On Tuesday, 17 June 2014 at 09:10:14 UTC, Walter Bright wrote:
On 6/17/2014 1:59 AM, Nick Sabalausky wrote:
Oh, I totally understand where it's coming from. I'm trying to
point out that ARC is not a magic zero-cost system. Its costs
are SUBSTANTIAL. But in order to understand those costs, it is
necessary to understand how exception handling works.
It is not (only) about cost, it is about determinism. Exceptions
are on the error recovery path, so they are less important to be
deterministic.
What is really critical is not that the execution time of such or
such function, but the moment when it is called. And on the
normal execution path.
This is what manual memory management (and, to a degree, ARC) and
the GC fails to do: determinism of the calls on the normal
execution path (and in the call of finalizers).
Yes, both ARC and manual memory management may be
non-deterministic, but not on the normal execution path and not
with respect to the calls (a malloc is nedeterministic, but its
call is; you could always statically allocate beforehand).
