No of threads
Ali Çehreli
acehreli at yahoo.com
Tue Dec 19 18:42:01 UTC 2017
On 12/19/2017 02:24 AM, Vino wrote:
> Hi All,
>
> Request your help in clarifying the below. As per the document
>
> foreach (d; taskPool.parallel(xxx)) : The total number of threads that
> will be created is total CPU -1 ( 2 processor with 6 core : 11 threads)
>
> foreach (d; taskPool.parallel(xxx,1)) : The total number of threads that
> will be created is total CPU -1 ( 2 processor with 6 core : 12 threads)
That parameter is workUnitSize, meaning the number of elements each
thread will process per work unit. So, when you set it to 100, each
thread will work on 100 elements before they go pick more elements to
work on. Experiment with different values to find out which is faster
for your work load. If each element takes very short amount of time to
work on, you need larger values because you don't want to stop a happy
thread that's chugging along on elements. It really depends on each
program, so try different values.
> foreach (d; taskPool.parallel(xxx,20)) : As in Windows 2008 whatever
> value is set for the parallel the total number of threads does not
> increase more than 12.
taskPool is just for convenience. You need to create your own TaskPool
if you want more threads:
import std.parallelism;
import core.thread;
import std.range;
void main() {
auto t = new TaskPool(20);
foreach (d; t.parallel(100.iota)) {
// ...
}
Thread.sleep(5.seconds);
t.finish();
}
Now there are 20 + 1 (main) threads.
Ali
More information about the Digitalmars-d-learn
mailing list