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I no longer understand my PhD dissertation

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Re: I no longer understand my PhD dissertation

#141
post #14

TLDR: The author independently re-discovered what you may know as Old Code Syndrome. I think that's because mathematical papers place too much value on terseness and abstraction over exposition and intuition. This guy's basically in the position of a fairly new developer who's just been asked to do non-trivial update of his own code for the first time. All those clever one-liners he put into his code made him feel sm…

It would be really nice if all it took to understand difficult mathematics were some easy programming tricks.

The problem with looking at old code is you forget what is going on or what the purpose of different components are. The problem with looking at old mathematics is that it is genuinely very difficult to understand. You work very hard to be an expert in a field and get to a level where you can read a cutting-edge research paper. Then if you let that knowledge atrophy, you won't be able to understand it without a lot of re-learning when you look at it again.

Unfortunately cute tricks like comments and concrete examples won't save you here (if concrete examples even exist -- oftentimes their constructions are so convoluted the abstract theorem is far easier to understand, and often times they are misleading. The theorem covers all cases, but all of the easily understandable concrete examples are completely trivial and don't require the theorem at all.)

Programming has existed for, say, 50-100 years. We have recorded mathematical history going back thousands, with contributions from most of the most brilliant human beings to ever exist. Do you think perhaps there's a reason why a simple and easy trick like commenting and renaming lemmas has been discovered and solidified as standard practice in programming, but hasn't been adopted in mathematics? Are mathematicians really just SO dumb?

The answer is those tricks just aren't good enough. Mathematicians do exposition. They do plenty of explaining. Any textbook and even many research papers spend a huge amount of time explaining what is going on as clearly as is possible. As it turns out the explanation helps, but the material is just plain hard.

Re: I no longer understand my PhD dissertation

#142
To make an admittedly bad metaphor, it's likely a lot of that knowledge has been moved from main memory to cold storage, and it would take some time to bring it back. It certainly makes the case for why we write things down! Although the part about having to dig for the main result makes me think the abstract could be improved...

Re: I no longer understand my PhD dissertation

#143

Math is the shadow universe of physics. Most theorems may not look like they are useful for anything real world till someone is able to peg all the variables to real world. And then as if by magic we realize we already know how how the real world behaves. Till someone does this pegging, the theorems sit idle waiting for problems to solve. I believe this is actually a good thing. We are letting people find solutions b…

> I believe this is actually a good thing. We are letting people find solutions before someone finds problems to use them for.

This may lead to a few problems too:

(1) Prior knowledge can serve as a blinder. Our conceptual toolkits may end up consisting of unwieldy theorems that while useful are cumbersome to use.

(2) The number of theorems with no immediately evident practical use is so large that they may end up being "forgotten" anyways, and this will result in us having to do the "mental heavy lifting" all over again.

Re: I no longer understand my PhD dissertation

#145
post #14

TLDR: The author independently re-discovered what you may know as Old Code Syndrome. I think that's because mathematical papers place too much value on terseness and abstraction over exposition and intuition. This guy's basically in the position of a fairly new developer who's just been asked to do non-trivial update of his own code for the first time. All those clever one-liners he put into his code made him feel sm…

That doesn't help. Arthur has written a very nice hundred page introduction to the trace formula. You can read that, and it won't tell you why you should care about the trace formula. But if you know Langlands-Tunnels and how it was proven, or how Jacquet-Langlands was proven, you already know to care about the trace formula because you know that it will prove similar results.

The abstraction is necessary: you cannot do algebraic geometry with varieties alone. But while the core of the subject is a multithousand page jewel of abstraction, Vakil is a perfectly readable, example filled introduction to algebraic geometry, covering most of the contents of the glory that is EGA.

Only the rare lemmas are intrinsically interesting. Most often it's the theorems that are worth knowing as steps on the path to understanding something much more. Those lemmas that get used again and again are named, often descriptively.

Re: I no longer understand my PhD dissertation

#146

Earlier quoted context omitted.

The downside of course is that comments aren't compiled/run - so they often become out of date. "Often" might actually be an understatement. I can't tell you how many times I've been reading a comment that runs quite contrary to what the code really does. You then end up reading the code to reason about it anyway, paying two taxes. After too many of those experiences, you just end up going straight to the code as the…

Names for classes, methods, parameters, and variables all suffer from this same problem. I think the solution to align code and comments is code reviews. Not writing comments also works but fails to solve related issues.

Where I work, I've always required that code that's submitted for review has a descriptive commit message. That is, the commit should explain what the problem was and how it was fixed, and why it was done that way.

This way, I can run git blame (or the equivalent VCS command) on the file and get a reasonable set of comments that usually match up with the code.

Re: I no longer understand my PhD dissertation

#147
post #14

TLDR: The author independently re-discovered what you may know as Old Code Syndrome. I think that's because mathematical papers place too much value on terseness and abstraction over exposition and intuition. This guy's basically in the position of a fairly new developer who's just been asked to do non-trivial update of his own code for the first time. All those clever one-liners he put into his code made him feel sm…

Completely agree.

"Everyone knows that debugging is twice as hard as writing a program in the first place. So if you're as clever as you can be when you write it, how will you ever debug it?" -Brian W. Kernighan

I read a book by Brian Kernighan a few years back, "The Elements of Programming Style" and for me it has so much good advice. The book may not be as relevant in the days of Ruby, C99 and the like, but valuable advice nevertheless.

I wonder if reading the literature (countless books written by the early adopters and renowned engineers) would mould the programmers to do things differently. For instance, reading "JavaScript: The Good Parts" completely changed the perspective with which I look at the language. It made me fall in love with it.

Re: I no longer understand my PhD dissertation

#148
post #14

TLDR: The author independently re-discovered what you may know as Old Code Syndrome. I think that's because mathematical papers place too much value on terseness and abstraction over exposition and intuition. This guy's basically in the position of a fairly new developer who's just been asked to do non-trivial update of his own code for the first time. All those clever one-liners he put into his code made him feel sm…

Completely agree. "Everyone knows that debugging is twice as hard as writing a program in the first place. So if you're as clever as you can be when you write it, how will you ever debug it?" -Brian W. Kernighan I read a book by Brian Kernighan a few years back, "The Elements of Programming Style" and for me it has so much good advice. The book may not be as relevant in the days of Ruby, C99 and the like, but valuabl…

I've just started playing around with JavaScript and I'm definitely gonna check this book out now, thanks.

Re: I no longer understand my PhD dissertation

#150
This post inspired me to re-read my thesis (well browse through it). Although it has been 16 years since I last looked at it, I didn’t have any problem understanding it and I didn’t even really cringe reading it. I guess it depends on your field how bad this effect is.
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