On Sunday, 4 January 2015 at 01:02:07 UTC, Matt wrote:
What I mean is that I don't understand what atomicStore, atomicLoad, etc. actually DO, although in the case of the two mentioned, I can hazard a pretty good guess. The documentation doesn't exist to tell me how to use the functions found in the module. I've never used any atomic functions in any language before.
Atomic operations are guaranteed to happen in "one step". For example, x += 1 will load the value of x into a register, increment it by 1, then write the value back to memory, while atomicStore (x, x+1) will cause all three steps to be executed as if they were instantaneous. This prevents a thread writing to an address that another thread just read from, causing that thread's view of the data to be silently outdated (aka a race condition, because the final value of x depends on which thread writes first).
However, thank you for the simple double buffered example, I do appreciate it. How would another thread gain access to the instance in use, though? Am I able to pass references to instances of this class via events?
You can if they're shared. You can pass the reference via message, or have the reference exist at a location both threads have access to. The two @property functions in the example are meant to be used by the writing and reading thread, respectively.
I go about the swap by letting the reader thread message the writer to inform it that it is ready for more data, at which point the writer thread is free to call .swap () once it is done writing (though you can do it the opposite way if you want).
'synchronized' is also something I'm clueless about, and again the D documentation doesn't help, as the section in the class documentation basically says "synchronized classes are made of synchronized functions", without explaining what a synchronized function IS. The function section makes no mention of the synchronized keyword, either.
A synchronized class has a hidden mutex, and any thread that calls a member method acquires the lock. The synchronized keyword isn't limited to classes, though - you can find a detailed description of synchronized's various uses here: http://ddili.org/ders/d.en/concurrency_shared.html
Sorry, it feels like there's a load of stuff in the library and language to make multithreading easier, but with little to no explanation, so it feels like you're expected to already know it, unless I'm looking in the wrong places for my explanations. If I am, please do give me a kick, and point me in the right direction.
Yeah, I think the docs are meant to be a reference if you already have in mind what you're looking for, and just need to know how to wire it up.
I recommend Ali's book (linked in the previous paragraph) in general as its the most comprehensive and up-to-date explanation of the language as a whole that I've yet seen (and its free).
