Publications

• DBLP
• Google Scholar
• Scopus

Talks

• List of Talks

Preprints

• volesti: Volume approximation and sampling for convex polytopes in R.
  Apostolos Chalkis, Vissarion Fisikopoulos under submission.

Peer-reviewed Conferences

1. Sampling from feasible sets of SDPs and volume approximation.
   Apostolos Chalkis, Vissarion Fisikopoulos, Panagiotis Repouskos, Elias Tsigaridas
   ISSAC '20 SIGSAM Communications in Computer Algebra. ACM, 2020. (Distinguished poster award).
2. Practical Volume Estimation of Zonotopes by a New Annealing Schedule for Cooling Convex Bodies.
   Apostolos Chalkis, Ioannis Z. Emiris, Vissarion Fisikopoulos
   ICMS '20 Mathematical Software – ICMS 2020 (Lecture Notes in Computer Science), Germany.
3. Geodesic algorithms: an experimental study.
   Vissarion Fisikopoulos
   FOSS4G '19 International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Bucharest, Romania.
4. Polytope Membership in High Dimension.
   Evangelos Anagnostopoulos, Ioannis Emiris, Vissarion Fisikopoulos
   ISCO '18 LNCS Proceedings of 5th International Symposium on Combinatorial Optimization, Marrakesh, Morocco.
5. Practical volume computation of structured convex bodies, and an application to modeling portfolio dependencies and financial crises.
   Ludovic Cales, Apostolos Chalkis, Ioannis Z. Emiris, Vissarion Fisikopoulos
   SoCG'18 Proceedings of Annual Symposium on Computational Geometry, Budapest, Hungary.
6. Experimental Study of the Ehrhart Interpolation Polytope.
   V.Fisikopoulos, Zafeirakis Zafeirakopoulos.
   MACIS '17 LNCS Proceedings of 7th International Conference on Mathematical Aspects of Computer and Information Sciences, Vienna, Austria.
7. Two-level Polytopes with a Prescribed Facet.
   Samuel Fiorini, V.Fisikopoulos, Marco Macchia.
   ISCO '16 LNCS Proceedings of 4th International Symposium on Combinatorial Optimization, Salerno, Italy.
8. Enumeration of 2-level polytopes.
   Adam Bohn, Yuri Faenza, Samuel Fiorini, V.Fisikopoulos, Marco Macchia, Kanstantsin Pashkovich.
   ESA '15 LNCS Proceedings of European Symposium on Algorithms, 2015, Patras, Greece.
9. Efficient random-walk methods for approximating polytope volume.
   I.Z.Emiris, V.Fisikopoulos.
   SoCG '14 Proceedings of 30th ACM Annual Symposium on Computational Geometry, 2014, Kyoto, Japan.
10. Combinatorics of 4-dimensional Resultant Polytopes.
    A.Dickenstein, I.Z.Emiris, V.Fisikopoulos.
    ISSAC '13 Proceedings of the 38th ACM International Symposium on Symbolic and Algebraic Computation, 2013, Boston, Massachusetts, USA.
11. Faster Geometric Algorithms via Dynamic Determinant Computation.
    V.Fisikopoulos, L.Peñaranda.
    ESA '12 LNCS Proceedings of European Symposium on Algorithms, 2012, Ljubljana, Slovenia.
12. An output-sensitive algorithm for computing projections of resultant polytopes.
    I.Z.Emiris, V.Fisikopoulos, C.Konaxis, L.Peñaranda.
    SoCG '12 Proceedings of 28th ACM Annual Symposium on Computational Geometry, 2012, Chapel Hill, NC, USA.
13. In silico tomographic image generation using monte carlo and computational geometry.
    K.Eftaxias, V.Fisikopoulos, G.M.Spyrou.
    ITAB '10 Proceedings of 10th IEEE International Conference on Information Technology and Applications in Biomedicine, pp.1-4, 3-5 Nov. 2010
14. Meshing of Triply-Periodic Smooth Surfaces in CGAL.
    M.Caroli, V.Fisikopoulos, M.Teillaud.
    Curves and Surfaces '10 Seventh International Conference on Curves and Surfaces, 2010. Note: Poster presentation.

Peer-reviewed Journals

1. Enumeration of 2-level polytopes
   Adam Bohn, Yuri Faenza, Samuel Fiorini, V.Fisikopoulos, Marco Macchia, Kanstantsin Pashkovich
   Mathematical Programming Computation, Springer, 2018.
2. Practical polytope volume approximation.
   I.Z.Emiris, V.Fisikopoulos.
   ACM Transactions on Mathematical Software, vol 44, issue 4, 2018.
3. Biogeographical, environmental and anthropogenic determinants of global patterns in bird taxonomic and trait turnover.
   J.Y.Barnagaud, W.Kissling, C.Tsirogiannis, V.Fisikopoulos, S.Villéger, C.Sekercioglu, J.C.Svenning.
   Global Ecology and Biogeography, vol. 26, pp. 1190--1200, 2017.
4. Faster Geometric Algorithms via Dynamic Determinant Computation.
   V.Fisikopoulos, L.Peñaranda.
   Computational Geometry: Theory and Applications, vol. 54, pp. 1-16, April 2016.
5. Efficient edge skeleton computation for polytopes defined by oracles.
   I.Z.Emiris , V.Fisikopoulos, B.Gaertner.
   Journal of Symbolic Computation, vol. 73, pp. 139-152, March–April 2016.
6. An oracle-based, output sensitive algorithm for projections of resultant polytopes.
   I.Z.Emiris, V.Fisikopoulos, C.Konaxis, L.Peñaranda.
   International Journal of Computational Geometry and Applications, vol. 23, pp. 397-423, (Special issue) World Scientific 2013.

Conferences and Workshops with Limited Review

1. Computing the expected area of an induced triangle.
   V. Fisikopoulos, F. Staals, C. Tsirogiannis.
   Computational Geometry: Young Researchers Forum Boston, USA 2016.
2. Efficient random-walk methods for approximating polytope volume.
   I.Z.Emiris, V.Fisikopoulos.
   EuroCG '14 Proceedings of 30th European Workshop on Computational Geometry, Dead sea, Israel 2014.
3. A software framework for computing Newton polytopes of resultants and (reduced) discriminants.
   I.Z.Emiris, V.Fisikopoulos, C.Konaxis.
   MEGA '13 12th International Conference on Effective Methods in Algebraic Geometry , Frankfurt, Germany. Note: Poster presentation.
4. Efficient Volume and Edge-Skeleton Computation for Polytopes Given by Oracles.
   I.Z.Emiris, V.Fisikopoulos, B.Gaertner.
   EuroCG '13 Proceedings of 29th European Workshop on Computational Geometry, Braunschweig, Germany 2013.
5. Optimizing the computation of sequences of determinantal predicates.
   I.Z.Emiris, V.Fisikopoulos, L.Peñaranda.
   EuroCG '12 Proceedings of 28th European Workshop on Computational Geometry (EuroCG12), Assisi, Perugia, Italy, 2012.
6. Exact and approximate algorithms for resultant polytopes.
   I.Z.Emiris, V.Fisikopoulos, C.Konaxis.
   EuroCG '12 Proceedings of 28th European Workshop on Computational Geometry (EuroCG12), Assisi, Perugia, Italy, 2012.
7. Regular triangulations and resultant polytopes.
   I.Z.Emiris, V.Fisikopoulos, C.Konaxis.
   EuroCG '10 Proceedings of 26th European Workshop on Computational Geometry (EuroCG10), pages 137-140, Dortmund, Germany, 2010.

Theses

1. High-dimensional polytopes defined by oracles: algorithms, computations and applications.
   PhD thesis, University of Athens, 2014.
   Advisor: I.Z.Emiris
   Abstract in: ACM Communications in Computer Algebra, Vol. 48, No. 2, Issue 188, June 2014.
   
2. Triangulations of point sets, high dimensional Polytopes and Applications.
   Master's thesis at University of Athens, 2010.
   Advisor: I.Z.Emiris
   (In selected Master thesis of Department of Informatics and Telecoms of University of Athens, 2011)
3. Study of the effect of cost policies in the convergence of selfish strategies in Pure Nash Equilibria in Congestion Games. (in Greek) (extented abstract in English)
   Bachelor's thesis at University of Patras, 2007.
   Advisors: Paul Spirakis, Spyros Kontogiannis
   

Technical reports

1. I.Z.Emiris, V.Fisikopoulos. Algorithms for volume approximation of convex bodies.
   Technical Report CGL-TR-76, November 2013.
2. I.Z.Emiris, V.Fisikopoulos, B. Gaertner. Efficient edge skeleton computation for polytopes defined by oracles.
   Technical Report CGL-TR-75, November 2013.
3. I.Z.Emiris, V.Fisikopoulos, C.Konaxis, L.Penaranda. An oracle-based, output-sensitive algorithm for projections of resultant polytopes.
   Technical Report CGL-TR-28, October 2012.
4. I.Z.Emiris, V.Fisikopoulos, L.Penaranda. High-dimensional predicates: Algorithms and software.
   Technical Report CGL-TR-27, October 2012.
5. I.Z.Emiris, V.Fisikopoulos, L.Peñaranda. Optimizing the computation of sequences of determinantal predicates.
   Technical Report CGL-TR-14, October 2011.
6. I.Z.Emiris, V.Fisikopoulos, C.Konaxis. An output-sensitive algorithm for computing projections of resultant polytopes.
   Technical Report CGL-TR-08, October 2011.
7. M.Koubarakis, C.Nikolaou, V.Fisikopoulos. Theoretical results on query processing for RDF/SPARQL with time and space.
   Technical Report TELEIOS-D2.3, 2011.
8. V.Fisikopoulos. An implementation of range trees with fractional cascading in C++. [code]
   Technical Report, University of Athens, Comp. Geometry course, 2009.

Manuscripts

1. V.Fisikopoulos. Representation of complete and incomplete temporal constraint information in relational database systems., 2008. [PDF] (in Greek)

Invited Talks

1. "Polyhedral computations in computational algebraic geometry and optimization", London School of Economics, UK, 2015.
2. "Volume and edge-skeleton computation in high dimensions", INRIA Sophia-Antipolis, France, 2014.
3. "Polytopes defined by oracles: algorithms and combinatorics", KAIST Discrete Math Seminar, S.Korea, 2014.
4. "Polytopes defined by Oracles: Algorithms and Combinatorics", Seminar of Department of Mathematics, University of Padova, Italy, 2014.
   [slides]
5. "Efficient Edge-Skeleton and Volume Computation for Polytopes Defined by Oracles" In Discrete Mathematics and Optimization Seminar, McGill, Canada, 2013.
   [slides]
6. "Constructing Polytopes via a Vertex Oracle." In Mittagsseminar of Theory of Combinatorial Algorithms, Departement Informatik, ETH Zürich, Switzerland, 2012.
   [slides]

Conference/Workshop Talks and Posters

1. "Enumerating 2-level polytopes", ACA, Kalamata, and ESA, Patras, 2015.
2. "The Newton polytope of the sparse resultant", 3nd ERC "SDModels" Workshop, Berlin, 2015.
3. "The Newton polytope of the Sparse Resultant", Algebra and Combinatorics Seminar, ULB, Brussels, 2014.
4. "Efficient random-walk methods for approximating polytope volume", Optimization and Algebraic Geometry, National Institute for Mathematical Sciences (NIMS), Daejeon, Korea, 2014.
5. "Efficient random-walk methods for approximating polytope volume", SoCG, Kyoto, Japan, 2014.
   [slides]
6. "High-dimensional polytopes defined by oracles: algorithms, computations and applications", PhD thesis defence, University of Athens, 2014.
   [slides]
7. "Efficient random-walk methods for approximating polytope volume" EuroCG, Dead sea, Israel, 2014.
8. "Combinatorics of 4-dimensional Resultant Polytopes" In 2nd ERC "SDModels" Workshop: Delaunay Geometry: Polytopes, Triangulations and Spheres. Berlin, 2013.
   [poster]
9. "Efficient Edge-Skeleton Computation for Polytopes Defined by Oracles" In 8th Athens Colloquium on Algorithms and Complexity, University of Economics and Business, Greece, 2013.
   [slides]
10. "Combinatorics of 4-dimensional resultant polytopes" In ISSAC, Boston, 2013.
    [slides]
11. "Efficient Volume and Edge-Skeleton Computation for Polytopes Given by Oracles" In EuroCG13 Braunschweig, March 17-20, TU Braunschweig, 2013.
    [slides]
12. "Algorithms for high-dimensional polytopes defined by oracles." In Advanced Geometric Computing and Critical Applications Kickoff Meeting, Athens, 2013.
    [slides]
13. "Oracle-based algorithms for high-dimensional polytopes." In CGL 2nd review meeting, Berlin, Germany, 2012 and In Geom.Comp. workshop, Heraklion, Crete, 2013.
    [slides]
14. "Faster Geometric Algorithms via Dynamic Determinant Computation." In European Symposium on Algorithms, Ljubljana, Slovenia, 2012.
    [slides]
15. "Computing the volume of the discriminant polytope." In 7th Athens Colloquium on Algorithms and Complexity University of Athens, Greece, 2012.
    [slides]
16. "An output-sensitive algorithm for computing projections of resultant polytopes." In 28th Annual Symposium on Computational Geometry (SoCG 2012), Chapel Hill, NC, USA, June 2012
    [slides]
17. "Exact and approximate algorithms for resultant polytopes." In European Workshop on Computational Geometry (EuroCG), Assisi, Italy, 2012
    [slides]
18. "An output-sensitive algorithm for computing projections of resultant polytopes." In ErGA-GALAAD new year's meeting, Athens, Greece, 2012
    [slides]
19. "Enumerating Classes of Regular Triangulations." In 5th Athens Colloquium on Algorithms and Complexity (ACAC), Greece, 2010
    [slides]
20. "Regular triangularions and resultant polytopes." In European Workshop on Computational Geometry (EuroCG), Dortmund, Germany, 2010
    [slides]
21. "Enumerating classes of regular triangulations." In Shapes, Geometry, and Algebra (SAGA) Workshop-School, Kolympari, Greece, 2010
    [poster]
22. "Triangulations of point sets, high dimensional Polytopes and Applications." Master's thesis defence at University of Athens, 2010
    [slides]
23. "Mesh of Periodic Minimal Surfaces in CGAL." Internship's defence at INRIA Sophia-Antipolis, 2009
    [slides]

Videos

1. "An output-sensitive algorithm for computing projections of resultant polytopes." [video link]