Division of Theoretical Computer Science

Division of Theoretical Computer Science

theory.di.uoa.gr

Ioannis Emiris

Outline

• People• Teaching• Mobility/Collaborations• Research

People 10 faculty: 6 full, 2 associate, 2 assistant

(became 8 in 2004), average age=47,+1 emeritus

• Non-faculty: 21 MSc student theses,13 PhD students (funded), 17 completed since 2007,11 Postdocs / Collaborators (most unfunded),1 secretary

• Our graduates:* PhD students (UC Berkeley, Columbia, Cornell, Stony Brook, UIChicago, CWI, TUEindhoven, RISC-Linz)* Postdocs (MPI, CNRS, INRIA, U.Aarhus, U.Vienna),* Faculty (U.Liverpool, AUEB, U.Piraeus, U.Crete, U.Aegean, U.Peloponnisos, ATEI)

Teaching• 6 core undergrad courses,

Service outside the Dept,Most popular non-core course: Graphics

• Participate in 4 graduate programs:* own (new for modernity/strengths),* Μεταπτυχιακό Πρόγραμμα Λογικής και Αλγορίθμων (joint w/Math, NTUA),* Econ. & Admin. of Telecom Networks,* Info Tech. in Medicine & Biology.

New Theoretical CS direction Algorithms Computational Complexity

Randomized Algorithms Algorithmic Game theory Approximate Algorithms Combinatorial Optimization Theory of Programming Languages Cryptography Computational Geometry Graphics and Visualization Parallel Algorithms Scientific Computing

Online Algorithms Algorithmic Graph theory Computational Algebra Algorithms in Structural bioinformatics Linear and Nonlinear programming

Mobility/CollaborationsErasmus for under/grad students, faculty:* outgoing (U.Paris 6, U.Nice, U.Lugano),* incoming (U.Evry).* Internships at INRIA.

Collaborations:* UC Berkeley, Microsoft, McMaster* INRIA, Paris 6* U.Crete, U.Patras, NTUA (CS, Naval), Math dept

Sabbaticals:* Columbia, Houston, Tel Aviv U.* CNRS, ECP, ENS Paris, U.Cyprus

Visitors/sabbaticals from:* Stanford, U.Paris-Dauphine, W.Laurier U.

ResearchPublications:* Nature, Science, J. ACM, SIAM J. Computing, SIAM J. Numerical Analysis, Numerische Mathematik, Linear Algebra & Applications,IEEE Trans. Parallel Distr. Systems, IEEE TPAMI, IJCV.* FOCS, STOC, SODA, Crypto, Eurocrypt.* US Patents

•EU funding:2 ERC Startup Grants, IST, FET, Marie Curie Net+ Greek projects (ΠΕΝΕΔ, Πυθαγόρας, Ηράκλειτος)+ NSF, NSERC

•Visibility/service:* PCs, e.g. chair ACM ISSAC'11,co-chair IEEE Soft. Engin. Context Aware Syst. & Appl. '08,'09.* Journal editors, e.g. J.Computer & System Sciences.

Research areas

1) Algorithms and Complexity2) Theory and Applications3) Scientific Computing

Covers almost all areas of CS Theory

Research area 1

1. Algorithms and Complexity2. Theory and Applications3. Scientific Computing

• Dimitris Achlioptas• Elias Koutsoupias• Stavros Kolliopoulos• Vassilis Zissimopoulos

From Graphs to the Internet

Dimitris Achlioptas

Specializes in: Dimension reduction

Recent Work: Algorithmic Phase Transitions in Constraint Satisfaction Problems

Publishes in: Science, Nature,J.ACM, SIAM J.Computing, FOCS, STOC

Random structures and Stochastic Algorithms

Solution-Space Geometry

No SolutionsAlgorithmic ThresholdNP-hardness

Density

Elias Koutsoupias

Algorithmic Decision Making

Price of Anarchy & Mechanism Design

STOC, FOCS, Algorithmica

- Online algorithms -Algorithmic game theory

• Specializes in:

• Recent Work:

• Publishes in:

Price of anarchy

Price of anarchy = Selfish solution / Optimal solutionQuantifies loss due to selfishness. Selfish behavior can lead to suboptimal traffic.

Applications: game theory, networks, Internet[K-Papadimitirou'99] (>1000 citations)

Vassilis Zissimopoulos

Design and Analysis of Algorithms

Approximation algorithms for graph problems

IEEE Trans. Parallel Distributed Systems, Computer Networks, Discrete Applied Math, Theoretical Comp. Science

Graph Algorithms• Specializes in:

• Recent Work:

• Publishes in:

clustering data represented by big graphs: genetic/social nets

Constrained-cardinality optimization : Densest k-subgraph

Stavros Kolliopoulos

Approximation Algorithms for Combinatorial Optimization

Algorithmic graph theory from the viewpoint of parameterized complexity

FOCS, SODA; ACM Trans. Algorithms,SIAM J.Computing

- Scheduling, Packing and Covering- Algorithmic game theory• Specializes in:

• Recent Work:

• Publishes in:

Approximate optimization

• Given machine, N weighted tasks,fixed number of disinct due dates:

• Settle approximability, design FPTAS(Fully Polynomial-Time Approximation Scheme).

• k disjoint paths in f(k)n3, huge f(k):

• Algorithm for planar graphs, tight bound on f(k); improving f(k) requires new approach.

• [Kolliopoulos et al, ACM Transact. on Algorithms'11, Proc. ICALP'11]

Research area 2

1. Algorithms and Complexity2. Theory and Applications3. Scientific Computing

• Panagiotis Rondogiannis• Aggelos Kiayias• Ioannis Emiris• Theoharis Theoharis

Panagiotis Rontogiannis

- Math semantics for Boolean grammars- First purely logical semantics of negation

ACM Trans. Computational Logic, Information & Computation, Intern. Conf. Logic Programming, Developments in Language Theory

- Logic and Functional Programming- Non-monotonic Reasoning

• Specializes in:

• Recent Work:

• Publishes in:

Theory of Programming Languages

Aggelos Kiayias

Cryptography, Computer Security

Applications of coding theory to cryptography

Book: Encryption for Digital ContentCrypto, Eurocrypt

• Specializes in:

• Recent Work:

• Publishes in:

Public-key cryptography

Discrete math in broadcast encryption

Key-poset representation of 8-user broadcast encryption[Encryption for Digital Content, Springer]

Kiayias' talk follows

Ioannis Emiris

Computational Algebra and Geometry

- Real root isolation- Structural bioinformatics

ACM Int. Symp. Symbolic & Algebraic ComputationIEEE FOCS, SIAM/ACM SPModeling, IEEE ICRA, J.ACM, J.Symbolic Computation

- Sparse resultants for system solving- Nonlinear computational geometry• Specializes in:

Recent Work:

• Publishes in:

Lab of Geometricand Algebraic Algorithms

erga.di.uoa.gr

• People: 1 faculty,2 collaborators (in other dept's),3 funded Postdocs / another 3 since 2002,2 PhD students / 4 completed,3 Msc students / 9 graduated+ collaboration with INRIA Sophia-Antipolis

• Current projects: FET-Open, M. Curie NetworkSince 2002: FET, ΠΕΝΕΔ, Πυθαγόρας, ΕΝΤΕR

PhD theses

Completed:- Fastest equation solver over the reals (C++)- Real-time complex Voronoi diagrams (1s/ellipse)- Matrix formula for sparse resultant- Robotics platform for ankle physiotherapy

Current:- Change of representation in CAD- High-dim data-structures: polytopes and searching

From geometric to molecular modeling

Theoharis Theoharis

Top results in NIST's Face Recognition Challenge

International textbook “Graphics & Visualization”IJCV, IEEE Trans. PAMI, IEEE CG&A

- 3D object retrieval- Face recognition

• Specializes in:

• Recent Work:

• Publishes in:

Graphics and Biometrics

Shape descriptors for 3D Object Retrieval

InterClass IntraClass

Research area 3

1. Algorithms and Complexity2. Theory and Applications3. Scientific Computing

• Nikolaos Misirlis• Filippos Tzaferis• Nikolaos Apostolatos (emeritus)

Nikolaos Missirlis

Numerical Solution of PDEs

Iterative methods for Load Balancing

Numerische Mathematik, SIAM J.Numerical Analysis, Linear Algebra & Applications, Theoretical Computer Science, EuroPar, PARA, ENUMATH

Parallel Iterative Methods• Specializes in:

• Recent Work:

• Publishes in:

Philippos Tzaferis

Parallel Numerical Methods

Iterative methods for 2-cyclic matrices

Linear Algebra & Applications, Parallel Algorithms & Appli., EUROPAR, PARA, ENUMATH, ParCo

Parallel solution of linear systems• Specializes in:

• Recent Work:

• Publishes in:

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Load Balancing for Numerical Weather Prediction

SKIRON was a featured EPET-II project.Now in operation at the Hellenic Meteorological Office (EMY).

Future work

• Collaboration within division / dept• Recruit the best• Strong(est) theory group in Greece• Strong at the European level

Thank you