Re: [Caml-list] Performance penalty for using monad

[Yaron Minsky <yminsky@janestreet.com>]

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On Sun, Sep 24, 2017 at 5:22 AM, David Allsopp <dra-news@metastack.com>
wrote:

> Helmut Brandl wrote:
> > One more question: It seems that flambda is necessary in order to
> optimize
> > monadic code. Is there a plan that flambda will be included in a base
> > release of ocaml?
> >
> > Up to now all base releases like 4.03.0, 4.04.0, etc. do not include
> > flambda. I have to request the extension if I want it.
>
> flambda work is still ongoing (work-in-progress sounds a bit mean - it's
> more that it's still evolving!) and it's not yet in a position to be
> enabled by default. This is the ultimate plan, though there is no nominated
> version at which we yet expect to make it the default.


For what it's worth, the main blocker for us turning Flambda on by default
in classic mode is getting build artifact size and compilation speed down
basically to the same level as closure-compilation. We're getting pretty
close to that goal, though it will take a bit more time to get the
improvements in question upstreamed.

So getting Flambda enabled by default isn't that far away (though most of
the real benefits will require -O3, which will still lengthen compilation
by quite a bit.)


>
> Jesper Louis Anderson wrote:
> > That decoder used monads heavily as well, and flambda provided roughly
> > an order of magnitude speedup (and a lower GC pressure as well in
> addition).
> > It was enough that I made a mental note of using flambda if this ever
> went
> > into a system with high throughput requirements.
>
> Just for added interest, there are things being worked on in opam 2 which
> should allow you to be able to declare such a package as either needing an
> OCaml compiler with flambda enabled or which would let you display a
> warning message if the package is installed in a compiler which doesn't
> have flambda enabled.
>
>
> David
>
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