September 2016 - Boost - lists.preview.boost.org

[range] sub_range of istream_range
by Andrew Hundt 26 Sep '16

26 Sep '16

I’m trying to iterate through a file using sub_ranges of an istream_range of an ifstream. However, it seems if I construct sub ranges of various subsets of the full istream_range, try to adjust the limits with advance_begin and advance_end, and then access them I get null dereferences. Any thoughts? I can produce an example if needed. Cheers! Andrew Hundt

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markable -- informal review request
by Andrzej Krzemienski 24 Sep '16

24 Sep '16

Hi Everyone, I would like to ask your opinion, suggestions, and perhaps an informal review of the 'markable' library. An alternative to boost::optional when performance really matters. It is the second incarnation of the 'compact_optional' library that I have presented last year. The main differences from the previous version: * name change: it is called 'markable' so that it is not confused with 'optional'. It uses "mark values" and mark policies" * it has the ability to mark an empty state even for the types with strong invariants, by marking a bit pattern rather than any proper value of T (an idea by Matt Calabrese) An example use case: typedef markable<mark_int<int, -1>> opt_int; opt_int oi; opt_int o2 (2); assert (!oi.has_value());assert (o2.has_value());assert (o2.value() == 2); static_assert (sizeof(opt_int) == sizeof(int), ""); The github repository: https://github.com/akrzemi1/markable And documentation therein: https://github.com/akrzemi1/markable/tree/master/documentation Any comments, suggestions or critique are most welcome. Regards, &rzej;

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[fiber] Suggestions regarding asio
by Tatsuyuki Ishi 22 Sep '16

22 Sep '16

The current example seems non-flexible and very hacky. 1. The timer handler has no problem, since it's expected to be called from any thread. (Description in "Deeper Dive into asio" is meaningless) 2. Possible alternatives: * A post(empty lambda) is a little bit waste but solves the threading problem. It wakes up one thread by doing interrupt of epoll etc. Maybe adding a interrupt method to asio codebase could be more efficient. * One thread doing event polling and the other doing condvar is enough. Since we're not expecting a slow handler (most times, it just make a fiber ready), this should be sufficient. Correct me if I'm wrong.

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[interprocess] Improved shared_memory lifetime using file locks?
by Sebastian Theophil 21 Sep '16

21 Sep '16

Hi, coming from Windows, the filesystem persistence of basic_managed_shared_memory is giving us headaches. When we have N processes accessing the same shared memory, and one of them crashes, the other N-1 are in an undefined state. That’s the same on Windows and POSIX platforms and is ok for us. On Windows, the problem resolves itself when the other N-1 processes are all closed and then restarted, because Windows deletes the shared memory automatically. On POSIX systems, I think we can use file locks to make sure that the shared memory is reinitialized by the first process to access it. I’d appreciate any feedback, especially if it points out the problems with this approach: - basic_managed_shared_memory(boost::interprocess::open_or_create, …) opens the backing file with flags O_CREAT | O_EXLOCK | O_NONBLOCK - if that succeeds: - we are the first - (re-) initialize shared memory - also a good time to unlink/open the named POSIX semaphore that’s hanging around in an invalid state too! - degrade exclusive lock using flock(LOCK_SH) - else - open file with flag O_SHLOCK (open only, and blocking!) - when that succeeds, open shared memory Problems I can see: - Only works when (advisory) shared and exclusive locking and the degradation of one to the other is supported (at least flock not supported on Windows, e.g.) - What about other file systems? NFS? - Somebody could lock all your files. (OTOH, sb could also delete all my backing files all the time. My application would run, but not have any shared memory. Might be an advantage that my application does *not* run when the file is locked.) - What else? Is this worth implementing in boost.interprocess? I appreciate any feedback, Sebastian PS: I’ve googled previous discussions about shared memory lifetime in boost.interprocess. I don’t claim that my proposal gives the same semantics as Windows shared memory. It doesn’t and it seems impossible to achieve. I’m looking for, erm, usable semantics on POSIX systems. Clearly, everybody has to implement some lifetime tracking. It would be nice if boost.interprocess provided one or more solutions. -- Dr. Sebastian Theophil | stheophil(a)think-cell.com Senior Software Engineer We are looking for C++ Developers: https://www.think-cell.com/career think-cell Software GmbH | Chausseestr. 8/E | 10115 Berlin | Germany https://www.think-cell.com | phone +49 30 666473-10 | US phone +1 800 891 8091 Amtsgericht Berlin-Charlottenburg, HRB 180042 Directors: Dr. Markus Hannebauer, Dr. Arno Schödl

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[release] 1.62.0 Master branch is closed
by Rene Rivera 21 Sep '16

21 Sep '16

The master branch is now closed for all changes, except by permission from a release manager. Thanks, The Release Team -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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[release] Boost 1.62.0. Beta 2
by Rene Rivera 20 Sep '16

20 Sep '16

The packages for 1.62.0 beta 2 are now available: <https://sourceforge.net/projects/boost/files/boost/1.62.0.beta.2/> The SHA256 checksums are as follows: 95feae3620b3e604e93f14d97195fc04a4b67063692859af8df19657d41b82d5 boost_1_62_0_b2.7z 27bc9b328ff73d7dbf80cd9d4b5f79b0878221e5d8e4b6c47444b135edc1080a boost_1_62_0_b2.tar.bz2 3939d5efa683449e87b374d7e92e3eeb6490063ddb2877919f0fad26e3a0f53e boost_1_62_0_b2.tar.gz cff9ab5db0928244c4c836cf3da5140e6e93db7756e2791ba99a21104ad3aa72 boost_1_62_0_b2.zip As always, the release managers would appreciate it if you download the archive of your choice and give building and using it a try. Please report both success and failure, and anything else that is noteworthy. Thanks! -- The release managers -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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Re: [boost] first steps to submitting - boost :: observers
by Bjorn Reese 19 Sep '16

19 Sep '16

On 09/17/2016 08:10 PM, Robert McInnis wrote: > https://github.com/tiny/boost_observers.git What are the advantages of this library over Boost.Signals2 [1]? Same question with regards to the Boost.Synapse [2] proposal. My impression from a brief look at your repository is that you need to focus more on thread-safety. Is there any way to avoid the overhead of thread synchronization in a single-threaded application? Observers are invoked while the mutex is locked, so observers cannot make calls on the subject. How does the lock-free mutex perform, especially when congested? Why is the lock-free mutex recursive? There are several member variables that are used as if they are atomic but they are not declared as such, e.g. Subject::_block, Numeric<T>::_x (think T == long long.) The Scope template can be replaced by lock_guard if you model the LockFreeMutex after the BasicLockable concept [3]. The thread_self() and thread_pid() functions can be replaced by this_thread::get_id(). Replace the hAtomic macro with a type alias. Use <cstdint> instead of <stdint.h> to reduce polution of the global namespace. [1] http://www.boost.org/doc/html/signals2.html [2] http://zajo.github.io/boost-synapse/ [3] http://en.cppreference.com/w/cpp/concept/BasicLockable

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[density] version 7
by Giuseppe Campana 19 Sep '16

19 Sep '16

Hi to all, I’ve just merged to the master branch a major review of density, an header-only library of heterogeneous dense containers. Unfortunately this update includes some renamings. Anyway the new names are simpler and more explicative: heterogeneous_array, heterogeneous_queue, function_queue, lifo_array. The update consists of fixes and optimizations. The results of the benchmarks are included in the documentation. The container function_queue gives the best results, being many times faster than an std::queue of std::function’s (http://peggysansonetti.it/tech/density/html/func_queue_bench.html) The library is not yet ready for asking a formal review, but hopefully it will be in a few months. Html overview (now a little more schematic) and reference doc at http://peggysansonetti.it/tech/density/html/index.html Repository at https://github.com/giucamp/density/tree/master Giuseppe Campana.

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Fuzzy string search to the Boost String Algortihm
by Зайцев Александр 19 Sep '16

19 Sep '16

Hello. I want to discuss about some proposals. I am working on Levenshtein distance and Damerau-Levenshtein distance algortihms. I hope, that these implementations will be pulled to the Boost String library. But i think that we can add to the Boost String Library some more algorithms for fuzzy searhing. I mean these algortihms: Levenshtein distance Damerau-Levenshtein distance Bitap algorithm with modifications by Wu and Manber Spell-checker method N-gram method Signature hashing method BK-trees What do you think about this idea? If you think that it can be implemented to the Boost String Algo, i will start work on this list immediately. Best regards, Zaitsev Alexander.

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first steps to submitting - boost :: observers
by Robert McInnis 19 Sep '16

19 Sep '16

G'afternoon, This is my first time submitting to a public repo, please be gentle I'd like to submit a series of classes I have been using since '90. The initial set implements a thread safe subject/observer pattern. I have included a handful of example programs, two fairly trivial and the third more in-depth. All examples are single file examples to make compilation trivial. This is the first re-work of my original tools, making them more boost-friendly. I expect to add more default observer templates and observable objects, but that will come with time. WHY? -- The reason for these classes is to help insure the mathematical integrity of your data model in relation to your business rules. If at any time you were to change one of your data elements without updating all those dependent on it, then your data integrity would be compromised. These classes look to solve that. As an example: -- using namespace boost::observers ; Numeric<long> x, y, z ; // rules: y = x + 2; z = y * 3 ; x = 5 ; printf( "%d \n", z ) ; x = 1 ; printf( "%d \n", z ) ; -- Setting the rules properly, the classes allow for 'z' to be correct each time it's printed using code almost exactly like this. This will remove the possibility of accidently forgetting to trigger the rule update. WHERE? -- The repo can be found here: git clone https://github.com/tiny/boost_observers.git Any input on how to continue from this point would also be much appreciated. I have skype and ventrilo servers available if that helps. Thanks in advance, Rob -- Robert McInnis

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