Nikolaos Efthymiou

Connections beneath the surface.

Nikolaos Efthymiou portrait

About Me

My expertise lies at the intersection of Theoretical Computer Science, Combinatorial Optimization, and Machine Learning, disciplines I leverage to tackle inherently intractable, structured problems. In my current role, I tackle challenging optimization problems within the airline industry. As I look ahead, with AI models and agentic architectures reshaping the frontier of intelligence, I am inspired to advance systems rooted in formal and verifiable reasoning and principled design. I play the piano, I love classical music, especially Bach and Rachmaninoff, and I find beauty in the structures underlying both mathematics and music.

The Capsule

A curated collection of insights, thoughts, and intentions

Source: Link

Selected Projects

A few explorations at the intersection of Machine Learning, algorithms and structure.

Neural SAT solver

Research on differentiable loss functions for unsupervised SAT solving with Graph Neural Networks using tools from Probabilistic Combinatorics.

Approximation algorithms for consistent clustering

Approximation algorithms and impossibility results for a new, two-stage version of consistent clustering. Natural extension to a stochastic optimization setting.

Expander graphs and applications in Proof Complexity

Survey on expanders, their combinatorial construction of Reingold et al. and some surprising applications in Proof Complexity, a major subfield of Complexity Theory.

Predict-then-optimize for Hoist Scheduling Problems

Supervised Learning methods for speeding up a Constraint Programming solver for the Cyclic Hoist Scheduling Problem.

Highlights of my journey

Oct. 2025 - Present

Crew Optimization Developer

Swiss International Air Lines

Tackling large-scale discrete optimization problems in crew scheduling.

Aug 2024 - Sep. 2025

Collaborating Researcher

MIT Computer Science and Artificial Intelligence Laboratory (CSAIL)

Research in Machine Learning for Combinatorial Optimization: neural SAT solvers and differentiable primal-dual algorithms for MaxCUT.

Nov. 2025

Ken Wang Scholar

AGIFORS

Recognition for airline Operations Researchers in the early stages of their careers.

Sep. 2022 - Sep. 2025

MSc Computer Science

École Polytechnique Fédérale de Lausanne (EPFL)

Specialization in Computer Science Theory. Master thesis jointly conducted at SWISS and the Risk Analytics and Optimization laboratory led by Prof. Daniel Kuhn.

Sep. 2024 - Aug. 2025

Operations Research & Machine Learning Intern

Swiss International Air Lines

Discrete algorithms for passenger recovery problems. Cost-saving contributions to the OPSD project of Lufthansa Group.

Sep. 2019 - Jul. 2022

BSc Computer Science and Engineering

Delft University of Technology (TU Delft)

Specialization in Big Data. Research in Machine Learning for Scheduling Problems.

Apr. 2021- Jun. 2021

Software Engineer Intern

PricewaterhouseCoopers (PwC)

Development of clustering algorithms for internal applications.

Feb. 2019

Third place in music composition competition

Hellenic Authors' Society

National competition for film music composition.

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