CS229r: Spectral Graph Theory in Computer Science

Semester: Fall
|
Year offered: 2020

The webpage for offerings after 2020 is here.

Spectral graph theory is about how eigenvalues, eigenvectors, and other linear-algebraic quantities give us useful information about a graph, for example about how well-connected it is, how well we can cluster or color the nodes, and how quickly random walks converge to a limiting distribution.  Spectral graph theory has turned out to be extremely useful in theoretical computer science, with applications ranging from solving linear systems, converting randomized algorithms to deterministic algorithms, sampling via Markov Chain Monte Carlo, counting, web search, and maximum flow.  In this course, we will study both the mathematics and the algorithmic applications of spectral graph theory, including some results from the past couple of years.  Along the way, we will cover a number of concepts and tools that are quite broadly useful, such as mixing of Markov chains, expander graphs, algorithmic linear algebra, and the multiplicative weights method for optimization. 

Links


Class Materials:

Schedule, Lecture Notes, and Assignments

Date
Title
Reading
Lecture Notes
Assignments & Other Handouts

1. Introduction

 
 
 
Aug 20
Course overview
 
syllabus, ps0 due 9/11 (pdf, tex)
Sep 3
Graphs, matrices, spectral theorem
 Spielman, Ch. 1-2
 
Sep 8
  Connectivity, graph drawing, interlacing, graph coloring
Spielman, Ch. 3-4
 
Sep 10
  Cayley graphs
   Trevisan, Ch. 16; Spielman Ch.7
  ps1, due 9/25 (pdf, tex)

2. Markov Chains

 
 
 
Sep 15
 Cayley graphs (cont.), Random walks on undirected graphs
 Spielman, Sec. 4.5, Ch. 10
 
Sep 17
 Random walks on undirected graphs (cont.)
 Spielman, Sec. 4.5, Ch. 10
 
  Sep 22
    Random walks on directed graphs, Pagerank, and MCMC
Babai Ch.8, Madry lecture notes
 

 3.  Partitioning and Clustering

 
 
 
Sep 24
  Graph coloring, isoperimetry
 Spielman, Sec 19.5, Ch. 20
ps2 (pdf, tex), due 10/9
Sep 29
  Cheeger's Inequality
 Spielman Ch. 21
 
Oct 1
  Higher-order Cheeger
 Trevisan Chs. 7-8
 
Oct 6
  The Power Method
 Trevisan Sec. 9.3
 

 4.   Expander Graphs

 
 
 
Oct 8
 Measures of expansion
 Vadhan Sec. 4.1
ps3 (pdf, texpsheader.texmacros.tex), due 10/23
Oct 13
 Measures of expansion (cont.)
 Vadhan Sec 4.1
 
Oct 15
 Expansion of random graphs, random walks on expanders
 Vadhan Sec. 4.1-4.2
 
Oct 20
  Explicit constructions, Undirected Connectivity in logspace
 Vadhan Sec. 4.3-4.4
 

  5.   Effective Resistances and Spectral Sparsification

 
 
 
Oct 22
 Resistor networks
 Spielman Sec, 11.7-12.4
 ps4 (pdf, tex, due 11/17)
Oct 27
 Schur complements
Spielman Sec. 12.5-12.8
 
Oct 29
 The Matrix-Tree Theorem
Spielman Ch. 13
 
Nov 3
 Spectral approximation
Spielman Ch. 5
 
Nov 5
 Spectral sparsification
 Spielman Ch. 32
Detailed Project Description due Nov 8

  6.   Solving Laplacian Systems

 
 
 
Nov 10
 Iterative methods for linear systems
Spielman Ch. 34-Sec. 35.2
 
Nov 12
 Preconditioned iterative methods
Spielman Sec. 36.0-36.5
 
 Nov 17-19
   NO CLASS - FOCS & TCC conferences
 
 
 
Nov 24
 A preconditioner from squaring and sparsification
Murtagh Ch. 2
 Problem Set 5 (pdf, tex zip, due 12/4)
  Nov 26
   NO CLASS - THANKSGIVING
 
 
 
Dec 1
  Faster max flow via electrical flows
 Vishnoi Sec. 8.2
 
 

  7. Wrap Up

 
 
 
  Dec 3
   High-dimensional expanders and sampling spanning forests
 
 
 
Dec 8
 Conclusions and survey of other topics
 
 
 
Dec 9
Final project draft papers due
 
 
 

   Dec 11

 

   Final project presentations
 
 
 
   Dec 14
   Final project presentations
 
 
 
   Dec 16
   Final project revised presentations due