Social networks, auctions, and stock-markets appear to be very different phenomena, but they share a common foundation—the science of networks. The learning goal: to provide a broad, accessible introduction to the foundations of network science. We shall draw on ideas from mathematical sociology, and from game theory to understand strategic interaction over networks. We shall develop algorithms to identify network properties, and models for explaining network dynamics, including viral behavior.
Prerequisites: CS 225, CS 173, one of (MATH 225 or MATH 257 or MATH 415 or MATH 416 or ASRM 406), CS 361.
Meeting Times and Location: Wednesdays and Fridays, 12:30pm–1:45pm, online over Zoom. The Zoom link is on Canvas.
Prof. Hari Sundaram, hs1@illinois.edu, Office hours: Wednesdays 10am-11am, Online
Fall 2026 TAs: Agam Goyal, agamg2@illinois.edu, and Yian Wang, yian3@illinois.edu
You can find the join codes for Campuswire and Gradescope on Canvas.
Fall 2026: This is an online, flipped, class, taught across two locations: Urbana and Chicago. We'll connect the classrooms via Zoom. In this class, students shall watch short pre-lecture videos that cover essential ideas (available on canvas) and then complete in-class computational worksheets on PrairieLearn.
This class focuses on students learning by doing — students will learn key ideas by work on computational worksheets in class and through short exams (held at CBTF) and a long homework programming assignment. Note: late assignments are not accepted; see the late submissions policy below.
Four credits students have the opportunity to dive deeper into the topics discussed in class through developing a functional app related to any topic relevant to the class. For example, build a new social media app focused on say privacy concerns, develop an agentic moderation system, or develop a better social media feed construction algorithm that supports greater user engagement while reducing the spread of AI slop. The expectation is that the prototype is mature and ready to be put into development. Here are two examples of app development projects [App 1], [App 2].
Four-credit students may do the project individually or in a group of at most two. Partners submit identical deliverables with both names on each, and from the mid-semester report on, each deliverable ends with a short statement of who did what. Both partners receive the same project grade, and when we grade the prototype and the evaluation, we take the size of the group into account. Within the project grade, the proposal counts for 5%, the mid-semester report 25%, the final report 35% and the presentation 35%.
Use of generative AI technologies is allowed and encouraged in this class, provided you engage with them critically and transparently. Large language models can serve as valuable thinking partners—helping you explore ideas, debug code, understand complex concepts, or refine your writing—but they cannot replace your own deep engagement with the material. When you use AI tools for course assessments (homework, projects), you must demonstrate that you understand the underlying concepts and can critically evaluate AI-generated content.
Your Obligation: clearly documenting when and how you used AI, verifying any claims or code the AI produces, and being able to explain your reasoning independent of the tool. Think of AI as a collaborator that helps you think more deeply, not a shortcut that thinks for you. Your submissions should reflect your own critical analysis, original insights, and genuine understanding of social and information networks concepts. Tools for grammar, spell-checking, and rephrasing remain welcome as before. The goal is to develop your ability to think causally and statistically—skills that require active reflection, not passive consumption of AI outputs.
| Short Exam | Testing window (CBTF) | Reservations open | Duration |
|---|---|---|---|
| #1 | Tue, Sep 15 – Thu, Sep 17, 2026 | Thu, Sep 3, 2026 | 50 min |
| #2 | Tue, Sep 29 – Thu, Oct 1, 2026 | Thu, Sep 17, 2026 | 50 min |
| #3 | Tue, Oct 13 – Thu, Oct 15, 2026 | Thu, Oct 1, 2026 | 50 min |
| #4 | Tue, Oct 27 – Thu, Oct 29, 2026 | Thu, Oct 15, 2026 | 50 min |
| #5 | Tue, Nov 10 – Thu, Nov 12, 2026 | Thu, Oct 29, 2026 | 50 min |
| #6 | Tue, Dec 1 – Thu, Dec 3, 2026 | Thu, Nov 12, 2026 | 50 min |
| Final Exam | Thu, Dec 10 – Wed, Dec 16, 2026 | Mon, Oct 19, 2026 | 1 hr 50 min |
| Type | Number | Weight (3-credit) | Weight (4-credit) | Location |
|---|---|---|---|---|
| In-class worksheets | 25 | 10% | 7.5% | PrairieLearn |
| Short Exam (best 5 out of 6) | 6 | 50% | 37.5% | CBTF |
| Long Homework | 1 | 20% | 15% | Gradescope |
| Final Exam | 1 | 20% | 15% | CBTF |
| Final Project (4-credit students): proposal 5%, mid-semester report 25%, final report 35%, presentation 35% | 1 | — | 25% | Gradescope |
| Total | 100% | 100% |
Extra credit is available in three ways. First, the third programming question in each part of the long homework is required for four-credit students; three-credit students may attempt those two questions for up to 3% of extra credit. Second, four extra-credit worksheets are released on the four own time days shown in the course schedule — two for Lesson 5, one for Lesson 12, and one for Lesson 14 on the last day of class. Students who complete all four earn 1% of extra credit. Worksheets #5.1, #5.2 and #12.2 are due Wednesday, Dec. 9th at 5:00pm; Worksheet #14.1, released on the last day of class, is due Wednesday, Dec. 16th at 11:59pm. Third, all students can earn up to 1% of extra credit by completing the teaching survey; this is allocated to everyone in proportion to the fraction of the class that responds, so if half the class completes the survey then all students receive 0.5%, and if everyone completes it all students receive the full 1%.
The grade cutoffs are (lower end of the range is shown for each grade; the upper bound is below the next higher grade):
A+: ≥ 98, A ≥ 90, A- ≥ 85, B+ ≥ 80, B ≥ 75, B- ≥ 70, C+ ≥ 65, C ≥ 60, C- ≥ 55, D ≥ 45, E ≥ 35, F ≤ 35
The scores will be rounded upwards and then the grade will be assigned. So for example, a score of 89.4 would be rounded to 90 and receive an A.
All class meetings are online over Zoom. Worksheets are completed on PrairieLearn and are due at 11:59pm one week after they are released; after the deadline a worksheet stays open for practice, but not for credit. The four extra-credit worksheets have their own deadlines — see Extra credit opportunities above.
The six CBTF short exams take 300 minutes of your time in total (6 × 50 minutes). That time is given back to you as four own time days (4 × 75 minutes = 300 minutes), marked below: there is no class meeting on those days. The worksheet for each of those days is released as an extra-credit worksheet instead — complete all four for 1% of extra credit (see Extra credit opportunities above).
| Class Date | Topic | Lesson | Worksheets | CBTF Short Exam date | Long Homework & Project |
|---|---|---|---|---|---|
| Wed, Aug 26, 2026 | Introduction | Lesson #0 | Worksheet #0 | ||
| Fri, Aug 28, 2026 | ties, triads and holes (chapter 3) | Lesson #1 | Worksheet #1.1 | ||
| Wed, Sep 2, 2026 | structural balance (chapter 5) | Worksheet #1.2 | |||
| Fri, Sep 4, 2026 | homophily (chapter 4) | Worksheet #1.3 | |||
| Wed, Sep 9, 2026 | Introduction to Game Theory (chapter 6) | Lesson #2 | Worksheet #2.1 | ||
| Fri, Sep 11, 2026 | Game Theory contd. (chapter 6) | Worksheet #2.2 | |||
| Wed, Sep 16, 2026 | Introduction to Auctions (chapter 9) | Lesson #3 | Worksheet #3.1 | Short Exam #1: Tue, Sep 15 – Thu, Sep 17 | |
| Fri, Sep 18, 2026 | Auctions contd. (chapter 9) | Worksheet #3.2 | |||
| Wed, Sep 23, 2026 | Matching Markets (chapter 10) | Lesson #4 | Worksheet #4.1 | ||
| Fri, Sep 25, 2026 | Matching Markets contd. (chapter 10) | Worksheet #4.2 | Long Homework released, 5:00pm | ||
| Wed, Sep 30, 2026 | No class, own time. Bargaining and Power in Networks (chapter 12) | Lesson #5 | Extra credit Worksheet #5.1 | Short Exam #2: Tue, Sep 29 – Thu, Oct 1 | |
| Fri, Oct 2, 2026 | No class, own time. Bargaining and Power contd. (chapter 12) | Extra credit Worksheet #5.2 | Project proposal due, 5:00pm (4-credit) | ||
| Wed, Oct 7, 2026 | Introduction to the Web (chapter 13) and Web search (chapter 14) | Lesson #6 | Worksheet #6.1 | ||
| Fri, Oct 9, 2026 | Web search contd. (chapter 14) | Worksheet #6.2 | |||
| Wed, Oct 14, 2026 | Introduction to Sponsored Search Markets (chapter 15) | Lesson #7 | Worksheet #7.1 | Short Exam #3: Tue, Oct 13 – Thu, Oct 15 | |
| Fri, Oct 16, 2026 | Sponsored search contd. (chapter 15) | Worksheet #7.2 | |||
| Wed, Oct 21, 2026 | Random Graphs Introduction (Instructor Notes) | Lesson #8 | Worksheet #8.1 | ||
| Fri, Oct 23, 2026 | Random Graphs contd. (Instructor Notes) | Worksheet #8.2 | Long Homework Part A due, 5:00pm | ||
| Wed, Oct 28, 2026 | Power Laws (chapter 18) | Lesson #9 | Worksheet #9.1 | Short Exam #4: Tue, Oct 27 – Thu, Oct 29 | |
| Fri, Oct 30, 2026 | Power Laws contd. (chapter 18) | Worksheet #9.2 | Mid-semester report due, 5:00pm (4-credit) | ||
| Wed, Nov 4, 2026 | Community Discovery (Instructor Notes) | Lesson #10 | Worksheet #10.1 | ||
| Fri, Nov 6, 2026 | Community Discovery contd. (Instructor Notes) | Worksheet #10.2 | |||
| Wed, Nov 11, 2026 | Network Effects Introduction (chapter 17) | Lesson #11 | Worksheet #11.1 | Short Exam #5: Tue, Nov 10 – Thu, Nov 12 | |
| Fri, Nov 13, 2026 | Network effects contd. (chapter 17) | Worksheet #11.2 | |||
| Wed, Nov 18, 2026 | Cascading behavior Intro (chapter 19) | Lesson #12 | Worksheet #12.1 | ||
| Fri, Nov 20, 2026 | No class, own time. Cascading behavior contd. (chapter 19) | Extra credit Worksheet #12.2 | Long Homework Part B due, 5:00pm | ||
| 11/21—11/29 | Fall & Thanksgiving Break | ||||
| Wed, Dec 2, 2026 | Small World Phenomena (chapter 20) | Lesson #13 | Worksheet #13.1 | Short Exam #6: Tue, Dec 1 – Thu, Dec 3 | |
| Fri, Dec 4, 2026 | Small World Phenomena contd. (chapter 20) | Worksheet #13.2 | |||
| Wed, Dec 9, 2026 | No class, own time. Markets and Information (chapter 22) | Lesson #14 | Extra credit Worksheet #14.1 | Final project report and presentation due, 5:00pm (4-credit) |
| Class | Topic | Lesson | Broad Learning Goals | Learning Outcome #1 | Learning Outcome #2 | Learning Outcome #3 | |
|---|---|---|---|---|---|---|---|
| Wed, Aug 26, 2026 | Introduction | Lesson #0 | |||||
| Fri, Aug 28, 2026 | ties, triads and holes (chapter 3) | Lesson #1 | Be able to appreciate: the role of ties in information diffusion; how tie asymmetry affects persuasion Understand how tie strength is manifest in observed behavior on Social and Communication Networks | Students will identify nodes in example graphs that violate strong triadic closure property | Students will be able to compute node properties including node clustering coefficients as well as identify essential graph elements including bridges and local bridges in graphs | Students will be able to prove that local bridges attached to nodes that satisfy the strong triadic closure property in a graph must be weak ties | |
| Wed, Sep 2, 2026 | structural balance (chapter 5) | Understand that structural balance is both a local and a global property Understand evolution of structural balance Understand how to extend structural balance theory to non-complete graphs | Students will identify triangles in example graphs that violate structural balance | Students will be able to prove the structural balance theorem | Students will analyze non-complete, signed graphs to determine if they are balanced | ||
| Fri, Sep 4, 2026 | homophily (chapter 4) | Understand homophily and mechanisms for its existence. Selection and Socialization mechanisms are generically confounded in observational social network data Spatial segregation can arise out of weak preferences. | Students will change the degree of homophily in example graphs, by adding or removing edges and vertices | Students will be able to prove that we cannot dis-entangle homophily from influence in observational data. | Students will apply Schelling’s model with different mobility thresholds to example spatial graphs and evaluate degree of segregation. | ||
| Wed, Sep 9, 2026 | Introduction to Game Theory (chapter 6) | Lesson #2 | Be able to identify essential elements of Game Theory Understand the differences between dominant strategies, best-responses and Nash equilibria Understand the different kinds of welfare | Students will identify best-responses, dominant strategies in example payoff matrixes | Students will determine pure or mixed Nash equilibria in example payoff matrixes | Students will identify strategies that are either Pareto-optimal or which maximize social welfare in example payoff matrixes | |
| Fri, Sep 11, 2026 | Game Theory contd. (chapter 6) | ||||||
| Wed, Sep 16, 2026 | Introduction to Auctions (chapter 9) | Lesson #3 | Understand the differences and equivalencies between different auction types Understand differences between mechanisms and games Know if an auction has a dominant strategy | Students will be able to prove that bidding true value is the dominant strategy in a second priced auction | Students will be able to show that degree of shading in first-price auctions depends on the number of participants | Students will be able to determine optimal reserve price in a second priced auction | |
| Fri, Sep 18, 2026 | Auctions contd. (chapter 9) | ||||||
| Wed, Sep 23, 2026 | Matching Markets (chapter 10) | Lesson #4 | Be able to use bi-partite graphs to represent a buyer-seller market Know the central role of constricted sets in preventing maximal matching Understand the importance of matching in social welfare | Students will be able to identify constricted sets in example graphs | Students will be able to construct that a preferred seller graph given buyer valuations and seller prices. | Students will be able to construct market clearing prices in an example buyer-seller graph. | |
| Fri, Sep 25, 2026 | Matching Markets contd. (chapter 10) | ||||||
| Wed, Sep 30, 2026 | Bargaining and Power in Networks (chapter 12) (own time, no class) | Lesson #5 | Understand that power-asymmetries may arise out of network structure Understand the importance of an outside option in bargaining | Students will be able to identify nodes in simple graph that exhibit limited, weak or strong power | Students will be able to determine the bargaining outcome across an edge using Nash Bargaining Solution. | ||
| Fri, Oct 2, 2026 | Bargaining and Power contd. (chapter 12) (own time, no class) | ||||||
| Wed, Oct 7, 2026 | Introduction to the Web (chapter 13) and Web search (chapter 14) | Lesson #6 | Know that the Web is a large directed graph, with several strongly connected components Understand that searching the Web is difficult because of: polysemy\sidenote{same word has different meanings}; synonymy\sidenote{different words mean the same thing}; the large number of authors; and the dynamic nature of web content. The key idea behind web search is recursive: a web page's importance lies in its ability to point to useful web pages, and that a page's utility depends on the number of important pages that point to it. | Students will be able to identify strongly connected components in example directed graphs | Students will be able to compute the hub and authority scores in example directed graphs by applying the HITS algorithm. | Students will be able to compute the PageRank scores in example directed graphs by applying the PageRank algorithm. | |
| Fri, Oct 9, 2026 | Web search contd. (chapter 14) | ||||||
| Wed, Oct 14, 2026 | Introduction to Sponsored Search Markets (chapter 15) | Lesson #7 | Know the role of Sponsored search advertising in facilitating free access to services, including search, and social media. Understand the importance of auctions for efficiently allocating advertising slots to prospective advertisers. Know that VCG auctions are incentive-compatible, but widely used GSP auctions are not. | Students will be able to compute costs of each ad slot in an example auction. | Students will be able to compute the harm that a participant causes by participating in a VCG auction. | Students will be able to identify the assignments of slots to advertisers in a GSP auction. | |
| Fri, Oct 16, 2026 | Sponsored search contd. (chapter 15) | ||||||
| Wed, Oct 21, 2026 | Random Graphs Introduction (Instructor Notes) | Lesson #8 | Know how Erdös-Réyni (E-R) family of random graphs are parameterized. Know different properties to characterize Erdös-Réyni family of random graphs ; clustering coefficient; degree distribution; diameter. Know that Erdös-Réyni family of random graphs undergo phase transitions resulting in a giant component. | Students will be able to compute the degree distribution of an Erdös-Réyni graph when $np = \lambda$, for large $n$. | Students will be able to show that the diameter of an Erdös-Réyni graph is $O(\frac{\log n}{\log z})$, where $z=(n-1)p$. | By examining example graphs, students will be able to reason about the value of $p$ in relation to the phase transition point probability. | |
| Fri, Oct 23, 2026 | Random Graphs contd. (Instructor Notes) | ||||||
| Wed, Oct 28, 2026 | Power Laws (chapter 18) | Lesson #9 | Know how large scale networks exhibit Power-law like distributions and are not well described by Erdös-Réyni family of random graphs. Power-law distributions can emerge from simple preferential attachment (i.e., ``rich get richer'') processes. Know that scaling laws appear in a variety of contexts. | Students will be able to derive basic properties of a Power-law distribution. | Students will be able to compute the exponent of a Power-law distribution given data. | Students will be able to show the preferential attachment process leads to a power-law | |
| Fri, Oct 30, 2026 | Power Laws contd. (chapter 18) | ||||||
| Wed, Nov 4, 2026 | Community Discovery (Instructor Notes) | Lesson #10 | 1. Know that community discovery aims to identify groups of individuals consistent with prior work on homophily, triadic-closure and weak ties. 2. That algorithms for discovering communities are part of a larger family of graph partitioning algorithms. | Students will be able to compute the betweenness centrality measure in an undirected graph. | Students will be able to compute the partition quality using modularity. | ||
| Fri, Nov 6, 2026 | Community Discovery contd. (Instructor Notes) | ||||||
| Wed, Nov 11, 2026 | Network Effects Introduction (chapter 17) | Lesson #11 | 1. Know what externalities are. 2. Intrinsic interest in a good along with population effects, that is multiplicative benefits from a fraction of the population adopting the good, can cause rapid adoption of the good. | Students will be able to identify the market equilibrium when there are no population effects. | Students will be able to compute the market equilibrium when there are intrinsic and population effects. | ||
| Fri, Nov 13, 2026 | Network effects contd. (chapter 17) | ||||||
| Wed, Nov 18, 2026 | Cascading behavior Intro (chapter 19) | Lesson #12 | Know the linear threshold model of behavior spread in a social network. | Given payoffs of two behaviors A, B and a graph, and locations of initial adopters of the superior behavior A, students will be able to determine how the behavior A spreads in the graph by applying the linear threshold model. | The students will be able to identify the cascade capacity of an arbitrary graph. | The students will determine how a superior behavior spreads when nodes in a social network can be bi-lingual. | |
| Fri, Nov 20, 2026 | Cascading behavior contd. (chapter 19) (own time, no class) | ||||||
| 11/21—11/29 | Fall & Thanksgiving Break | ||||||
| Wed, Dec 2, 2026 | Small World Phenomena (chapter 20) | Lesson #13 | Know that short paths are in abundance in social networks and that individuals can efficiently discover them through decentralized search. | Be able to reason the importance of random links in reducing the diameter. | Be able to reason about the presence of attribute that acts as information gradient that allows for efficient myopic search. | Prove that when the probability of random links between nodes 𝑢, 𝑣 encodes distance information as in$p(u,v) \propto d(u,v)^{-q}$, the social network supports efficient myopic search. | |
| Fri, Dec 4, 2026 | Small World Phenomena contd. (chapter 20) | ||||||
| Wed, Dec 9, 2026 | Markets and Information (chapter 22) (own time, no class) | Lesson #14 | 1. Know that we can compute accurate aggregates from crowd estimates, provided there is cognitive diversity and independence of observations. 2. Understand the role of signaling in markets with asymmetric information. | Be able to compute the state prices in horse racing and in the stock market. | Be able to reason about the self fulfilling expectations equilibria in markets with asymmetric information. |
All assignments are due at the date and time marked for the Assignments. Late submissions will not be accepted except in the case of documented emergencies or religious absences approved in advance. If you have any questions about the policies, please ask the instructor.
The University of Illinois at Urbana-Champaign Student Code should also be considered as a part of this syllabus. Students should pay particular attention to Article 1, Part 4: Academic Integrity. Read the Code at the following URL:http://studentcode.illinois.edu/ Also, read the CS honor code here.
Academic dishonesty may result in a failing grade. Every student is expected to review and abide by the Academic Integrity Policy. Ignorance is not an excuse for any academic dishonesty. It is your responsibility to read this policy to avoid any misunderstanding. Do not hesitate to ask the instructor(s) if you are ever in doubt about what constitutes plagiarism, cheating, or any other breach of academic integrity.
Illinois law requires the University to reasonably accommodate its students' religious beliefs, observances, and practices in regard to admissions, class attendance, and the scheduling of examinations and work requirements. You should examine this syllabus at the beginning of the semester for potential conflicts between course deadlines and any of your religious observances. If a conflict exists, you should notify your instructor of the conflict and request appropriate accommodations. This should be done in the first two weeks of classes.
All members of the Siebel School of Computing and Data Science - faculty, staff, and students - are expected to adhere to the CS Values and Code of Conduct. The CS CARES Committee is available to serve as a resource to help people who are concerned about or experience a potential violation of the Code. If you experience such issues, please contact the CS CARES Committee. The instructors of this course are also available for issues related to this class.
To obtain disability-related academic adjustments and/or auxiliary aids, students with disabilities must contact the course instructor and the Disability Resources and Educational Services (DRES) as soon as possible. To contact DRES, you may visit 1207 S. Oak St., Champaign, call 333-4603, email or go to this URL. If you are concerned you have a disability-related condition that is impacting your academic progress, there are academic screening appointments available that can help diagnosis a previously undiagnosed disability. You may access these by visiting the DRES website and selecting “Request an Academic Screening” at the bottom of the page.
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Counseling Center: 217-333-3704, 610 East John Street Champaign, IL 61820
McKinley Health Center: 217-333-2700, 1109 South Lincoln Avenue Urbana, IL 61801
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