I am using a boost::io_service to build a thread pool that executes computational jobs in parallel. Some jobs are not allowed to run concurrently, which - I think - is the ideal application of a boost::io_service::strand. As the order in which the sequential jobs are executed does not matter, I am asking, which of the two ways to use the strand I should use:
strand.post(bind(jobA...));
or
io_service.post(strand.wrap(bind(jobA...)))
If I understand the boost docs correctly, the first version will insure that the jobs are executed in the same order they were posted, whereas the second version does not give any guarantee.
My question is: Which one is faster?
You can use the two methods described above interchangeably and it will result in identical results. I doubt very much that there is any performance difference, but if there is, it's in the overhead of the two function (strand.post vs io_service.post) calls but not in the actual execution of the io_service since they both do the same thing under the hood and have the same path of execution.
I would guess that io_service.post() requires a handful fewer clock cycles, but in the same breath I'm also guessing that such micro-optimizations are as noticeable in your application as interference from solar radiation and the CPU having to re-execute instructions. I don't even know if that's a real phenomena or not, but it sounded cool when trying to come up with a verbose way of saying, "don't worry about it". If there is in fact a performance difference, please share the benchmarks. *rolls eyes at self*