Linear Programming: Optimization Reduces to Feasibility || @ CMU || Lecture 17d of CS Theory Toolkit

Linear Programming: Optimization Reduces to Feasibility || @ CMU || Lecture 17d of CS Theory Toolkit

🎙 Ryan O'Donnell 👥 14K 📅 June 3, 2020 ⏱ 22 min 👁 2K 📄 lecture 🧭 2026-08-17
Available in: English (current) Français

Keywords

linear programmingfeasibilityoptimizationreductionpolynomial time

Summary

This lecture, part of the CS Theory Toolkit course at CMU, focuses on the relationship between the feasibility and optimization problems in linear programming. The instructor, Ryan O’Donnell, begins by stating that if we have an oracle for deciding whether a system of linear inequalities is feasible, we can solve the search problem (finding a point in the polytope) and the optimization problem (maximizing a linear objective) via polynomial-time reductions. For the search problem, he shows how to iteratively add equality constraints (setting variables to zero) to reduce the dimension until a solution is found, using the oracle to guide the process. For optimization, he explains how to use binary search on the objective value, with the oracle checking feasibility of the constraint set plus a lower bound on the objective. He discusses handling unbounded cases and achieving approximate solutions. He then addresses the challenge of finding an exact optimal vertex, which requires number-theoretic techniques such as continued fractions and the LLL algorithm. The lecture concludes with a historical note on the development of these methods by Grötschel, Lovász, and Schrijver.

181 words

Critical Evaluation

Value of the Information & Strength of the Argument

The lecture provides a clear and rigorous explanation of the reduction from optimization to feasibility in linear programming. The argumentation is solid, building step by step from the feasibility oracle to solving the search and optimization problems. The instructor anticipates potential issues, such as unboundedness and the need for exact solutions, and addresses them with appropriate techniques. The value lies in the pedagogical clarity and the connection to deeper algorithmic concepts.

Scientific Rigor, Source Quality, Title Accuracy

The scientific rigor is high, as the lecture is part of a graduate course at a top institution. The instructor references standard textbooks on linear programming and combinatorial optimization. The title accurately reflects the content, focusing on the reduction. The lecture is well-structured and technically accurate, with appropriate caveats and historical context.

138 words

Title / Content Match

The title accurately describes the lecture's content: showing how optimization in linear programming reduces to feasibility.

Quality & Reliability

9/10

Lecture by a renowned professor at CMU, part of a graduate course, with rigorous mathematical content and references to standard textbooks. The presentation is clear and technically accurate.

Key Moments

Cited Sources

  • Understanding and Using Linear Programming — Referenced as a resource for the lecture.
  • Geometric Algorithms and Combinatorial Optimization — Referenced as a resource for the lecture.
  • Ryan O'Donnell's homepage — Instructor's academic page.
  • Course homepage on Diderot — Course materials and information.
  • Rebecca Kiger photography — Thumbnail photo credit.

Concurring Sources

  • Understanding and Using Linear Programming — Standard textbook on LP, supports the lecture's content.
  • Geometric Algorithms and Combinatorial Optimization — Classic reference for combinatorial optimization and LP.

Contribution & Novelties

The lecture provides a clear exposition of the reduction from optimization to feasibility in linear programming, emphasizing the use of an oracle and binary search. It also touches on the number-theoretic aspects of exact optimization, including continued fractions and the LLL algorithm, which are often omitted in introductory treatments.

Pour aller plus loin :

95 words

Radar Profile

The profile shows high scores across all dimensions, indicating a technically rigorous and informative lecture. The balance between theoretical depth and practical implications is well maintained.

Reliability 9/10