YouSaid · the spoken record

George Hotz

lines on the record: 283
first: 2023-06-30
most recent: 2023-06-30
sittings or episodes: 1
sources: podcast

Every line below is reproduced as it was said and linked to the record it came from. Nothing here is summarised or generated. Directory · Search · Corrections

“Yeah, print everything, right? And yeah, like if you want a pretty printer, maybe. I'm like, yeah, you know what? I think in two years I'm going to start using these plugins. Little bit, and then in five years, I'm going to be heavily relying on some AI augmented flow. And then in 10 years.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“One of my coworkers says he uses them for print statements. Like every time he has to, when he needs the only thing it can really write is, okay, I just want to write the thing to print the state out right now.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Don't know. I downloaded the plugin maybe like two months ago. I tried it again and found the same. Look, I don't doubt that these models are going to first become useful to me, then be as good as me and then surpass me. But from what I've seen today, it's like someone occasionally taking over my keyboard that I hired from Fiverr.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“That I didn't like messenger types up, but again, like, my pie is getting really good, and I love it, and I can't wait for some of these tools to become AI powered. I want AIs reading my code and giving me feedback. I don't want AIs writing half-assed autocomplete stuff for me.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Something like this. Well, no, to give a warning where, like, my pie is a static type checker, but I'm asking just for a runtime type checker. There's ways to hack this in, but I wish it was just a flag, like Python 3-T.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“C would have you brutally type out string iterator, right? Now I can just type auto, which is nice. And then Python used to just have A. What type is A? A colon str. Oh, okay, it's a string. Cool. I wish there was a way, like a simple way in Python, to turn on a mode which would enforce the types.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Absolutely. I think optional typing is great. I mean, look, I think that it's like a meet in the middle, right? Like Python has this optional type hinting and C++ has auto.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“This fancy type checker for Py And actually, I tried Microsoft released one too, and it was like 60% false positives. My pie is like 5% false positives. 95% of the time, it recognizes, I didn't really think about that typing interaction correctly. Thank you, Pi.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“But I never used any of the plugins in Vim either. I had the most vanilla Vim. I have a syntax highlighter. I didn't even have autocomplete. These things, I feel like help you so marginally that like. Now, okay, now VS Code's autocomplete has gotten good enough that, like, okay, I don't have to set it up. I can just go into any code base and autocomplete's right 90% of the time. Okay, cool. I'll take it. I don't think I'm going to have a problem at all adapting to the tools once they're good. But the real thing that I want is not something that tab completes my code and gives me ideas. The real thing that I want is a very intelligent pair programmer that comes up with a little pop-up saying, hey, you wrote a bug on line 14 and here's what it is. Now, I like that. You know what does a good job of this? My pie.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Like, yeah, sure. If I like, yeah, I'm great, GPT. Thanks for reminding me to free my variables. Unfortunately, you didn't really recognize the scope correctly and you can't free that one. But like, you put the freeze there and like, I get it”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, I think that. I don't know. I mean, there's just a little of this in Python. Maybe if I was coding more in other languages, I would consider it more. But I feel like Python already does such a good job of removing any boilerplate. The closest thing you can get to pseudocode, right?”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Just constantly reminds me of like bad stuff. I mean, I tried the same thing with rap, right? I tried the same thing with rap and actually think of a much better programmer than rapper. But I even tried, I was like, okay, can we get some inspiration from these things for some rap lyrics? And I just found that it would go back to the most like cringy tropes and dumb rhyme schemes. And I'm like, yeah, this is what the code looks like too.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, I find that a lot of it is noise. I do use VS Code and I do like some amount of autocomplete. I do like a very feels like rules-based autocomplete, like an autocomplete that's going to complete the variable name for me. So I don't have to type it. I can just press tab. That's nice. But I don't want an autocomplete. You know what I hate when auto completes, when I type the word for and it puts two parentheses and two semicolons and two braces, I'm like, oh.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I love doing nuke programming tutorials and doing them. I did all this for Rust. It keeps some of it upsetting JVM roots, but it is a much nicer. In fact, I almost don't know why Kotlin took off and not Scala. I think Scala has some beauty that Kotlin lacked. Whereas Kotlin felt a lot more. I mean, it was almost like, I don't know if it actually was a response to Swift, but that's kind of what it felt like. Like Kotlin looks more like Swift and Scala looks more like a functional programming language, more like an OCaml or Haskell.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I like it more than I thought. I did the tutorials. I was very new to it. It would take me six months to be able to write Good Scala.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Maybe have some hyper And I'm willing to make that trade off, right? I'm willing to make, and this is why people think that dictators take power through some untoward mechanism. Sometimes they do, but usually it's because the people want them. And the downsides of a dictatorship, I feel like we've gotten to a point now with the oligarchy where. Yeah, I would prefer the dictator.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, I mean, monarchy has problems, right? But I mean, would I trade right now the current oligarchy, which runs America for the monarchy? Yeah, I would. Sure. The Elon monarchy, yeah, you know why? Because power would cost one cent a kilowatt hour. Of a cent a kilowatt hour Now, I pay about 20 cents a kilowatt hour for electricity in San Diego. That's like the same price you paid in 1980.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Wouldn't define the ideal so simply? I think you can define the ideal no more than just saying Elon's idea of a good world. Freedom of expression is.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, like the War on the Woke. It's just man and like. He doesn't have to do this, you know. He doesn't have to. He could go like Parague and go chill at the four seasons Maui, you know, but see, one person I respect and one person I don't.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“My respect for him is unchanged. And I did have to think a lot more deeply about some of the decisions he's forced to make”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Whether they're right or not, it's definitely not for that reason, right? It's definitely not a question of engineering prowess. It is a question of maybe what the priorities are for the company. And I did get more intelligent feedback from people I think in good faith saying that. Actually, from Elon. And like, you know, from Elon's people were like, well, you know, a stop the world refactor might be great for engineering, but you know, we have a business to run. Hey, above my pay”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“George, your junior software engineer, every junior software engineer wants to come in and refactor all code. Okay. Like, that's like your opinion, man.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I don't want to be a manager. I don't want to do that. If you really forced me to, yeah, it would make me maybe. Make me upset. I had to make those decisions. I don't want to.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I think I could lead a very good refactor of Twitter and it would take like six months to a year and the results to show at the end of it would be feature development in general takes 10x less time, 10x less man hours. That's what I think I could actually do. Do I think that it's the right decision for the business above my grade?”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“You know, and I'm not the right person to run Twitter. Just not. And that's the problem. I don't really know. I don't really know if that's, you know, a common thing that I thought a lot while I was there was whenever I thought something that was different to what Elon thought I'd have to run something in the back of my head reminding myself that Elon is the richest man in the world. And in general, his ideas are better than mine. Now, there's a few things I think I do understand and know more about, but in general, I'm not qualified to run Twitter. I was going to say qualified, but like, I don't think I'd be that good at it. I don't think I'd be good at it. I don't think I'd really be good at running an engineering organization at scale.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“You know what? This is something that I do differently from Elon with comma about self driving cars. Know, I hear the new version's going to come out and the new version is not going to be better. But at first, and it's going to require a ton of refactors, I say, okay, take as long as you need. Like you convinced me this architecture is better? Okay, we have to move to it, even if it's not going to make the product better tomorrow. The top priority is getting the architecture right.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Problem is more like why did the code base have to grow? What new functionality has been added to compensate for the lines of code that are there?”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Runs in three data centers, and that's it. No other place you can run Twitter, which is like George, you don't understand this is modern software development. No, this is bullshit. Like, why can't it run on my laptop? What do you do? Twitter can run on it. Yeah, okay. Well, I'm not saying you're going to download the whole database to your laptop, but I'm saying all the middleware and the front end should run on my laptop, right?”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Redirect some of the traffic to your modified version and diff those two. It was all online. There was no CI in the traditional sense. I mean, there was some, but it was not full coverage.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I'll tell you what my plan was at Twitter. It's actually similar to something we use at comma. So, a comma we have this thing called process replay. We have a bunch of routes that will be run through. So comma is a microservice architecture too. We have microservices in the driving. We have one for the cameras, one for the sensor, one for the planner, one for the model. And we have an API, which the microservices talk to each other with. We use this custom thing called serial, which uses ZMQ. Twitter uses Thrift and then it uses this thing called Finagle, which is a Scala RPC backend. But this doesn't even really matter. The thrift and finagle layer was a great place, I thought, to write tests. To start building something that looks like process replay. So Twitter had some stuff that looked kind of like this, but it wasn't offline. It was only online. So you could ship like a modified version of it, and then you could...”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“We look at this thing that's 100,000 lines and we're like, well, okay, maybe this did even make sense in 2010, but now we can replace this with an open source thing, right? And we look at this here. Here's another 50,000 lines. Well, actually, we can replace this with 300 lines ago. And you know what? I trust that the Go actually replaces this thing because all the tests still pass. So step one is testing. And then step two is like the programming language is an afterthought, right? You know, let a whole lot of people compete be like, okay, who wants to rewrite a module, whatever language you want to write it in, just the tests have to pass. And if you figure out how to make the test pass but break the site, we got to go back to step one. Step one is get tests that you trust in order to make changes in the code base.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Before touched any code, I would actually say no one touches any code. The first thing we do is we test this code base. I mean, this is classic. This is how you approach a legacy code base. This is like how to approach a legacy code base book will tell you.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I mean, the first thing that I would do is build tests. The first thing I would do is get a CI to where people can trust to make changes.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Is the main philosophy of Tiny Grad. You have never refactored enough. Your code can get smaller. Your code can get simpler. Your ideas can be more elegant.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“It was fun. It was fun. It was stressful. But I felt like I was at a cool point in history. And like, I hope I was useful. I probably kind of wasn't. But maybe I was.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I love that Elon gave me this opportunity. It does. And like, you know, he came with my day I quit, he came on my Twitter spaces afterward and we had a conversation. Like, I just, I respect that so much.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Main thing I would do is first of all identify the pieces and then put tests in between the pieces. So there's all these different Twitter as a microservice architecture. There's all these different microservices. And the thing that I was working on there, look, George didn't know any JavaScript. He asked how to fix search, blah, blah, blah, blah, blah. Look, man. Thing is, like, I just, you know, I'm upset that the way that this whole thing was portrayed because it wasn't like it wasn't like taken by people like honestly. It wasn't like it was taken by people who started out with a bad faith assumption. And I mean, look, I can't like.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Transparent, it's a transparent dictatorship, right? And you can choose to opt in, or you get free exit, right? That's the beauty of companies. If you don't like the dictatorship, you quit.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“It's an absolute dictatorship, right? Elon does the same thing. Now, the thing about my dictatorship is here are my values.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I took a political approach at comma too that I think is pretty interesting. I think Elon takes the same political approach. Google had no politics. And what ended up happening is the absolute worst kind of politics took over. Comma has an extreme amount of politics, and they're all mine, and no dissidence is tolerated.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Like, you know, and this is just, I've instilled this culture at comma, and comma has better programmers than me who work there, but again, I'm like the old guy from Goodwill Hunting. It's like, look, man, you know. Might not be as good as you, but I can see the difference between me and you, right? And like, this is what you need, this is what you need at the top. Or you don't necessarily need Manager to be the absolute best. I shouldn't say that, but they need to be able to recognize skill.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“So, what I do at comma and at Tiny Corp is you have to explain it to me. You have to explain to me what this code does. And if I can sit there and come up with a simpler way to do it, you have to rewrite it. Have to agree with me about the simpler way. Obviously, we can have a conversation about this. It's not dictatorial. But if you're like, wow, wait, that actually is way simpler. Like the simplicity is important.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Real thing that I spoke to a bunch of. Know like individual contributors to Twitter. And I stast, I'm like, okay, so what's wrong with this place? Why does this code look like this? And they explained to me what Twitter's promotion system was. The way that you got promoted to Twitter was you wrote a library that a lot of people used. So, some guy wrote an Nginx replacement for Twitter. Why does Twitter need an NGINX replacement? What was wrong with Nginx? Well, you see, you're not going to get promoted if you use Nginx. But if you write a replacement and lots of people starting. Then you're going to get promoted, right?”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“One of my favorite things to look at today is how much do you trust your tests? We've put a ton of effort in comma and I've put a ton of effort in TinyGrad into making sure if you change the code and the tests pass that you didn't break the code. Now, this obviously is not always true, but the closer that is to true, the more you trust your tests, the more you're like, oh, I got a pull request and the tests pass, I feel okay to merge that. The faster you can make progress.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Some people in the world like to create complexity. Some people in the world thrive under complexity, like lawyers, right? Lawyers want the world to be more complex because you need more lawyers, you need more legal hours, right? I think that's another. If there's two great evils in the world, it's centralization and complexity.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“No, but the markers aren't experts. The people who are mocking are not experts with carefully reasoned arguments about why you need 8,000 people to run a bird app. But the people are going to lose their jobs.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Know what it is, and it's the same. This is my summary of the hate I get on hacker news. It's like When I say I'm going to do something, Have to believe that it's impossible Because if doing things was possible, they'd have to do some soul searching and ask the question, why didn't they do anything?”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“I still believe in the amount of hate I got for saying this, that 50 people could build and maintain Twitter pretty much.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“So my technical recommendation to Elon, and I said this on the Twitter spaces afterward, I said this many times during my brief internship. Was that you need refactors before features. This code base was, and look, I've worked at Google, I've worked at Facebook, Facebook has the best code. Then Google, then Twitter. And you know what? You can know this because look at the machine learning frameworks, right? Facebook released PyTorch. Google released TensorFlow and Twitter released. Okay, so you know.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, so here's a problem with that. It's not going to win in a free market What wins in a free market is all television today is reality television because it's engaging. Engaging is what wins in a free market. So it becomes hard to keep these other more nuanced values.”
2023-06-30 · Lex Fridman Podcast · #387 – George Hotz: Tiny Corp, Twitter, AI Safety, Self-Driving, GPT, AGI & God · IDENTIFIED FROM THE TRANSCRIPT · source