Wowza, that was quite the semester. A list of the classes I took, also the order I’ll cover them in:

• 10-405 Machine Learning With Large Datasets
• 17-200 Ethics And Policy Issues In Computing
• 21-301 Combinatorics
• 15-410 Operating System Design And Implementation

10-405

Taught by Prof. Virginia Smith, this class was an introduction into how you’d actually construct machine learning systems to perform well at scale. “At scale” usually meant “on multiple computers”, which is indeed a challenge due to things like communication overhead. We started small, covering things like distributed Linear Regression and distributed PCA, and ended with state-of-the-art approaches to Neural Architecture search and Federated Learning.

Overall, I liked this class a lot. The lectures were very good and the homeworks chill. One common complaint about homeworks that I share is that they were sometimes too structured; there was a lot of “fill in this function signature that we’ve made for you already”. The later homeworks did a better job of this, and I can understand why they did this in the first place (makes grading easier and eases the learning curve for frameworks like Apache Spark and Tensorflow).

This class was within its unit count of 9hrs/week.

17-200

Co-taught by Prof. Michael Skirpan and Prof. Sarah Fox, this class was a very practical overview of contemporary policy issues in computing and how to apply ethical thinking to those. I really liked this compared to the previous ethics class I took, which covered ethical frameworks in a more abstract term; getting to learn about surveillance as “instrumentarian power”, unionization movements in big tech, and dark patterns in UX felt much more real. This class humbled me with the realization of just how much power is wielded by broken systems, but also gave some concrete paths for improvement as future tech workers.

This class fulfilled my writing requirement, and overall the weekly writing assignments and writing midterm/final weren’t all that bad. I only wish I had more time to work on the assignments (no fault of the class, just busy with all other classes too) and was better at the writing process (mental block on drafting + reviewing…).

This class was within its unit count of 9hrs/week.

21-301

Taught by Prof. Irina Gheorghiciuc, this class covered some novel ways of, you guessed it, counting things. It started off simple like “what a combination is” and then quickly progressed to wild things like using functions and their derivatives (whose coefficients of their Taylor polynomial are the things we want to count) to do counting, then expanding on that to cool theorems like Hands and Decks, Lagrangian Inversion, and Inclusion/Exclusion. Very cool to know that $u(x) = x\phi(u(x))$ has a unique solution,

$[x^n]\left\{u(x)\right\}=\frac{1}{n}[x^{n-1}]\left\{\left(\phi(x)\right)^n\right\}$

Absolutely magic how this is proved :)

I can see why all my math major friends meme about Irina’s lectures (very unique and humorous style) and her tests (some problems are quite hard). I really enjoyed this class; while I probably won’t get to use much directly later on, it’s nice to keep my mathematical thinking sharp.

This class was within its unit count of 9hrs/week.

15-410

Taught by Prof. Dave Eckhardt, this class covered everything you need to know about writing a simple UNIX-inspired OS kernel, and then some. x86 cdecl stack layout and calling convention, x86 memory model/atomic operations, x86 interrupts (traps, exceptions, faults, hardware), x86 segmentation, x86 virtual memory mapping, how to structure a large software project, the thread/process abstraction model (and how to implement it), concurrency problems like deadlock, syscalls (and how to implement them), and more stuff that we didn’t get around to implementing like filesystems, transactions, IPC/RPC, paravirtualization, memory consistency, and the experimental CHERI architecture. In case you couldn’t tell from the previous sentence, we wrote our OS for the x86 architecture and got very familiar with its idiosyncrasies. In the end, we had a lightly-featured (and working!!) kernel with a simple threading library able to run some useful multithreaded programs with keyboard input and console output.

The class moved at a breakneck pace to cover all of these topics (which were all covered in a lot of detail!); there was hardly a point in lecture where I wasn’t moving my pencil. There was also hardly a day past the first week where I wasn’t working on the OS project; a final sloccount of the kernel showed 5000+ lines of mixed C and Assembly (however it counts that (and there was probably more documentation than that too)).

This class was not within its unit count of 15hrs/week :) More like 25 I think? Didn’t keep too close track, just estimating from the times I tended to program every day.

15-410: It’s A Partner Class

For those familiar with 15-410, you may recall that it’s mainly a partner class; 10 of the 14 weeks are spent working on projects with another person.

This did not turn out well.

I didn’t realize that people generally find OS partners before class starts, so everyone I already knew in the class had already found someone by the time I started looking. In a historic twist of fate, I talked to the person who always sat next to me in the front row, who turned out also to not have a partner, and we quickly made a group.

Keep in mind, I had never even seen this person before this class. I had no idea how this was going to go, but given the questions they asked in class (and the fact they showed up to class at all) I was fairly optimistic.

They turned out to have many issues. Mental health, physical health, and family issues, all in a negative feedback cycle. Naturally, this precluded getting work done, often in week-long stretches during schedules where missing a single day could be a bad setback.

I ended up designing and implementing every single syscall, and every submodule to support all those syscalls. They contributed some good code and helped walk through design decisions (especially in the P2 and P4 projects before and after the big P3 kernel), but overall I’m still a bit salty about the work distribution even though nothing could really be done.

The course staff knew about these issues and we were awarded generous (and very necessary) late days. I’m (moderately) proud of what we turned in, but holy cow I don’t want to crunch that hard ever again.

Random Other Stuff

• OS sapped all my time and I couldn’t make many late-night or weekend Frisbee practices this semester :(
• My knee is fully better by now though, been working out and going for runs just fine
• I’ve been voted in as Tech Chair for AAC for the second year in a row! Wow thank you!
• Speaking of, I’ll try to do more sketching practice this summer. I completed Figuary again this year and have been using Hampton’s book a lot and I can see the results (from just the parts I’ve read tho)
• StuCo thoughts coming soon! (when I finish “grading” the finals)