Re: [boost] [thread] Alternate future implementation and future islands.

On Fri, Mar 27, 2015 at 5:35 PM, Giovanni Piero Deretta wrote:

On Fri, Mar 27, 2015 at 8:24 PM, Gottlob Frege wrote:

...

...

Just to be clear, my non-allocating promise/future was meant to be more of a proof-of-concept, not necessarily optimal efficiency. I would need to recheck, but I think most of it requires only acquire or release, not full sequential consistency, if that helps. I rarely write anything that requires full sequential consistency.

Hum, I do not think you can implement it with just plain load and stores, I think you need at least one RMW there. Probably acq_rel is enough for that, but that's no less expensive than seq_cst on x86.

You are probably right, but for each move, all you are doing is publishing where you moved to, so you need a release, and then an acquire when you want to read that, not acq_rel together on one operation. But I haven't thought about it since I gave the presentation!, so I don't know. Maybe I'll have time to think about it at C++Now, which is coming up soon. (Feels soon to me at least - more things to prepare...) Tony