[go: up one dir, main page]
More Web Proxy on the site http://driver.im/ skip to main content
10.1145/380752.380790acmconferencesArticle/Chapter ViewAbstractPublication PagesstocConference Proceedingsconference-collections
Article

Loss-less condensers, unbalanced expanders, and extractors

Published: 06 July 2001 Publication History

Abstract

An extractor is a procedure which extracts randomness from a detective random source using a few additional random bits. Explicit extractor constructions have numerous applications and obtaining such constructions is an important derandomization goal. Trevisan recently introduced an elegant extractor construction, but the number of truly random bits required is suboptimal when the input source has low-min-entropy. Significant progress toward overcoming this bottleneck has been made, but so far has required complicated recursive techniques that lose the simplicity of Trevisan's construction.
We give a clean method for overcoming this bottleneck by constructing {\em loss-less condensers}. which compress the n-bit input source without losing any min-entropy, using O(\log n) additional random bits. Our condensers are built using a simple modification of Trevisan's construction, and yield the best extractor constructions to date.
Loss-less condensers also produce unbalanced bipartite expander graphs with small (polylogarithmic) degree D and very strong expansion of (1-\epilon)D. We give other applications of our construction, including dispersers with entropy loss O(\log n), depth two super-concentrators whose size is within a polylog of optimal, and an improved hardness of approximation result.

References

[1]
M. Ajtai, J. Komlos, and E. Szemeredi. Sorting in clogn parallel steps. Combinatorica, 3:1-19, 1983.
[2]
M. Ajtai, J. Komlos, and E. Szemeredi. Deterministic simulation in Logspace. In 19th STOC, pages 132-140, 1987.
[3]
N. Alon, 1999. Personal communication.
[4]
S. Arora, F. T. Leighton, and B. M. Maggs. On-line algorithms for path selection in a nonblocking network. SIAM Journal on Computing, 25(3):600-625, June 1996.
[5]
H. Buhrman, P.B. Miltersen, J. Radhakrishnan, and S. Venkatesh. Are bitvectors optimal? In 32nd STOC, pages 449-458, 2000.
[6]
P. Feldman, J. Friedman, and N. Pippenger. Wide-sense nonblocking networks. SIAM Journal on Discrete Mathematics, 1:158-173, 1988.
[7]
O. Gabber and Z. Galil. Explicit construction of linear sized superconcentrators. Journal of Computer and System Sciences, 22:407-420, 1981.
[8]
O. Goldreich, R. Impagliazzo, L. Levin, R. Venkatesan, and D. Zuckerman. Security preserving amplification of hardness. In 31st FOCS, pages 318-326, 1990.
[9]
R. Impagliazzo, R. Shaltiel, and A. Wigderson. Near-optimal conversion of hardness into pseudo-randomness. In 40th FOCS, pages 181-190, 1999.
[10]
R. Impagliazzo, R. Shaltiel, and A. Wigderson. Extractors and pseudo-random generators with optimal seed length. In 32nd STOC, pages 1-10, 2000.
[11]
N. Kahale. Eigenvalues and expansion of regular graphs. Journal of the ACM, 42:1091-1106, 1995.
[12]
G.A. Margulis. Explicit construction of concentrators. Problems of Inform. Transmission, 9:325-332, 1973.
[13]
N. Nisan and A. Ta-Shma. Extracting randomness: A survey and new constructions. Journal of Computer and System Sciences, 58:148-173, 1999.
[14]
N. Nisan and A. Wigderson. Hardness vs. randomness. Journal of Computer and System Sciences, 49:149-167, 1994.
[15]
N. Nisan and D. Zuckerman. Randomness is linear in space. Journal of Computer and System Sciences, 52(1):43-52, 1996.
[16]
N. Pippenger. Sorting and selecting in rounds. SIAM Journal on Computing, 16(6):1032-1038, December 1987.
[17]
J. Radhakrishnan and A. Ta-Shma. Bounds for dispersers, extractors, and depth-two superconcentrators. SIAM Journal on Discrete Mathematics, 13(1):2-24, 2000.
[18]
R. Raz and O. Reingold. On recycling the randomness of states in space bounded computation. In 31st STOC, pages 159-168, 1999.
[19]
R. Raz, O. Reingold, and S. Vadhan. Extracting all the randomness and reducing the error in Trevisan's extractors. In 31st STOC, pages 149-158, 1999.
[20]
O. Reingold, R. Shaltiel, and A. Wigderson. Extracting randomness via repeated condensing. In 41st FOCS, pages 22-31, 2000.
[21]
M. Saks, A. Srinivasan, and S. Zhou. Explicit OR-dispersers with polylog degree. Journal of the ACM, 45:123-154, 1998.
[22]
M. Santha. On using deterministic functions in probabilistic algorithms. Information and Computation, 74(3):241-249, 1987.
[23]
M. Sipser. Expanders, randomness, or time vs. space. Journal of Computer and System Sciences, 36:379-383, 1988.
[24]
M. Sipser and D. A. Spielman. Expander codes. IEEE Transactions on Information Theory, 42(6):1710-1722, 1996.
[25]
A. Srinivasan and D. Zuckerman. Computing with very weak random sources. SIAM Journal on Computing, 28:1433-1459, 1999.
[26]
A. Ta-Shma. On extracting randomness from weak random sources. In 28th STOC, pages 276-285, 1996.
[27]
A. Ta-Shma. Almost optimal dispersers. In 30th STOC, pages 196-202, 1998.
[28]
L. Trevisan. Construction of extractors using pseudo-random generators. In 31st STOC, pages 141-148, 1999.
[29]
C. Umans. Hardness of approximating p2 minimization problems. In 40th FOCS, pages 465-474, 1999.
[30]
L.G. Valiant. Graph theoretic properties in computational complexity. Journal of Computer and System Sciences, 13:278-285, 1976.
[31]
A. Wigderson and D. Zuckerman. Expanders that beat the eigenvalue bound: Explicit construction and applications. Combinatorica, 19(1):125-138, 1999.
[32]
D. Zuckerman. General weak random sources. In 31st FOCS, pages 534-543, 1990.
[33]
D. Zuckerman. Simulating BPP using a general weak random source. Algorithmica, 16:367-391, 1996.
[34]
D. Zuckerman. Randomness-optimal oblivious sampling. Random Structures and Algorithms, 11:345-367, 1997.

Cited By

View all

Index Terms

  1. Loss-less condensers, unbalanced expanders, and extractors

      Recommendations

      Comments

      Please enable JavaScript to view thecomments powered by Disqus.

      Information & Contributors

      Information

      Published In

      cover image ACM Conferences
      STOC '01: Proceedings of the thirty-third annual ACM symposium on Theory of computing
      July 2001
      755 pages
      ISBN:1581133499
      DOI:10.1145/380752
      Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from [email protected]

      Sponsors

      Publisher

      Association for Computing Machinery

      New York, NY, United States

      Publication History

      Published: 06 July 2001

      Permissions

      Request permissions for this article.

      Check for updates

      Qualifiers

      • Article

      Conference

      STOC01
      Sponsor:

      Acceptance Rates

      STOC '01 Paper Acceptance Rate 83 of 230 submissions, 36%;
      Overall Acceptance Rate 1,469 of 4,586 submissions, 32%

      Upcoming Conference

      STOC '25
      57th Annual ACM Symposium on Theory of Computing (STOC 2025)
      June 23 - 27, 2025
      Prague , Czech Republic

      Contributors

      Other Metrics

      Bibliometrics & Citations

      Bibliometrics

      Article Metrics

      • Downloads (Last 12 months)14
      • Downloads (Last 6 weeks)2
      Reflects downloads up to 01 Mar 2025

      Other Metrics

      Citations

      Cited By

      View all

      View Options

      Login options

      View options

      PDF

      View or Download as a PDF file.

      PDF

      eReader

      View online with eReader.

      eReader

      Figures

      Tables

      Media

      Share

      Share

      Share this Publication link

      Share on social media