Re: Question on shared memory concurrency

[Andy Valencia via Digitalmars-d-learn]

On Monday, 4 March 2024 at 16:02:50 UTC, Andy Valencia wrote:
On Monday, 4 March 2024 at 03:42:48 UTC, Richard (Rikki) Andrew 
Cattermole wrote:
... I still hope to be able to share memory between spawned 
threads, and if it isn't a shared ref of a shared variable, 
then what would it be?  Do I have to use the memory allocator?

For any other newbie dlang voyagers, here's a version which works 
as expected using the system memory allocator.  On my little i7 I 
get 1.48 secs wallclock with 5.26 CPU seconds.



import core.atomic : atomicFetchAdd;
import std.concurrency : spawn;
import core.time : msecs;
import core.thread : Thread;
import core.memory : GC;

const uint NSWEPT = 100_000_000;
const uint NCPU = 4;

void
doadd(shared uint *buf)
{
    for (uint count = 0; count < NSWEPT/NCPU; ++count) {
        atomicFetchAdd(buf[0], 1);
    }
}

void
main()
{
    shared uint *buf =
        cast(shared uint *)GC.calloc(uint.sizeof * 1, 
GC.BlkAttr.NO_SCAN);

    for (uint x = 0; x < NCPU-1; ++x) {
        spawn(&doadd, buf);
    }
    doadd(buf);
    while (buf[0] != NSWEPT) {
        Thread.sleep(1.msecs);
    }
}