One-Dimensional Computational Topology

CS 598 JGE, Fall 2017

The most recent offering of this class is available here.
Jeff Erickson (
TuTh 11:00-12:15
1022 Lincoln Hall
Office Hours
Friday 4-5
3304 Siebel Center

Paul Klee, Zur Gruppe geschlungen [Entwined in a Group] (1930)
Paul Klee Zentrum, Bern


December 1
The makeup lectures will be held from 12 to 1:15 in 3401 Siebel, both today and next Friday.
November 16
I will give makeup lectures on the next two Fridays after Thanksgiving break. Please fill out this Doodle poll to let me know when you're available.
November 10
An archive of all submitted project proposals is available. Check your email for the required login credentials.
November 6
The twice-weekly lecture videos (~1Mb each) have put my web site over quota (~20Mb). I'm looking for alternate storage space, but meanwhile, posting of new lecture videos will be delayed.
November 1
Project proposals are due next Friday, November 10. Please submit your proposals on Gradescope. I will present an overview/summary of all submitted proposals on Tuesday, November 14.
October 9
Homework 3 is available.
September 20
Homework 2 is available.
September 15
Thanks to everyone who filled out the Doodle poll. My regular office hours will be Fridays 4–5, starting tomorrow (but not next Friday, because I will be on a plane).

Please sign up on Gradescope so that you can submit homework solutions. The self-enrollment code is MRWX3N. You can sign up using any name and email address you like, but please use a consistent identity in all homework submissions. If you are using anything other than your real name and email address, please fill out this form so I know who you are.

September 8
I am holding office hours next Monday, September 11, 3-4pm (not Friday as I announced in class) outside 3304 Siebel. Please fill out this Doodle poll to help me choose a time for regular weekly office hours.
September 7
Class is canceled on September 19 and 21, because I will be out of the country. I will schedule makeup lectures later in the semester.
September 5
Homework 1 is available. Stay tuned for Gradescope submission instructions.
August 31
Registration is now open to everyone. If you are still unable to register for any reason, please let me know.
August 29
Please also fill out this form to tell me about your background and interests. This will help be tune both the specific content and the level of detail/difficulty of the class. Thanks!

About this class

This course will be an introduction to my favorite facet of computational topology: Algorithms for curves and graphs embedded in the plane or other surfaces. Algorithmic questions about curves have been a driving force in topology since its inception more than a century ago. Planar and near-planar graphs have long been fertile ground for algorithms research, both because they naturally model many classes of networks that arise in practice, and because they admit simpler and faster algorithms than more general graphs. There is a rich interplay between these two domains, drawing on a common pool of techniques from geometry, topology, and combinatorics. Potential topics include topological graph theory; homotopy, homology, and other topological invariants; specialized algorithms for shortest paths, maximum flows, and minimum cuts; efficient approximation schemes for NP-hard problems; and applications in VLSI design, computer graphics, computer vision, motion planning, geographic information systems, and other areas of computing. Specific topics will depend on the interest and expertise of the students.

Students in all areas of computer science, mathematics, and related disciplines are welcome. CS 473 and/or Math 525 are recommended as prerequisites, but not required; necessary background material will be introduced as needed. Undergraduates interested in taking this course can get a registration override at the first lecture.

Other computational topology classes

The selection of topics in this class is necessarily limited by the finiteness of a single semester and by my own interests and expertise. Important topics in computational topology that I will not cover this semester, except perhaps briefly in passing, include automatic groups, knot theory, 3-manifolds, cell complexes (simplicial, cubical, Delta, CW, simplicial sets), discrete Morse theory, normal surface theory, configuration spaces, dynamical systems, persistent homology and its generalizations, surface reconstruction, manifold learning, topological data analysis, embedding obstructions, higher-order homotopy, discrete differential geometry, fixed-point theorems, applied Hodge theory, algebraic complexity, evasiveness of graph properties, impossibility results in distributed computing, and topological quantum computing. The full diversity of techniques, results, applications, and even definitions of computational topology could easily fill a dozen courses.

Here is an incomplete list of other recent courses in computational topology with publicly available course materials (beyond just a syllabus). Please let me know if you'd like to add your course!


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