Hacker News Reader

Comment by alecco | Hacker News Reader

I still don't understand how they choose languages with garbage collection for systems that should be real time or similar.

View on HN

Erlang is not "real time" in the hard, embedded systems sense, but it does pretty well and has GC.

Here's a bit more information: http://www.erlang.org/faq/academic.html#id55755

I don't know what sorts of 'real time' properties trading systems are required to have - can anyone talk about it with a bit more in-depth knowledge?

I don't know much, but for high-frequency trading, fast is never fast enough. response times are measured in microseconds.

http://richg74.wordpress.com/2010/10/25/speedy-new-lse-tradi...

http://www.h-online.com/open/news/item/Linux-boosts-Stock-Ex...

Speed isn't all. The system should be based in algorithms with manageable worst case time.

I don't buy Erlang camp's reports.

A GC will always trash the cache, and that's the worst issue right now in hardware. (If you take out HDD I/O.)

GC isn't a problem for realtime systems, if configured correctly. For example, have the GC running incrementally in a separate thread.

Close, you do need to stop the world every once in a while to GC some of the harder stuff.

But it's true, there's flavors of Java that are certified for hard realtime. If you stop the GC for 100ms every 2s regardless if you need it or not, that's pretty nice and predictable behavior for a realtime system.

100ms is an eternity. You can do GC with 1ms pauses.

http://www.infoq.com/articles/azul_gc_in_detail, for one example.

It's not F# or Java, it's C++. http://news.ycombinator.com/item?id=2261896

It could be some left over system from the previous .Net platform causing a knock-on effect.

It could be anything. Why do you want it to be that?

I don't want it to be that. I'm saying the rumour sounds plausible.

Not so plausible to me, considering that the old system was in C#.

I'm pretty sure I've read somewhere that they where using F# for some parts.

Can we have a link please?

That seems unlikely. F# only recently moved from being an experimental language from Microsoft Research to a supported .NET language. The previous system is old enough to predate that.

Agreed. and Anderson consulting using an experimental, non-obvious language? I don't see it.

You may be interested in the Metronome project, which aims to provide a GC suitable for realtime use: http://domino.research.ibm.com/comm/research_projects.nsf/pa...

An academic paper about the project, Design and Implemention of a Comprehensive Real-Time Java Virtual Machine: http://domino.research.ibm.com/comm/research_people.nsf/page...

Reply on news.ycombinator.com