the number of computation steps (time) can generally be reduced. www.cs.brown.edu /people/jes/book/BOOK/node17.html   (428 words)

An Introduction to Time-Space Tradeoff As for Time-space tradeoff for Sorting, there are many traditional algorithms for sorting, but few of them can make tradeoff between Time and Space. [3] A. Borodin, "Time Space Tradeoffs (Getting Closer to the Barrier?)," in Algorithms and Computation; 4th International Symposium, ISAAC'93 (K. Ng, P. Raghavan, N. Balasubramanian, and F. Chin, eds.), Springer-Verlag, LNCS 762, December 1993. Of course in these algorithms the time and space and space in the algorithm are fixed and can not be trade-off. www.arches.uga.edu /~luoxz/luo6610/report   (685 words)

Principles There were two reasons that the reduction in space led to a reduction in time: less data to process means less time to process it, and keeping data in main memory rather than on disk avoids the overhead of disk accesses. It took him a couple of hours to implement the program in a few dozen lines of code, which was far superior to the hundreds of lines of code and the week of programming time that we had feared at the start of the phone call. Those facts contain the first lesson from this case study: careful analysis of a small problem can sometimes yield tremendous practical benefits. cm.bell-labs.com /cm/cs/pearls/sec015.html   (653 words)

Dictionary attack It is possible to achieve a time-space tradeoff through precomputation by encrypting and storing a list of encrypted dictionary words, sorting by the encrypted 'value'. It is worth noting that dictionaries for most human languages (even those no longer used) are now easily accessible on the Internet so using little known foreign words (eg Maori words) no longer helps prevent dictionary attacks in principle, and to a considerable extent in practice. For example, one can attempt to guess a password on a computer in an English speaking country by encrypting each of a list of English words and comparing each encryption against the stored encrypted version of users' passwords. www.brainyencyclopedia.com /encyclopedia/d/di/dictionary_attack.html   (363 words)

programming projects in cryptography 40-60 points b) Implement Shanks algorithm (space-time tradeoff) to attack the Discrete Log problem using Bignum or LIP. Assume that plaintext input is in the form of upper case and punctuation and spaces are not encrypted. Every time a character is encrypted the first rotor revolves one position clockwise. www.cs.umbc.edu /~stephens/crypto/project1.html   (2606 words)

Cprogramming.com - Article - Efficiency, Time and Space Of course, the type of compromise made depends on the situation, but generally, for most programmers, time is of the essence, while for locations in which memory is scarce, of course, space is the issue. Thus, there has to be a balance in the space and time aspects of computing. This adds an amount of space to the program, but it helps speed it up by avoiding otherwise time consuming calculations. www.cprogramming.com /tutorial/computersciencetheory/timespace.html   (896 words)

Meet-in-the-middle attack - Wikipedia, the free encyclopedia The Meet-in-the-middle attack is a cryptographic attack which, like the birthday attack, makes use of a space-time tradeoff. Diffie and Hellman, however, devised a time-memory tradeoff that could break the scheme in only double the time to break the single-encryption scheme It was first developed as an attack on an attempted expansion of a block cipher by Diffie and Hellman in 1977. en.wikipedia.org /wiki/Meet-in-the-middle_attack   (283 words)

Labio, W.; Quass, D.; Adelberg, B.: Physical Database Design for Data Warehousing To improve query response time, the warehouse administrator (WHA) will often materialize views defined on the local relations to support common or complicated Unfortunately, the requirement to keep the views consistent with the local relations creates additional overhead when the remote sources change. Often the down time can be reduced by adding carefully selected materialized views or indexes to the physical schema. This paper studies how to select the sets of supporting views and of indexes to materialize to minimize the down time. dbpubs.stanford.edu:8090 /pub/1996-40   (463 words)

Ashfaq's Homepage That was the same time when a spate of amazing innovations in the field of computer and software technology ushered into the global scenario, leaving a deep, indelible impact on my slowly expanding mind. That was a time when I was to take a decision, a decision about my life’s vocation, a decision to blend my future pursuits into the right stride. At the same time, I along with my group of friends, kept working hard to devise some innovative software systems, systems that might be of value to our surroundings, systems which people around us will find interesting and useful. www.cis.upenn.edu /%7Eashfaq/ps.html   (2864 words)

NIST's AES Round 1 Report NIST agrees that such tradeoffs were undoubtedly made, and that the candidates should be neither rewarded nor penalized based purely on their decision for handling the security/speed tradeoff. Another consideration is the extra space needed for decryption, in the event that the decryption function is different from the encryption function and both must be included in an implementation. That is, timing and power analysis are implementation-dependent attacks; the vulnerability of candidates to such attacks is not an intrinsic algorithm characteristic. csrc.nist.gov /encryption/aes/round1/r1report.htm   (13423 words)

NetResearch Instructor's Guide: Hidden CS Topics Space efficiency vs. time efficiency: This is perhaps the most fundamental tradeoff in all of computer science, and it appears (in disguise) in several aspects of Internet searching. A copy may be accessed more rapidly than the original, saving time, but it takes up space on one's hard drive. This tradeoff is found throughout the experimental sciences, and Internet searching brings it to the general population. www.blazemonger.com /netresearch/cstopics.html   (1394 words)

Is and Is-Not, A Look at Superposition This is a tradeoff between time and space. This suggests that space and time are inversely proportionate, literally, space would be the inverse of time. This was the first in a series of either/or tradeoffs that they encountered as the macroscopic world gave way to the microscopic one. www.virtualchaos.org /science/is-not.html   (1838 words)

Achieving the Rate-Diversity Tradeoff of Space-Time Codes V. Kumar, "Rate-diversity tradeoff of space-time codes with fixed alphabet and optimal constructions for PSK modulation," IEEE Trans Information Theory, Vol. It turns out that for a fixed signal constellation, there is a tradeoff between the rate at which information can be transmitted and the rapidity (diversity gain) with which the error probability decays with increase in SNR. In this work, we have recently succeeded in constructing signal sets that are capable of achieving any given point on the rate-diversity gain tradeoff. ece.iisc.ernet.in /~vijay/Space-Time_Blurp.htm   (247 words)

The Great Debates: Pass Phrases vs. Passwords. Part 2 of 3 The time-space tradeoff means that you do not store all possible hashes, which would require more storage than exists in the universe (if you try to store NT hashes). What is new is the theory and practice behind the space-time tradeoff, advanced by Dr. Phillippe Oechslin. If there are 5 characters per word, we have 25+4=29 characters, where 4 are spaces, in the pass phrase. www.microsoft.com /technet/security/secnews/articles/itproviewpoint100504.mspx   (2281 words)

Baby-step giant-step - Wikipedia, the free encyclopedia The algorithm is based on a space-time tradeoff. Since hash tables can retrieve and add elements in O(1) time (constant time), this does not slow down the overall baby-step giant-step algorithm. The hashing is done on the second component, and to perform the check in step 1 of the main loop, γ is hashed and the resulting memory address checked. en.wikipedia.org /wiki/Baby-step_giant-step   (393 words)

Module4.doc So we have a classical space/time tradeoff: a relatively larger directory may enhance the hit-rate, which lowers the average time needed to fetch data or instructions; a relatively smaller directory saves space, but perhaps at the expense of lowering the hit-rate and, therefore, increasing the average amount of time required to fetch data or instructions. Suppose, for example, that the access time to an L1 instruction cache (i.e., a cache dedicated to holding instructions) is 1ns, whereas access time to RAM is 100ns. This tradeoff should be kept squarely in mind throughout the discussion that follows. condor.depaul.edu /~mkalin/345ol/Module4.doc   (3102 words)

Garbage Collection The natural space/time tradeoff would create an anti-correlation, so the effects of that tradeoff were small compared to the algorithmic effects. In other words, the renewal-older-first collector performed better in terms of space on the same benchmarks for which it performed better in terms of time, and performed worse in terms of space on the benchmarks for which it performed worse in terms of time. The extra gc time was generally offset by lower mutator time, however, so the overall time was usually comparable. www.ccs.neu.edu /home/will/GC   (1018 words)

Pierrette P. Zouein's Dissertation Abstract When no solution is found, i.e., when the resources needed in a given time period cannot be accommodated on site without violating constraints on their positions, MoveSchedule adjusts durations or start dates of activities to lower the total space need over the problematic time period. More importantly, it helps identify construction time periods with potential spatial conflicts due to limited space so that they can be avoided in early project plans. Solving it involves creating a sequence of layouts that span the entire project duration, given resources, the timing of their presence on site, their changing demand for space over time, constraints on their location, and costs for their relocation. www.ce.berkeley.edu /~tommelein/95-Zouein-PhD.html   (856 words)

Super-linear time-space tradeoff lower bounds for randomized computation Our techniques are an extension of those used by M. Ajtai (1999) in his time-space tradeoffs for deterministic RAM algorithms computing element distinctness and for deterministic Boolean branching programs computing an explicit function based on quadratic forms over GF(2). For the same functions considered by Ajtai, we prove a time-space tradeoff of the form T=/spl Omega/(n/spl radic/(log(n/S)/log log(n/S))). In particular for space 0(n/sup 1-/spl epsiv//), this improves the lower bound on time to /spl Omega/(n/spl radic/(log n/log log n)). csdl.computer.org /comp/proceedings/focs/2000/0850/00/08500169abs.htm   (293 words)

Rico Mariani's Performance Tidbits : My mom doesn't care about space There is still a time-space tradeoff, but with a dependency between the time to access 1 memory unit and the overall memory consumption. Time-space tradeoffs are out there, but it's only by being very clever that you can actually gain speed by using space. Yup you heard it here first folks, all that stuff they taught you about time-space tradeoffs is bunk: your default assumption should be that smaller is faster. blogs.msdn.com /ricom/archive/2004/03/15/89934.aspx   (1223 words)

Berkeley Lab Technology Dramatically Speeds Up Searches of Large Databases A bitmap index is a method of reducing the response time of queries involving common types of conditions in data objects, such as "state = CA" and "age >= 21." It achieves this by storing certain pre-computed answers as bitmaps. Compounding the complexity of the search is the fact that the data files are on mass storage systems around the world, so locating and extracting these scientific needles from a virtual haystack of information would be very time-consuming and labor-intensive. At Supercomputing 2004, a preliminary version of the software was demonstrated to display in real time the isosurfaces of large complex data produced from a simulation of the Rayleigh-Taylor instability in computational fluid dynamics. www.physorg.com /news4137.html   (1668 words)

UW-Madison Theory of Computing Seminar 10/14/02 We prove a time-space tradeoff that interpolates these two simulations. Nisan showed that any randomized logarithmic space algorithm (running in polynomial time and with two-sided error) can be simulated by a deterministic algorithm that runs in simultaneous polynomial time and O(log^2 n) space. Subsequently Saks and Zhou improved the space bound and showed that the deterministic simulation can be carried out in space O(log^1.5 n). www.cs.wisc.edu /areas/theory/Seminar/Fall02/021014.html   (158 words)

2005gmk.html An integral part of the algorithm is an interesting use of F_0 (the number of distinct elements) estimation algorithms; we also provide other results along the space/time/approximation tradeoff curve. In a stream setting (sublinear space), we give the first algorithm for estimating the entropy of a distribution. In many problems in data mining and machine learning, data items that need to be clustered or classified are not points in a high-dimensional space, but are distributions (points on a high dimensional simplex). www.research.att.com /areas/visualization/papers_videos/2005gmk.html   (377 words)

Journal of the ACM -- 1979 A linear time algorithm for deciding interval graph isomorphism. Time bounded random access machines with parallel processing. Estimating the mean of a correlated binary sequence with an application to discrete event simulation. theory.lcs.mit.edu /~jacm/jacm79.html   (260 words)

RCS—A System for Version Control Usage statistics show that RCS’s delta storage method is space and time efficient. The piece table approach has the property that the time for applying a single delta is roughly determined by the size of the delta, and not by the size of the revision. Thus, the regeneration time for all revisions is the same: all headers must be inspected, and the associated blocks either copied or skipped. www.uvm.edu /%7Eashawley/rcs/tichy1985rcs/rcs.xml   (6783 words)

Re: [UAI] how to evaluate approximate algorithms It allows "smooth" time-space tradeoff as you can trade space at the increment of X-bytes, where X is the number of bytes needed to store a floating point number in a cache. The algorithm is then helpful if "space" is the bottleneck instead of "time." There is no publically available implementation at this stage, but I am planning to make one available later this summer. One can also predict the running time of the algorithm under different amounts of space. www.mail-archive.com /uai@cs.orst.edu/msg01269.html   (118 words)

Computer Science 68, Notes 02-20 This illustrates a general space-time tradeoff in copying collection: the more space given to the collector, the less time it spends collecting (the tradeoff also holds for mark-sweep collection, although the impact is less dramatic). Allocation in a contiguous space is incredibly fast: just keep a pointer to the boundary between the allocated and free areas, and increase this pointer to allocate a new object. In fact, during the next collection, the collector can use the old from-space as a new to-space, and overwrite whatever data happened to be left there; after each collection, the roles of to-space and from-space are swapped. www.cs.dartmouth.edu /~cs68/04w/notes-02-23.html   (2870 words)

Footprint and Performance Brownbags Promote unused members of frequently used objects into parent/owner of object as lists (space/time tradeoff). The keep it alive for 10 secs is for Space Trace - it by default ignores all allocations that live for less than 10 secs. Focus on objects that are allocated many times and long lived. www.mozilla.org /performance/footprint-brownbag.html   (450 words)

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