On Thursday, 24 June 2021 at 18:23:01 UTC, seany wrote:
I have seen
[this](https://forum.dlang.org/thread/akhbvvjgeaspmjntz...@forum.dlang.org).
I can't call break form parallel foreach.
Okey, Is there a way to easily call .stop() from such a case?
Yes there is, but it won’t break the `foreach`:
```d
auto tp = taskPool;
foreach (i, ref e; tp.parallel(a))
{
// …
tp.stop;
}
```
The reason this does not work is because `stop` terminates the
worker threads as soon as they are finished with their current
`Task`, but no sooner. `parallel` creates the `Task`s before it
presents a range to `foreach`, so no new `Task`s are created
during iteration. Therefore all elements are iterated.
outer: foreach(i, a; parallel(array_of_a)) {
foreach(j, b; parallel(array_of_b)) {
By the way, nesting parallel `foreach` does not make much sense,
as one level already distributes the load across all cores (but
one). Additional parallelisation will likely just add overhead,
and have a net negative effect.
— Bastiaan.
