Kostas
Tsichlas Assistant Professor Department of Computer Engineering & Informatics University of Patras

I am Assistant Professor in the Department of Computer Engineering & Informatics of the University of Patras since 2020. I was part of the faculty in the School of Informatics of the Aristotle University of Thessaloniki between 2008 to 2020. From 2005 until 2014 I was Adjunct Professor in Greek Open University as well. From 1/5/201131/10/2011 I was on sabbatical at MADALGO institute (center for MAssive Data ALGOrithmics) of the Department of Computer Science of the University of Aarhus in Denmark. From 4/1/2004 until 4/6/2005 I was a research assistant in the Department of Informatics of King's College London in the Algorithm Design Group. I was awarded a Ph.D. diploma in 2004. I have completed my military service in the Greek army in 2003. Extended Bio.
Teaching Research Interests Publications Open ProblemsDiscussion Forums Nice Stuff
Teaching (in Greek)
Data Structure (mainly known "hard problems")
Design and Analysis of Algorithms (few words to rule them all !!!)
Computational Geometry (fundamental operations and apps to other areas)
String Algorithms (Bioinformatics  Music Analysis)
Dynamic Graph Algorithms (with respect to data structures)
Complexity (mainly interest on how Physics interact with Informatics)
Analysis of Complex Networks
Natural Algorithms (this slime mould found the shortest path again!)
Distributed Algorithms (mainly cellular automata)
Journals
Optimal Solutions for the Temporal Precedence Problem. G. S. Brodal, C. Makris, S. Sioutas, A. Tsakalidis and K. Tsichlas. Algorithmica, 33(4):494510, 2002.
Approximate String Matching with Gaps. M. Crochemore, C. Iliopoulos, C. Makris, W. Rytter, A. Tsakalidis and K. Tsichlas. Nordic Journal of Computing, 9:5465, 2002.
Reflected MinMax Heaps. C. Makris, A. Tsakalidis and K. Tsichlas. Information Processing Letters (IPL), 86(4):209214, 2003.
Optimal Finger Search Trees in the Pointer Machine. G. S. Brodal, C. Makris, G. Lagogiannis, A. Tsakalidis and K. Tsichlas. Journal of Computer and System Sciences, Special Issue on STOC 2002, 67(2):381418, 2003.
Rectangle Enclosure Reporting in Linear Space Revisited. G. Lagogiannis, C. Makris, Y. Panagis, S. Sioutas and K. Tsichlas. Journal of Automata, Languages and Combinatorics, 8(4):633645, 2003.
New Dynamic Balanced Search Trees with WorstCase Constant Update Time. G. Lagogiannis, C. Makris, Y. Panagis, S. Sioutas and K. Tsichlas. Journal of Automata, Languages and Combinatorics, 8(4):607632, 2003.
Geometric Retrieval of Grid Points in the RAM model. C. Makris, S. Sioutas, A. Tsakalidis, J. Tsaknakis, K. Tsichlas and B. Vassiliadis. Journal of Universal Computer Science, 10(9):13251353, 2004.
Computation of Repetitions and Regularities on Biological Weighted Sequences. M. Christodoulakis, C. Iliopoulos, L. Mouchard, K. Perdikuri, A. Tsakalidis and K. Tsichlas. Journal of Computational Biology, 13(6):12141231, 2006.
2D Monotone Spatial Indexing Scheme with Optimal Update Time. L. Drossos, S. Sioutas, K.Tsichlas and K.Ioannou. Transactions on Systems, ISSN: 11092777, 5(1):142147, 2006.
Locating Maximal Multirepeats in Multiple Strings Under Various Constraints. A. Bakalis, C. Iliopoulos, C. Makris, S. Sioutas, E. Theodoridis, A.Tsakalidis and K.Tsichlas. Computer Journal, 50(2):178185, 2007.
Algorithms for Extracting Motifs from Biological Weighted Sequences. C. Illiopoulos, K. Perdikuri, E. Theodoridis, A. Tsakalidis and K. Tsichlas. Journal of Discrete Algorithms, Special Issue on SPIRE 2004, 5(2):229242, 2007.
Efficient Access Methods for Temporal Interval Queries of Video Metadata. S. Sioutas, K. Tsichlas, B. Vassiliadis and D.K. Tsolis. Journal of Universal Computer Science, 13(10): 14111433, 2007.
Scheduling Algorithms for Procrastinators. M. Bender, R. Clifford and K. Tsichlas. Journal of Scheduling, 11(2):95104,2008.
A New Approach on Indexing Mobile Objects on the Plane. S. Sioutas, K. Tsakalidis, K. Tsichlas, C. Makris, Y. Manolopoulos. Data Knowledgment Engineering, 67(3): 362380, 2008.
Canonical Polygon Queries on the Plane: A New Approach. S. Sioutas, D. Sofotassios, K. Tsichlas, D. Sotiropoulos and P. Vlamos. Journal of Computers, 4(9):913919, 2009.
An Experimental Performance Comparison for Indexing Mobile Objects on the Plane. S. Sioutas, G. Papaloukopoulos, K. Tsichlas and Y. Manolopoulos. Special issue of ACMSIGAPP MEDES '09 on Collectively Intelligent Information and Knowledge Management, Journal on Organizational and Collective Intelligence (IJOCI), 1(4):7896, 2010.
ISBTree: A New Indexing Scheme with Efficient Expected Behaviour. Ch. Makris, S. Sioutas, Tsakalidis, K. Tsichlas, Y. Ch. Zaroliagis. Journal of Discrete Algorithms, 8(4):373387, 2010.
Improved Bounds for Finger Search on a RAM. A. Kaporis, C. Makris, S. Sioutas, A. Tsakalidis, K. Tsichlas and C. Zaroliagis. Algorithmica, 66(2):249286, 2013.
On the Discovery of GroupConsistent Graph Substructure Patterns from Brain Networks. N.D. Iakovidou, S.I. Dimitriadis, N.A. Laskaris, K. Tsichlas, Y. Manolopoulos. Journal of Neuroscience, 213(2):204213, 2013.
ART: SubLogarithmic Decentralized Range Query Processing with Probabilistic Guarantees. S. Sioutas, P. Triantafillou, G. Papaloukopoulos, E. Sakkopoulos, K. Tsichlas, Y. Manolopoulos. Distributed and Parallel Databases, 31(1):71109. 2013.
Going over the three dimensional protein structure similarity problem. N. Iakovidou, E. Tiakas, K. Tsichlas and Y. Manolopoulos. Artificial Intelligence Review, 42(3):445459, 2014.
Dynamic 3sided Planar Range Queries with Expected Doubly Logarithmic Time. G.S. Brodal, A. Kaporis, A.N. Papadopoulos, S. Sioutas, K. Tsakalidis and K. Tsichlas. Theoretical Computer Science, 526:5874, 2014.
The D^2tree: a new P2P deterministic data structure. G.S. Brodal, S. Sioutas, K.Tsichlas and C. Zaroliagis. Algorithmica, 72(3):860883, 2015.
Practical Algorithms for Execution Engine Selection in Data Flows. G. Kougka, A. Gounaris and K. Tsichlas. Future Generation Computer Systems, 45(C):133148, 2015.
Efficient and Flexible Algorithms for Monitoring Distancebased Outliers over Data Streams. M. Kontaki, A. Gounaris, A.N. Papadopoulos, K. Tsichlas and Y. Manolopoulos. Information Systems, 55:3753, 2016.
HiNode: An Asymptotically SpaceOptimal Storage Model for Historical Queries on Graphs. A. Kosmatopoulos, K. Tsichlas, A. Gounaris, S. Sioutas and E. Pitoura. Distributed and Parallel Databases, 35(34):249285, 2017.
A Symbolic Dynamics Approach to Epileptic Chronnectomics: Employing Strings to Predict Crisis Onset. N.D.Iakovidou, N.A.Laskaris, K. Tsichlas, Y. Manolopoulos, M. Christodoulakis, E.S.Papathanasiou, S.S. Papacostas and G.D. Mitsis. Theoretical Computer Science, 710:116125, 2018.
Hinode: Implementing a VertexCentric Modelling Approach to Maintaining Historical Graph Data. A. Kosmatopoulos, A. Gounaris and K. Tsichlas. Computing, pp. 124, 2019.
Virus Propagation: Threshold Conditions for Multiple Profile Networks. A. Rapti, K. Tsichlas, S. Sioutas, G. Tzimas. Knowledge and Information Systems, 60(2):807836, 2019.
Dynamic Interpolation Search Revisited. A. Kaporis, C.
Makris, S. Sioutas, A. Tsakalidis, K. Tsichlas and C. Zaroliagis.
Information and Computation}, to appear.
Conferences
Approximate String Matching with Gaps. M. Crochemore, C. Iliopoulos, C. Makris, W. Rytter, A. Tsakalidis and K. Tsichlas. In Proc. of the World Multiconference on Systemics, Cybernetics and Informatics (SCI), vol. X, pp. 4550, July 2225, 2001.
Time and Space Efficient Content Queries for Video Databases. C. Makris, K. Perdikuri, S. Sioutas, A. Tsakalidis and K. Tsichlas. In Proc. of the 1st International Workshop on Multimedia Data and Document Engineering (MDDE), pp. 18, 2001.
Optimal Finger Search Trees in the Pointer Machine. G.S. Brodal, C. Makris, G. Lagogiannis, A. Tsakalidis and K. Tsichlas. In Proc. of the 34th Annual ACM Symposium on Theory of Computing (STOC), pp. 583591, 2002.
Identifying Occurrences of Maximal Pairs in Multiple Strings. C. Iliopoulos, C. Makris, S. Sioutas, A. Tsakalidis and K. Tsichlas. In Proc. of the 13th Annual Symposium on Combinatorial Pattern Matching (CPM), pp. 133143, 2002.
Rectangle Enclosure Reporting in Linear Space Revisited. G. Lagogiannis, Y. Panagis, S. Sioutas and K. Tsichlas. In Proc. of the 13th Australian Workshop on Combinatorial Algorithms (AWOCA), 2002.
New Dynamic Balanced Search Trees with WorstCase Constant Update Time. G. Lagogiannis, C. Makris, Y. Panagis and K. Tsichlas. In Proc. of the 13th Australian Workshop on Combinatorial Algorithms (AWOCA), 2002.
Data Structuring Applications for String Problems in Biological Sequences. Y. Panagis, E. Theodoridis, K. Tsichlas. In Proc. of the International Conference of Computational Methods in Science and Engineering (ICCMSE), pp. 479483, 2003.
Temporal Selection Queries in Video Databases. S. Sioutas, C. Makris, G. Lagogiannis, E. Sakkopoulos, K. Tsichlas, V. Delis and A. Tsakalidis. In Proc. of the 3rd International Workshop on Multimedia Data and Document Engineering (MDDE), collocated with VLDB, 2003.
Improved Bounds for Finger Search on a RAM. A. Kaporis, C. Makris, S. Sioutas, A. Tsakalidis, K. Tsichlas and C. Zaroliagis. In Proc. of the 11th Annual European Symposium on Algorithms (ESA), LNCS 2832, pp. 325336, 2003.
The Pattern Matching Problem in Biological Weighted Sequences. C. Iliopoulos, K. Perdikuri, A. Tsakalidis and K. Tsichlas. In Proc. of FUN with Algorithms, edited by Paolo Ferragina & Roberto Grossi, 106117, 2004.
On the Canonical kvertex Polygon Spatial Retrieval Problem. V. Bistiolas, S. Sioutas, D. Sofotassios and K. Tsichlas. In Proc. of the 15th Australian Workshop on Combinatorial Algorithms (AWOCA), 2004.
Motif Extraction from Weighted Sequences. C. Illiopoulos, K. Perdikuri, E. Theodoridis, A. Tsakalidis and K. Tsichlas. In Proc. of the 11th Symposium on String Processing and Information Retrieval (SPIRE), pp. 286297, 2004.
Searching for Regularities in Weighted Sequences. M. Christodoulakis, C. Iliopoulos, K. Tsichlas and K. Perdikuri. In Proc. of the International Conference of Computational Methods in Science and Engineering (ICCMSE), pp. 701704, 2004.
Pattern Matching on Weighted Sequences. M. Christodoulakis, C. Illiopoulos, L. Mouchard and K. Tsichlas. In Proc. of Algorithms and Computational Methods for Biochemical and Evolutionary Networks (CompBionets), pp. 1730, 2004.
Algorithms for Extracting Structured Motifs from Biological Weighted Sequences. C. Iliopoulos, K. Perdikuri, A. Tsakalidis and K. Tsichlas. In 16th Australasian Workshop on Combinatorial Algorithms (AWOCA), 2005.
Finding Multirepeats in a Set of Strings. A. Bakalis, C. Makris, S. Sioutas, E. Theodoridis and K. Tsichlas. In International Conference of Computational Methods in Sciences and Engineering (ICCMSE), 2005.
ISBTree: A New Indexing Scheme with Efficient Expected Behaviour. A. Kaporis, C. Makris, G. Mayritsakis, S. Sioutas, A. Tsakalidis, K. Tsichlas and C. Zaroliagis. In Proc. of the 16th Annual International Symposium on Algorithms and Computation (ISAAC), pp. 318327, 2005.
Dynamic Interpolation Search Revisited. A. Kaporis, C. Makris, S. Sioutas, A. Tsakalidis, K. Tsichlas and C. Zaroliagis. In Proc. of the 33rd International Colloquium on Automata, Languages and Programming (ICALP), pp. 382394, 2006.
Algorithms for Bitmasking Strings. A. Bakalis, C. Iliopoulos, S. Sioutas and K. Tsichlas. In International Conference of Computational Methods in Sciences and Engineering (ICCMSE), 2006.
Purely Functional Worst Case Constant Time Catenable Sorted Lists. G.S. Brodal, C. Makris and K. Tsichlas. In Proc. of the 13th Annual European Symposium on Algorithms (ESA), pp. 172183, 2006.
Indexing of mobile objects on the plane revisited. S. Sioutas, K. Tsakalidis, K. Tsichlas, C. Makris and Y. Manolopoulos. In Proc. of the 11th EastEuropean Conference on Advances in Databases and Information Systems (ADBIS), 2007.
An Experimental Performance Comparison for Indexing Mobile Objects on the Plane. S. Sioutas, G. Papaloukopoulos, K. Tsichlas and Y. Manolopoulos. In Proc. of MEDES, pp. 210217, 2009.
Dynamic 3Sided Planar Range Queries with Expected Doubly Logarithmic Time. G.S. Brodal, A.C. Kaporis, S. Sioutas, K. Tsakalidis and K. Tsichlas. In Proc. of the 20th Annual International Symposium on Algorithms and Computation (ISAAC), pp. 193202, 2009.
A Novel Distributed P2P Simulator Architecture: DP2Psim. S. Sioutas, G. Papaloukopoulos, E. Sakkopoulos, K. Tsichlas and Y. Manolopoulos. In Proc. of CIKM, pp. 20692070, 2009.
ARTsubLogarithmic Decentralized Range Query Processing with Probabilistic Guarantees. S. Sioutas, G. Papaloukopoulos, E. Sakkopoulos, K. Tsichlas, Y. Manolopoulos and P. Triantafyllou. Brief Announcement in PODC, pp. 118119, 2010.
D^2tree: A New Overlay with Deterministic Bounds. G.S. Brodal, S. Sioutas, K. Tsichlas and C.D. Zaroliagis. In Proc. of the 21st Annual International Symposium on Algorithms and Computation (ISAAC), pp. 112, 2010.
Efficient Processing of 3sided Range Queries with Probabilistic Guarantees. A.C. Kaporis, A.N. Papadopoulos, S. Sioutas, K. Tsakalidis, K. Tsichlas. In Proc. of ICDT, pp. 3443, 2010.
NEFOS: Rapid CacheAware Range Query Processing with Probabilistic Guarantees. S. Sioutas, K. tsichlas, I. Karydis, Y. Manolopoulos and Y. Theodoridis. In Proc. of DEXA, pp. 6277, 2011.
Continuous monitoring of distancebased outliers over data streams. M. Kontaki, A. Gounaris, A.N. Papadopoulos, K. Tsichlas and Y. Manolopoulos. In Proc. of ICDE, pp. 135146, 2011.
Fully Persistent Btrees. G.S. Brodal, S. Sioutas, K. Tsakalidis and K. Tsichlas. In Proc. of the 23rd Symposium on Discerete Algorithms (SODA), pp. 602614, 2012.
DISCO: a New Algorithm for Detecting 3D Protein Structure Similarity. N.D. Iakovidou, E. Tiakas, K. Tsichlas. In Proc. of the 1st Workshop on Algorithms for Data and Text Mining in Bioinformatics (WADTMB) (Artificial Intelligence Applications and Innovations), 622631, 2012.
I/OEfficient Orthogonal Planar Range Skyline Reporting and Catenable Priority Queues with Attrition. C. KejlbergRasmussen, Y. Tao, K. Tsakalidis, K. Tsichlas, J. Yoon. Accepted for presentation in (PODS), 2013.
Multiobjective optimization of data flows in a multicloud environment. E. Tsamoura, A. Gounaris, K. Tsichlas. Accepted for presentation in Workshop on Data analytics in the Cloud (DanaC), 2013.
Continuous Outlier Detection in Data Streams: An Extensible Framework and StateOfTheArt Algorithms. D. Georgiadis, M. Kontaki, A. Gounaris, A. Papadopoulos, K. Tsichlas, Y. Manolopoulos. SIGMOD Demonstration, 2013.
Querying Functional Brain Connectomics to Discover Consistent Subgraph Patterns. N. Iakovidou, S.I. Dimitriadis, N. Laskaris and K. Tsichlas. In Proc. of the 13th IEEE International Conference on BioInformatics and BioEngineering (BIBE), pp. 14, 2013.
Dynamic Processing of Dominating Queries with Performance Guarantees. A. Kosmatopoulos, A.N. Papadopoulos and K. Tsichlas. In Proc. of the 17th International Conference on Database Theory (ICDT), pp. 225234, 2014.
ART++ : A FaultTolerant Decentralized Tree Structure with Ultimate Sublogarithmic Efficiency. S. Sioutas, E. Sourla, K. Tsichlas and C. Zaroliagis. In Proc. of the 1st International Workshop on Algorithmic Aspects of Cloud Computing (ALGOCLOUD), pp. 126137, 2015.
An Overview of Methods for Handling Evolving Graph Sequences. A. Kosmatopoulos, K. Giannakopoulou, A.N. Papadopoulos and K. Tsichlas. In Proc. of the 1st International Workshop on Algorithmic Aspects of Cloud Computing (ALGOCLOUD), pp. 181192, 2015.
D^3Tree: A Dynamic Deterministic Decentralized Structure. S. Sioutas, E. Sourla, K. Tsichlas and C. Zaroliagis. In Proc. of the 23rd European Symposium on Algorithms (ESA), pp. 9891000, 2015.
Virus Propagation in Multiple Profile Networks. A. Rapti, S. Sioutas, K. Tsichlas and G. Tzimas. In Proc. of the 21st ACM Conference on Knowledge Discovery and Data Mining (KDD), pp. 975984, 2015.
Mining Uncertain Graphs: An Overview. V. Kassiano, A. Gounaris, A.N. Papadopoulos and K. Tsichlas. In Proc. of the 2nd International Workshop on Algorithmic Aspects of Cloud Computing (ALGOCLOUD), pp. 87116, 2016.
Parallel Continuous Outlier Mining in Streaming Data. T. Toliopoulos, A. Gounaris, K. Tsichlas, A.N. Papadopoulos and S. Sampaio. In Proc. of the 5th International Conference on Data Science and Advanced Analytics (IEEE DSAA), pp. 227236, 2018.
Conferences without Proceedings
Continuous Monitoring of Distancebased Outliers Over Streams. M. Kontaki, A. Gounaris, Y. Manolopoulos, A. Papadopoulos and K. Tsichlas. Presented at the 10th Hellenic Data Management Symposium (HDMS), 2011.
Fully Persistent $B$trees. G.S. Brodal, S. Sioutas, K. Tsakalidis and K. Tsichlas. 4th Workshop on Massive Data Algorithmics (MASSIVE), 2012.
I/O Efficient Dynamic Planar Range Skyline Queries. C. KejlbergRasmussen, K. Tsakalidis, K. Tsichlas. 4th Workshop on Massive Data Algorithmics (MASSIVE), 2012.
Books and Chapters in Books
Graph Theory and Algorithms (in greek). Y. Manolopoulos, A. Papadopoulos and K. Tsichlas. New Tech Publications, 2014.
Design and Analysis of Algorithms (in greek). K. Tsichlas, A. Gounaris and Y. Manolopoulos. Association of Greek Academic Libraries, 2015. Online Book. (URI: http://hdl.handle.net/11419/4005)
Mining of Massive Datasets (in greek). Scientific translation of the book titled "Mining of Massive Datasets" by A. Rajaraman and J.D. Ullman. A. Gounaris, Y. Manolopoulos, A. Papadopoulos and K. Tsichlas. New Tech Publications, 2014.
New Upper Bounds on Various String Manipulation Problems. C. Makris, Y. Panagis, K. Perdikuri, S. Sioutas, E. Theodoridis, A. Tsakalidis and K. Tsichlas. Chapter in Text in Algorithms vol. 2: String Algorithmics, eds. C. Iliopoulos and T. Lecroq, King's College Publications, ISBN 1904987028, pp. 171193, 2004.
Access Methods. A.N. Papadopoulos, K. Tsichlas, A. Gounaris, Y. Manolopoulos. Chapter in Information Systems and Information Technology, Volume 2 (Computing Handbook Set, Third Edition,) edited by Heikki Topi and Allen Tucker. Boca Raton: Taylor and Francis, 2014.
Open Problems  Discussion Forums
The following papers (reports) provide open problems to various areas of algorithms (some of them may have been solved). In addition, you can follow the links to some discussion lists for very interesting open problems.
The following link contains a list of open problems on algorithms with updated information on their status.
A very good site for making questions and getting good answers. In addition, of you search you will find a lot of open problems (usually hard or very hard).
Theoretical Computer Science  Stack Exchange
Solve puzzles for science and maybe you will get your name on a published paper!!!!
Here are some articles, books and videos I enjoyed reading or watching.
For the people that think that Acceptance Ratios of conferences shows the value of the accepted paper please take a look at the following paper (there are a lot more). Or else take a look at my publications to see a lot of "weak" publications with very high ARs.
G. Cormode, A. Chumaj and S. Muthukrishnan. How to Increase the Acceptance Ratios of Top Conferences, In Proc. of the 3rd Int. Conf. on Fun with Algorithms (FUN), 262273, 2004.
Cities of course are not built overnight and according to some predefined plan. At least this is what happens in Greek cities. But what would be the best shape of a city if we could built them all over again?
C.M. Bender, M.A. Bender, E. Demaine and S. Fekete. What is the Optimal Shape of a City?, Journal of Physics A: Mathematical and General, 37(1):147159, 2004.
War has been declared to the impact factor. http://www.currentscience.ac.in/Volumes/104/10/1267.pdf