[Haskell-cafe] Why functional programming matters

Jan-Willem Maessen jmaessen at alum.mit.edu
Thu Jan 24 18:57:40 EST 2008

On Jan 24, 2008, at 6:04 PM, Evan Laforge wrote:
>> Well... ghc still has a single-threaded garbage collector, so all the
>> "par" threads must stop for garbage collection.  So scaling to the
>> level of a cluster would be significantly sub-linear.
> A real time incremental gc would be really cool.  Some people claim
> they exist, but which languages have one?

Define "real time".  I'll note that, after all the mud that's been  
slung at Java, you've been able to get low-pause-time parallel GC in  
Java for years and years, and can get "real time" GC for various of  
your favorite definitions of that term if you're willing to look a  

Relatively few other language implementations can claim the same.   
Writing a decent parallel GC (eg, faster than the tuned sequential GC  
it's replacing on 2 or more CPUs) is hard.  Sounds like GHC is nearly  
there, though.  GC implementors dream of systems where read barriers  
are nearly free.  Better still, everything that's been learned about  
and published in Java-land carries across to Haskell (though the  
tradeoffs in eg mutation behavior are often different).

-Jan-Willem Maessen

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