On 6/10/15 3:52 AM, Steven Schveighoffer wrote:
On 6/9/15 5:46 PM, Andrei Alexandrescu wrote:
On 6/9/15 1:53 PM, Steven Schveighoffer wrote:
On 6/9/15 2:59 PM, Andrei Alexandrescu wrote:
On 6/9/15 11:42 AM, Dennis Ritchie wrote:
"And finally `std.bigint` offers good (but not outstanding)
performance."
BigInt should use reference counting. Its current approach to
allocating
new memory for everything is a liability. Could someone file a report
for this please. -- Andrei
Slightly OT, but this reminds me.
RefCounted is not viable when using the GC, because any references on
the heap may race against stack-based references.
How do you mean that?
If you add an instance of RefCounted to a GC-destructed type (either in
an array, or as a member of a class), there is the potential that the GC
will run the dtor of the RefCounted item in a different thread, opening
up the possibility of races.
That's a problem with the GC. Collected memory must be deallocated in
the thread that allocated it. It's not really that complicated to
implement, either - the collection process puts the memory to deallocate
in a per-thread freelist; then when each thread wakes up and tries to
allocate things, it first allocates from the freelist.
Can we make RefCounted use atomicInc and atomicDec? It will hurt
performance a bit, but the current state is not good.
I spoke with Erik about this, as he was planning on using RefCounted,
but didn't know about the hairy issues with the GC.
If we get to a point where we can have a thread-local GC, we can remove
the implementation detail of using atomic operations when possible.
The obvious solution that comes to mind is adding a Flag!"interlocked".
Can you explain it further? It's not obvious to me.
The RefCounted type could have a flag as a template parameter.
Andrei
