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Events

• Aug

  17

  Can Gurkan Final Defense August 17: Evolving Code with LLMs: Representation, Selection, and the Limits of Open-Ended Exploration

  Department of Computer Science (CS)

  10:00 AM 3514, Mudd Hall ( formerly Seeley G. Mudd Library)

  EVENT DETAILS

  This dissertation investigates the use of large language models (LLMs) as variation operators for evolving programs. Whereas a traditional variation operator modifies program syntax without regard to program behavior, an LLM can propose changes informed by the semantics of the code. This capability has enabled new forms of program evolution and produced promising results, yet the behavior of LLM-based evolutionary operators remains comparatively understudied. This dissertation examines three forces that shape the resulting evolutionary process: the representation of candidate programs, the method of selection that determines which candidates persist across generations, and the dynamics of the variation operator itself. Each of these factors influences the capacity for sustained, open-ended exploration.
  
  To study representation, we evolved agent rules for multi-agent simulations implemented in NetLogo and introduced three benchmark environments for evaluating LLM-generated code in this setting. Three ways of representing the same rule were compared: executable code, code with comments, and pseudocode that a separate model call converts into executable code. Across all three environments, evolving commented code produced the highest-performing agents, while evolving pseudocode produced the lowest-performing agents, indicating that natural language aids the variation operator when it augments executable code rather than replacing it.
  
  To study selection, we varied the balance between objective performance and behavioral novelty while evolving agent rules. Final fitness was largely unaffected by this balance, but greater emphasis on novelty consistently yielded a higher proportion of qualitatively superior code structures. These findings suggest that diversity-driven search can improve the quality of evolved code, revealing a hidden cost of objective-centric optimization.
  
  To study the operator itself, we asked whether a language model that repeatedly mutates a program continues to explore new forms or instead returns to recurring structures. Mutation chains were analyzed in the absence of selection pressure within a domain-specific language, varying prompt design, model family, and stochastic replication. The chains converged on restricted regions of program space, with most variation confined to substitutions within recurring structural templates, while a classical genetic programming mutation operator showed no comparable convergence under matched conditions.
  
  These three forces do not act independently. The representation determines the extent to which the capabilities of the variation operator can be exploited, selection determines which resulting programs persist and become available for further variation, and the dynamics of the operator shape the structures that repeated mutation continues to produce. LLM-driven program evolution can effectively evolve agent rules for multi-agent systems, but its outcomes are sensitive to design choices that are easily left implicit. The selection regime changes the quality of the program structures that survive, while the same semantic capabilities that allow an LLM to transform programs can also introduce a systematic bias toward structural homogeneity. Whether these systems can sustain open-ended exploration depends on the interaction among representation, selection, and variation.

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  TIME Monday, August 17, 2026 at 10:00 AM - 12:00 PM

  LOCATION 3514, Mudd Hall ( formerly Seeley G. Mudd Library)    map it

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  CONTACT Jensen Smith    jensen.smith@northwestern.edu EMAIL

  CALENDAR Department of Computer Science (CS)

• Aug

  20

  Nathaniel Hejduk Qualifying Exam Presentation August 20: Navigating Mixed-Typed Migration with Profilers

  Department of Computer Science (CS)

  1:00 PM Mudd 3514, Mudd Hall ( formerly Seeley G. Mudd Library)

  EVENT DETAILS

  The component-by-component migration of a program from untyped to typed can trigger unintended performance degradations. When such a degradation occurs, typing well-chosen components can lessen the cost of type enforcement, while typing poorly chosen components can exacerbate it. In this talk, I examine whether off-the-shelf profiling tools deliver information that helps programmers navigate these migration choices effectively in Typed Racket.

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  TIME Thursday, August 20, 2026 at 1:00 PM - 4:00 PM

  LOCATION Mudd 3514, Mudd Hall ( formerly Seeley G. Mudd Library)    map it

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  CONTACT Jensen Smith    jensen.smith@northwestern.edu EMAIL

  CALENDAR Department of Computer Science (CS)

• Sep

  14

  Welcome & Breakfast for New McCormick PhD Students

  McCormick School of Engineering and Applied Science

  9:00 AM LR2, Technological Institute

  EVENT DETAILS

  Enjoy a welcome from Dean Christopher A. Schuh and other McCormick leaders, and receive a Northwestern Engineering T-shirt. A free breakfast on the Tech East Plaza will follow.

  Register Now

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  TIME Monday, September 14, 2026 at 9:00 AM - 10:30 AM

  LOCATION LR2, Technological Institute    map it

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  CONTACT Andi Joppie    andi.joppie@northwestern.edu EMAIL

  CALENDAR McCormick School of Engineering and Applied Science

• Sep

  22

  Welcome & Luncheon for New Full-time Graduate Students

  McCormick School of Engineering and Applied Science

  11:00 AM Ryan Family Auditorium, Technological Institute

  EVENT DETAILS

  Enjoy a welcome from Dean Christopher A. Schuh and other McCormick leaders, and receive a Northwestern Engineering T-shirt. A free lunch on the Tech East Plaza will follow.

  Register Now

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  TIME Tuesday, September 22, 2026 at 11:00 AM - 12:30 PM

  LOCATION Ryan Family Auditorium, Technological Institute    map it

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  CONTACT Andi Joppie    andi.joppie@northwestern.edu EMAIL

  CALENDAR McCormick School of Engineering and Applied Science

• Sep

  24

  Bagel Thursday + Discussion

  Department of Computer Science (CS)

  9:00 AM 3514, Mudd Hall ( formerly Seeley G. Mudd Library)

  EVENT DETAILS

  tba

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  TIME Thursday, September 24, 2026 at 9:00 AM - 11:00 AM

  LOCATION 3514, Mudd Hall ( formerly Seeley G. Mudd Library)    map it

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  CONTACT Wynante R Charles    wynante.charles@northwestern.edu EMAIL

  CALENDAR Department of Computer Science (CS)

• Sep

  28

  CS Seminar

  Department of Computer Science (CS)

  12:00 PM 3514, Mudd Hall ( formerly Seeley G. Mudd Library)

  EVENT DETAILS

  Monday / CS Seminar
  September 28 / 12:00 PM
  Hybrid / Mudd 3514

  Speaker
  TBA

  Talk Title
  TBA

  Abstract
  TBA

  Biography
  TBA

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  Zoom Link
  Panopto Link

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  TIME Monday, September 28, 2026 at 12:00 PM - 1:00 PM

  LOCATION 3514, Mudd Hall ( formerly Seeley G. Mudd Library)    map it

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  CONTACT Wynante R Charles    wynante.charles@northwestern.edu EMAIL

  CALENDAR Department of Computer Science (CS)

• Oct

  5

  CS Seminar: Formal Relational Equivalence for SQL, GenAI, and Beyond (Brian Suchy)

  Department of Computer Science (CS)

  12:00 PM 3514, Mudd Hall ( formerly Seeley G. Mudd Library)

  EVENT DETAILS

  Monday / CS Seminar
  October 5 / 12:00 PM
  Hybrid / Mudd 3514

  Speaker
  Brian Suchy, Software Engineer Google DeepMind

  Talk Title
  Formal Relational Equivalence for SQL, GenAI, and Beyond

  Abstract
  Verifying that complex query rewrites from database optimizers or AI-driven generators preserve exact bag semantics under three-valued logic is an NP-hard challenge. To address this, we present an MLIR-native compiler framework that formally reasons about relational algebra. By decoupling query semantics from specific execution engines and lowering queries into a unified Relational Algebra Intermediate Representation, our language-agnostic methodology definitively proves semantic equivalence across all possible database states.

  The core of the presentation will deep-dive into our multi-tiered proving architecture, which synthesizes several advanced academic methodologies. First, we utilize E-Graphs and Equality Saturation to rapidly explore the equivalence space and detect structural congruence between query abstract syntax trees using fast, algebraic rewrite rules. Second, we employ Semiring Arithmetic, treating relational algebra as expressions over K-relations to leverage algebraic simplification and canonical forms under semiring laws. Finally, we implement a First-Order Logic and SMT translation path, lowering Relational Algebra into Relational Calculus and then into First-Order Logic to evaluate constraints and domain-specific axioms using parallel solvers like Z3 and CVC5, which either formally proves equivalence or synthesizes concrete counter-examples.

  Finally, we will discuss the practical implications of combining these formal mathematical methods with modern compiler design. Attendees will leave with a comprehensive understanding of how bridging database theory, equality saturation, and SMT solving can create robust solutions for verifying query optimizers, enforcing semantic correctness, and validating automated SQL generation at scale.

  Biography
  Brian Suchy is a Software Engineer within Google DeepMind.
  In his time at Google he has worked on F1 Query (Google's internal SQL query engine), hardware development, and (of course) AI.
  Prior to joining Google, Brian received his PhD student at Northwestern University, advised by Peter Dinda, with a focus on hardware/software codesign and memory management.

  Research Interests: Artificial Intelligence, Query Processing and Formal Logic

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  Zoom Link
  Panopto Link

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  TIME Monday, October 5, 2026 at 12:00 PM - 1:00 PM

  LOCATION 3514, Mudd Hall ( formerly Seeley G. Mudd Library)    map it

  ADD TO CALENDAR

  CONTACT Wynante R Charles    wynante.charles@northwestern.edu EMAIL

  CALENDAR Department of Computer Science (CS)

• Oct

  29

  Bagel Thursday + Discussion

  Department of Computer Science (CS)

  9:00 AM 3514, Mudd Hall ( formerly Seeley G. Mudd Library)

  EVENT DETAILS

  tba

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  TIME Thursday, October 29, 2026 at 9:00 AM - 11:00 AM

  LOCATION 3514, Mudd Hall ( formerly Seeley G. Mudd Library)    map it

  ADD TO CALENDAR

  CONTACT Wynante R Charles    wynante.charles@northwestern.edu EMAIL

  CALENDAR Department of Computer Science (CS)

• Nov

  19

  Bagel Thursday + Discussion

  Department of Computer Science (CS)

  9:00 AM 3514, Mudd Hall ( formerly Seeley G. Mudd Library)

  EVENT DETAILS

  tba

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  TIME Thursday, November 19, 2026 at 9:00 AM - 11:00 AM

  LOCATION 3514, Mudd Hall ( formerly Seeley G. Mudd Library)    map it

  ADD TO CALENDAR

  CONTACT Wynante R Charles    wynante.charles@northwestern.edu EMAIL

  CALENDAR Department of Computer Science (CS)