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[GSOC] Are we going to participate?
by Antony Polukhin 02 May '13

02 May '13

Hi all, Today starts Google Summer of Code. Is Boost community will become one of the mentoring organizations? What project ideas are we proposing? (As for me, I'd love to see unique_ptr+unique_array implemented using Boost.Move; C++11 features support for MPL, Fusion, Graph, Bind, Optional; BTree library; library for getting system info) -- Best regards, Antony Polukhin

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[Log] Plans to use std::thread?
by Rich E 01 May '13

01 May '13

Hi all, As I've been testing out the newly added Boost.Log library, I noticed it is relying on Boost.Thread even when the C++11 <thread> library is present. Are there any plans to allow the native <thread> library to be used when it is available? I think this can be done with Boost.Config's BOOST_NO_CXX11_HDR_THREAD macro. Thanks, Rich

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Re: [boost] GSoC Boost.Multiprecision project
by Jyotesh Choudhari 01 May '13

01 May '13

Hello, > Hi Jyotesh. >>>> Looking at the project description, I think >>>> I have understood what needs to be implemented >>>> in this project. > Yes, you seem to have a good grasp of the issues. > Good work. >>>> I have also gone through the current >>>> code cpp_bin_float.hpp and I have understood some >>>> part of it. I want to know how >>>> detailed should my proposal be? What details >>>> should I include in my proposal? >>>> What should be the deliverables for the project? > Go ahead and add some details from cpp_bin_float > if you like. You can mention that this is a potential > solution method. Thank you for your valuable feedback. I have written project proposal for the first time in my life. So, I did not know what details to include. I have made some changes to my proposal as per your suggestions. > Other than that, I believe you have found > the right level of detail, with a few more suggestions > from my side below. >> I have attached my proposal with this mail. >> Please have a look at it and let me know your feedback. >> Thanks and regards, > I suggest you move the FFT algorithms to an optional > part, add a bit more time for the elementary transcendental > functions, and add some time for testing the various > milestones in the project. > After that, you should start submitting your proposal. > As far as I know, you can modify your proposal up > to May 03. I have written FFT algorithm as an optional algorithm now and made some changes to schedule. Please let me know if it is fine now. > Keep up the good work. > Sincerely, Chris I was studying the code for cpp_bin_float and I have some doubts in my mind. 1. What are eval_ops_signed_type, eval_ops_unsigned_type and eval_ops_float_type? 2. What is the use of following lines? typedef mpl::list<eval_ops_signed_type> signed_types; typedef mpl::list<eval_ops_unsigned_type> unsigned_types; typedef mpl::list<eval_ops_float_type> float_types; These are not used in the class elsewhere. Similar lines are present in cpp_dec_float.hpp also and not used elsewhere in the class. 3. In the function from_float_type, I think the variable number_of_digits should be initialized to zero before using it in while loop. Lastly, I have seen on mailing list, that some of the students are submitting code samples. As I am busy with my end-semester exams and R&D project, I am not able to send any sample code. As soon as I get free, I will send it. Thanks and regards, Jyotesh Choudhari

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[gsoc-13][proposal] Boost.uBLAS
by Aditya Avinash 01 May '13

01 May '13

Hi, I have a proposal for boost in gsoc-13 under boost.ublas *Proposal: SIMD abstraction for uBlas.* - I want to develop SIMD abstraction for uBlas. Goal 1: Develop the Intel SSE & AVX backend for SIMD abstraction in uBLAS. Goal 2: Develop AMD SSE backend for SIMD abstraction in uBLAS. Goal 3: Develop frontend for SIMD abstraction in C++. Goal 4: Joining of frontend and backend, so the the code is flexible to implement on both AMD and INTEL. Goal 5: Develop the ARM-NEON backend for SIMD abstraction in uBLAS. (if time permits). -- ---------------- Atluri Aditya Avinash, India.

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Re: [boost] [gsoc-2013] Boost.Thread/ThreadPool project
by Niall Douglas 01 May '13

01 May '13

> Le 29/04/13 21:35, Niall Douglas a ?crit : > > No major changes to the C++11 futures API is needed. Rather that a > > different, but compatible, optimized implementation of future<> gets > > returned when used from a central asynchronous dispatcher. So the C++ > > standard remains in force, only the underlying implementation is more > > optimal. > > 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. > 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. > > Futures come in because you'd naturally use std::packaged_task<> with > > Boost.ASIO. It returns a future. > Could you point me to the Networking paper proposal that has > packaged_task<> on its user interface. I would expect this to be an > implementation detail. You misunderstand me. *If* you want Boost.ASIO to dispatch unknown std::function<>, *then* std::packaged_task<> is the most obvious route forwards. And the correct way to pass a value from one execution context to another is std::future<>. This includes the single threaded case e.g. when going through a C++ -> C -> C++ transition as a stack unwinds. > > For reference, the AFSIO/AFIO project is *not* a threadpool. It's a batch > > asynchronous execution engine based on Boost.ASIO that lets you chain, in > > vast numbers, huge arrays of std::function<> whose returns are fetched using > > std::future<> to be executed asynchronously according to specified > > dependencies e.g. if A and B and C, then D, then E-G. That sort of thing. > So the thread pool you need is an internal one that is adapted to you > particular needs, isn't it? I think you don't understand what Boost.ASIO is or how it works. 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. So is my thread pool an internal one adapted to my particular needs? In the sense I need not use threads at all, yes. In the sense that boost::asio::io_service's use scenario is inviolate, no. Boost.ASIO has its API, and you have to use it. And Boost.ASIO's API will be similar to the TR2 networking API. There is nothing stopping a person merging a Boost.ASIO managed thread pool with a traditional thread pool. I would struggle to see the use case though - this would an excellent thought project actually which would benefit any Boost.ThreadPool. > > One thing presently implemented on that engine is asynchronous file i/o, but > > in the next month or two you'll hopefully see batch parallel SHA256 using > > 4-SHA256 SSE2 and NEON implementations also added to the asynchronous > > engine. The idea is that the engine is fairly generic for anywhere where you > > do need to chain lots of coroutine type items together (not that it supports > > Boost.Coroutine yet). v1 isn't particularly generic nor optimal, but I'm > > hoping with feedback from Boost that v2 in a few years' time would be much > > improved. > > > As Oliver noted you could take a look at Boost.Fiber and Boost.Task. Right now anything Boost.Context based can't have multiple contexts simultaneously entering the kernel apart from on QNX and possibly Hurd. Therefore, for the time being, full fat threads are the only thing being considered. If kernel support ever includes coroutines or fibres, that will be eagerly added (I like coroutines, I use them a lot on Python). Note that on async i/o capable platforms multiple threads are solely used for non-async APIs like batch directory creation and batch chmod. Normal i/o gets multiplexed using completion handlers. Currently on Windows for example, threads are barely used at all. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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Re: [boost] [operators] moving forward use return by reference for compilers with proper support?
by Andrew Ho 01 May '13

01 May '13

> They do NOT apply to this scenario: > > X&& func(X&& x) { return std::move(x); } > const X& r3 = func(temporary()); // DANGLING REFERENCE > X&& r4 = func(temporary()); // DANGLING REFERENCE Hmm, I see. sub-clause of 12.2 clause 5: > The lifetime of a temporary bound to the returned value in a function return statement (6.6.3) is not extended; the temporary is destroyed at the end of the full-expression in the return statement. I presume there must be some implementation detail on why a returned temporaries' lifetime can't be extended. Too bad, looks like return by value is the best option available.

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[operators] moving forward use return by reference for compilers with proper support?
by Andrew Ho 01 May '13

01 May '13

Following some feedback I got from MS about the disparity between VS2012 and GCC/Clang in how some the lifetimes of temporaries are handled, it appears that going forward (possibly C++14) overloading operators in the same fashion as Dfrey operators should be safe. For reference, these overloads for a single argument commutative operator are: T operator OP(const T&, const T&); T&& operator OP( T&& lhs, const T& rhs); T&& operator OP( const T& lhs, T&& rhs); T&& operator OP( T&& lhs, T&& rhs); They referred me to http://www.open- std.org/jtc1/sc22/wg21/docs/papers/2012/n3337.pdf (draft of C++ standard), which in section 12.2, clause 5 says that a temporary's lifetime is extended to the lifetime of the reference it is bound to. I checked draft n3376 (latest publicly available draft as of today), and the same clause was present. This is the current behavior in VS2012 and it's likely that future compilers will support this as well. Should we start tracking which compilers do exhibit this behavior in Boost.Config and use the return by rvalue ref code if proper compiler support is available? I know these are just working drafts and can change in the future, but I can't think of a reason why they would remove this clause from the C++14 standard, or of any test cases which would cause a program to fail assuming this clause is properly implemented. We'll have to provide an implementation which supports return by value as well for compilers which don't support this clause, and possibly a third implementation for compilers which don't support move semantics at all, though I have demonstrated that Boost.Move can be used to merge these latter cases.

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GSoC 2013
by Anoop C S 30 Apr '13

30 Apr '13

I wish to participate in GSoC 2013 along with the Boost C++ libraries. I plan to take up the problem of Unified Representation of Vector and Matrix into a unique matrix class. Which of the Boost libraries are to be studied thoroughly inorder to achieve the goal. I already started reading Boost Documentation.

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[GSoC 2013] Boost.Math Bernoulli Numbers and Applications to Special Functions
by Łukasz Marecik 30 Apr '13

30 Apr '13

Hi, My name is Lukasz Marecik, I am fifth year student of Mathematics and fourth year student of Computer Science at Warsaw University. I would like to apply to Google Summer of Code 2013 project. I am interested in Bernoulli Numbers and their applications. While thinking about this project and doing some research, I collected some questions and issues, which I would like to discuss with my (potential) mentors. The answers can have strong influence at my official proposal. 1. Is (one of) the goal of this project to implement FROM SCRATCH completely new boost library, which will calculate Bernoulli Numbers ? I have already found two great C++ open-source programs: - http://www.bernoulli.org/ - http://web.maths.unsw.edu.au/~davidharvey/papers/bernmm/ They are already extremely efficient and fast (the funny thing is that they use completely different approach). Can boost project include and adapt one of them ? Why not ? 2. Are we going to implement only precise calculation of Bernoulli numbers or also Bernoulli numbers modulo p (where p is prime) ? 3. How the implementation of method of computing Bernoulli numbers will look like? Will it be a big template which works with all (reasonable) types (built-in, multiprecision) in the same way ? I was thinking for a while about this and I think it would be better to implement separately computing rational Bernoulli numbers (e.g. gmp_rational type) in a modern way: compute B_n modulo a lot of small primes and then reconstruct B_n via Chinese Remainder Theorem. This algorithm is one of the faster for this concrete type: precise rational numbers, but (in my opinion) it will be inefficient, when we want the output be built-in types. I do not know if I express precise what I want. For example: naive Akiyama–Tanigawa algorithm does not assume the type of output: the calculation can be performed at any type. Will our library work with all types in the same manner, or will our library run different algorithms and choose which one is better in this concrete case ? 4. Do I need to make my own research, reads papers about Bernoulli numbers, find the best practical algorithm and then propose it to my mentor or my mentor will help me to find and choose algorithm ? (so: Can I rely on myself only ?). Until now I have found three interesting approach: - use Chinese Remainder Theorem (described above) - use Euler's formula and the zeta-function algorithm - use completely new subquadratic algorithm (the paper was "submitted to publication", but it was not published in magazine until now ; it is online) The first two of them all already implemented and work (I think) in O(n^(2+eps)) time (it is good to mention that we need \theta(n log n) bits to represent precise number). The third one had (asymptotically) better complexity, but it goes throw a lot of complicated Maths, p-adic numbers etc and it has been not implemented yet - so it can turn out that the constant hidden in Big O notation is so big, that it is unpractical. But who knows. Do I need to discuss in my proposal different approach ? 5. Do I need to include in my proposal some words about applications to boost function: - theoretical view: where bernoulli numbers appear - practical view: how those functions are implemented now and how there will be implemented - and why they will be better ? I am sorry, that I am writing so late, but I was not sure for a long time if I want to apply ; I hope I finish my proposal in time. Kind regards, Lukasz Marecik

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[type_traits] boost::decay vs std::decay
by Agustín K-ballo Bergé 30 Apr '13

30 Apr '13

Hello, It has been pointed out before that `boost::decay` and `std::decay` are not exactly the same. The standard does remove CV qualifiers while boost doesn't. See https://svn.boost.org/trac/boost/ticket/7760 I would like to know if there is a resolution on this issue. If the difference is intentional, then I suggest a note be added to the documentation. I could prepare a patch either way. Regards, -- Agustín K-ballo Bergé.- http://talesofcpp.fusionfenix.com

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GAL (Generic Audio Library) based on GIL
by Brendon Costa 30 Apr '13

30 Apr '13

I am looking into the possibility of developing a library based on the same concepts and a similar interface to Boost.GIL call Boost.GAL. The idea is simply to define something very similar to GIL but for audio processing instead of image processing. Most of the concepts in GIL map almost 1 to 1 to audio processing as well. What are peoples thoughts on such a project? Is there anything in Boost.GIL that we have learn't from that should be done differently? --- Basic Premise --- The base concepts for GAL are described below and shown are the direct equivalents in the GIL library: * GAL.Sample ~= GIL.Channel Represents the amplitude of a single audio sample (float32, int16, ...) * GAL.SampleTime ~= GIL.Point Identifies the "time" a sample was taken (in units of the SampleRate) * GAL.Channel ~= GIL.Colour Identifies an audio channel location (FRONT_LEFT, or FRONT_RIGHT might be a channel for example) * GAL.ChannelMapping ~= GIL.Colour-space Maps channels to specific layout in memory (offset 0 is FRONT_LEFT, ...) * GAL.Frame ~= GIL.Pixel Identifies a single time slice (multiple channels for single sample point in time) * GAL.Block ~= GIL.Image Identifies a 1D sequence of Frame's * GAL.SampleRate ~= GIL.PPI I don't think GIL has this concept at the moment, but would be similar to Pixels Per Inch in the image world * GAL.Layout ~= GIL.?? This is the same in GIL and GAL the memory layout can be interleaved or not (planar for GIL) * GAL.Format ~= GIL.?? I don't think GIL has this concept at the moment but it represents the format of data without actually storing any data. It contains: - Sample type - ChannelMapping (implicitly identifies count of channels) - SampleRate - Layout

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[Boost.FixedPoint] Choose notation
by Dmitriy Gorbel 30 Apr '13

30 Apr '13

Hello, community! I propose extending the Boost Libraries to provide binary fixed-point arithmetic, within GSOC project. Fixed-point library will provide nonnegative and negatable class templates for fractional arithmetic, and cardinal and integral for integer arithmetic. In total, four class templates. Fixed-point arithmetic use more than one notation, and I want to provide several notation to make happy all. Now I plan to implement two notations - Q notation and notation from C++1y proposal. Examples: C++1y proposal notation: cardinal<16> 0 <= n < 65536 integral<4> -16 < n < 16 nonnegative<8,-4> 0 <= n < 256 in increments of 2^-4 = 1/16 negatable<16,-8> -65536 < n < 65536 in increments of 2^-8 = 1/256 Q notation: cardinal<16> 0 <= n < 65536 integral<4> -16 < n < 16 nonnegative<8, 4> 0 <= n < 256 has 4 bit for fractional part negatable<16, 8> -65536 < n < 65536 has 8 bit for fractional part Please, help me to choose default notation, propose other notation, or just make any feedback. Sincerely, Dmitriy. -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-FixedPoint-Choose-notation-tp46462… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[GSoC 2013] Moving to Boost to Boost.Move
by Vicente J. Botet Escriba 30 Apr '13

30 Apr '13

Hi, In case there are some students that are looking for a last idea. There a re a lot of Boost libraries that don't support move semantics. It would be nice if one student propose to adapt the some of the existing libraries. The idea is to use Boost.Move so that an emulation is provided for compilers not supporting rvalue references. Some of the libraries (let me know if I'm wrong are). My priority is given between [], lower numbers means higher priority. Of course others would have others priorities: C++11 * [0] Tuple or * Fusion/tuple (it seems that it support or will support c++11 move semantics but don't use Boost.Move) * [0] Bind * [1] Function * [2] SmartPtr * [8] Array ? Accepted for C++14 * [5] optional Having an active proposal for C++1y * [3] Heaps * [6] Any * [7] Variant Other * [4] LockFree * [9] Parameters * [10] Signals? Please help me to complete this list. Adding constexpre and noexcept would be welcome also. Best, Vicente

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Re: [boost] [gsoc-2013] Boost.Thread/ThreadPool project
by Niall Douglas 30 Apr '13

30 Apr '13

> > There are many ways systemically of implementing futures. The way you > > and Anthony have taken to date is a non-intrusive approach such that > > futures stand alone. This is great for not forcing design onto third > > parties and is a decentralised POSIX-y approach, but it comes with > > significant performance and memory costs because it's hard to get > > standalone, non-intrusive futures to batch themselves without > > sacrificing performance. > > I have no merit here. This is the approach the standard has defined futures. No major changes to the C++11 futures API is needed. Rather that a different, but compatible, optimized implementation of future<> gets returned when used from a central asynchronous dispatcher. So the C++ standard remains in force, only the underlying implementation is more optimal. > > An alternative approach is to assume a central dispatcher/event loop > > which can optimize then() chaining because it knows of all futures and > > their relationships currently in flight (this is a much more > > centralized statist NT-y approach, and it you can see that philosophy > > clearly in Microsoft's N3428). You can see an example of this approach > > to implementing future chaining with multiple dependencies which > > extends Boost.ASIO in > > https://github.com/ned14/TripleGit/blob/master/triplegit/include/async > > _file_ io.hpp#L785. I also went ahead and implemented N3428's > > when_all() which returns a future chained to multiple input futures, > > not that I claim the implementation mature yet. > > I don't know ASIO enough to understand the advantages or liabilities. > While a central dispatcher/event loop could be useful for some applications > other need more concurrency. > I'll need to take a deep look at ASIO when I would have enough time. I know you'll have studied Microsoft's N3428 in depth. Their proposal is quite trivial to implement when you have an NT kernel to hand where the kernel directly manages all multithreading primitives and there is a top quality APC implementation. Implementing N3428 without a NT kernel to hand is very considerably harder, indeed there are many, many gotchas as I know you know. Even then() is tricky, because code called from then() needs two main call forms, asynchronous and synchronous (i.e. the original object completes only after type B then() completes, whereas type A then() lets the original complete first). Not introducing race conditions is quite hard (for me at least). > > My concern with Boost.ThreadPool right now is that it could get in the > > way of the latter approach. I have zero objection to a formulation > > which embraces both approaches, but when you ask why a thread pool > > isn't in the standard, I think it's because until we've fixed futures > > implementation and all the composibility and chaining we're sure we > > need, and made sure that interops smoothly with the forthcoming TR2 > > networking proposal, then and only then is it wise to proceed with > > threadpool design. > > I'm not aware of the TR2 networking proposal needs respect to futures or > thread pool. Again I'll take a look to the current proposals. Futures come in because you'd naturally use std::packaged_task<> with Boost.ASIO. It returns a future. > > All that said, this is purely a cautious opinion of mine. You're one > > of the Boost.Thread maintainers, so I happily defer to your judgment > > on this. If you think we need a threadpool now, you'll find no > > opposition from me. > > If IIUC you are not suggesting that the student uses the ASIO approach, but that > it is not time to solve the thread_pool now. Could you confirm? > If yes, could you tell me what is blocking that we can not try to solve? We ought to finish N3428 for pure POSIX first. During implementation, you will find many areas where significant optimization using a central dispatcher become possible. Specialisations of N3428 for some arbitrary central dispatcher might be worth prototyping as a thought exercise. After that I see no reason to hesitate on thread_pool as it now has the type inferences available to it to have an optimal design. > I was not aware that there was a AFSIO GSoC project as described here > https://svn.boost.org/trac/boost/wiki/SoC2013#Boost.ASIO and that this > project propose also thread pool. I understand better now your concerns. I hadn't announced it to this list for various reasons. Hopefully I'll have news there soon. For reference, the AFSIO/AFIO project is *not* a threadpool. It's a batch asynchronous execution engine based on Boost.ASIO that lets you chain, in vast numbers, huge arrays of std::function<> whose returns are fetched using std::future<> to be executed asynchronously according to specified dependencies e.g. if A and B and C, then D, then E-G. That sort of thing. One thing presently implemented on that engine is asynchronous file i/o, but in the next month or two you'll hopefully see batch parallel SHA256 using 4-SHA256 SSE2 and NEON implementations also added to the asynchronous engine. The idea is that the engine is fairly generic for anywhere where you do need to chain lots of coroutine type items together (not that it supports Boost.Coroutine yet). v1 isn't particularly generic nor optimal, but I'm hoping with feedback from Boost that v2 in a few years' time would be much improved. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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[iterator] Is there general const_iterator adaptor?
by TONGARI 30 Apr '13

30 Apr '13

Hi folks, I wonder if there's a general const_iterator adaptor that transforms any iterator to a const one: template<class Iterator> struct const_iterator : iterator_adaptor < const_iterator<Iterator>, Iterator , typename iterator_value<Iterator>::type const > { const_iterator() {} const_iterator(Iterator const& base) : const_iterator::iterator_adaptor_(base) {} }; Which is simple but handy for use in that we don't have to make 2 versions for both const & non-const iterators each time we make a container. Does Boost offer this which I missed somewhere, or would you think it's a good idea to add? Thanks

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GSOC 2013
by Razvan Florea 29 Apr '13

29 Apr '13

Hello, I'm a student interested in working on odeint project this summer in GSOC. In the last weeks I spoke with Mario Mulansky about my ideas. After he gave me a task in order to accustom with odeint project, I started building my proposal. He suggested me to put my first version of proposal on the mailing list to get feedback or some advice about what should I change. Is this the right mailing list to share my proposal? If yes, how should I share my proposal with you? Should I put on melange or can I put it on a google doc and give you a link to it? Have a nice day, Razvan

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Re: [boost] hi
by dominic ibeme 29 Apr '13

29 Apr '13

http://expecthead.com/wp-content/plugins/wp-plugin-repo-stats/china.php?ygf… \\\\\\ The improver of knowledge absolutely refuses to acknowledge authority, as such. For him, skepticism is the highest of duties, blind faith the one unpardonable sin. -- Thomas Huxley (1866)

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Re: [boost] [gsoc-2013] Boost.Thread/ThreadPool project
by Niall Douglas 29 Apr '13

29 Apr '13

> > I'm not ruling out the merit of a Boost.Thread threadpool. For me > > personally though, the hurdle is very significantly raised: you need > > to strongly prove to me why your proposed thread pool is much superior > > to a Boost.ASIO based threadpool. Otherwise I will zero score the GSoC > > proposal, because in the end we need other proposed projects more. > This is your right, but I don't know how the fact you can write easily the thread > pool you need to diminish a generic thread pool working well with futures. > [snip] > Hopping this helps you to understand the project I'm looking for. There are many ways systemically of implementing futures. The way you and Anthony have taken to date is a non-intrusive approach such that futures stand alone. This is great for not forcing design onto third parties and is a decentralised POSIX-y approach, but it comes with significant performance and memory costs because it's hard to get standalone, non-intrusive futures to batch themselves without sacrificing performance. An alternative approach is to assume a central dispatcher/event loop which can optimize then() chaining because it knows of all futures and their relationships currently in flight (this is a much more centralized statist NT-y approach, and it you can see that philosophy clearly in Microsoft's N3428). You can see an example of this approach to implementing future chaining with multiple dependencies which extends Boost.ASIO in https://github.com/ned14/TripleGit/blob/master/triplegit/include/async_file_ io.hpp#L785. I also went ahead and implemented N3428's when_all() which returns a future chained to multiple input futures, not that I claim the implementation mature yet. My concern with Boost.ThreadPool right now is that it could get in the way of the latter approach. I have zero objection to a formulation which embraces both approaches, but when you ask why a thread pool isn't in the standard, I think it's because until we've fixed futures implementation and all the composibility and chaining we're sure we need, and made sure that interops smoothly with the forthcoming TR2 networking proposal, then and only then is it wise to proceed with threadpool design. All that said, this is purely a cautious opinion of mine. You're one of the Boost.Thread maintainers, so I happily defer to your judgment on this. If you think we need a threadpool now, you'll find no opposition from me. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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[interprocess] [container] Can iterator hold raw-pointer instead of offset_ptr?
by TONGARI 29 Apr '13

29 Apr '13

Hi there, When putting containers in shared memory, offset_ptr is used internally, and IIUC, the iterator of the container will also use offset_ptr. But it seems to me that in most cases we only use iterator locally rather than putting those iterators in shared memory as well, so the plain-old-raw-pointer is sufficient and hopefully more efficient for iterator's usage. What do you think?

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[gsoc 2013] Approximate string matching
by Jan Strnad 29 Apr '13

29 Apr '13

Hi, I'm Jan Strnad, currently a Master's student at CTU in Prague, Czech Republic. This summer, I would like to participate in GSOC and I believe that approximate string matching is a good match for me, since my background i this area is quite strong. Now more specifically. I would like to implement approximate string matching algorithm(s) based on the NFA. I would like to support various approximate distances, such as Hamming distance [1], Levenstein distance [2], Damerau-Levenstein distance [3], Delta distance, Gamma distance and finally (delta, gamma) distance. Sorry no explanation of the last three found on the Web, but I can provide one if interested. In the matter of NFA implementation, I would probably choose dynamic programming approach, but I'm thinking of shift-or algorithm as well. Can I ask you for any kind of thoughts or feedback regarding this topic? Best regards, Jan Strnad [1] http://en.wikipedia.org/wiki/Hamming_distance [2] http://en.wikipedia.org/wiki/Levenstein_distance [3] http://en.wikipedia.org/wiki/Damerau%E2%80%93Levenshtein_distance

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[Property Map] put_get_helper, keys are passed by value
by ilker 29 Apr '13

29 Apr '13

Hello, I require a pm which returns passed key (itself or a 'part' of it) as mapped value. For this purpose I wrote another helper since boost::put_get_helper's put function passes keys by value. // Pasted as a reminder template <class PropertyMap, class Reference, class K, class V> inline void put(const put_get_helper<Reference, PropertyMap>& pa, K k, const V& v) { static_cast<const PropertyMap&>(pa)[k] = v; } Is there any way to accomplish this by not introducing another custom helper ? (may be there already something similar exists in boost) Thanks. -- View this message in context: http://boost.2283326.n4.nabble.com/Property-Map-put-get-helper-keys-are-pas… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[operators] What is the correct overload set for a binary operator?
by Daniel Frey 28 Apr '13

28 Apr '13

Hi, after some more experiments, I convinced myself that I should explore the option of returning an rvalue (not an rvalue reference) in all cases when implementing operator+ based on operator+= (as an example). But I wonder what the most efficient overload set would look like. With this post I'll concentrate on same-type operations (T+T). Given a class T with operator+= like this: T& T::operator+=( const T& ); T& T::operator+=( T&& ); // if useful the class provides it and it should be used if applicable I think the following is currently the best overload set for operators: T operator+( T lhs, const T& rhs ) { lhs += rhs; return lhs; // no std::move needed } T operator+( T&& lhs, T&& rhs ) { lhs += std::move( rhs ); return std::move( lhs ); } T operator+( const T& lhs, T&& rhs ) { #ifdef COMMUTATIVE rhs += lhs; return std::move( rhs ); #else T nrv( lhs ); nrv += std::move( rhs ); return nrv; #endif } I tested this with the following expressions with both COMMUTATIVE defined and not defined: T a, b, c; // initialized to something T r1 = a + b + c; T r2 = a + ( b + c ); T r3 = ( a + b ) + ( b + c ); and with both GCC 4.7.3 and Clang 3.2. Could someone please test this with VC++? (complete code below) Generally: Any thoughts? Examples of expressions where and how it could be improved? Theoretical improvements are also welcome, but please mark them as such and always test your code to prevent pessimizations in practice! One remarks about the proposed full version of operators2.hpp: Andrew, I really appreciate your work and enthusiasm, but please understand that IMHO this needs to be done step-by-step and much more slowly than you probably hope for. Let's figure out the proper overload set for T+T first, then T+U/U+T (again both commutative and non-commutative), noexpect-specifier for all overloads, etc. After that, we need to decide on whether or not to improve the existing operator library or to provide an independent V2. This might include rethinking the grouped templates. Using Boost.Move might help with the implementation or not, depending on what overload set we want/need. It all needs tests and documentation and it will be quite some work… hope you and others are still with me on this :) Best regards, Daniel Here's the complete test code I used: #include <iostream> #include <utility> struct MyClass { MyClass() { std::cout << "MyClass::MyClass()" << std::endl; } MyClass( const MyClass& ) { std::cout << "MyClass::MyClass( const MyClass& ) COPY" << std::endl; } MyClass( MyClass&& ) { std::cout << "MyClass::MyClass( MyClass&& ) move" << std::endl; } ~MyClass() { std::cout << "MyClass::~MyClass()" << std::endl; } MyClass& operator+=( const MyClass& ) { std::cout << "MyClass::operator+=( const MyClass& ) +=" << std::endl; return *this; } MyClass& operator+=( MyClass&& ) { std::cout << "MyClass::operator+=( MyClass&& ) += &&" << std::endl; return *this; } }; MyClass operator+( MyClass lhs, const MyClass& rhs ) { lhs += rhs; return lhs; } MyClass operator+( MyClass&& lhs, MyClass&& rhs ) { lhs += std::move( rhs ); return std::move( lhs ); } // #define COMMUTATIVE MyClass operator+( const MyClass& lhs, MyClass&& rhs ) { #ifdef COMMUTATIVE rhs += lhs; return std::move( rhs ); #else MyClass nrv( lhs ); nrv += std::move( rhs ); return nrv; #endif } int main() { MyClass a, b, c; std::cout << "--- r1" << std::endl; MyClass r1 = a + b + c; std::cout << "--- r2" << std::endl; MyClass r2 = a + ( b + c ); std::cout << "--- r3" << std::endl; MyClass r3 = ( a + b ) + ( b + c ); std::cout << "--- done" << std::endl; }

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GSOC 2013
by Dmitriy 28 Apr '13

28 Apr '13

Hi folks! I am Dmitriy Gorbel, a computer science student at the Kharkiv Polytechnic University from Ukraine. I browsed Boost C++ Libraries home page for GSoC and I want to propose a project to implement of a Fixed Point library. I read open standard on open-std.org http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3352.html and tried implementation by Vicente J. Botet Escriba at the https://svn.boost.org/svn/boost/sandbox/fixed_point/ Now I prepare my proposal. So I will take implementation by Vicente J. Botet Escriba in the first place, and I found few more simple implementations, but can anyone advise me other implementations of Fixed Point arithmetic, which I must pay attention? Not necessarily in C++, pure C also would be good. Thanks

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Re: [boost] [GSOC] XML library of Boost
by Amos Ji 28 Apr '13

28 Apr '13

On Apr 28, 2013, at 12:11 PM, Andrey Semashev <andrey.semashev(a)gmail.com> wrote: > On Monday 29 April 2013 02:08:01 Amos Ji wrote: >> Hi All, >> >> I'm a graduate student from Fudan University in China. And I hope to >> contribute some code to Boost during the GSOC. >> >> I've scanned the idea page. The ideas in the page are all very interesting >> and challenging. But what I'm interested in most is XML library, which is >> at the bottom of page. I think the XML format is the most popular standard >> for storing information so it's important for Boost to have a good XML >> library. > > Agreed, a good and fast XML library would be most useful. >> In my opinion, an XML parser must be able to do these things: >> >> 1. To Iterate over DOM nodes tree; >> 2. To access the values of nodes and their attributes quickly; >> 3. To insert or delete nodes or attribute of an exact node easily; >> 4. To generate new XML from the structure which stores XML in the >> library. > > IMHO, support for SAX is also mandatory. I would even say that SAX should be > the first and the primary thing to be implemented in Boost.XML, as DOM can be > added later on top of it if the time for GSOC allows. > I agree. SAX parser will use less memory than DOM parser. I'll add it into my proposal. > You also listed support for encodings in the optional features. I agree with > it being optional with exception for Unicode. At least UTF-8 should be > supported from the very start. But that should not be a problem now that we > have Boost.Locale. I know little about Boost.Locale. I'll see how it can help support other encodings when I need. Thanks a lot for your suggestions. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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Google Summer of Code 2013
by sskytyba＠gmail.com 28 Apr '13

28 Apr '13

I’m student from Ukraine. My name is Skytyba Sergij. I want to get some information. I’m interested in such projects as Boost.uBLAS, Boost.Math Bernoulli Numbers and Applications to Special Functions (very) , Boost.Multiprecision (very) , Boost.Thread/SyncQueue, Moving Boost to Boost.Move. To whom can I send my proposal and how can I contact with mentors of these projects?

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