OFFTOPIC: GPars performance vs Go [was Re: A few notes on choosing between Go and D for a quick project]

Russel Winder via Digitalmars-d digitalmars-d at
Wed Mar 18 01:40:06 PDT 2015

On Tue, 2015-03-17 at 20:50 +0000, Bienlein via Digitalmars-d wrote:
> > Go is only a CSP-like, it isn't CSP. cf Python-CSP and PyCSP, 
> > not to
> > mention JCSP and GPars.
> I'm not really sure whether this can be put exactly that way. On 
> a machine with 4 GB RAM you can spawn about 80.000 goroutines 
> (aka green threads). Let's say each threads calculates a large 
> fibonacci number. If the fibonacci calculation yields the 
> processor frequently all 80.000 run seamingly in parallel and 
> return their result almost "at the same time".
> With GPars this would not work. You can only start some 2.000 
> Java threads on a machine with the same amount of memory. If also 
> the fibonacci calculation in Groovy/GPars yields the processor, 
> using GPars the first 2.000 fibonacci calculations will 
> nevertheless crowd out the following 2.000 threads of all those 
> 80.000 fibonacci calculations and so on. I once tried this out 
> with both Go and Groovy/GPars.

<This needs to go to the GPars mailing lists list so I have cross

A priori I do not believe the claim made here: a GPars task is submitted
to a thread pool, which is exactly what the goroutines are. Thus the
number of Java threads is not a bound on the number of GPars tasks. Any
bounds will be provided by the Fork/Join pool.

If you have code you can send me, I will run it and do the benchmarking.
If not I guess I will have to write some. Until we have the results of
executing code, the above must be treated as pure conjecture, which I
believe will be refuted. If the claim however turns out to be true, then
it highlights a bug in GPars.

Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder at
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel at
London SW11 1EN, UK   w:  skype: russel_winder
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