He's a okay lecturer, or whatever, but he often asks for class input. The class usually just gives him blank stares, and when someone does answer his question, they are wrong 100% of the time. When he tells them that they are wrong, he says "No, that's not quite what we're looking for." And that's it. Occasionally, he'll say "Someone already said that" if you unintentionally paraphrased what someone else said, but the fact of the matter is that he provides little to no reasoning as to how we are supposed to correctly approach these problems. I, for example, came into this class with no experience with proofs and I can safely say that, having shown up to class every day, I still have no clue as to what makes a proof a proof. Is it the way I phrase it? What makes statement A any less "proofy" than statement B? He never addressed these problems in class, even though there is a large chunk of the class (75%+) that still doesn't know how to do proofs properly.

Honestly, I think the reason his rating of "Is concerned" is just because of the way he talks to students. I, however, find it condescending, especially when he outwardly laughs at what the students suggest for proofs. Altogether, I would have gladly taken the class from a clam rather than from Sahai, as at least a clam wouldn't laugh at me when I make a suggestion for a proof.

In my opinion, this class is completely worthless and a waste of time. It is a seminar where a different professor from the computer science department comes in every week to talk about a particular subject field/research interest. The lectures are pretty interesting usually, but the weekly quizzing and essay writing at the end of the quarter just make you hate the class. My essay was also given a 100 within a day after the essays were due, which makes me think that it was never even actually read. This really shouldn't be a required class and should just be advertised as a weekly seminar that you can attend if you want to hear about what professors in the department are researching.

Biggest waste of my time this past quarter. The class format is one guest speaker each week that talks about their specific subfield of computer science and on the day of discussion you are given a five question quiz on the speaker of the prior week.

Most of the speakers give very boring and confusing presentations. On two occasions we had our speakers forget to come. Four weeks in I stopped going to the speaker presentations and only went to the mandatory discussion to take the quiz. The quizzes are usually pretty easy, but sometimes they were more difficult. I found that the more difficult quizzes were just asking very specific memory questions from the presentations that were typically over 50 slides long. Most TAs will review the presentation during discussion before you take the quiz, but my TA was impossible to actually understand so that didn't help much.

Honestly, you don't really have much of a choice in taking this class as it is a requirement for any computer science student. Just know that you won't be missing much if you skip out on the presentations.

Professor Sahai is a kind, engaging professor. He is genuinely excited to dive into the theory of computation during every class, which creates a very positive learning environment. The class is difficult and heavily proof-based. The homework is lengthy but doable if you have friends to collaborate with, which is strongly encouraged by the professor. There are ample opportunities for extra credit. I typically don't have perfect attendance, but I made sure to attend every lecture for this class.

Ignore all other reviews for this class, as most of them are either outdated or from math people who love sitting at their desks for 10+ hours a week thinking about theory. This class, if not already known, is the advanced mathematical offering of CS 181, meaning that instead of studying application, you study the theory of this class. The lectures are "lead" by students, which often involve questions not pertaining to curriculum and you often go off on tangents. Additionally, this class format creates an environment where you do not know what you need to learn and what is irrelevant, often making the class even harder than before. Also, don't get me started on the homework, which by his syllabus, takes 15-20 hours each.
Summary: Avoid this class with Sahai at all costs unless you like torturing yourself with math theory.

Lots of the reviews hate on his class because it focuses more on "theoretical mathematics" rather than applications. This is absolutely true. If you hate theoretical math then you might want to consider taking an easier prof this class. Although, I'm not sure what they expected from a class named "An Introduction to Computability THEORY"...

That being said, Prof. Sahai is hands down the best lecturer on campus. It is not a traditional lecture where the professor bestows you divine knowledge that was discovered by the forefathers of computer science. Instead, Prof. Sahai structures the class so that you slowly and methodically uncover this knowledge. He conducts his lectures in a socratic style and is always looking for student ideas to guide the lecture. Because of this, the lectures are super engaging and interesting through cycles of trial and error with lots of interesting ideas from the class. You'll get to discover why some of the ideas work while others don't.

It's important to note that this is the "unofficial honors section" so Prof. Sahai expects a deeper understanding of the content. His exams are certainly more difficult than other sections and not super traditional either. They don't test the materials in class directly. Rather, he makes up questions very similar to the content done in class, but with a bit of a spin. As a very simple example, suppose that you learned about how to add 2 real numbers in class. The exam might give you the definition for imaginary numbers and then ask you to add 2 imaginary numbers. You'll be able to do it with what is learned in class, but it's going to be something new that is similar to content in class.

There are lots of extra credit in this class: anytime you contribute to the lecture and there's always EC problems on the exams. Final exam is take home on week 10.

Light workload, homeworks were mostly completion graded but exams were difficult.

I honestly loved this class. I wasn’t expecting to at all, but I think that if you like math you will have a good time. I also think that Sahai is the best lecturer I’ve had at ucla (especially within the CS dept). I never missed a lecture because I was genuinely excited and interested to learn the material. The homeworks are meant to be difficult and did take up a fair amount of time, but I feel like they were graded leniently because averages were quite high.