On 7/24/2010 3:49 PM, Tim Blechmann wrote:
I think it would be nice to propagate the links to the data structure references up to the contents page. Right now they appear to be 'hidden' under introduction.
not sure, how this can easily be achieved with quickbook ... any pointers?
Sorry, I have no experience with quickbook :(
Specifically speaking about http://tim.klingt.org/boost_lockfree/boost/lockfree/fifo.html, now:
0. "It uses a freelist for memory management, freed nodes are pushed to the freelist, but not returned to the os. This may result in leaking memory." Presumably this means memory may not be reclaimed until the fifo is destroyed, rather than an indefinite leak?
yes.
In that case, I wonder if it's worth rephrasing those notes?
1. "Limitation: The fifo class is limited to PODs". I really would like to be able to use this with arbitrary objects. I'm sure PODs are required for good reason, but a rationale somewhere would be greatly appreciated.
it is a limitation of the michael/scott algorithm. if you want to pass non- pods, you have to use heap-allocated pointers.
Ok. But then would it be worth having a version of a fifo that does the heap-allocation indirection, to save everybody from re-writing it every time they need a non-POD fifo?
2. For the is_lock_free() method, it says "Warning: It only checks, if the fifo head node is lockfree. on most platforms, this should be sufficient, though". Sufficient for what? If the implementation can't guarantee lock-free behaviour throughout, I'd simply return false. Lock-free (typically) means something very specific, after all.
the c++0x semantics of atomics, provide a per-object member function. all implementations thati am familiar with will always either provide lockfree cas operations for all atomic<> instances or for no. the current implementation will give a hint. otherwise i can simply remove this function from the interface ...
I see. FWIW, I can't imagine that an implementation would restrict the number of atomic<>s that provide a lock-free CAS. That's probably your reasoning too I guess. Is this something that can be clarified by the authors of Boost.Atomic?
3. For the empty() method, it says "Not thread-safe, use for debugging purposes only". Does this mean calling it might destroy the data structure's invariants? Or is it always safe in that regard? In which scenarios can it be used, specifically?
calling it may return a wrong result. the data structure is not corrupted.
Then I would vote to add such a note to the documentation, clarifying the way in which it's not thread-safe. It could still be useful for some cases outside of debugging. Kind regards, Edd