On Saturday, 1 December 2012 at 12:51:27 UTC, thedeemon wrote:
On Saturday, 1 December 2012 at 11:36:16 UTC, Zardoz wrote:
The prevois code should work better if i set "total" to be
sahred and hope that D shared vars have nnow the internal
barries working ,or I need to manually use semaphores ?
Probably core.atomic is the way to go. Semaphore is an overkill.
The easiest and fastest way is probably using taskPool.reduce,
like this:
auto total = taskPool.reduce!"a+b"(
iota(10_000_000).map!(a => log(a + 1.0)));
writeln(total);
Functions in core.atomic use instructions with lock prefix and
according to http://www.agner.org/optimize/instruction_tables.pdf
that "typically costs more than a hundred clock cycles,", so
calling them for every element will probably slow things down
significantly. It's best to just avoid accessing same memory from
multiple threads wherever possible.
