Question on shared memory concurrency

[Andy Valencia]

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);
     }
}