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:
https://gist.github.com/2902247
https://gist.github.com/2922399
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.
