→ Let's think about a soft blog

## Daniel Porumbel
Associate professor/maître de conférences |

- exact methods for solving linear programs with prohibitively-many constraints in
column generation [J1, J3, J6, J7], in the Benders reformulation [J2], or also in
submodular function
minimization.
I proposed modifying the standard Cutting-Planes, by
upgrading the widely-used
separation sub-problem
to a projection sub-problem [J1,J2]: given feasible
*x*(sometimes*x=0*) in some polytope*P*and direction*d*, what is the maximum*t*value such that*x+td∈P*? - heuristic algorithms for very hard large problems [J4,J6,J8,J10,J11,C1,C3-C6], often using local search.
For instance, I worked on the idea of guiding search algorithms using distances between candidate
solutions [J4,C1,C5,J11] or classification techniques (I obtained a Simon Régnier PhD prize, section
Awards below).
I must confess I could not recently find as much time as I wanted to work in this area, although I
know we are condemned to live with heuristics for many years.
This shall
*not*mean that I am a die-hard fan of those who search deep algorithmic insights in ants, honey/bumble bees, etc.

I have applied such techniques to different problems: Graph-Coloring [J4,J11,C1,C3-C6], Vehicle or arc routing [J1,J7,J12], Cutting-Stock [J1,J3,J7], Isomorphism [J8,C2], p-median [J7], MaxMin Diversity [J10].

Daniel Porumbel,
Trying to demystify the characterizations of SDP matrices.pdf:
I wrote this document, because I needed something I did not find elsewhere: a self-contained
introduction to SDP for people who did learn (a lot of) maths in the past but do
not work full time in (SDP) matrix theory. All in 100 pages, not 700.
Suggestions or corrections are welcome. Self contained means that everything is proven from
scratch, because I can't stand taking things for granted: no secret,
no empty jargon, no more formulae out of the blue, no longer my(s)thification.

D. Porumbel, Cutting Planes by Projecting Interior Points onto Polytope Facets: pdf, source code

D. Porumbel, J.-K. Hao,
Distance-Guided Local Search
*Submitted *
pdf draft

[J1] Daniel Porumbel,
Ray Projection for Optimizing Polytopes with Prohibitively Many Constraints in
Set-Covering Column Generation,
*Mathematical Programming*
(pdf draft,
source code), 155(1): 147-197, 2016
Springer©, doi link

[J2] Daniel Porumbel,
From the Separation to the Intersection Sub-problem
in Benders Decomposition Models with Prohibitively-Many Constraints,
*Discrete Optimization*, 29:148-173, 2018
(pdf draft, source code, slides [fr]),

[J3] Daniel Porumbel, François Clautiaux,
Convergent Dual Bounds Using an Aggregation of Set-Covering Constraints for Capacitated Problems,
*INFORMS Journal of Computing*, 29(1):170-184, 2017.
(pdf draft,
slides,
supplement)

[J4] D. C. Porumbel, J-K. Hao and P. Kuntz,
A Search Space "Cartography" for Guiding Graph Coloring Heuristics.
*Computers & Operations Research*, 37(4):769-778, 2010.
(pdf draft),
Elsevier©, doi link

[J5] Daniel Porumbel,
Prize-Collecting Set Multi-Covering With Submodular Pricing,
*International Transactions in Operational Research*, 25 (4):1221-1239, 2018,
(pdf draft),
Wiley-Blackwell©

[J6] D. Porumbel, G. Goncalvez, H. Allaoui; T. Hsu;
Arc-Routing via Column Generation and Iterated Local Search in a Permutation Set-Covering Framework,

*European Journal of Operational Research* 256(2):349-367, 2017
pdf draft,
slides Roadef 2015 (French OR congress)
Elsevier© ,

[J7] D. Porumbel, G. Goncalves,
Using Dual Feasible Functions to Construct Fast Lower Bounds for Routing and Location Problems,
*Discrete Applied Mathematics*,
196: 83-99, 2015,
(pdf draft),
Elsevier©,
doi

[J8] Daniel Porumbel.
Isomorphism Testing using Polynomial-Time Graph Extensions.
*Journal of Mathematical Modelling and Algorithms*, 10(2):119-143, 2011
(pdf draft,
slides [fr],
isomorphism program GI-Ext),
Springer©,
doi

[J9] D. C. Porumbel, J-K. Hao and P. Kuntz.
An Efficient Algorithm for Computing the Distance Between Close Partitions.
*Discrete Applied Mathematics*, 159(1):53-59, 2011,
(pdf draft),
Elsevier©,
doi

[J10] D. C. Porumbel, Jin-Kao Hao, Fred Glover,
A Simple and Effective Algorithm for the MaxMin Diversity Problem.
*Annals of Operations Research*, 186 (1):275-293, 2011,
(pdf draft, source code),
Springer©,
doi

[J11] D. C. Porumbel, J-K. Hao and P. Kuntz.
An Evolutionary Approach with Diversity Guarantee and Well-Informed Grouping Recombination for Graph Coloring,
*Computers & Operations Research*, 37(10):1822-1832, 2010
(pdf draft),
Elsevier©,
doi

[J12]
Nathalie Helal, Frédéric Pichon, D. Porumbel, David Mercier, Éric Lefèvre.
The capacitated vehicle routing problem with evidential demands,
*International Journal of Approximate Reasoning* 95:124-151, 2018
(pdf)
Elsevier©

[J13] D. C. Porumbel, J-K. Hao and P. Kuntz.
Informed Reactive Tabu Search for Graph Coloring.
*Asia Pacific Journal of Operations Research*, 30(4),
pp. 1350010, 2013
(pdf draft),
World Scientific Publishing©

[C1] D. Porumbel, J-K. Hao and P. Kuntz,
Spacing Memetic Algorithms. In proceedings of *GECCO 2011, GA track*, 1061-1068. ACM. (pdf draft, slides)

[C2] G. Audemard, C. Lecoutre, M. S. Modeliar, G. Goncalves, D. Porumbel
Scoring-based Neighborhood Dominance for the Subgraph Isomorphism Problem.
The 20th International Conference on
Principles and Practice of
*Constraint Programming (CP 2014)*

[C3] Philippe Galinier, Jean-Philippe Hamiez, Jin-Kao Hao, Daniel Porumbel,
Recent advances in graph vertex coloring, In I. Zelinka, V. Snasel, A. Abraham (eds.), *Handbook of Optimization*, Springer© (Intelligent Systems Series)

[C4] D. Porumbel, J-K. Hao and P. Kuntz,
Diversity Control and Multi-Parent Recombination for Evolutionary Graph Coloring Algorithms.
Evocop 2009 (*9th European Conference on Evolutionary Computation in Combinatorial Optimisation*, Tübingen, Germany), LNCS 5482: 121-132, 2009.
(ps, pdf) Springer©
* among the three best paper nominees*

[C5] D. Porumbel, J-K. Hao and P. Kuntz,
Position-Guided Tabu Search for Graph Coloring.
Accepted for the post-proceedings of LION 2009 (*Learning and Intelligent OptimizatioN * conference, Trento, Italy), LNCS 5851:148-162, 2009.
(paper draft, slides) Springer©

[C6] D. Porumbel, J-K. Hao and P. Kuntz,
A study of evaluation functions for the graph K-coloring problem.
Selected papers from the *8th International Conference on Artificial Evolution* (Tours, France),
LNCS 4926: 124-135, 2008.
(ps, pdf)
Springer©

[E1] D. Porumbel, Trying to demystify the Karush-Kuhn-Tucker conditions (pdf, html).

[E2] D. Porumbel, Revisiting the bijection between planar maps and well labeled trees (pdf). In this work, we provide alternative arguments and correct a slight error of a graph theory article from around 1970s/1980s.

[PhD] D. Porumbel, PhD thesis,
English version,
French version,
dedicated to my grandfather.

More[+] (Seminars, theses)

Projective Cutting Planes for Benders decompositions, Column Generation, a robust programming problem, ...

Replacing the separation sub-problem with the intersection sub-problem to solve a Benders reformulation model (2018)

Distance Guided Local Search for maximum weighted k-cluster or k-clique (2018)

Integer Ray Method for Column Generation for Cutting Stock and Capacitated Arc Routing (2014)

Heuristic for maximum minimum diversity (2011)

Isomorphism tool GI-Ext (2010)

I received the __Simon Régnier__ prize in 2011. This prize is awarded each year by the "Société
Francophone de Classification" (French-speaking Classification Society) to a researcher of maximum
35 years with a PhD thesis on classification. (slides)

Nominated for Best Paper Award (3 papers selected among more than 50), EvoCOP 2009

Bronze medal at the 41st International Mathematical Olympiad, a problem-solving competition with contestants from almost 100 countries (ranked 2nd in the qualification rounds of Romania), South Korea, 2000

Diploma for Academic Excellence of Romania's President Emil Constantinescu, 2000

I accepted review invitations from the editorial board of different journals since 2017:
*Computational Optimization and Applications*,
*European Journal of Operational Research*,
*IEEE Transactions on Cybernetics*,
*Computers and Operations Research *,
*Transportation Research part E*.
*Engineering Optimization*.
Before 2017, I performed reviews for journals like:
*Canadian Mathematical Bulletin*,
*Journal of Artificial Intelligence Research*,
*The Computer Journal*,
*IEEE Transactions on Evolutionary Computation*,
*European Journal of Operations Research*,
*Computers and Operations Research *,
*Evolutionary Computation*,
*Computers & Mathematics with Applications*,
*Information Processing Letters*,
*Expert Systems and Applications*,
*Engineering Applications of Artificial Intelligence*,
*Computing*.
I was in the program committee of
different conferences (Evocop 2012, Evocop 2013, Evocop 2014, Evocop 2019, Gecco Ecom 2013, Gecco Ecom 2014, Gecco Ecom 2015, Gecco Ecom 2016, Gecco Ecom 2017, Gecco Ecom 2018, Gecco Ecom 2019).
I also reviewed some papers indirectly (as a sub-reviewer) a few times (e.g., for ICTAI, CEC, GECCO, MOSIM).

I (co-)advised a PhD thesis: * Nathalie Helal*, An evidential answer for the capacitated
vehicle routing problem with uncertain demands, defended in 2017 (main adviser: Eric Lefèvre, second adviser Frédéric Pichon, collaboration
with David Mercier).
I adivised some master theses along the years:
Thomas Ridremont (Robust optimisation of wiring in renewable-energy installations, with Marie-Christine Costa and Cédric Bentz, 2015);
Hubert Arnoux (A tool of visualisation techniques for local search methods, with J-K Hao, P. Kuntz, 2012);
Junlin Zhu (Mathematical Programming Models for Graph Isomorphism, with Amélie Lambert, 2015);
Ben Ibrahima Badji (Meta-heuristics for the Arc-Routing Problem, with T. Hsu, H. Allaoui, G. Goncalves, 2014);
Fahrur Rozi and Mochammad Luthfi (Airport passenger flow simulation in Quest and Arena and resource allocation optimization, with G. Gonvalves, 2011).

I created a library for Graph Coloring Benchmarking during my PhD thesis.

- Computer Science Departement of CNAM, 2014-...: teaching different modules in Computer Science and Optimization (e.g., a course on Integer Programming, a course on professional (re)training in computer science)
- University of Artois (IUT Béthune), 2010-2014,
**responsability of a dozen of 30-hours modules**in 4 years: Network Programming (sockets), Event-Driven Programming (Swing graphical interface), Operating Systems, Security, Advanced Algorithms
▼ 2013-2014 (~250h)
- *Programmation événementielle et réseaux: cours (sockets, fils d'exécutions, événements, interface graphique Swing, etc.)
- *Programmation orientée objets: cours , tp1 (classes de bases, une première interface graphique), tp2 (fenêtres Swing, animations 2D basiques)
- *Sécurité cours (exemples d'attaques, cryptographie, routage et filtrage à l'aide d'iptables, etc) , problem class (td) computer class (tp)
- *Algorithmique avancée cours (exemples de problèmes algorithmiques, complexités, bases mathématiques de la cryptographie, etc)
- *Système d'exploitation et programmation système cours (fils d'exécutions, signaux, bash), un tp sur de commandes utiles Bash
- Bases de la programmation
- *Consolidation des bases de la programmation un mini-projet sur une recherche locale pour un problème d'ingénierie de trafic réseau, TP1 (tableaux, calculs de séries, 𝛑²/6)
- University of Angers (Computer Science department), 2008 - 2009, responsability of the Networks module, assisting with many other problem and computer classes (Artificial Ingelligence, Web Programming, Compilation) More[+] (2008-2010)
- Univeristy of Nantes (Ecole Polytechnique), 2006 - 2008, assisting in "Metaheuristics and Optimisation" More[+] (2006-2008)
- Faculty of Automatic Control and Computers (University Politehnica of Bucharest) 2004-2006, teaching assistant on a dozen of subjects (e.g., Artificial Intelligence, OpenGL Computer Graphics, Algorithm Design and Complexity) More[+] (2004-2006)