John Carmack on Functional Programming (2013) [video]

https://www.youtube.com/watch?v=1PhArSujR_A

by tosh • 9 years ago

258 84 9 years ago

cthulhujr• 9 years ago

I really like John's perspective on things, he can take a listener or reader from the most abstract concepts to the nitty-gritty without losing focus. He's a tremendous asset to the programming world.

ksk• 9 years ago

I agree with the second part of your sentence. I have watched every single one of his talks, and while I find them entertaining, I don't think his brain-dump style of communication is appropriate for teaching/instruction (to clarify: I use his talks as a springboard for my own discovery, not as a terminal point to aggregate knowledge).

waivek• 9 years ago

https://youtu.be/lHLpKzUxjGk

I disagree. See the above link for a lecture where he describes the difficulties in VR in a manner that anybody with minimal programming experience can understand.

babuskov• 9 years ago

It actually starts here: https://youtu.be/1PhArSujR_A?t=2m7s

ballpark• 9 years ago

Should add (2013) and [video] to the title

keymone2• 9 years ago

this is a best video to explain to your C++ friend why functional programming is worth it even in gamedev world.

pjmlp3• 9 years ago

C++ has been getting functional programming goodies since C++11.

Nowadays with C++17, functional programming in C++ is a common talk subject at C++ conferences.

keymone2• 9 years ago

that's nice, but generally speaking the mindset is still very much imperative.

ece7• 9 years ago

I wonder about the present state of the functional projects he talks about and is currently working on. A bit old, but good video talking about FP and static typing from a veteran perspective.

Would like to see a conversation between Sid Meier and Carmack, the modern Civ engines seem to have made some strides in stability methinks.

jandrese2• 9 years ago

Interesting that he ran into friction exactly where you would expect him to.

He was talking about having the AI scripts running in different purely functional threads. Later (around 21 minutes in) he mentions what happens when two AIs decide to move to the same place at the same time, and has not figured out the solution.

Of course parallel programming is easy if you ignore the data dependencies, but eventually you run into unavoidable dependencies and your clean elegant system has to pick up some smell.

ece7• 9 years ago

He talked about a whole FP-powered architecture to solve this.

sololipsist4• 9 years ago

Motivated reasoning. He prefers imperative programming (or something other than functional programming), so he hears the "criticism" without hearing the solution. I mean, of course he physically hears both, but one is prominent in his consciousness. It doesn't matter that there is a solution, he heard what he needed to hear to get the evidence he needs to maintain his bias, and shuts off his frontal lobe.

To be clear: Everyone does this. I just think it's interesting.

jandrese2• 9 years ago

Yes, and I'm curious how it turned out. Are there any followup talks on this that anybody knows about? It's certainly a solvable problem, but how many of the advantages remain once the data dependency problem is solved?

craigsmansion2• 9 years ago

As I heard it, he talked about independent agents which traverse a world by taking it as an input and reporting their own state as an output, and how easy to code such a model was in functional languages because the world was immutable. You don't have to mess around with the world data to keep the actions in sync.

Of course there's a level of conflict resolution needed at some point, which wasn't something he had not figured out, but something that was out of line with the elegance and simplicity of how the basic game mechanics were implemented so far.

As I understood if, it's wasn't so much about easy parallel programming as it was his discovery of clean models and elegant solutions as encouraged by functional programming.

crimsonalucard6• 9 years ago

It's not about either. He is illustrating a problem that only occurs in functional programming:

There is no concept of time in pure functions.

In imperative programming when two actors approach the same spot, whether the application is parallel or not, one actor ALWAYS arrives first and the other will arrive subsequently. Therefore the Second actor can read the state of the first and act accordingly...

This is not the case for functional programming. Per frame the state of each actor changes (or in other words: new actors with updated states are created) at the same time and thus you can have two actors approach the same spot at the same time. You will then need an extra step for conflict resolution. Of course there's a bunch of ways to deal with this. Carmack briefly mentioned something about using some other attribute of the actor as a priority number... it's not like this is some crazy issue that's impossible to solve.

pmarreck3• 9 years ago

He wrote a very good piece here: http://www.gamasutra.com/view/news/169296/Indepth_Functional... on the same topic (is it in fact the same?)

seanalltogether• 9 years ago

I come back to this quote over and over when talking about desktop and mobile apps/games, especially since they tend to be highly state driven view collections and devs are always trying to come up with DRY patterns to bury important features in subclasses or helper utils.

A large fraction of the flaws in software development are due to programmers not fully understanding all the possible states their code may execute in.

pmarreck3• 9 years ago

This is also simultaneously a strong argument for unit tests (which encode knowledge of that state into a proof of sorts).

The limit of a programmer is his/her brain's ability to contain all these possible states. Bugs always come from missing some mental modeling of state or having a flawed conception of it, either at the point of design, the version 1, or the rewrite.

OO just buries that state "elsewhere", so things seem easier superficially to contain mentally (but the state is still there, ready to get corrupted and pounce on you). FP makes the state explicit, so you're forced to deal with it at all times (this perhaps not uncoincidentally also makes FP easier to unit-test AND reason about). If managing that state upfront becomes unwieldy, then that becomes a good code smell/indicator that your design is suboptimal.

The upshot of all this is that I think that using FP in conjunction with unit-testing reduces bug production by some statistically-significant amount, especially as a codebase grows. We definitely need more empirical data about this, though. But that's what my intuition says.

vog3• 9 years ago

EDIT: Why all those downvotes? Are famous developers not supposed to criticized on HN?

While John has a lot of interesting things to say, the presentation is awful, almost an imposition to the audience.

There's not a single slide, or any repetition to clarify structure, or any notable gestures to make up for that. A simple overview, just a damn simple list of keywords, would already go a long way. That would add a lot of structure and would make the talk so much easier to follow, especially for non-native speakers.

Just because one is so much respected by the audience that they will tolerate everything, one should not act like the audience will tolerate everything.

rootlocus• 9 years ago

This was a keynote at a Quakecon, a conference for game players, not a technical presentation for software developers.

vog3• 9 years ago

If the audience isn't even technical, isn't that even more a sign that more effort should be put into the presentation, especially for a keynote?

savanaly2• 9 years ago

Personally, I watched it with rapt attention throughout and I'm eagerly anticipating having time later to do so for the other 6 parts of the keynote. Can't remember the last presentation that captured me so. I think he is a very good public speaker and the talk did not meander and was not hard to follow in any way.

I did crank the playback speed up a lot though, which helps considerably (I'm not sure I would enjoy it half as much if it were live, where of course I have to hear it at 1x speed).

saganus• 9 years ago

HN's downvote mechanism is a funny one.

As far as I know there's no clear meaning to what a downvote means and it seems like everyone has their own definition.

For some, downvoting is a way of "flagging" out of place comments, aggressive ones, etc. However for others it's just a way of disagreeing.

The guidelines don't seem to establish any particular definition to it, so it's kind of a community-driven thing.

At first I was certain that downvoting was a way for the crowd to silence unwanted comments, but "unwanted" has many values depending on the person. Personally, I prefer to downvote when there are clearly aggressive or out-of-place comments, and if I disagree I rather respond with my disagreement. That's the way to have a civil discussion in my opinion.

However, like I said, other people give downvoting a different meaning, so it's not so much that you can't criticize famous celebrities, but that the community seems to disagree with you. I don't see anything "flaggable" about your post so that's why I assume it's the reason.

But again, downvoting is an "undefined" behavior in HN. Guidelines don't mention what shoul or should not be downvoted so it's kind of up for debate.

Don't worry too much about it, as long as you are not clearly being uncivil, downvotes are probably just a lazy way of saying "I don't agree with you" :)

optimusclimb2• 9 years ago

imho this isn't specific to HN, Reddit is plagued by "downvote to disagree."

Downvoting should be for, as you said, flagging aggressive, off-topic comments.

I've really lost interest in commenting on reddit, because if you say anything that disagrees with or goes against a certain sub-reddits current group think on a subject, you're just going to get downvoted into oblivion. It really just intensifies the echo-chamber effect.

Kiro• 9 years ago

I downvoted you because:

1. You state your criticism like it's an objective fact. I think it was a brilliant talk.

2. Your edit. It violates the HN guidelines and you insinuate people only downvote you because they are Carmack fans.

optimusclimb2• 9 years ago

You state your criticism like it's an objective fact, when in reality I'm sure most would disagree with you.

He stated his opinion, it's how people discuss things. Ironically, by saying "in reality, I'm sure most would disagree with you", you do the same thing (express your opinion as if it is fact), AND use the weasel words of "in reality" to add gravitas to your opinion. I didn't like the talk either FWIW.

joncampbelldev2• 9 years ago

Perhaps native speakers enjoy this kind of talk a lot. I can't speak for others but I certainly did.

I don't feel that listening attentively for a couple of hours is that much of an imposition.

dingo_bat2• 9 years ago

I am not a native speaker. I watched the linked part while I was having my dinner (or whatever you'd call a couple of McBurgers at 10pm). I think it needs attention, but that is needed for anything that's not fluff.

wtetzner• 9 years ago

Just because one is so much respected by the audience that they will tolerate everything, one should not act like the audience will tolerate everything.

He gives these talks because there's a demand for them (from previous audiences). He's not on stage talking because he wants to force people to consume the information.

I suspect it's a trade-off between a talk of this format or no talk at all. Preparing slides etc. takes a time investment, and if it takes too much time, maybe he just wouldn't be able to do the talks.

zerr• 9 years ago

I guess we all had that FP click at some point in our lives, but then we got back to our regular (imperative) flow, hopefully as better engineers :)

yogthos• 9 years ago

I got that FP click, switch to Clojure, and pretty happy with that move 7 years later. :)

bmc7505• 9 years ago

Has there been any progress on garbage collection since then? He discusses GC in games starting here: https://youtu.be/1PhArSujR_A?t=1443

vog3• 9 years ago

While he says a lot of interesting things, it is too bad he is really just sitting and talking. No slides, gestures or any other facilities. Those would have brought more structure into the talk, making it easier to follow - especially for non-native speakers.

epigramx• 9 years ago

Or more distracting and annoying.

JohnCarmack• 9 years ago

I am aware that my presentations aren't optimal for communicating targeted information, and it does weigh on me more and more as the years go by.

So far, I haven't been able to justify to myself the time required to do a really professional job, so I just show up and talk for a few hours. I like to think there is some value in the spontaneity and unscripted nature, but I don't kid myself about it being the most effective way to communicate important information.

I'm taking some baby steps -- I at least made a rough outline to guide my talking at last year's Oculus Connect instead of being in full ramble mode.

tosh• 9 years ago

Might not be the easiest if you intend to get a certain thought or point across but I really enjoy the format. Reminds me of long-form radio shows.

dgritsko• 9 years ago

While this may be true, please don't let it cause you to shy away from "full ramble mode" when the opportunity presents itself! I know I speak for many when I say that I have learned much from hearing these sorts of talks of yours over the years. Your willingness to share your wealth of experience is inspirational, regardless of the format.

bluejellybean• 9 years ago

Agreed, full ramble isn't something many people do well and it's fun too watch. Random but useful information will fall out of peoples brain and it's great!

joncampbelldev2• 9 years ago

Just to say, from my perspective I love your talks, zero distractions, just a long cogent train of thought to follow. Please don't feel the need to make too many changes.

treebeard901• 9 years ago

Your contributions to computing over the years more than outweigh any lack of preparation for a presentation.

leggomylibro• 9 years ago

Along the lines of 'functional' programming, Jonathan Blow reposted an old email of yours which I thought was a nice format for getting across some points about reliability, consistency, and minimizing side effects:

http://number-none.com/blow/blog/programming/2014/09/26/carm...

pera• 9 years ago

Actually I really like the format of your presentations: just yesterday I watched your live coding session with vrscript (https://www.youtube.com/watch?v=ydyztGZnbNs) and it was fantastic because, first, you were showing to your audience how to work with Racket (and some of the features in DrRacket), and second, you build from zero a demo in a very casual, easy going way. I honestly don't think that a standard slide-based presentation would have been better in any way...

hdhzy• 9 years ago

Ha, it's funny because for me the format is just perfect. There are numerous presentations on the internet focused on one specific topic but your free form style is just like I'd talk with a friend. The interdisciplinary nature and hands on examples are nice added bonus.

Please don't change this unique approach too much.

savanaly2• 9 years ago

For me, at least, it's not a problem that it doesn't optimally communicate targeted information. I watch talks like this for entertainment and maybe to pick up some information by osmosis and the undirected style is good for that. This was a very good talk by the way, and reinforced my positive feelings towards functional programming, thanks for doing it.

cm2187• 9 years ago

Actually I prefer it a lot more to something scripted. It's normally hard to stay focused watching a guy talking for 1 hour on a youtube video. But with your presentations, I find myself looking for more at the end of the hour!

jasonkostempski• 9 years ago

When exploring lisp, did you have a chance to play with Clojure?

fatso83• 9 years ago

Really interested in hearing if the ideas on how to transform game programming into a more productive form panned out. Did you end up using the ideas in a later product?

mmargerum• 9 years ago

I actually prefer your data dump continuous talking style. I find myself having a hard time paying attention in talks with lots of pauses or segues.

I really appreciate your insights because I'm dabbling in functional programming after 25 years of c/c++/objc

zengid• 9 years ago

The thing that's interesting about Haskell is that lazyness had a payoff of leading to the discovery of monad-based IO [1].

[1] https://youtu.be/re96UgMk6GQ?t=31m22s

John Carmack on Functional Programming (2013) [video]

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