Ariel Procaccia

I am an Assistant Professor in the Computer Science Department at Carnegie Mellon University, and an Affiliated Faculty in the Machine Learning Department. I am also a member of the theory group and the ACO program.

I usually work on problems at the interface of computer science and economics. I write papers, teach courses, serve on various editorial boards and program committees, and, best of all, advise wonderful students and postdocs.

Current Highlights


Spliddit: Provably Fair Solutions


RoboVote: AI-Driven Collective Decisions


Handbook of Computational Social Choice


New Scientist published a story about our EC’16 rent division paper, which will also be presented at the IJCAI’17 Sister Conference Track.

New Scientist just published a nice story about our IJCAI’17 paper with the catchy title “Why You Should Charge Your Friends for Borrowing Your Stuff” (short answer: because in a game where non-rivalrous goods are bought and shared on a network, equilibria are more efficient, in theory and experiments, when access costs are imposed).

Here are some other random topics I’ve weighed in on recently (not covered by other news):

* Aziz and Mackenzie’s breakthrough result on bounded envy-free cake cutting, in the Sydney Morning Herald and Quanta Magazine.

* AI and online dating, in the Boston Globe.


Congratulations to Swaprava Nath, who will join the Indian Institute of Technology, Kanpur, as Assistant Professor in July. I’ve hosted Swaprava as a postdoc since 2015; he is supported by the Fulbright-Nehru postdoctoral fellowship.

I am co-PI on a new 3-year grant from the Office of Naval Research, entitled “Provably Impartial Peer Assessment for Expert Hiring”, with PI Chinmay Kulkarni.


My former PhD student Nisarg Shah won the Victor Lesser Distinguished Dissertation Award, given annually for the best thesis in the area of autonomous agents and multiagent systems. His thesis is entitled “Optimal Social Decision Making.” He will present his thesis research in a plenary talk at AAMAS-17 in Brazil.

An opinion piece that I wrote was published today in Wired. It’s about computational social choice (although I don’t call it that) and a bit of politics.

I was interviewed by Tim Grant from the Pittsburgh Post-Gazette about RoboVote and voting more generally. Worth checking out, if only for the bizarre portrait photo with the hovering phones!

RoboVote (, a not-for-profit voting website that provides optimization-driven methods for making collective decisions, has launched today! Check out RoboVote’s about page for (somewhat AI-centric) information about the website, its algorithms, and the theory underlying them, as well as info about the amazing team.

Press coverage (newest to oldest): Wired, Pittsburgh Post-Gazette, ExtremeTech, Daily Mail, Digital Trends, Marketplace, CMU homepage

I received a new 3-year grant from the Office of Naval Research, entitled “Robust Aggregation of Noisy Estimates”.


Our paper “Which Is the Fairest (Rent Division) of Them All” has been selected to receive the best paper award at the 17th ACM Conference on Economics and Computation, out of 242 submissions. The paper is joint work with Kobi Gal and Moshik Mash of Ben Gurion University, and my postdoc Yair Zick.

Abstract: What is a fair way to assign rooms to several housemates, and divide the rent between them? This is not just a theoretical question: many people have used the Spliddit website to obtain envy-free solutions to rent division instances. But envy freeness, in and of itself, is insufficient to guarantee outcomes that people view as intuitive and acceptable. We therefore focus on solutions that optimize a criterion of social justice, subject to the envy freeness constraint, in order to pinpoint the “fairest” solutions. We develop a general algorithmic framework that enables the computation of such solutions in polynomial time. We then study the relations between natural optimization objectives, and identify the maximin solution, which maximizes the minimum utility subject to envy freeness, as the most attractive. We demonstrate, in theory and using experiments on real data from Spliddit, that the maximin solution gives rise to significant gains in terms of our optimization objectives. Finally, a user study with Spliddit users as subjects demonstrates that people find the maximin solution to be significantly fairer than arbitrary envy-free solutions; this user study is unprecedented in that it asks people about their real-world rent division instances. Based on these results, the maximin solution has been deployed on Spliddit since April 2015.

Congratulations to Nisarg Shah, who has accepted a tenure-track faculty position in the Department of Computer Science at the University of Toronto! He will join U of T in fall 2017, after spending a year as a postdoc at Harvard’s Center for Research in Computation and Society. I have had the privilege of advising Nisarg since he joined our PhD program in fall 2011 (which is the same time I myself joined CMU); he is defending on June 28.

The Handbook of Computational Social Choice, which I have co-edited together with Felix Brandt, Vince Conitzer, Ulle Endriss, and Jerome Lang, has been officially published.

Description: The rapidly growing field of computational social choice, at the intersection of computer science and economics, deals with the computational aspects of collective decision making. This handbook, written by thirty-six prominent members of the computational social choice community, covers the field comprehensively. Chapters devoted to each of the field’s major themes offer detailed introductions. Topics include voting theory (such as the computational complexity of winner determination and manipulation in elections), fair allocation (such as algorithms for dividing divisible and indivisible goods), coalition formation (such as matching and hedonic games), and many more. Graduate students, researchers, and professionals in computer science, economics, mathematics, political science, and philosophy will benefit from this accessible and self-contained book.

A PDF of the book is freely available online. To open the document, please enter the password cam1CSC (strangely enough, this password can be disseminated legally, so you are encouraged to shout it from the rooftops). The link is here:

Alternatively, the book can be purchased through the Cambridge University Press website (, Amazon, and other retailers.

Congratulations to Yair Zick for accepting a faculty position at the National University of Singapore! He will join NUS as Assistant Professor of Computer Science in the summer. Yair has been a postdoc at CMU since April 2014, jointly hosted by Anupam Datta and me. Before that he completed his PhD at Nanyang Technological University, Singapore, where he worked with Edith Elkind.

Congratulations to Nika Haghtalab for winning a 2016-2018 Microsoft Research PhD fellowship. Nika is co-advised by Avrim Blum and me.

Together with Yonathan Aumann, Steven Brams, and  Jérôme Lang, I am organizing a Dagstuhl workshop on Fair Division. The workshop will take place on June 6-10, 2016.

New Scientist published a “one minute interview” with me about AI and fair division.

I received the IJCAI Computers and Thought Award at IJCAI’15 in Buenos Aires. A narrated video of my presentation at the conference is now available online.

I received a new NSF grant, entitled “Fair Division at Scale”.


The mathematical study of fair division dates back to the 1940s. Nowadays the literature encompasses provably fair solutions for a wide variety of problems, many of them relevant to society at large. But, to date, very few fair division methods have been implemented. Building on its rich history, the field of fair division is poised to impact society on a grander scale, for example, via Spliddit (, a fair division website created by the PI. The overarching theme of this proposal is that the advent of fairness at scale gives rise to novel algorithmic challenges, revolving around the design of methods that are practical, widely applicable, and provably fair. Solutions to these challenges call for a synthesis of ideas from theoretical computer science and microeconomic theory.

The evolution of Spliddit plays a key role in the project: Insights arising from the research will be implemented to improve Spliddit’s publicly accessible methods. Moreover, new applications will be added in order to further widen the website’s reach. The project also includes plans to enhance Spliddit’s educational content through the creation of instructive videos, thereby making the website a valuable learning and teaching resource. Finally, the project contains plans to make a societal impact that extends beyond Spliddit. In particular, the PI will work with California school districts to develop a fair method for allocating unused space.

On a technical level, the thrust of the project is twofold. (i) Dividing indivisible goods: One of five applications currently available on Spliddit, the division of indivisible goods is a notoriously difficult problem from a fair division perspective. To obtain a provably fair method, Spliddit relies on the notion of maximin share (MMS) guarantee. While exact MMS allocations may be infeasible, the project explores several notions of approximation. The project also explores the feasibility boundary of MMS allocations. Foundational algorithmic challenges lie at the heart of these research directions. (ii) Sharing credit: Spliddit’s credit calculator fairly determines the contribution of each individual to a group project, using a method developed by de Clippel et al. Perhaps the method’s most compelling guarantee is impartiality: a player’s report does not affect her own share of the credit. Dividing credit for a scientific paper, with the goal of fairly ordering the authors by contribution, is an especially attractive potential application; but there is no guarantee that players will not be able to affect their position in the resultant ranking. The project aims to circumvent this obstacle via randomization and approximation.

A new version of Spliddit, featuring two new apps and improvements to the old ones, has officially launched!
Press coverage (newest to oldest): Quanta Magazine, The New York Times #2, New Scientist, Pittsburgh Magazine, GeekWire, NSF podcast, Fast Company, Pittsburgh Post-Gazette, Lifehacker, Slashdot, Gizmodo, Nautilus Magazine, The New York Times #1.

Congratulations to Nika Haghtalab for winning a 2015-2016 IBM PhD fellowship, with a statement entitled “Learning Theory for Societal Good”. Nika is co-advised by Avrim Blum and me.

I was named a Sloan Research Fellow, together with 125 other young researchers in chemistry, computer science, economics, mathematics, computational and evolutionary molecular biology, neuroscience, ocean sciences, and physics.

Congratulations to Junxing Wang for winning the best student paper award at EC-14, for our joint paper “Fair Enough: Guaranteeing Approximate Maximin Shares”.

The New York Times published a story about the rent division problem — they even implemented the algorithm of Francis Su, and illustrated Sperner’s lemma! The story includes a paragraph about Spliddit, and a rather inarticulate quote from me.

Congratulations to Nisarg Shah for winning a 2014-2015 Facebook PhD fellowship, with a statement entitled “Economic Foundations of Social Computing”.  There are 11 winners overall, 3 of whom are from CMU!

Please check back later for more fascinating news!

Contact Information

  •    Computer Science Dept.
  •    Carnegie Mellon University
  •    Pittsburgh, PA 15213
  •    Gates-Hillman Center
  •    Office #7002