January 09

https://dlang.org/library/std/parallelism/task_pool.parallel.html#workUnitSize

Basically have no difference than the above but when I change the workUnitSize to 1, 4, whatever it is always running 8 parallel loops.

Either a bug or workUnitSize is not what I think it is. I simply want to execute n iterations of the loop at the time, not fixed at 8.

January 08
On 1/8/22 7:18 PM, Booster wrote:
> https://dlang.org/library/std/parallelism/task_pool.parallel.html#workUnitSize 

>
>
> Basically have no difference than the above but when I change the
> workUnitSize to 1, 4, whatever it is always running 8 parallel loops.
>
> Either a bug or workUnitSize is not what I think it is. I simply want to
> execute n iterations of the loop at the time, not fixed at 8.

Work unit size is the number of elements each thread will work sequentially before causing a context switch. You need to create a TaskPool object to configure the number of threads because the default TaskPool uses all cores.

I have a slide about this in my DConf Online 2020 presentation right here:

  https://www.youtube.com/watch?v=dRORNQIB2wA&t=1700s

import std.parallelism;

void main() {
    int[] elements;

    auto tp = new TaskPool(totalCPUs / 2); // 1. Thread count
    foreach (e; tp.parallel(elements, 1)) { // 2. Work unit size
        // ...
    }
    tp.finish(); // Don't forget
}

Ali