April 2013 - Boost - lists.boost.org

library to support async/await pattern
by Valentin Milea 21 Apr '13

21 Apr '13

Is there interest for a coroutine-based library to make asynchronous APIs easier to deal with? Typically, for each task there is cruft: chaining callbacks, managing intermediate state and error codes (since exceptions don't fit this model). The code flow get inverted and becomes difficult to follow. Recent versions of F# and C# solve this problem. They implement an await operator that effectively suspends the executing method until a task completes. The compiler takes care of transforming subsequent code into a continuation. Everything runs on the main thread, with asynchronous methods spending most time awaiting. N3328 proposes resumable functions of this kind in C++. For an immediate solution we could leverage the Boost.Context/Coroutine library. The resulting code may look like this: try { task = do_a_async(...) // yield until task done task.await(); } catch (const some_exception& e) { // exceptions arrive in awaiting context } // normal code flow for (auto& task : tasks1) { task.await(); } taskAny = await_any(tasks2); taskAny.await(); ... There needs to be a representation for Awaitable tasks (similar to std::future but non-blocking). The other requirement is to have a Scheduler (run loop) in order to weave between coroutines. Benefits: - normal code flow: plain conditionals, loops, exceptions, RAII - algorithm state tracked on coroutine stack - async tasks are composable - any async API can be wrapped Cons: - must wrap async APIs (e.g. Boost.Asio) - needs std::exception_ptr to dispatch exceptions - stackful coroutines are sometimes difficult to debug I wrote an open-source library that does this: https://github.com/vmilea/CppAwait. It's far from Boost style but the concept looks sane. For a comparison between async patterns please see: https://github.com/vmilea/CppAwait/blob/master/Examples/ex_stockClient.cpp Making a Boost version would involve serious redesign. So is this worth pursuing? Thanks!

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Re: [boost] GSoC: More mentors?
by Christopher Kormanyos 21 Apr '13

21 Apr '13

> From Monday on students can apply for GSoC projects. > Mentors can already apply at > <https://google-melange.appspot.com/gsoc/homepage/google/gsoc2013>. > So far we have four possible mentors (for uBLAS, odeint, > graph and benchmark). Are there others who would like > to mentor? Then please pick a project from > <https://svn.boost.org/trac/boost/wiki/SoC2013> or propose > your own. > Thank you, Boris Hello, Christopher Kormanyos (who is me) just signed up as a potential mentor for the GSoC projects with Boost.Math and Boost.Multiprecision. We have already had contact with some good candidates. Thank you. Sincerely, Chris.

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GSOC - Boost.uBLAS interest
by deck léa 21 Apr '13

21 Apr '13

Hi Boost C++ Team ! My name is Lea Deck, I'm French and I study in fourth year in computer science (security in computer science), but I really like mathematics. So I look for projects that mix the two. I would be interesting in adding new mathematics properties to your uBLAS libraries, like Hadamard, Toeplitz and Block matrices, the generation of matrices, Strassen multiplications and possibly new algorithms. You also alluded to the Bernoulli numbers, but I don't see any mention in the list of new features. Is the project still available? If so, should its implementation also contain the Bernoulli polynomials? About the question of optimisation, I have some skills in Cuda (GPU) and OpenMP and so in parallelization of code. So I am able to produce a correct parallelized code. Also, my knowledge of C++ is beginning to spread to the use of C++11 ( including unordered structure map). One last question, what do you mean by "Pretty display" in your list of new features? My CV is available here <http://dla.immortal-pc.info/>. ( http://dla.immortal-pc.info/) Thank you for taking the time to read my e-mail, and I look forward to receive a response from you. With regards, DECK Léa

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[GSoC 2013] SVN?
by Vicente J. Botet Escriba 21 Apr '13

21 Apr '13

Hi, would all the GSoC projects be stored under SVN? Best, Vicente

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Qustion about GSOC Project
by Hardy Huang 20 Apr '13

20 Apr '13

Hi, there. I am a graduate student in Peking University. I have known Boost library for long. And I used it for several times. This year I wanted to get involved in GSOC, and I was happy when I see Boost in the list, it is my dream and it will be honor to contribute to such a powerful library. Since I am good at algorithm and data structure, knowing that there are some idea projects relative with algorithm and data structure, like radix sort, trie, I want to know something detail about the plan to develop algorithm and data structure. Thanks, I am expecting to receive some useful replies.

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Re: [boost] [config][mpl][type_traits][integer] BOOST_STATIC_CONSTANT should use constexpr
by Vicente J. Botet Escriba 20 Apr '13

20 Apr '13

Le 20/04/13 14:33, Vicente J. Botet Escriba a écrit : > Le 20/04/13 13:18, Antony Polukhin a écrit : >> 2013/4/20 John Maddock<boost.regex(a)virgin.net>: >> <...> >>> No that's correct as is: >>> >>> * if BOOST_NO_INCLASS_MEMBER_INITIALIZATION is defined, then the constant is >>> really an enum and there should be no out-of-line definitions. >>> * if BOOST_NO_INCLASS_MEMBER_INITIALIZATION is *not* defined, then the >>> constant *should* have the out-of-line definition in case it's address is >>> taken/used. >> Oh, now I see, thanks. >> >>> As for the original question, this is such a pervasive breaking change, I >>> think a new macro is inevitable I'm afraid :-( >> New macro will do exactly what the old macro did, but using C++11 >> feature. Code in all Boost libraries will be changed to use new macro. >> So the old macro will be required only for users code that use macro >> and attempts to take address of constant... >> >> To me, it looks less obscuring to have one macro and a note for users >> to use BOOST_CONSTEXPR_OR_CONST for out-of-line definition; than two >> macro (which one shall be used by default?) that do the same thing but >> very slightly differ in details. >> > Just to add some information about some uses > > grep -r BOOST_NO_INCLASS_MEMBER_INITIALIZATION * | wc -l > 113 > grep -r BOOST_STATIC_CONST * | wc -l > 6598 > The figures are a little bit better :) grep -r BOOST_STATIC_CONSTANT * | grep -v svn | wc -l 3030 grep -r BOOST_NO_INCLASS_MEMBER_INITIALIZATION * | grep -v svn | wc -l 57 Best, Vicente

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Trac: Add ref library
by Vicente J. Botet Escriba 20 Apr '13

20 Apr '13

Hi, Boost.Ref is not included as a library on the Trac system. Coul dit be added? Best, Vicente

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[log] Permission to merge to trunk
by Andrey Semashev 20 Apr '13

20 Apr '13

Hi, I'd like to ask for permission to merge Boost.Log v2 to Boost trunk. The library has passed the review back in 2010 and was provisionally accepted [1]. It has been reworked since then, and in a few recent posts I described the changes [2][3]. [1] http://lists.boost.org/boost-announce/2010/03/0256.php [2] http://thread.gmane.org/gmane.comp.lib.boost.devel/237748 [3] http://thread.gmane.org/gmane.comp.lib.boost.devel/239313

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Google Summer of Code - 2013: Boost C++ Libraries
by Ketan Akade 20 Apr '13

20 Apr '13

Hi, I am Ketan Akade, Graduate student at University of Southern California. I am majoring in Computer Science. I went through the project ideas of Boost C++ Libraries, and would like to work on it. I am particularly interested in the *Boost.uBLAS* project idea which is unifying representation of vector and matrices into a unique matrix class. Could you please let me know further details of the same? What steps should I take to start on this? PFA project proposal in which I have mentioned my academic and technical background. Thanks and regards, Ketan Akade Graduate Student, University of Southern California.

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[gsoc 2013] chrono::date
by Anurag Kalia 20 Apr '13

20 Apr '13

I saw the chrono::date library proposal in the ideas page of gsoc 2013. It already seems quite solid and fleshed out; I am confident that I have understood it and can carry it out. Here it is for reference: <http://tinyurl.com/ct4tc3m> I have a few questions though. 1) Is this proposal in its final stages? The Boost chrono library docs mention in appendices that they intend to implement it in later releases. What I want to ask is if I am allowed to propose changes in the library if I want to. For example, the proposal proposes that adding a year to 'Feb 29' (leap year) should result in 'Feb 28 of next year' (non-leap year). I tend to think this is counter-intuitive. The author already gives the excellent idea of using a syntax like "last/february/2013" which also covers the case of anniversaries falling on 'Feb 29' pretty well. Moreover, it is a pretty big assumption that a person would want to celebrate the 'Feb 29' anniversaries on 'Feb 28' and not on 'Mar 1'. Moreover, adding a month to '31 January' results in an invalid date (31 February). Why shouldn't we mirror the behaviour for years? We can just make a library function to cover this issue. In short, am I allowed to propose such changes? 2) How should I apply for gsoc now that I have found my area of interest? What is the last date of application? Shall I post a draft of my application here first for review before submitting it officially? Am I allowed to? 3) I have my final examinations scheduled during three weeks in the coming month of May after which I am totally free to pursue gsoc internship. Though I will use this time to research for design and implementations of other similar libraries, I would still need to channel much time into my examinations. How am I supposed to circumvent this conflict, given that I do have ample time to dedicate to my internship later on? Thanks.Anurag.

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