[boost] [compute] Some remarks

Subject: [boost] [compute] Some remarks
From: Thomas Heller (thom.heller_at_[hidden])
Date: 2015-01-01 13:55:51

Hey list,

These are just a few remarks I wanted to share that I made during the compute 
review phase. Unfortunately, I don't have the time to write a full review. As 
I mostly skimmed over everything so take it with a grain of salt.

First of all, I really like the general idea of Boost.Compute. That is, I like 
the idea of having a proper API for OpenCL capable devices and I like the idea 
of having parallel algorithms. With that being said, i think it is a waste of 
opportunities to have the two tied together so closely especially considering 
N4104 with the combination of different execution policies which would allow 
for a wonderful API for using different parallelization backends (where 
boost.compute could be the reference implementation or some such).
Additionally, I think that the author and other reviewers are running in 
circles when it comes to synchronization. IMHO, the event alone is enough and 
perfectly fine. An OpenCL event has interesting similarities to 
std::future<void>, and the clEnqueue functions to std::async. I'd consider the 
command queue however similar to std::thread (and threads should be considered 
harmful...). With that being said, a event should be perfectly fine to express 
synchronization points. Together with executors, it would even fit into the 
more higher level stdlib parallel algorithms. It would be very nice to get rid 
of a publicly exposed event class though and have one future to rule them all 
(one can dream...). But having a future and event in Boost.compute is, IMHO, 
not a good idea.

Cheers,
Thomas