The Ellipsoid Algorithm || @ CMU || Lecture 19a of CS Theory Toolkit

The Ellipsoid Algorithm || @ CMU || Lecture 19a of CS Theory Toolkit

🎙 Ryan O'Donnell 👥 14K 📅 June 10, 2020 ⏱ 30 min 👁 6K 📄 lecture 🧭 2026-08-17
Available in: English (current) Français

Keywords

ellipsoid algorithmlinear programmingconvex optimizationseparation oraclesemi-definite programming

Summary

This lecture, part of the CS Theory Toolkit course at Carnegie Mellon University, presents the ellipsoid algorithm for solving linear programs in polynomial time. The instructor, Ryan O’Donnell, begins by reducing the general linear programming problem to a robust emptiness testing problem, where the goal is to decide if a polytope is empty or contains a small cube. He then explains the ellipsoid algorithm, which iteratively maintains an ellipsoid containing the feasible region, and at each step checks if the center is feasible; if not, it uses a separating hyperplane to shrink the ellipsoid. The analysis shows that the volume of the ellipsoid decreases by a constant factor each iteration, leading to a polynomial-time algorithm. The lecture also highlights the crucial role of a separation oracle, which allows the algorithm to work even when the polytope is not explicitly given. Finally, the instructor mentions applications to semi-definite programming and the max cut problem, referencing the work of Grötschel, Lovász, and Schrijver, and Delorme and Poljak.

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Critical Evaluation

Value of the Information & Strength of the Argument

The lecture provides a clear and rigorous explanation of the ellipsoid algorithm, emphasizing its theoretical significance and practical implications. The argumentation is solid, with careful reductions and a proof sketch that highlights the key ideas. The instructor effectively motivates the need for a robust version of the problem and demonstrates how the algorithm leverages a separation oracle. The value of the information is high for those interested in theoretical computer science and optimization, as it bridges fundamental concepts with advanced applications.

Scientific Rigor, Source Quality, Title Accuracy

The lecture is scientifically rigorous, with references to standard literature such as ‘Geometric Algorithms and Combinatorial Optimization’ by Grötschel, Lovász, and Schrijver, and ‘Laplacian eigenvalues and the maximum cut problem’ by Delorme and Poljak. The title accurately reflects the content, and the lecture is well-structured. The instructor is a recognized expert, and the content is presented with appropriate mathematical detail. No public comments were provided for analysis.

163 words

Title / Content Match

The title accurately reflects the content: a lecture on the ellipsoid algorithm, part of a CS theory toolkit course.

Quality & Reliability

8/10

Lecture by a recognized expert in theoretical computer science, with clear mathematical explanations and references to standard literature. The content is rigorous and well-structured, though it is a lecture sketch rather than a peer-reviewed publication.

Key Moments

Cited Sources

  • Geometric Algorithms and Combinatorial Optimization — Referenced as a resource for the lecture, covering the ellipsoid method and combinatorial optimization.
  • Laplacian eigenvalues and the maximum cut problem — Referenced in relation to semi-definite programming and the max cut problem.
  • Ryan O'Donnell's homepage — Instructor's academic page.
  • Course homepage on Diderot — Course materials and information.
  • Rebecca Kiger Photography — Photographer of the thumbnail image.

Concurring Sources

  • Geometric Algorithms and Combinatorial Optimization — Standard reference for the ellipsoid method and combinatorial optimization.
  • Laplacian eigenvalues and the maximum cut problem — Relevant to the application of SDP to max cut.

Contribution & Novelties

The lecture provides a clear and accessible explanation of the ellipsoid algorithm, emphasizing its theoretical foundations and practical implications. It highlights the importance of separation oracles and the reduction to robust emptiness testing, which are key insights for understanding the algorithm’s power. The lecture also connects the algorithm to semi-definite programming and the max cut problem, illustrating its broader applicability.

Pour aller plus loin :

112 words

Radar Profile

The radar profile shows high scores in information quality, technical level, and reliability, with a slightly lower score in information quantity. This indicates a dense, rigorous lecture that may be challenging for beginners but offers substantial depth for those with a background in theoretical computer science.

Reliability 8/10