6.854/18.415J: Advanced Algorithms (Fall 2020) Course Information
Instructor:
David Karger, 32G592. karger@mit.edu. http://people.csail.mit.edu/karger/
Class webpage: http://courses.csail.mit.edu/6.854/.
Summary
The need for efficient algorithms arises in nearly every area of
computer science. But the type of problem to be solved, the notion of
what algorithms are "efficient," and even the model of computation can
vary widely from area to area.
This course is designed to be a capstone course in algorithms that surveys some of the most powerful algorithmic techniques and key computational models. We will cover a broad selection of topics including amortization, hashing, dimensionality reduction, bit scaling, network flow, linear programing, and approximation algorithms. Domains that we will explore include data structures; algorithmic graph theory; streaming algorithms; online
algorithms; parallel algorithms; computational geometry; external memory/cache oblivious algorithms; and continuous optimization.
Online Class Experimentation
This semester's pandemic has forced us into purely online teaching. In an effort to make lemons from lemonade, I plan to experiment with a variety of different approaches to teaching and grading in order to determine what works best. Among experiments I'm already considering are:
 Lectures: Realitme online lectures, watching prerecorded (i) together with answers in realtime, (ii) in advance with discussion after, (iii) with online annotation
 Grading: Peer grading; selfgrading with supervision
 Collaboration: requiring some problems be done with new collaborators
I will be developing other experiments on the fly.
Goals
We hope that this class will confer
 some familiarity with several of the main lines of work in
algorithmssufficient to give you some context for formulating and
seeking known solutions to an algorithmic problem;
 sufficient background and facility to let you read current
research publications in algorithms;
 a set of tools for design and analysis of new algorithms for new
problems that you encounter.
Content:
The goal is to be broad rather than deep. This
list is approximate.
 Data Structures: Persistent data structures, splay trees.
 Bit Tricks: Wordlevel parallelism. Transdichotomous model.
o(n log n integer sorting.
 Network Flows: Augmenting paths.
Mincost flows. Bipartite matchings.
 Linear Programming: Formulation of problems as linear
programs. Duality. Simplex, Interior point, and Ellipsoid
algorithms.
 Continuous Optimization: Gradient descent. Newton's method.
 Dimensionality Reduction: JohnsonLindenstrauss lemma. Compressive sensing.
 Online Algorithms: Ski rental. Paging.
The kserver problem.
 Approximation Algorithms:
Greedy approximation algorithms. Dynamic programming and weakly
polynomialtime algorithms. Linear programming relaxations.
Randomized rounding. Scheduling, vertex cover, and TSP.
 FixedParameter Algorithms: Another way to cope with
NPhardness. Parametrized complexity. Kernelization. Vertex
cover. Connections to approximation.
 Parallel Algorithms: PRAMs. Circuits. Maximal
independent set.
 ExternalMemory Algorithms: The cost of
accessing data from slow memory. Buffer trees.
Cacheoblivious algorithms.
 Computational Geometry: Convex hull. Orthogonal range search. Voronoi diagrams.
 Streaming Algorithms: Sketching. Distinct and frequent
elements.
Prerequisites:
Strong performance in an
undergraduate class in algorithms (e.g., 6.046/18.410), discrete mathematics and
probability (6.042 is more than sufficient), and substantial mathematical maturity.
Requirements:
 Peer Grading (10%). Help grade a problem set.
 Homework (70%). Weekly problem sets, with collaboration
usually allowed.
Many of the problems already have solutions posted on the
internet or in course bibles. No preexisting solutions may be used. Violations of this policy will be dealt with severely.
 Independent Project (20%). You will carry out independent
work to exercise your new mastery of algorithms. It can have
several forms, or be a combination:
 Read some new (not yet textbook) algorithms from the recent research
literature, and provide an improved (of greater clarity)
presentation/synthesis of the results
 Research a new algorithm that improves upon the state of the
art, either for a classical problem or one that arises naturally
from your own work
 Implement some interesting algorithms and study/compare their
performance. Considerations include choice of algorithm, design of
good tests, interpretation of results, and design and analysis of
heuristics for improving performance in practice.
Collaboration (in groups of at most 3) is encouraged on these final projects.
Homework/Collaboration Policy.
 Homework is due Wednesdays at the beginning of class. We'll have boxes or piles for dropping them off at the back of the room. Those boxes will be collected a few minutes in, and homework arriving after will be considered late.
 Each student has a total budget of 15 “slack” points to accommodate his/her late problem submissions.
 Each problem that is submitted late but before class Friday will consume one slack point (and incur no grade penalty).
 If that problem is submitted in before Monday class, it will consume two slack points (and, again, incur no grade penalty).
 No late problem will be considered if submitted after the Monday class begins.
So, for example, if there is a problem set with a total of five problems on it, submitting three of these problems on time, one of them before Friday class, and one of them before Monday class will consume three slack points in total.

Write each subproblem (each separately labeled part) on a separate sheet of paper and include your name and email address. Also, make sure your name appears on each page.
 Collaboration is encouraged, except where explicitly forbidden.
 All collaboration (who and what) must be clearly indicated in
writing on anything turned in.
 Collaborators should discuss solutions, but must write up all
solutions independently.
 Groups must be small so that each member
plays a significant role (usually 3 or 4 students).
 For projects every collaborator must contribute significantly to
reading, implementation, and writeup. To allow this, groups should
limit their size to 3 unless the project is unusually large. All
members should be involved with all parts of the project and writeup.
 You may not seek out answers from other sources without prior permission. In particular, you may not use bibles or posted solutions to problems from previous years.
 Each student is required to grade (at least) one problem in the semester. We will have a TAsupervised grading session each week. This session is used to make sure that the graders fully understand the solution, while they can grade the problems at home after this session.
 For questions about grading, please contact the graders (emails listed on the website) first. Once you reach an agreement, the grader should send an email to the grading supervisor with a short explanation and a new grade.
 All late psets should be sent electronically to the TA supervising the grading.
Textbooks.
There are no textbooks covering a majority
of the material we will be studying.
Lectures will often draw from the following (optional) texts, all of
which are nice to have.
 Cormen, Leiserson, Rivest, and Stein. Introduction to Algorithms. MIT Press. 2001.
 Ahuja, Magnanti, and Orlin. Network Flows. Prentice Hall,
1993.
 Motwani and Raghavan. Randomized Algorithms. Cambridge
University Press, 1995.
 Dan Gusfield. Algorithms on Strings, Trees, and Sequences: Computer Science and Computational Biology. Cambridge University
Press, 1997.
 Allan Borodin and Ran ElYaniv. Online Computation and Competitive Analysis. Cambridge University Press, 1998.
 Robert Tarjan. Data Structures and Network Algorithms.
Society for Industrial and Applied Mathematics, 1983. A classic—no
longer up to date, but outstanding writing.
 Mark de Berg, Marc van Kreveld, Mark Overmars, Otfried
Schwarzkopf. Computational Geometry: Algorithms and
Applications. Springer Verlag, 2000.
 Williamson and Shmoys. The Design of Approximation
Algorithms. Cambridge University Press, 2011.