Comment by secondcoming
8 hours ago
If you enforce that the buffer size is a power of 2 you just use a mask to do the
if (next_head == buffer.size())
next_head = 0;
part
8 hours ago
If you enforce that the buffer size is a power of 2 you just use a mask to do the
if (next_head == buffer.size())
next_head = 0;
part
If it's a power of two, you don't need the branch at all. Let the unsigned index wrap.
You ultimately need a mask to access the correct slot in the ring. But it's true that you can leave unmasked values in your reader/writer indices.
Interesting, I've never heard about anybody using this. Maybe a bit unreadable? But yeah, should work :)
I believe ConcurrencyKit's impl does this.
https://github.com/concurrencykit/ck/blob/master/include/ck_...
See https://fgiesen.wordpress.com/2012/07/21/the-magic-ring-buff... which takes it even further :)
1 reply →
Indeed that's true. That extra constraint enables further optimization
It's mentioned in the post, but worth reiterating!
This was, in fact, mentioned in the article.