Shared keyword and the GC?

Araq rumpf_a at
Wed Oct 24 10:42:48 PDT 2012

> I haven't seen proper benchmarks but some time ago I wrote in D 
> and OCaml  basically the same simple program which read and 
> parsed some text and performed some calculations, allocating a 
> lot of temporary arrays or lists:
> and OCaml version was 2 times faster than D (29 and 59 seconds 
> on input file of 1 million lines). After disabling GC on 
> reading/parsing stage and doing calculations without 
> allocations and using std.parallelism I made D version work in 
> 4.4 seconds.
And that makes it the "fastest GC ever made"?

> One place where immutability really helps is in a generational 
> GC: runtime needs to track all the pointers from old generation 
> to the young generation, if most of the data is immutable there 
> are not so many such pointers, this makes collection faster. 
> When all data is immutable there is no such pointers at all, 
> each object can only have pointers to older ones.

That's true. But you don't need to know about immmutability at 
compile time to get this benefit.

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