CS 201 - Spring 2025. 2/21/2025.


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Welcome to CS 201!

Video of the Day

Turing Complete David Brailsford

I hereby solicit suggestions for the video of the day. Please email me your ideas with explanations. Selected entries will win 5 homework points. If your video is played at the beginning of class, you must also briefly explain something about the video and something about yourself - in person.

Image of the day


Turing-complete

Logical problem of the day

Who is the author of the following three laws?

  1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
  2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
  3. Any sufficiently advanced technology is indistinguishable from magic.

https://pollev.com/slade You may also download the app to your phone. Use the "slade" poll id.

Canvas Quiz of the Day (need daily password)

Most days, there will be a simple canvas quiz related to the lecture. You need a password to activate the quiz, which I will provide in class. These quizzes will count toward your class participation grade. The quiz is available only during class.

Click for today's quiz.

Guest speaker: Jeanette Andrews

As mentioned on Wednesday, Turing's paper "Computing Machinery and Intelligence" discussed the possibility of a computer surprising us.

Taken by Artificial Surprise and more artificial surprise

Utilizing her decades-long technical training in sleight-of-hand magic, Jeanette Andrews creates interactive, surreal vignettes that explore the nature of perception and cognition. She invites audiences to co-create her illusory performances, which function as live thought experiments. Often utilizing refined yet common items, such as glassware, paper, plants, and fabric, her works investigate perceptual anomalies, expectation violation, and the nature of belief. She also works in sound, installation, film, and objects to bring her ideas about hidden worlds to life. Dean of Arts and Sciences at Yale Tamar Gendler calls Jeanette "scholar of perception disguised as a magician" and Artnet says, “Andrews’s avant-garde approach to magic transforms it into performance art.”
Jeanette is currently a visiting artist at MIT's Center for Art, Science and Technology (CAST).

Lecture 17: Computability.

  • I have office hours Wednesdays from 4-6 pm, on zoom, id 459 434 2854.

  • I am available for lunch on Mondays at 1 pm in Morse.

  • ULA office hours are found at https://csofficehours.org/CS201/schedule. Sign up via the queue.

  • Homework assignments: [Assignments]. hw3 is now available.

    Announcements

  • Midsemester feedback is open on canvas starting 2/17/2025 for one week. It is anonymous. This is Yale's version of Yelp.

  • If you have an upcoming performance or athletic event, I am happy to promote it during class. Just send me a note.

  • CS Colloquium, Thursday, February 27, 10:30am. DL 220.
    Host: Arman Cohan

    Title: Specializing LLMs for Reliability

    Abstract:

    Large language models (LLMs) have advanced the frontiers of AI reasoning: they can synthesize information from multiple sources, derive new conclusions, and explain those conclusions to their users. However, LLMs do not do this reliably. They hallucinate facts, convincingly state incorrect deductions, and exhibit logical fallacies like confirmation bias. In this talk, I will describe my lab’s work on making LLM systems reliable by introspecting their behavior. First, I will demonstrate that better understanding of LLMs helps us train them to be more reliable reasoners. Our work shows that model interpretation techniques can advance training methodology and dataset curation for reasoning models. Second, I will argue that automating fine-grained evaluation of LLM output provides a level of understanding necessary for further progress. I will describe the ingredients of effective automated evaluators and a state-of-the-art factuality evaluation system, MiniCheck, showing that analyzing the nature of hallucinations can help reduce them. Finally, I will describe how deeper understanding of LLMs will let us tackle their most fundamental limitations, such as their inconsistency when given different inputs. I will propose how these pieces might soon be combined to form reliable AI systems.

    Bio:

    Greg Durrett is an associate professor of Computer Science at UT Austin. His research is broadly in the areas of natural language processing and machine learning. His group develops techniques for reasoning about knowledge in text, verifying factuality of LLM generations, and specializing LLMs to make them more reliable. He is a 2023 Sloan Research Fellow and a recipient of a 2022 NSF CAREER award. His work has been recognized by paper awards at EMNLP 2024 and EMNLP 2013. He was a founding organizer of the Workshop on Natural Language Reasoning and Structured Explanations at ACL 2023 and ACL 2024 and is a current member of the NAACL board. He received his BS in Computer Science and Mathematics from MIT and his PhD in Computer Science from UC Berkeley, where he was advised by Dan Klein.

    Website: https://www.cs.utexas.edu/~gdurrett/

    Refreshments from Koffee Katering will be available.

    Midterm Exam

    The midterm will be Tuesday February 25th at 7pm in Davies Auditorium. It will be a 2 hour hand written exam. No computers. No notes. No books. No kidding. Students registered with Student Accessibility Services will take the exam at Becton C031 next door.

    Sample Midterm Exam available . (solutions) The midterm will not have a boolean function question. Instead, it will have a struct question. The actual exam will also include UNIX questions (Principles 1 and 2). I will give you a transcript with some of the commands X'd out. You will have to deduce those commands (solutions).

    You should be familiar with the recursion and tail recursion examples from the recursion.rkt and Recursion.html For more details on the wonders of tail recursion, see TailRecursion.html and this tail recursion article.

    Also, the paper Music and Computation, discussed below, is also in scope, up to but not including Music. There will be true/false questions about binary encodings of numbers, text, images, and sound. No questions about music.

    See Point.html for a sample struct question.

    Owen Prem will hold a review session Sunday, February 23rd, from 1-3pm, at DL 220. Check Ed Discussios for details.

    Lecture: Computability.

    Computer Machinery and Intelligence Turing (1950). Mind 49: 433-460. The origin of the Turing Test. Did not coin "artificial intelligence." Try to read this before Friday's class. Pay attention to the question "can a computer take us by surprise?"

    Structs.html (covered on Monday)

    Hw3.html Problem 2.

    Execute examples from tmcopy.rkt using hw3 simulator.

      (simulate tm1 (conf 'q1 '(b) 0 '(1 1 1)) 20)
      (simulate tmcopy (conf 'q1 '(b) 0 '(1)) 200)
    

    See Turing Machine Notes Detailed explanation of tmcopy.

    Everything is a string of bits

    See Music and Computation

    Computability.html (jupyter) Part 2. What is computable?

    Getting to know UNIX

    UNIX Introduction Principle 3.
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