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Ask HN: What's your favorite illustration in computer science?

461 points| gnull | 3 years ago

I'm curious to see some examples of what people consider good visual illustrations of CS concepts, from both usefulness and aesthetics perspectives.

312 comments

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[+] Phemist|3 years ago|reply
I, unfortunately, cannot find an online copy currently.

Knuth's TAOCP's latest published part, Volume 4 Fascicle 6, on Satisfiability contains a number of visualizations that really are amazing and worth just buying a copy of the book for, just to ponder over these images.

The satisfiability problem of whether there exists an assignment of boolean values that makes a given boolean formula evaluate to TRUE is, IMO, truly a fundamental problem in computer science.

Any piece of code with some inputs and outputs can be transformed into a boolean formula (albeit a huge one). This process feels akin to expressing molecules, from simple ones like H2O, to the highly complex proteins that make up much of our Cells, in their constituent atoms and more importantly the atom interactions.

Knuth (EDIT: Actually, Carsten Sinz) takes this concept one step further and produces visualizations of non-trivial boolean formulas that clearly show the regular, both symmetrical and asymmetrical, sometimes fractal-like nature of these formulas.

In my mind, these visualizations are quite powerful and strikingly show the fundamental building blocks of (digital) computation.

[+] Eduard|3 years ago|reply
> Knuth takes this concept one step further and produces visualizations of non-trivial boolean formulas that clearly show the regular, both symmetrical and asymmetrical, sometimes fractal-like nature of these formulas.

The visualizations were done by Carsten Sinz.

This is his paper describing the technique:

Carsten Sinz. Visualizing SAT Instances and Runs of the DPLL Algorithm. J. Automated Reasoning, 39(2):219-243, 2007.

https://www.carstensinz.de/papers/JAR-2007-Visualization.pdf

https://doi.org/10.1007/s10817-007-9074-1

[+] k0k0r0|3 years ago|reply
I am lucky to be paid to work on SAT. I wouldn't yet say I am an expert, yet, but it is really a pleasure to do so. Trying to improve on algorithms to solve these problems is truly humbling.

Edit: Fixed a typo.

[+] varjag|3 years ago|reply
The spread on page 300 (iirc) is really stunning.
[+] puglr|3 years ago|reply
Wow, you weren't kidding about those images.

What I found particularly striking about them was how much they reminded me of both neurons and larger brain structures, as well as some of those newer, ML-assisted FMRI imagery.

Probably just coincidence and wishful thinking, but it instills a sense of daydream-like wonder all the same.

[+] weswilson|3 years ago|reply
The sound of dial-up explained:

https://oona.windytan.com/posters/dialup-final.png

from https://www.windytan.com/2012/11/the-sound-of-dialup-picture...

[+] Dalewyn|3 years ago|reply
I pity the youngsters who will never be able to mentally playback the dialup sound.
[+] ramblerman|3 years ago|reply
On that topic. I never understood why the initiation needed to be audible, but afterwards the connection was silent.
[+] FearNotDaniel|3 years ago|reply
Is it just me or... does the modem audibly say "Hi" when the connection is successful? Probably just me projecting from my imagination, but listen to the part after the handshaking and before the white-noise dataflow. There's a very clear 'boing-boing' sound and then a bunch of static that sort-of sounds like someone whispering the word "Hi". It's not just on the linked recording above, I remember being conscious of this back in the day when dial-up was "normal". Just curious to know if anyone else encountered this trick of perception...

Anyway, hearing those tones again did bring back all the feels, the joy of hearing that "boing-boing-Hi" greeting as I stepped once again onto the "Information Superhighway".

[+] bobsmooth|3 years ago|reply
That would make a good poster.
[+] sophacles|3 years ago|reply
I often cite this diagram: https://upload.wikimedia.org/wikipedia/commons/3/37/Netfilte... as my favorite picture. It shows the logical flow of packets through Linux. I'm pretty sure my career would be on a very different trajectory had I not discovered an earlier version of it back in ~2006.
[+] CurleighBraces|3 years ago|reply
This is great. Don't suppose you've seen anything similar for the flow when you include SR-IOV/DPKD a google didn't help.
[+] rottc0dd|3 years ago|reply
There are some great visualizations by 3b1b: https://www.3blue1brown.com/

Recently he had done a video about convolution. And his videos about neural networks are pretty good. He has recommendation video for other good channels too.

Great blog on Myers diff series: https://blog.jcoglan.com/2017/02/12/the-myers-diff-algorithm...

Not technical illustrations but, some funny jokes in unix haters handbook is pretty funny. https://web.mit.edu/~simsong/www/ugh.pdf

There is also unix magic poster: https://archive.org/details/unix-magic-poster-gary-overcare-...

[+] supernova87a|3 years ago|reply
The video on FFT finally, after decades of casual understanding, helped me better understand what it was all about.
[+] hbcondo714|3 years ago|reply
I don't remember the original source of this image but it's a comical take on the SDLC, showing how different roles / teams understand what the customer wanted versus needed when building a tree swing:

https://www.amarkota.com/Content/images/portfolio/trees.jpg

[+] echelon|3 years ago|reply
Completely orthogonal to yours, but the undergraduate text "Operating Systems Concepts" by Silberschatz et al. has always been good.

Every edition features dinosaurs, which totally relate to the concepts of CPU scheduling, IPC, memory management, etc.

The seventh edition is the absolute pinnacle, as the sauropod family on the front cover enjoy a host of electronic devices from the 80's and 90's:

https://i.imgur.com/5U87Pgt.png

Most of the covers are great.

[+] eurasiantiger|3 years ago|reply
Interesting that what operations supposedly installed was closest to what was actually needed, and only an additional binding away from a complete solution.
[+] k__|3 years ago|reply
I worked in many companies that had it at the door to the Dev department.
[+] sideproject|3 years ago|reply
This is exactly what I thought of coming into this post! I think I actually saw this first nearly 20 years ago and boy oh boy things don't change much (or should I say, people don't change much)
[+] charcircuit|3 years ago|reply
I thought it was from commitstrip
[+] blakesterz|3 years ago|reply
https://paleofuture.com/blog/2009/3/23/computer-criminals-of...

  "The 1981 book School, Work and Play (World of Tomorrow) features this beautiful two-page spread. Apparently, thanks to computers, there's no crime in the future outside of the computerized variety. The "computer criminal" pictured really doesn't appear to be running very fast. Maybe they're playing a game of freeze-tag. Or maybe that policeman's gun has special settings the author didn't tell us about. I like to believe the former, but that's just me."
The book is full of really cool images like that one of "The Future" as seen from '81
[+] makeworld|3 years ago|reply
Unix Magic is pretty good.

https://jpmens.net/2021/04/09/the-unix-magic-poster/

[+] pram|3 years ago|reply
I have one of these hanging in my living room, they're beautiful!
[+] hot_gril|3 years ago|reply
The classic sorting algo videos with sound come to mind first: https://www.youtube.com/watch?v=kPRA0W1kECg . Mergesort is my favorite video.

The main resource on learning Erlang, https://learnyousomeerlang.com, has a lot of funny ones, some of which are useful.

[+] martopix|3 years ago|reply
Various things explained without words in the same style as IKEA mounting instructions. Here is public key cryptography: https://idea-instructions.com/public-key/ and quicksort (KVICK SÖRT) https://idea-instructions.com/quick-sort/
[+] largolagrande|3 years ago|reply
Concerning the public key cryptography for the exchange of private encrypted messages, I would have rather represented the shared public keys by padlocks, and the private key by the key allowing to open the padlocks. This way, it is easier to understand that there is a relationship between the two keys. In his drawing, 2 different keys can open the safe door, which is not possible in the physical world...
[+] rfonseca|3 years ago|reply
In Networking, two illustrations of congestion control are just fantastic IMO.

First one is [1], by Chiu and Jain (page 7, figure 5), showing that Additive Increase / Multiplicative decrease is the only simple policy that converges among 2 senders (with rates x and y) to a rate that is fair (along the y=x diagonal) and efficient (along the x+y=Bandwidth). This is the basis of the algorithm that made TCP (and the Internet as we know it today) possible.

The other one is this diagram from BBR [2] (from the paper in [3]), that shows how BBR sets the window ("amount in flight") to the bandwidth-delay product (BDP) of the bottleneck link (the "volume" of the pipe in a water analogy). The cool thing is that you can only measure the delay of the link if you window is <= the BDP, and you can only measure the bandwidth if your window is >= the BDP, so the algorithm has to hover around this point to make sure it can determine both.

[1] Chiu and Jain, Analysis of the Increase and Decrease Algorithms for Congestion Avoidance in Computer Networks, 1989, https://www.cse.wustl.edu/~jain/papers/ftp/cong_av.pdf

[2] https://dl.acm.org/cms/attachment/9cf72499-b32d-4426-914b-cd...

[3] BBR: Congestion-Based Congestion Control https://queue.acm.org/detail.cfm?id=3022184