Re: concurrent computation of a function

[Max Alekseyev <maxale@gmail.com>]

Hi Bill,

Thank you for the elegant solution!

Could you please elaborate on why the use of error() is not recommended? Is it because of side effects related to garbage collection or alike?

And is there a recommended alternative?

Regards,

Max

On Thu, Sep 19, 2024 at 11:57 AM Bill Allombert <Bill.Allombert@math.u-bordeaux.fr> wrote:

On Thu, Sep 19, 2024 at 10:40:45AM -0400, Max Alekseyev wrote:
> Hello,
>
> Suppose I have two functions func1(x) and func2(x) computing the same
> entity, where depending on the input one may be much faster than the other
> (or vice versa).
> For the same input x, I'd like to compute them in parallel and return the
> result as soon as one of them completes, and terminate execution of the
> other.
> Is there a way to achieve this in PARI/GP?

The issue to terminate the second computation safely.
You can do that with pthread using error() but this is not recommended.

f1(a,b)=a+b
f2(a,b)=a*b

export(f1,f2);
{
  iferr(pareval([
       ()->error(f1(5,6)),
       ()->error(f2(5,6))
  ]),E,return(component(E,1)[1]),err_name(E)="e_USER")
}

Cheers,
Bill.