And the visual effects Oscar goes to...

@TheRandomSpectator

5 жыл бұрын

You could even see the reflection of both of them in that monitor behind them!

@brod515

5 жыл бұрын

@@TheRandomSpectator I mean that comes for free

@STRAIGHTBOXMUSIC

5 жыл бұрын

@@TheRandomSpectator u noticed too

@dipi71

5 жыл бұрын

Best Computerphile video ever, I'd say. Congrats! But was it also the most difficult Computerphile video to produce?

@taylorfaucett8282

5 жыл бұрын

Who? You forgot to finish your sentence.

When he handed the token to the clone I was really impressed. This was great

@OpenGL4ever

4 жыл бұрын

The force is strong with this one.

@yato3335

2 жыл бұрын

Oh wow I didn't even notice that 🤣 It was so seamless, I forgot it was the same person

this is next level editing

@atlantic_love

Жыл бұрын

What was the video about?

I get the impression the University of Nottingham once ordered 5000050000 boxes of that old style continuous feed printer paper back in the 80's and still don't know what to do with it all.

@kemfic

5 жыл бұрын

VredesbyrdNoir they feed it to the grad students

@pewp43

5 жыл бұрын

I wouldn't recommend using their washrooms.

@kemfic

5 жыл бұрын

@@pewp43 new channel: physicsphile - where physicists solve problems with single-ply toilet paper

@derpmarine216

5 жыл бұрын

you literally get it in giant crates for cheap.

@MrLampbus

5 жыл бұрын

Although they did get an Acorn A5000 out of the deal (lowest machine in the stack on the desk behind). I had (have in store still) one - great ARM machine but a bit light on RAM.

My husband works from home. He is a very intelligent programmer, he talks to me everyday. This stuff is one of them. I am just drinking coffee while listening to him. I had no idea what he is talking about every single day. Thanks for helpful video. I will watch this everyday.

Just a reminder that the point of the video wasn’t to optimize the code for finding the sum of all the numbers that add up to 1,000,000, but to break down how multi-threading works and some solutions you would use for more common scenarios. Great video!

@nullvoid3545

2 жыл бұрын

thanks for this. My first thought was making "a" into 2 variables and then adding the results would be faster at the expense of some memory. Am i right is assuming this?

@bernardoborges8598

2 жыл бұрын

There is a close formula for adding numbers in order so this is really just for demonstration purposes. Sum(1 to N) = N*(N+1)/2

@Lightbringer7734

Жыл бұрын

Wouldn't that be optimized away by the compiler with optimization flags on anyways? You should just write your code to be readable, then only optimize if you're sure there's a bottleneck(by profiling)

@nickwilson3499

Жыл бұрын

@@Lightbringer7734 no one cares. This isn't a video about compilers. Sounds like you're scared of having to think for yourself

@Lightbringer7734

Жыл бұрын

@@nickwilson3499 wut?

What still amazes me. This is "just" an educational tech related channel, were a professor/teacher is explaining stuff about computers and IT stuff. Yet, it has 1.2 MILLION subscribes and around 20k views in a few hours. Great job guys, you show that learning (tech) stuff is just really enjoyable! On a way that apparently a lot of people can understand! thumbs up!

The first time I felt smart watching a Computerphile video. I saw the code and the fact that both threads use the same variable and thought "That's not gonna work as intended.".

A good Part 2 would be explaining how the mutex works, because implementing the mutex also runs into the read-modify-write problem. Kudos for the visual effect of two Steves, especially handing the disk back and forth. Steve gets credit for his acting skills, and bonus points for having a 3 1/2" floppy disk just lying around on the desk.

The floppy disk transition was pretty clever

@simontay4851

5 жыл бұрын

Yes, i want to know how that was done. Steve 1 seamlessly passed it to steve 2 as if he was real.

@ais4185

5 жыл бұрын

@@simontay4851 Are you trying to say he isn't real?

@snooks5607

4 жыл бұрын

never done any video CGI but if I'd have to guess someone was sitting there accepting the disk initially, then they switched places and had real time split-screen of the previous footage running on a screen so they can verify the disk aligns on the second pass.

@carlosmspk

4 жыл бұрын

@@snooks5607 Still how did he deliver the disk at the precise level each time. You'd expect some altitude difference that would make the floppy disk "snap" from one altitude to another (and there is, but very, very little, which is impressive).

@nightshadefns

3 жыл бұрын

@@carlosmspk Any imperfections in position are masked by the outline

Insta-liked for multiple Steves :-)

That was some great editing! Good job and great video!

@lawrencedoliveiro9104

5 жыл бұрын

Not just editing, but also choreography of Steve’s movements.

Wow, finally after a while I understood how threads and mutexes work. The visuals are great

I want 8x Steve solving all my tech problems and projects.

Bagley is exactly like this in lectures. The only difference is he has awesome, black, heavily animated keynotes.

@recreant359

5 жыл бұрын

Max Taylor I woulda stayed in college if these guys were my professors.

@MatthewTaylor86

5 жыл бұрын

That sounds amazing

@maxtaylor3531

5 жыл бұрын

He’s honestly a legend. Gutted I haven’t got any modules with him next semester.

Steve literally divided himself like a cell just for this example thats some true dedication

@gravity6316

5 ай бұрын

steve just forked himself

I've always had love for parallelism and multi threading. This video explained it even more. Thank you!

The numberphile and computerphile people have seemingly endless amounts of feed printer paper and butcher paper for some reason

@gmc9753

3 жыл бұрын

Maybe back in the 1980's, some company offered the university a great deal for a huge number of boxes of green bar paper.

Having the multiple Steves talking over each other and interfering with each others task to explain what happens in multithreaded tasks was quite brilliant!

This is one of the best videos posted to this channel in a while. Really really great upload! I like that we actually got to see some code. I'm finishing my second year toward my degree in computer science and this is right at the level that's great for me. Cheers!

Needed this month's ago for my exams but was a great reminder! Your videos always help me and other programmers understand the concepts visually and practically!

The method of explaining how a thread works and how we can use mutex for the solution was exemplary. Great editing.

One of the highest value channels on the platform, thanks so much for the fantastic content!!

3:00 for completeness, there's also a thing called "green threads" where OS is cut out of the resource management and it's all done by the user-space application. reasons for this vary but for one it might avoid context switching in compute intensive cases.

10:57 I need a 10 hour version of this.

explanation and visual presentation are just outta the world. teaching every CS student wishes for

The best explanation of threads that I've even seen -- great job! Oh, and of course brilliant video production.

One of the best multithread examples ever! Well done!!

This video was just brilliant. Great production

Oh, what a great video. I wish I was introduced to it when I was learning about multithreading because it makes it look so easy despite the fact that all the things in this video I learned in a very hard way.

Merry Christmas Computerphile!!!!

This was a great video. The visualizations were awesome and I love seeing actual code.

The `time` process is not well equipped at all for measuring performance at the microsecond level, as you found. Many things skew the results, as a whole process needs to be spawned and torn down, and this stuff is included in the total; context switching also will bite you. I only use `time` for benchmarking when the benchmarked process is expected to run for longer than one half second. Also, remember that there's a Bash built-in also named `time`, which is even worse than /usr/bin/time. `gprof` or `prof stat` would have been a much better choice.

@sugarbooty

5 жыл бұрын

Would making the set of numbers being added together larger to make it last longer increase the accuracy of the time process?

@snooks5607

4 жыл бұрын

​@@sugarbooty sure, you could also measure the difference with a physical stopwatch but why make things hard for yourself. right tool for the right job.

3 жыл бұрын

Do we not have access to a low level high res timer?

Great to see Steve programming ! Very educational how he organizes the code and writer it!

Everyone learning programming should look at your video. Great explanations as usual.

Learned more in 15 minutes than I did in my entire university Concurrency module. Awesome stuff as always :)

@RoccoBruehl

5 жыл бұрын

nice profile pic ^^

@TheUglyGnome

5 жыл бұрын

You went to Patriot University?

@BassHelal

5 жыл бұрын

@Zero Cool Of course I was exaggerating, the course was bad and the lecturer didn't care, so I had to take things into my own hands but yes they did somewhat go over this stuff in that course just extremely poorly

@Toopa88

5 жыл бұрын

@Zero Cool my professor in databases was from Russia and couldn't speak English neither the language that's spoken in my country. I don't know how he hasn't been fired yet but I assure you that you learned more in 1 hour research than the entire course.

@vitfirringur

5 жыл бұрын

This is your problem. You're in a university. You're not supposed to be spoonfed by the professor. You're supposed to learn to study on your own. If you expect everything to be spoonfed to you, you'll have a hard time finishing your education.

This is so educational, please do more videos with multithreading subject! ❤️❤️❤️

Not sure if this is an actual educational video or just the editor and Steve flexing on their editing and acting skills respectively.

@oysteinsoreide4323

4 жыл бұрын

i found the content clear. but I already have been dealing with locks, and programs not always giving the same result. And of course the video production itself can be educational at the same time. Win win situation.

One of my favorite vids by yall guys. Thank you !

Best 15 minutes I've ever spent today

i really enjoy dr. bagleys explanations. keep up the good work

Getting more in-depth knowledge on parallelism and multi threading. Thanks!

Hats off to the editor and the presenter, and one more time to the editor.

Awesome special effects, and really good topic!

Very nicely done! We can never have enough Dr Steve Bagleys. ;)

The production quality is Insaneeeeee

Great job! I can see somebody had a bit of fun with this one

love the two Steves!

Thank you so much, this is channel is helping me tremendously.

Very helpful. I'm proficient in shell scripting and powershell overall for my work life, and recently started learning C. This helped me sort out a problem with one of my projects, so thank you for that. =)

Loved the video! Absolutely great!

wowww the editing was superb! nice job computerphile nice job

Find me a better channel on KZread, I'll wait . Every time I come to computerphile, it blows my mind open.

Interesting topic, well explained, nice editing. Thumbs up!

The presentation and editing in this video is the best I've found on KZread when it comes to explaining and demonstrating multithreaded execution. Amazing job Dr. Bagleys and Computerphile. I'm a computer engineering student and one of the concerns I had when learning about and experimenting with multithreaded programming was the _real_ performance gain. As was shown in the video, the summation example didn't benefit a ton from being multithreaded. I assumed that a lock like a mutex creates a major bottleneck in your code that really makes it no faster than the single-threaded, sequential case. Moving the lock to the end of the function to minimize its usage made a lot of sense and, at scale, I could definitely see how multithreading would be the way to go!

My vision for education in programming is that the students should learn multithreading right from the start - in the introduction course. That way we can form a "divide and conquer" approach to solving problems from the beginning and not struggle to fight their "linearity" in thinking afterwards. The problem is that most of the people tend to use the methods of programming they know best, they know best whatever they used most and they used most whatever they learned first. So when we introduce parallel programming say in third or fourth course in the Bachelors degree it's already too late. Nowadays the mainstream programming is over multicore computers and parallel thinking in problem solving is a must.

@mrrdelorenzi8478

5 жыл бұрын

scratch has multi-threading (it is taught at primary schools).

@theblackwidower

5 жыл бұрын

I spent three years studying programming in college, we never once covered multi-threading. Really annoying.

@justgame5508

5 жыл бұрын

T Duke Perry I stumbled upon multithreading myself during my final college assignment (not university), It was a cloud storage app programmed in windows forms(C#) I had to use multithreading for the networking aspect, ie keeping the user interface responsive while downloading/uploading files and on the server allowing multiple clients to access data simultaneously. It was never formally taught however

@philippetrov4881

5 жыл бұрын

@@theblackwidower that's very sad to hear...

@philippetrov4881

5 жыл бұрын

@@justgame5508 what I do in my courses is that we start directly from GUI programming (Java Swing in NetBeans). That way we directly hit the responsive interface issue in the second lecture. We usually make some simple game - like a bad guy chasing a hero around the board so the hero must be in one thread controlled by the human and the bad guy in another. We then follow the path down towards low level programming.

Superbs explanation. Well done! Great editing too!

Great Video!! he explained following things - Race Condition Problem - solved race condtion problem using mutex. - code inside lock and unlock is called critical section. i have read so much about this but never seen program which explain all these concepts!! AMAZING VIDEO!!!!!

I understand so much now 😌 Those visual effects helped a lot 🙌🏾

Really interesting video; explained concept of multi threading well and liked the example in code - thanks very much

Please do a video on how you had two Steves, apparently motionless wrt each other, while using a hand held camera, and interacting with each other. That was too cool for School.

This was really well made. Thanks!

When I was first at work 40 years ago, we used to call operations that interrupts or the threads can't interfer with Atomic operations. These days nobody has a clue what I'm talking about.

@X_Baron

5 жыл бұрын

Atomic operations are used in real-time computation, when you can't afford mutexes slowing things down or making response times unpredictable, and to prevent priority inversions. There is std::atomic now, and std::memory_order. Of the PC applications that people use daily, games are the most performance-critical and hence require these kind of features.

Steve and other Steve complement each other very well.

Very impressive! Merry Christmas.

Visuals were sick!

Visual effects were superb

Thanks, I learnt something today. Brilliant.

Learned a lot for this! Thanks!

Love the explanation, thanks other Steve!

Incredible video!

Great video as usual, though this one gets a prize for cool editing effects. I was wondering; how about using two separate accumulators, one for each thread, and adding them together after the join?

Amazingly explained !

Gauss' shortcut: The sum of positive integers from 1 to x, where x is even is equal to: (1+x) + (2+[x-1]) + (3+[x-2]) + ... (x/2+[x/2+1]) = (1+x) + (1+x) + (1+x)..., where there are x/2 terms, or (1+x)*(x/2). The example in the famous story about Gauss was finding the sum from 1 to 100 which is equal to (101)*50 = 5050. In this case, x=1,000,000, x/2 = 500,000 => The sum is (1+1,000,000)*(500,000) = 500,000,500,000.

really awesome explanation !!

holy moly that editing

very informative thank you for your brilliant work

Steve-P-U Huh? Sounds like a RISC-y piece of hardware ;)

I like this guys videos because they're a little more advanced.

It was the optimiser. It sees you are adding a fixed amount of numbers to a variable so it converts to a + sum(stuff) form and puts the mutex around it auto-magically.

This summarizes the difficulties in group work. All parties are working on the same thing, slowing down efficiency due to mutex locking. Of course, that assumes that there is even a mutex, because most of the time it's just a single guy doing all the work, with the other parties blackmailing that thread to credit them equally.

This is really helpful thank you Hussein. Fan from egypt😊

How the hell was there a second identical steve in the video at the same time and how did steve 1 on the right seamlessly pass a real floppy disk to steve 2 on the left as if he was there. That is some very clever filming and editing by Sean Riley. Sean, if you read this, please reply.

@Computerphile

5 жыл бұрын

Hah, it took five times longer to edit than any other, may have to do a behind the scenes on how.... Sean

@bsharpmajorscale

4 жыл бұрын

It must be the work of an enemy stand

What a great explanation!

Some damn fine editing here :)

Steve Ception!! I like it, that was awesome! :)

Love Steve's teaching

Please make more videos on threads 🙏 this was great ✨✨

can someone please explain the origin of &aLock as an argument passed in the mutex lock function?

i love his enthusiasm

Thanks for the great content. But how is locking a token to proceed with multithreading faster than just running the code on a single core? The other thread seems to have to wait, so it shouldn't be a performance boost at all to use multi threading this way. And you are adding more complexity. Are there benefits to this, that I'm missing here?

Nice explanation. We master the sequential process a long time ago. We have very good mathematical models on sequential processing but even now in 2019 we lack a good mathematical model on concurrency processing. Having a huge complex program and trying to split it in multiple threads is a nightmare. I think because we have only two hands our minds are not good at concurrency thinking. I would really like to see a programming language where the source code file has "normal code - handled by programmers" and on top of it there is a "synthetic code - handled by AI", the "synthetic code" is invisible to the programmer and it is in the same source code file. So the human job is to write the code and the AI job is to split the same code automatically. So as a human we don't need to know that the code was run in a complex concurrent fashion. This programming language can have multiple layers (Human layer + many AI layers). It is quite difficult to make a sequential looking code (TEXT) act concurrently (This just makes the code look quite complicated) .

@LuLeBe

Жыл бұрын

the two hands thing doesn't even hold up. We actually can't do more than a single thing consciously. Everything else consists of routines we learned and that only need our attention when they're being stopped, started, modified etc. Take walking down the street while talking on a phone. We can walk without consciously thinking about it, we are decent at observing our surroundings without it and we can produce speech without it. We only need to think about where we want to go and the content of our speech, all the muscular functions are completely automatic. Once you think "a quick brown fox" you don't need to actively think about how to produce that sound. And when learning to play an instrument, for example, you can quickly see how we are completely unable to coordinate both hands as long as we have to actively think about their movement.

I did a project rendering 2D fractals using multithreading. This video would have be SO helpful. I'm gonna share it with everyone who hasn't done the project yet.

What magic is this with the floppy disc :D:D Amazing!

Really interesting stuff! Thanks a lot!

Great video!

That's a great explanation!!

Just blew my mind

I loved second Steve!

Love you guys thanks