On the study of recompressing strings

• Project/Area Number: 16K16009
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Theory of informatics
• Research Institution: Kyushu Institute of Technology
• Principal Investigator: I Tomohiro 九州工業大学, 大学院情報工学研究院, 准教授 (20773360)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000); Fiscal Year 2018: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2016: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
• Keywords: 文字列処理 / 可逆圧縮 / 圧縮変換 / 圧縮文字列処理 / データ圧縮 / 文字列圧縮 / アルゴリズム理論 / 列挙

Outline of Final Research Achievements

We studied the theory of compression to process huge string data. We obtained the following results: (1) We proposed a grammar compression method that works in optimal working space. (2) We showed how to answer longest common extension queries in grammar compressed strings (3) We proposed a practical algorithm to compute run-length encoded Burrows-Wheeler transform (RLBWT) in an online manner. (4) We showed how to compute Lempel-Ziv 77 via RLBWT in an online manner. (5) We proposed the first algorithm to compute RePair (the most notable grammar compression for its high compression performance) in compressed space.

Academic Significance and Societal Importance of the Research Achievements

巨大データを解析・利用するために圧縮は欠かせない技術であり，様々な圧縮手法が提案されている．しかし，一般に圧縮手法には利点と欠点があるため，必要なデータ処理に応じて圧縮形式を変換する技術の発展が望まれる．本研究では，圧縮されたデータの利用価値を上げるために，圧縮形式間の効率的な変換技法を提案した．

Research Products

• [Journal Article] Improved Upper Bounds on all Maximal alpha-gapped Repeats and Palindromes (2019)
  • Author(s): Tomohiro I, Dominik Koeppl
  • Journal Title: Theoretical Computer Science Volume: 753 Pages: 1-15
  • DOI: 10.1016/j.tcs.2018.06.033
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] RePair in Compressed Space and Time (2019)
  • Author(s): Kensuke Sakai, Tatsuya Ohno, Keisuke Goto, Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Journal Title: Data Compression Conference (DCC) 2019 Volume: - Pages: 518-527
  • Peer Reviewed
• [Journal Article] Lempel-Ziv Factorization Powered by Space Efficient Suffix Trees (2018)
  • Author(s): Fischer Johannes, I Tomohiro, Koppl Dominik, Sadakane Kunihiko
  • Journal Title: Algorithmica Volume: 80 Issue: 7 Pages: 2048-2081
  • DOI: 10.1007/s00453-017-0333-1
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] A faster implementation of online RLBWT and its application to LZ77 parsing (2018)
  • Author(s): Ohno Tatsuya、Sakai Kensuke、Takabatake Yoshimasa、I Tomohiro、Sakamoto Hiroshi
  • Journal Title: Journal of Discrete Algorithms Volume: 52-53 Pages: 18-28
  • DOI: 10.1016/j.jda.2018.11.002
  • Peer Reviewed / Open Access
• [Journal Article] LZ-ABT: A Practical Algorithm for α-Balanced Grammar Compression (2018)
  • Author(s): Tatsuya Ohno, Keisuke Goto, Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Journal Title: IWOCA 2018 Volume: - Pages: 323-335
  • DOI: 10.1007/978-3-319-94667-2_27
  • ISBN: 9783319946665, 9783319946672
  • Peer Reviewed
• [Journal Article] Block Palindromes: A New Generalization of Palindromes (2018)
  • Author(s): Keisuke Goto, Tomohiro I, Hideo Bannai, Shunsuke Inenaga
  • Journal Title: SPIRE 2018 Volume: - Pages: 183-190
  • DOI: 10.1007/978-3-030-00479-8_15
  • ISBN: 9783030004781, 9783030004798
  • Peer Reviewed
• [Journal Article] Privacy-Preserving String Edit Distance with Moves (2018)
  • Author(s): Shunta Nakagawa, Tokio Sakamoto, Yoshimasa Takabatake, Tomohiro I, Kilho Shin, Hiroshi Sakamoto
  • Journal Title: SISAP 2018 Volume: - Pages: 226-240
  • DOI: 10.1007/978-3-030-02224-2_18
  • ISBN: 9783030022235, 9783030022242
  • Peer Reviewed
• [Journal Article] Approximate Frequent Pattern Discovery in Compressed Space (2018)
  • Author(s): Shouhei Fukunaga, Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Journal Title: IEICE Transactions Volume: 101-D(3) Pages: 593-601
  • NAID: 130006414054
  • Peer Reviewed
• [Journal Article] Tighter Bounds and Optimal Algorithms for All Maximal α-gapped Repeats and Palindromes - Finding All Maximal α-gapped Repeats and Palindromes in Optimal Worst Case Time on Integer Alphabets (2018)
  • Author(s): Pawel Gawrychowski, Tomohiro I, Shunsuke Inenaga, Dominik Koppl, Florin Manea
  • Journal Title: Theory Comput. Syst. Volume: 62(1) Issue: 1 Pages: 162-191
  • DOI: 10.1007/s00224-017-9794-5
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] The "Runs" Theorem (2017)
  • Author(s): Hideo Bannai, Tomohiro I, Shunsuke Inenaga, Yuto Nakashima, Masayuki Takeda, Kazuya Tsuruta
  • Journal Title: SIAM J. Comput. Volume: 46(5) Issue: 5 Pages: 1501-1514
  • DOI: 10.1137/15m1011032
  • Peer Reviewed
• [Journal Article] Inferring strings from Lyndon factorization (2017)
  • Author(s): Yuto Nakashima, Takashi Okabe, Tomohiro I, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Theor. Comput. Sci. Volume: 689 Pages: 147-156
  • DOI: 10.1016/j.tcs.2017.05.038
  • Peer Reviewed / Open Access
• [Journal Article] Longest Common Extensions with Recompression (2017)
  • Author(s): Tomohiro I
  • Journal Title: Proc. the 28th Annual Symposium on Combinatorial Pattern Matching (CPM 2017) Volume: －
  • DOI: 10.4230/LIPIcs.CPM.2017.18
  • Peer Reviewed / Open Access
• [Journal Article] A Space-Optimal Grammar Compression (2017)
  • Author(s): Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Journal Title: Proc. 25th Annual European Symposium on Algorithms (ESA 2017) Volume: －
  • DOI: 10.4230/LIPIcs.ESA.2017.67
  • Peer Reviewed / Open Access
• [Journal Article] A Faster Implementation of Online Run-Length Burrows-Wheeler Transform (2017)
  • Author(s): Tatsuya Ohno, Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Journal Title: Proc. 28th International Workshop on Combinatorial Algorithms (IWOCA 2017) Volume: － Pages: 409-419
  • DOI: 10.1007/978-3-319-78825-8_33
  • ISBN: 9783319788241, 9783319788258
  • Peer Reviewed
• [Journal Article] Fully Dynamic Data Structure for LCE Queries in Compressed Space (2016)
  • Author(s): Takaaki Nishimoto, Tomohiro I, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: MFCS 2016 Volume: -
  • DOI: 10.4230/LIPIcs.MFCS.2016.72
  • Peer Reviewed / Open Access
• [Journal Article] Dynamic index and LZ factorization in compressed space (2016)
  • Author(s): Takaaki Nishimoto, Tomohiro I, Shunsuke Inenaga, Hideo Bannai and Masayuki Takeda
  • Journal Title: Proc. The Prague Stringology Conference (PSC 2016) Volume: - Pages: 158-170
  • Peer Reviewed / Open Access
• [Journal Article] Online Grammar Compression for Frequent Pattern Discovery (2016)
  • Author(s): Shouhei Fukunaga, Yoshimasa Takabatake, Tomohiro I and Hiroshi Sakamoto
  • Journal Title: Proc. the 13th International Conference on Grammatical Inference (ICGI 2016) Volume: - Pages: 93-104
  • NAID: 130008061357
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Presentation] RePair in Compressed Space and Time (2019)
  • Author(s): Kensuke Sakai, Tatsuya Ohno, Keisuke Goto, Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Organizer: Data Compression Conference (DCC) 2019
  • Int'l Joint Research
• [Presentation] LZ-ABT: A Practical Algorithm for α-Balanced Grammar Compression (2018)
  • Author(s): Tatsuya Ohno, Keisuke Goto, Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Organizer: International Workshop on Combinatorial Algorithms (IWOCA) 2018
  • Int'l Joint Research
• [Presentation] Block Palindromes: A New Generalization of Palindromes (2018)
  • Author(s): Keisuke Goto, Tomohiro I, Hideo Bannai, Shunsuke Inenaga
  • Organizer: International Symposium on String Processing and Information Retrieval (SPIRE) 2018
  • Int'l Joint Research
• [Presentation] Privacy-Preserving String Edit Distance with Moves (2018)
  • Author(s): Shunta Nakagawa, Tokio Sakamoto, Yoshimasa Takabatake, Tomohiro I, Kilho Shin, Hiroshi Sakamoto
  • Organizer: International Conference on Similarity Search and Applications (SISAP) 2018
  • Int'l Joint Research
• [Presentation] The Runs Theorem and Beyond (2018)
  • Author(s): Tomohiro I
  • Organizer: Developments in Language Theory (DLT) 2018
  • Int'l Joint Research / Invited
• [Presentation] Longest Common Extensions with Recompression (2017)
  • Author(s): Tomohiro I
  • Organizer: the 28th Annual Symposium on Combinatorial Pattern Matching (CPM 2017)
  • Int'l Joint Research
• [Presentation] A Space-Optimal Grammar Compression (2017)
  • Author(s): Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Organizer: 25th Annual European Symposium on Algorithms (ESA 2017)
  • Int'l Joint Research
• [Presentation] A Faster Implementation of Online Run-Length Burrows-Wheeler Transform (2017)
  • Author(s): Tatsuya Ohno, Yoshimasa Takabatake, Tomohiro I, Hiroshi Sakamoto
  • Organizer: Proc. 28th International Workshop on Combinatorial Algorithms (IWOCA 2017)
  • Int'l Joint Research
• [Presentation] Online Grammar Compression for Frequent Pattern Discovery (2016)
  • Author(s): Shouhei Fukunaga, Yoshimasa Takabatake, Tomohiro I and Hiroshi Sakamoto
  • Organizer: the 13th International Conference on Grammatical Inference (ICGI 2016
  • Place of Presentation: デルフト（オランダ）
  • Year and Date: 2016-10-05
  • Int'l Joint Research
• [Presentation] Dynamic index and LZ factorization in compressed space (2016)
  • Author(s): Takaaki Nishimoto, Tomohiro I, Shunsuke Inenaga, Hideo Bannai and Masayuki Takeda
  • Organizer: The Prague Stringology Conference (PSC 2016)
  • Place of Presentation: プラハ（チェコ）
  • Year and Date: 2016-08-29
  • Int'l Joint Research
• [Presentation] Fully Dynamic Data Structure for LCE Queries in Compressed Space (2016)
  • Author(s): Takaaki Nishimoto, Tomohiro I, Shunsuke Inenaga, Hideo Bannai and Masayuki Takeda
  • Organizer: the 41st International Symposium on Mathematical Foundations of Computer Science (MFCS 2016)
  • Place of Presentation: クラクフ（ポーランド）
  • Year and Date: 2016-08-22
  • Int'l Joint Research