Hello from the other side! I spent a considerable amount of the time between October and now working on two labs: these were malloclab and tshlab. As the name may suggest, in malloclab, we have to implement a memory allocator. In tshlab, we have to implement a simple linux shell.

Malloc#

I have undoubtedly spent the plurality of my time these past few weeks implementing malloc. Malloc is a great assignment for a systems class, as it lets you explore a rich program design space where implementation decisions you make can have a great deal of influence on the benchmarks of your program.

A brief overview#

Why should someone implement malloc? What does implementing malloc do? First, if we read the question as asking “what function does malloc serve”, the answer is that we obtain a way of writing data structures of arbitrary or variable size by “allocating” memory in a region called the heap. “Well libc already has malloc, and it’s Production Grade so…”: have you considered that learning and trying things is good for you?

What is difficult about implementing malloc? You have no variable-size data structures! (Technically you have a GCC extension width 0 array in our implementation, but shhhhhh…..) You have to do everything via variables you store on the stack. Also, debugging utilities like gdb do not provide nearly as much help as they do on other comparable systems labs, so you end up having to do a lot of checking and generally have to have airtight implementation. I would talk more about this, but if I did that this would be less of a blog post and more of a summary of a lab handout, at which point you’d be better off taking the class instead :P

Model Theory#

I have also been spending a lot of time theseweeks on a DRP (Directed Reading Program) in which I meet weekly with a graduate student mentor and we talk about Model Theory. In the broadest possible sense, Model Theory is about the study of objects which capture a certain set of true statements generated by various symbols (which together are called a language). There are a lot of neat things you can do by studying various notions of constructing models, relationships between models and the statements contained within them, but I will wait for another time to talk about all of this.

Next Semester…#

Not learning from my past mistakes, I decided to challenge myself again with a record 3 CS courseload next semester. (On the bright side, this is it. I am not taking any other non-StuCo class!) I am by far the most excited about 15-411: Compiler Design and Implementation. This is sure to be by a considerable margin the most intense class, estimated at around 22-25 hours/week if FCE data is to be trusted. Also, I GET TO USE RUST!!!! :D and I am taking it with another furry! I genuinely like the content, I am very eager to do work on making several compilers and entering into this really neat area of study. The second class, one which I am also quite excited for, is 15-312: Foundations of Programming Languages. This is a class that I know many people become obsessed with and fell down the Type Theory/PL pipeline because of, if they hadn’t already by taking 15-150. I have for a long time now wanted to explore the abstract/structural properties of programming languages as systems because it tickles my brain in the same way that my interest in Logic does (at the very least so I can better understand what Lean is doing). The last (and least exciting) is 15-210 Parallel and Sequential DSA, which I don’t know what to expect from. I have heard very mixed things about it, but I am taking it with many friends so this will help me out with the material at any rate.

More importantly however, I will have no life or free time!! (again :3) so if I disappear off the face of the earth, this is why! I should have another update coming after I go ride lots of trains once the semester ends :)

Take care!

Aured