Professor Rubin is extremely careful, clear, and concise in everything he does which makes it easy to follow along and learn as well as understand what is expected of you on the homework and exams. Perhaps the only problem I had with this class was that the quizzes and exams were timed at a harsh pace. The entirety of the difficulty of the course that semester was finishing the work before the clock ticked down. The quizzes were often an incredibly stress-inducing 30 minutes every week of rushing to carefully write out the problems and upload them before the time limit, then receiving points off a week later because the proof was missing some minute polish. The final was "designed to take 3 hours" as prescribed by the mathematics department, but I spent about 12 hours and didn't finish. Spending more time on the exam could have given me a better score. I am frustrated at this because my grade essentially came down to not being able to find the trick and write the proofs quickly. It is highly disappointing to know that the grade distribution was skewed due not to the students understanding of the material, but the speed at which they could complete the problems and the amount of time they could afford to spend on the assignments.

Super nice and wholesome, take advantage of OH and start on the HW early. Weekly quizzes are alright, really just checking some basic understanding of what was covered. Midterm and final was pretty nasty, they require quite a bit of deep thought, though it might be because it is take home 24hr. Responds quickly on piazza and is pretty helpful.

This review is for 115A.
Professor Rubin is the best professor at UCLA, hands down. I'd definitely recommend him to anyone.

Professor Rubin's lectures are engaging and he made this course much easier to approach. His midterms and finals are fair with an average score of around 80, and he is really humorous and willing to help his students. His homework workload is heavy but these problems are really similar to the exam, (I got a B+ since I was sick during finals week.) and I believe that he is one of the best Math professors at UCLA.

This review is from the perspective of a pure math major. I hold an interest in this class mainly because I believe it helps with understanding graduate-level math. Professor Rubin is a great lecturer, as he did a great job explaining the terms and answering our questions. He is also very helpful in office hours and is easy to approach to. However, I do think the pace of the class is a bit quick since we basically skim through the whole textbook "Category Theory in Context". We didn't have a chance to learn many things in detail, and many useful facts are left out for us to read in our own time. I used a lot of textbooks and notes other than the recommended ones, and they turn out to be helpful for filling in the gaps. Another problem is that the concepts are sometimes way too abstract and it is difficult to figure out everything without having an understanding on them beforehand. It would be helpful if you have experience with graduate-level algebra (i.e. MATH 210A), or have read the Algebra book by Serge Lang since they give you a focus of Category Theory on abstract algebra (groups and rings).
Overall, very nice professor, but very hard class (at least for me).

Here are the grade components:
Homework (75%): weekly assignment containing 6 problems each.
Final (25%): take-home exam with a 2-week window to figure everything out.

The material is heavy and can be confusing, but Dr. Rubin is surely one of the friendliest professors one can have at UCLA. With the huge class we have, he does everything he could. Just a reminder that we have about 200 students, so be sure to do extra problems in the book (I didn’t do it till it was too late) because everyone will try their very best! Overall he is a wonderful professor, and I am grateful for everything he has done for us.

I feel like most of what I wanted to say has already been covered by the other reviews, but I’ll add some since I thought Rubin was a great professor.

His lectures were engaging and clear (very funny guy as well), he went at a very reasonable pace (decently quick but also took time to explain details). Participation, questions, etc. were encouraged but not forced.

I also went to his office hours once and got the information I needed. He runs it like a mini classroom setting (when I was there there were around 10 other people), and goes around answering people’s questions, so you might actually learn something you weren’t expecting as well.

The homework was admittedly extremely difficult at times and I was really worried for the first midterm. However the two midterms should be completely fine as long as you knew the content, the questions are fairly basic and nothing compared to the homework.

The final is also by no means unfair, but it was quite a bit harder than the midterms, so don’t be blindsided.

One of the best Professors out there. Definitely take him, he will help you anytime you would need.