The Haxl Project at Facebook [pdf] (opens in new tab)

(github.com)

71 pointsshangaslammi12y ago27 comments

27 comments

omn112y ago

Wait, Facebook uses Haskell? I had no idea. There is little information about the size of the codebase though. I could only dig up a talk from 2009 and a tool to modify a PHP codebase with abstract-syntax-tree transformers in Haskell [2]. Can somebody give some more insight on their internal use of the language?

Anyway I think it's great that they have a hybrid codebase. With projects like HipHop and this Haskell backend it looks like they are gradually moving away from PHP as their main language.

[1]: http://cufp.galois.com/2009/abstracts.html#ChristopherPiroEu... [2]: https://github.com/facebook/lex-pass/tree/master

Ixiaus12y ago

Yeah, they also bought out MailRank to get O'Sullivan.

mightybyte12y ago

Yeah, but that wasn't for Haskell.

1 more reply

asdasf12y ago

Facebook hasn't been a PHP shop in a long time. PHP is only used on the front end site. New projects that come along are written in whatever language makes sense. Like facebook chat being in erlang for example.

enigmo12y ago

I heard a rumor a while back that Facebook Chat was rewritten in C++... but I can't seem to find anything to verify that. Do you know if it's still Erlang?

2 more replies

shangaslammiOP12y ago

These are Simon Marlow's slides from his ZuriHac 2013 talk about Facebook's Haskell DSL for concurrent queries.

mcintyre199412y ago

I'm sort of surprised that Facebook's "friends of" is a directed graph, when the actual social graph is undirected. I guess they use enough directed edges for other things in that graph, but I'm sort of surprised their social graph isn't undirected and ridiculously optimised as its own separate thing.

Scaevolus12y ago

An undirected graph is equivalent to a directed graph with doubled edges.

The only efficient way to implement an undirected graph is as a directed graph with doubled edges.

You want to list friends of Alice. Directed: query all friend(Alice, X). Undirected: query all friend(Alice, X) OR friend(X, Alice). Finding all friend(X, Alice) will be very slow without an index of all friend relationships with Alice in the second position. Storing this is harder than just storing friend(Alice, X) and friend(X, Alice).

mcintyre199412y ago

Oh of course, I see what you mean, thanks for the explanation.

1 more reply

seiji12y ago

For surveillance it's of great importance to know the difference between me being friends with Iranian nuclear scientists, them being friends with me, or us having mutual hugs going on.

mercurial12y ago

That's extremely impressive. Datasources pluggable at runtime, no side-effect guarantee, hot-swapping code...

tel12y ago

The hot-swapping is very new and experimental, but if facebook has a need then Simon Marlow definitely has the capability bring that back to GHC core. He's already stated at least some of the hot swapping will make it.

boothead12y ago

I believe Simon is also talking about this at the London Haskell Exchange at skillsmatter in October. I will definitely be attending this one!!

AznHisoka12y ago

It's a shame such cool technology is being put to use for something as trivial as Facebook.

tel12y ago

There's a lot of critique that could be leveraged against Facebook, but I don't understand how you could call it trivial.

freyrs312y ago

Simon Marlow said on reddit this morning that some of the technology is getting merged upstream into GHC 7.8. So we'll all benefit from it.

freehunter12y ago

Is there any reason it can't be used elsewhere? You could repurpose the solution into your own project and do something less trivial.

j / k navigate · click thread line to collapse

27 comments

omn112y ago

Anyway I think it's great that they have a hybrid codebase. With projects like HipHop and this Haskell backend it looks like they are gradually moving away from PHP as their main language.

[1]: http://cufp.galois.com/2009/abstracts.html#ChristopherPiroEu... [2]: https://github.com/facebook/lex-pass/tree/master

Ixiaus12y ago

Yeah, they also bought out MailRank to get O'Sullivan.

mightybyte12y ago

Yeah, but that wasn't for Haskell.

1 more reply

asdasf12y ago

enigmo12y ago

I heard a rumor a while back that Facebook Chat was rewritten in C++... but I can't seem to find anything to verify that. Do you know if it's still Erlang?

2 more replies

shangaslammiOP12y ago

These are Simon Marlow's slides from his ZuriHac 2013 talk about Facebook's Haskell DSL for concurrent queries.

mcintyre199412y ago

Scaevolus12y ago

An undirected graph is equivalent to a directed graph with doubled edges.

The only efficient way to implement an undirected graph is as a directed graph with doubled edges.

mcintyre199412y ago

Oh of course, I see what you mean, thanks for the explanation.

1 more reply

seiji12y ago

For surveillance it's of great importance to know the difference between me being friends with Iranian nuclear scientists, them being friends with me, or us having mutual hugs going on.

mercurial12y ago

That's extremely impressive. Datasources pluggable at runtime, no side-effect guarantee, hot-swapping code...

tel12y ago

boothead12y ago

I believe Simon is also talking about this at the London Haskell Exchange at skillsmatter in October. I will definitely be attending this one!!

AznHisoka12y ago

It's a shame such cool technology is being put to use for something as trivial as Facebook.

tel12y ago

There's a lot of critique that could be leveraged against Facebook, but I don't understand how you could call it trivial.

freyrs312y ago

Simon Marlow said on reddit this morning that some of the technology is getting merged upstream into GHC 7.8. So we'll all benefit from it.

freehunter12y ago

Is there any reason it can't be used elsewhere? You could repurpose the solution into your own project and do something less trivial.

j / k navigate · click thread line to collapse