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I did do a bit to break the spell |
This is our key philosophy.txt, the only possible fuel for all work on this page From an implementation detail to an unlimited manifesto on the artificial&injurious distance between theory and real computing.htm On the tragic side of working for the truth.pdf |

## Daniel Porumbel
Associate professor (MCF),
Combinatorial Optimization Team,
CEDRIC CS Lab, CNAM,
Paris |

- exact algorithms for solving linear programs with prohibitively-many constraints in
column generation [J1, J2, J4, J8, J9], in the Benders reformulation [J1, J3], or also in
submodular function
minimization [J7].
I proposed modifying the standard Cutting-Planes, by
upgrading the widely-used
separation sub-problem
to a projection sub-problem [J1, J2, J3]: given feasible
*x*in some polytope*P*and direction*d*, what is the maximum*t*value such that*x+td∈P*? - heuristic and local search algorithms for very large problems [J6,J8,J10,J12,J13,C1,C3-C6].
For instance, I worked on the idea of guiding search algorithms using distances between candidate
solutions [J5,J6,C1,C5,J13] or classification techniques (I obtained a Simon Régnier PhD prize, section
Awards below).
Although I could not recently find as much time as I wanted to work in this area, I
know we are condemned to live with heuristics for many years.
This does
*not*mean I am a die-hard fan of searching deep algorithmic insights in ants, honey/bumble bees, etc.

Daniel Porumbel,
Demystifying the characterizations of SDP matrices in mathematical programming.pdf:
I wrote this introduction to SDP (semipositive definite) programming becase I found *no other introduction
that targets the same public*.
This work is intended to be accessible to anybody who learned (a lot of) maths in the past but does
not work full time in (SDP) matrix theory.
For instance, the eigen-decompostion is not a pre-requisite unlike in most other SDP
introductions; I even provide two proofs to gain full insight and to learn related properties.
All in 100 pages, not 700.
The text is self-contained in a strong sense,
*i.e.,* everything is proven from
scratch, because I can't stand taking things for granted: no secret,
no empty jargon, no more formula out of the blue, no longer my(s)thification.

Daniel Porumbel, Demystifying (a light variant of) the Karush-Kuhn-Tucker conditions with full proofs for the linear program with logarithmic barrier used in Interior Point Algorithms.pdf : I wrote this because I plan to attack Interior Point Algorithms (IPMs); my goal is to implement IPMs to solve linear programs with prohibitively many constraints (and later SDP programs). No joke; all I need is time, God willing.

Daniel Porumbel, Further experiments and insights on Projective Cutting-Planes pdf (technical report of CEDRIC CS Lab : CEDRIC-19-4550)

Daniel Porumbel, Igor Machao, El-Ghazali Talbi, Using an Exact Bi-Objective Decoder in a Memetic Algorithm for Arc-Routing (and Other Decoder-Based) Problems

[J1] Daniel Porumbel,
Projective Cutting-Planes,
*SIAM Journal on Optimization*,
30(1): 1007-1032, 2020
(pdf draft,
slides,
source code,
youtube 20 minutes,
youtube 40 minutes,
doi link)

[J2] Daniel Porumbel,
Ray Projection for Optimizing Polytopes with Prohibitively Many Constraints in
Set-Covering Column Generation,
*Mathematical Programming*
155(1): 147-197, 2016
(pdf draft,
source code),
Springer©, doi link

[J3] 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]),

[J4] 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)

[J5] Daniel Porumbel, J-K. Hao, Distance-Guided Local Search, Journal of Heuristics, 2020, 26(5):711-741. (pdf draft)

[J6] D. C. Porumbel, J-K. Hao, P. Kuntz,
A Search Space "Cartography" for Guiding Graph Coloring Heuristics.
*Computers & Operations Research*, 37(4):769-778, 2010.
(pdf draft),
Elsevier©, doi link

[J7] Daniel Porumbel,
Prize-Collecting Set Multi-Covering With Submodular Pricing,
*International Transactions in Operational Research*, 25 (4):1221-1239, 2018,
(pdf draft),
Wiley-Blackwell©

[J8] 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© ,

[J9] 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

[J10] 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

[J11] D. C. Porumbel, J-K. Hao, P. Kuntz.
An Efficient Algorithm for Computing the Distance Between Close Partitions.
*Discrete Applied Mathematics*, 159(1):53-59, 2011,
(pdf draft),
Elsevier©,
doi

[J12] 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

[J13] D. C. Porumbel, J-K. Hao, 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

[J14]
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©

[J15] D. C. Porumbel, J-K. Hao, 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, 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, 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, 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, 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, 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)

When I was a kid, I really liked mathematics problem-solving contests and I even
went to the international level, see below. Even later, in 2011,
I could receive a PhD prize called __Simon Régnier__ awarded by the "Société
Francophone de Classification" (French-speaking Classification Society), see
these slides. I now believe that science prizes make
sense for enthusiastic kids or students. For a grown-up man, thinking about prizes (even up to
the Nobel one) is short-sighted. The only prize I dream of is you -- any public reading my work. Yes, all I want is you,
I mean you and me wishing on the same star.

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:
*INFORMS Journal of Computing*,
*Computational Optimization and Applications*,
*European Journal of Operational Research*,
*Operational Research *,
*IEEE Transactions on Cybernetics*,
*Computers and Operations Research*,
*Transportation Research part E*,
*Engineering Optimization*,
*Theoretical Computer Science*,
*Discrete Applied Mathematics*,
*Journal of Computational Science*.
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, Evocop 2020, Evocop 2021, Gecco Ecom 2013, Gecco Ecom 2014, Gecco Ecom 2015, Gecco Ecom 2016, Gecco Ecom 2017, Gecco Ecom 2018, Gecco Ecom 2019, Gecco Ecom 2020, Gecco Ecom 2021, Ecta 2019).

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)conversion 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)