May 2013 - Boost - lists.boost.org

Company copyright release examples
by Brendon Costa 08 May '13

08 May '13

I am looking into asking the company I work at for an official written "release" on the copyright for work I with to contribute to boost as per the description at: http://www.boost.org/development/requirements.html I will be developing this in my own time outside of work hours but I will need this release due to clauses in my contract and the relationship that the proposed library would have to my normal work. Are there any examples of what this release should look like for boost to accept it? I think having a sample release available on the page I linked to above would be really useful. Thanks, Brendon.

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[iterator] Silent-but-deadly bug in iterator_facade category
by Gabriel Redner 08 May '13

08 May '13

Hi folks, I've stumbled across a nasty problem with iterator_facade in which code which appears correct and compiles fine can cause runtime problems. Consider an iterator_facade which just wraps a random access iterator and applies a transformation to it: char transform(int i) { return 'a'; } struct my_iterator : public boost::iterator_facade<my_iterator, char, // value_type std::random_access_iterator_tag, // *** char> // reference { my_iterator(const std::vector<int>::iterator& it) : _it(it) {} char dereference() const { return transform(*_it); } bool equal(const my_iterator& other) const { return _it == other._it; } void increment() { ++_it; } void decrement() { --_it; } void advance(int n) { std::advance(_it, n); } int distance_to(const my_iterator& other) const { return other._it - _it; } private: std::vector<int>::iterator _it; }; Now if I have an STL-style function which is overloaded on the iterator category, clearly the random-access version will be selected. template <typename TIterator> void funcImpl(TIterator it, std::input_iterator_tag) { std::cerr << "Running func treating 'it' as input iterator\n"; } template <typename TIterator> void funcImpl(TIterator it, std::random_access_iterator_tag) { std::cerr << "Running func treating 'it' as random access iterator\n"; } template <typename TIterator> void func(TIterator it) { funcImpl(it, typename std::iterator_traits<TIterator>::iterator_category()); } In the line marked ***, the docs suggest I should use boost::random_access_traversal_tag instead of std::random_access_iterator_tag - but when I do, the program no longer selects the random access version of 'func', choosing the forward-only version instead! The iterator_category of my_iterator ends up as: boost::detail::iterator_category_with_traversal<std::input_iterator_tag, boost::random_access_traversal_tag> The reason I called this a 'deadly' bug is that std::advance is suddenly a deathtrap: std::advance(it, -1); This is fine and legal for random access iterators, but if the forward-only version gets called instead, the behavior is undefined (on my system, it loops endlessly). The compiler doesn't complain either way - the problem surfaces only at runtime. Does the problem lie with iterator_category_with_traversal? It looks like it's intended in this case to be convertible to either std::input_iterator_tag or std::random_access_iterator_tag, but clearly something is wrong with the latter conversion. Any ideas? Thanks, -Gabe

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[gsoc 2013] draft proposal for chrono::date
by Anurag Kalia 07 May '13

07 May '13

Hi, I mistakenly sent this draft as a reply to personal email of Vicente. I am sorry! Here it is again, verbatim. One related question though. I still haven't got the hang of a Mailing List. Is there a software takes the pain away from it. For example, I use outlook.com and '>' get appended in front of only the start of paragraph making it wholly unreadable. Thanks, Anurag Kalia. ---------------------------------------- > Date: Sat, 27 Apr 2013 18:14:09 +0200 > From: vicente.botet(a)wanadoo.fr > CC: anurag.kalia(a)outlook.com > Subject: Re: [boost] [gsoc 2013] draft proposal for chrono::date > > Le 27/04/13 16:58, Anurag Kalia a écrit : > >> I understand that you want to design your own library, I did the same, > >> but getting a coherent design would take you some time. > >> I suggest you to start with the H. Hinnant proposal as a reference and > >> state what you want to added, changed or removes. State clearly why do > >> you want these changes, what would be improved/solved. > >> > >> Don't forget to inspect the threads/discussion related to the H.Hinnant > >> proposal, and the paper N3344 Toward a Standard C++ 'Date' Class > >> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3344.pdf > > Hi Vicente, > > > > Thanks a lot for the exhaustive reply! I will get back to you after going through all the things you pointed out and also the paper you forwarded. But I have one quick question for now, from where can I start my search for the threads and discussions around this date proposal? > > > > > > > Hi, > > There were some interesting exchanges in > https://groups.google.com/forum/?fromgroups=#!forum/kona-date-lib > > I guess that if you request to the administrator s/he will be able to > give you read access to the existing threads (there are not too much). > > Best, > Vicente > I have finally implemented some representative functions in date class and calendar to get a better idea of the proposal. I have dropped the JDN storage for another implementation that I thought of in the middle of the night. I think it is a hybrid approach between serial and field-based implementations. Off the top of my head, without any alternative implementations at hand and benchmarks too, I can't think of something inherently wrong in it. I would really like to hear its gotchas, if any. I have overhauled my proposal on the basis of it. It doesn't contain other headings like about me etc for today. I have tried to incorporate all the previous points you noted before and have also tried to keep naming consistent. I did use uppercase constants in there but they are meant to be private. Is that okay? I knew little about the benchmarks before you sent me that paper. From what I got, they just iterate over a significant period of time and note the start and ending time. Is it more than that? And should I make them before or after I have multiple implementations in hand. I could get hold of your and Howard Hinnant's implementations for them, but then the APIs would have to line up, wouldn't they? Hope you find my proposal better this time around. With an open ear, Anurag Kalia.

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[GitHelp] bootstrap.bat calls missing build.bat
by legalize+jeeves＠mail.xmission.com 07 May '13

07 May '13

[Please do not mail me a copy of your followup] OK, so I am experimenting with modular boost, following the instructions here: <https://svn.boost.org/trac/boost/wiki/TryModBoost> I cloned and did the submodule update. I didn't have CMake; is this why I experience a problem? What exactly does 'cmake -P forward_header.cmake' do? When I run boostrap.bat it fails early with an attempt to call build.bat which doesn't exist. Thanks for your time. -- "The Direct3D Graphics Pipeline" free book <http://tinyurl.com/d3d-pipeline> The Computer Graphics Museum <http://computergraphicsmuseum.org> The Terminals Wiki <http://terminals.classiccmp.org> Legalize Adulthood! (my blog) <http://legalizeadulthood.wordpress.com>

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[quickbook][random] Build under doc/ broken?
by John Maddock 07 May '13

07 May '13

I'm not sure if this is a random or quickbook issue, but building the doc build under doc/ fails with current quickbook trunk. Any ideas? Thanks, John.

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[wave] trace doesn't output errors.
by Adrian_H 07 May '13

07 May '13

I've got a really annoying and difficult to track down PP error. I'm attempting to use wave to see the expansion, but it is slow going. The output is correct, in both the g++ PP and the wave parser. g++ states: *error: macro "BOOST_PP_SEQ_ELEM_III" requires 2 arguments, but only 1 given*, wave states *warning: too few macro arguments: BOOST_PP_SEQ_ELEM_III*, but when I try using the tracer it doesn't say when this occurs. Is it possible to turn this on? Or is there no 'on' and I have to go into the wave code and code it on? If the latter, where would I do this? Thanks, Adrian -- View this message in context: http://boost.2283326.n4.nabble.com/boost-wave-trace-doesn-t-output-errors-t… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Git Modularization Ready for Review
by Niall Douglas 07 May '13

07 May '13

> After substantial work, including massive changes by me and Daniel Pfeifer to > KDE's svn->Git conversion tool, we have captured every Boost SVN commit in a > Git repository. You can view the results at > > http://github.com/boostorg > http://bitbucket.org/boostorg > > Daniel and I are ready to accept your feedback on the results of modularization, > and especially your pull requests containing edits to the ruleset. I will the > steering committee to establish a formal review period, though. I'm a bit confused. This looks like a hand written map of parts of Boost SVN onto multiple GIT repos. Am I understanding correctly? I'm far more confused as to why? Surely the conventional approach is to convert a SVN repo to GIT. Then people hive off their particular bits into submodules as and when they themselves decide and they are ready. It looks here that Boost has decided on skipping the intermediate stage and going straight to submodules. That sounds awfully fraught: it also demands a lot from those library maintainers not familiar with Git. Submodules are extremely different to SVN externals - they're a very light link, and in many occasions Git does not auto-update submodules even when you tell it (i.e. it'll fetch, but silently not checkout head if it thinks you might lose data). Also, how is Boost going to manage dependency breakage across multiple submodules? Are you planning to keep headers in one monolithic repo but keep anything resulting in a DLL/SO in a submodule? Or are you planning to break out the headers into submodules too? I can see it becoming quite easy for submodules or branches or forks thereof to get out of step with one another. I can see the present submodule heavy approach introducing a lot of anti-Git workflow because those submodules inside the boostorg organization are treated as special compared to other submodules. I'm confused. Sorry. I'm probably not making any sense. Is there a design rationale document somewhere? I can't see one up to date on Google. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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Re: [boost] Live read-only GIT mirrors of Boost trunk SVN
by Niall Douglas 07 May '13

07 May '13

> > All branches and tags, as far as I can tell, are mirrored correctly. I've > > set a cron job every 24 hours. Theoretically if we had an authors mapping > > file it would work in the opposite direction too i.e. be read-write. > > Nice. You can find a complete author mapping here: > https://github.com/ryppl/Boost2Git/blob/master/authors.txt Arse. I only rebuilt the mirror this weekend because it wasn't mirroring tags/release/* which has obvious value. Fixed now. > > My next task is to live mirror a github repo into Boost Sandbox. Currently > > SubGit segfaults on this due to the complex SVN properties auto-translation > > which requires a specially marked up .gitattributes, but the author is very > > keen to fix the problem. In theory then it ought to just work. > > > > Any mistakes in my Boost mirror, or any problems, or even thoughts are > > gratefully received. > > Don't put too much effort into this; Boost SVN->Git modularization is > just about ready for review :-) My experience with SubGit has been very, very good. I would *strongly* recommend it over git2svn. The company which develops it has been very impressive in response rate and going the extra mile to help me figure out problems. BTW Dave with much help from the same company I've figured out the opposite flow: automated Git => Boost SVN. It took a lot of trial and error to work around Boost's MIME type and EOL conventions, but you can see an exact automated mirror of https://github.com/ned14/TripleGit at http://svn.boost.org/svn/boost/sandbox/triplegit/. I had to squash history because of the MIME type problems though :( but from now on it should be live. I think it would be quite easy to set up a live perfect Git mirror of all Boost SVN, do a transition period where SVN is writeable but GIT read only, and then one day the switch is flipped and it goes the other way round. That way anyone dependent on SVN keeps on working, but without write access. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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[chrono/date] Unit specifiers arithmetic
by Vicente J. Botet Escriba 07 May '13

07 May '13

Hi, Moving from checked dates to unchecked ones by default and forcing to user the Unit specifiers year/month/day in any date constructor (even the unchecked ones) has some ugly consequences. Note that I was able to build an unchecked date as date d(2013,5,6, no_check); Given year y; month m; day d; the following will not compile now as the constructors expects a year but y+1 is an int. date d(y+1, m, d); The user needs to type date d(year(y+1), m, d); Is this what we want to provide to the user or should we add basic arithmetic on these unit specifiers? Best, Vicente

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Re: [boost] [gsoc-2013] Boost.Thread/ThreadPool project
by Niall Douglas 07 May '13

07 May '13

> Le 30/04/13 17:16, Niall Douglas a ?crit : > >> Le 29/04/13 21:35, Niall Douglas a ?crit : > >> Could you explain me what a central asynchronous dispatcher is? > > An asynchronous procedure call implementation. Here's Microsoft's: > > http://msdn.microsoft.com/en- > us/library/windows/desktop/ms681951(v=vs.85).as > > px. Here's QNX's: > http://www.qnx.com/developers/articles/article_870_1.html. > > Boost.ASIO is the same thing for Boost and C++ but implemented by > > application code. It is *not* like asynchronous POSIX signals which are a > > nearly useless subset of APCs. > I don't see the term "central asynchronous dispatcher" used in any of > the links. Could you clarify what it is? I have to admit I'm struggling to see where your block is, but Dave Abrahams often found the same with me, so it must be me. A central asynchronous dispatcher is the loop which sends callbacks/events to be invoked/processed by other execution contexts. Every OS has at least one in the kernel. Most GUI toolkits like Qt have one. Boost has at least one in the form of Boost.ASIO. The central means one execution context does the dispatch. The asynchronous means that callbacks are processed by recipients asynchronous to the dispatcher. And dispatcher, well that dispatches. > >> If not, please could you elaborate what kind of optimizations can be > >> obtained? > > If you have transactional memory in particular, you gain multi-CAS and the > > ability to (un)lock large ranges of CAS locks atomically, and a central > > dispatcher design can create batch lists of threading primitive operations > > and execute the batch at once as a transaction. Without TM, you really need > > the kernel to provide a batch syscall for threading primitives to see large > > performance gains. > I'm really lost. Multi-word Compare-And-Swap (MCAS) is one of the biggest gains from Transactional Memory. Indeed WG21 has SG5 dedicated to integrating TM into C++17. Some models of Intel's Haswell come with hardware TM assist. I'd take a reasonable guess that MCAS will benefit centralized kernel-based threading primitives architectures such as Windows NT more than decentralized threading primitive architectures such as POSIX. That said, I could see Linux using TM for batch multi-kernel-futex ops, though I'd have to say implementing that without breakage would be daunting. Either way, a central asynchronous dispatcher has information a decentralized implementation does not. That opens more scope for optimization. > > Boost.ASIO's core is boost::asio::io_service. That is its dispatcher > > implementation which each dispatch execution context being executed via > > boost::asio::io_service::run() which is effectively an event loop. Third > > parties then enqueue items to be dispatched using > > boost::asio::io_service::post(). You don't have to run Boost.ASIO using > > multiple threads: it can be single threaded. > > I could not comment until I understand what Boost.ASIO provides and it > can interact with thread_pools :( Boost.ASIO provides a per-thread capable event loop implementation. That automatically makes it an example of a thread pool manager. You may find N3562 Executors and schedulers coproposed March 2013 for Bristol by Google and Microsoft of use to you in understanding the relation between thread pools and Boost.ASIO (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3562.pdf) My proposed Boost.AFIO library is an implementation of that same N3562 idea, albeit I extend Boost.ASIO which is IMHO more C++-y whereas Google and Microsoft have gone with proprietary implementations. Also, they include timing and many other more general purpose features, and mine does not (currently) as it's mainly aimed at maximising input/ouput with highly jittery random latency storage. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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