March 2014 - Boost - lists.preview.boost.org

Post-git forking process
by Sohail Somani 29 Mar '14

29 Mar '14

Hey all, Often, I find bugs in Boost that I need to patch manually before the next release. What I used to do before was keep a copy of Boost in my source tree which made this easier: just patch it directly. This made it easy to modify, but annoying to post patches and honestly, they just got lost most of the time. With Git, it should become easier to contribute said patches as well as pull in whichever particular changes I need. However when I attempted such a fork recently, I was a bit lost. As I understood it, the process should have been: 1. Create a fork of https://github.com/boostorg/boost and use this fork in my project 2. Create a fork of the library/libraries I wanted to patch 3. Update the submodules in my boostorg/boost fork to point to my forked libraries 4. Post a pull request for the respective libraries. Once the changes have been accepted, point back to the official boostorg repo I failed terribly, no doubt due to PEBKAC. Is there a chance that someone could write a tutorial or a how-to guide for the recommended process of forking Boost with Git? The main thing I need is the ability to have a patched version of Boost that I can use while the patches are being reviewed/accepted/rejected. Thanks, Sohail

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[variant] assign and access the assigned value simultaneously
by feverzsj 28 Mar '14

28 Mar '14

hi list, for common case: boost::variant<Val,...> var; var = val; Val& v = boost::get<Val>(var); why not supply a interface like: Val& v = var.assign(val); for simplity, and the unnecessary "get" is also elimited. regards -- View this message in context: http://boost.2283326.n4.nabble.com/variant-assign-and-access-the-assigned-v… Sent from the Boost - Dev mailing list archive at Nabble.com.

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1.56 release
by Barend Gehrels 27 Mar '14

27 Mar '14

Hi, The last message about the release schedule was (if I see it correctly) at January 15, and the calendar is empty. Is there more news about the release planning? I'm especially interested in the planning for the 1.56 release. Thanks, Barend Gehrels

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[Parallel Algorithms] Queries regarding the Boost. Thread / Parallel Algorithms
by Naveen 26 Mar '14

26 Mar '14

Hi, I am look into various available reduction algorithms available to make a performance comparison for boost threads. I made a decent search on all the documents available for various reduction algorithms. If there are any specific implementations, please share the details. Regards, *NAVEEN* | Mobile: 832-720-2393 | about.me <http://about.me/naveen.namashivayam> |

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Creating a new(-ish) library in modular boost ?
by Paul A. Bristow 26 Mar '14

26 Mar '14

I have fumbled (and stumbled) trying to create a revised-possibly-to-be-proposed for Boost library in the new modular boost format. So far I have created a folder /modular-boost/svg_plot And copied all the files into it in the new modular format and got the library working OK (compiling, tests, examples, docs etc). Then I created my repository by doing I:\modular-boost\libs>git init svg_plot Initialized empty Git repository in I:/modular-boost/libs/svg_plot/.git/ Then I GIT Added various files, and committed these to my repository. (Should I have pushed?) I tried to tell git to ignore some files like log files, etc (but I don't get a .gitignore file when I think I should - the Tortoise GIT window has various options like .gitignore in the repos root, but no 'OK' button, just a close??? I have a .gitignore at /modular-boot/ but it does not contain the files to ignore (and I would not expect it to). I've set the GITHub default storage directory to \modular-boost\libs but a scan for repos only find modular-boost I went to my GITHUB page and followed the invitation to drag the svg_plot repository onto the page. Some files are listed (but ones I want to ignore) and then all options are unresponsive or greyed out and eventually GITHUB hangs and then crashes :-( So both GIT and I are confused ! Can anyone suggest what sequence of actions I should take to set this up? Thanks Paul Paul A. Bristow Prizet Farmhouse Kendal UK LA8 8AB +44 01539 561830 07714330204

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[range] Proposal: addition of front(), back(), at(), operator[]
by Adam Wulkiewicz 26 Mar '14

26 Mar '14

Hi, I propose to add the functions described below to the Boost.Range. I found the use of those very convenient WRT the corresponding use of begin() and end(), and a lot more readable. 1. front() returning the reference to the first element precondition (assert): !empty(rng) return *begin(rng); 2. back() returning the reference to the last element precondition (assert): !empty(rng) For BidirectionalRange return *(--end(rng)); For SinglePassRange it could iterate over the range and return the reference to the last element 3. at() returning the reference to the i-th element of the range precondition (throw std::out_of_range or assert): index < size(rng) For RandomAccessRange return *(begin(rng) + index); For SinglePassRange it could iterate over the range and return the required element For me, non-throwing at() would be more useful however this behavior won't be intuitive. So the following should also be provided: 4. sub(), subscript(), el(), element(), at_index(), at_(), index(), indexed(), access(), operator[], ...? the implementation of indexing operator[] same as 3 but instead of throwing an assert would be used The use of operator[] could be similar to this: { using boost::range::subscript_operator; rng[index]; } So not very convenient. But maybe you have a better idea? Regards, Adam

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Re: [boost] [Parallel Algorithms] Queries regarding the Boost.Thread / Parallel algorithms
by Naveen 26 Mar '14

26 Mar '14

Hi, In my previous mail, I was speaking about the compiler optimization dependencies while creating a parallel version of the following code: DO J = 1, 100 DO I = 1, 100 DO K = 1, 100 C(I,J) = C(I,J) + A(I,K) * B(K,J) END DO END DO END DO As you know, the above code is the 2D-Matrix multiplication logic. I tested the above logic using various compiler optimization levels from -o0, -o1, -o2 and -o3. There were no problems due to the compiler optimizations. I have used pthreads to convert the serial code to its parallel version. Initially, the serial version took 72sec to execute and the parallel version with 4 threads took around 16sec. Please have a look at the attachment for the complete working source code. The question now is, I have used the threads as shown in the pseudo code below: int main() { create_pthreads(assign_thread_ID, call the function); join_threads(thread_ID); destroy_threads(); } function_called_by_each_thread(thread_ID) { all_computations; } All thread documentation reaches to some sort of options like this. Is this the correct way to approach the problem for creating parallel algorithms for boost threads. Please clarify, whether there are any alternative approaches available to achieve parallelism using threads. PS: Please have a look at the code for further details Regards, *NAVEEN* | Mobile: 832-720-2393 | about.me <http://about.me/naveen.namashivayam> |

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Re: [boost] [Parallel Algorithms] Queries regarding the Boost.Thread / Parallel algorithms
by Naveen 26 Mar '14

26 Mar '14

Hi, Based on understanding the proposal, I'm just curious to know how we are gonna use the compiler optimizations when creating the parallel_xxx functions. Say any normal loop would be optimized by the compiler using any of the loop transformations like loop interchange, loop unrolling, loop fusion etc., let us consider a sample FORTRAN code to : DO J = 1, 100 DO I = 1, 100 DO K = 1, 100 C(I,J) = C(I,J) + A(I,K) * B(K,J) END DO END DO END DO which may or may not be optimized by the compiler into something like this DO K = 1, 100 DO I = 1, 100 DO J = 1, 100 C(I,J) = C(I,J) + A(I,K) * B(K,J) END DO END DO END DO so, when we try to introduce our parallel algorithm in to the loop containing J, it may be interchanged depending upon the compiler properties. So, should we plan for such scenarios. When we try to introduce our parallel functions the only way possible is to make the compiler optimizations temporarily inactive on those tasks. But, by doing so the performance of the application will be affected. Should we really tackle this scenario or am i looking into a completely irrelevant picture? Regards, *NAVEEN* | Mobile: 832-720-2393 | about.me <http://about.me/naveen.namashivayam> |

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[bind] BOOST_BIND_NO_PLACEHOLDERS and unspecified-placeholder-type's
by Joaquín Mª López Muñoz 25 Mar '14

25 Mar '14

Hello, The non-documented BOOST_BIND_NO_PLACEHOLDERS macro suppresses the definition of (anonymous namespace)::_1, (anonymous namespace)::_2, etc., presumably to cope with potential clashes with other libs' placeholders such as Boost.Lambda's when in the presence of using directives. The problem with this is that using Boost.Bind without placeholder names requires writing code such as bind(f,boost::arg<1>(),boost::arg<2>()); but boost::arg<> is not documented!! (in fact, Boost.Bind synopsis explicitly defines _1, _2 etc. as having undocumented types unspecified-placeholder-type-1, unspecified-placeholder-type-2 and so on). Maybe Boost.Bind documentation can be changed so that BOOST_BIND_NO_PLACEHOLDERS and boost::arg<> are documented? Thank you, Joaquín M López Muñoz Telefónica Digital ________________________________ Este mensaje se dirige exclusivamente a su destinatario. Puede consultar nuestra política de envío y recepción de correo electrónico en el enlace situado más abajo. This message is intended exclusively for its addressee. We only send and receive email on the basis of the terms set out at: http://www.tid.es/ES/PAGINAS/disclaimer.aspx

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[ANN] CppCon 2014 Call for Submissions
by Boris Kolpackov 25 Mar '14

25 Mar '14

Hi, CppCon is the annual, week-long face-to-face gathering for the entire C++ community. The conference is organized by the C++ community for the community and so we invite you to present. Have you learned something interesting about C++, maybe a new technique possible in C++11? Or perhaps you have implemented something cool related to C++, maybe a new C++ library? If so, consider sharing it with other C++ enthusiasts by giving a talk at CppCon 2014. Submissions deadline is May 15 with decisions sent by June 13. For topic ideas, possible formats, and submission instructions, see the Submissions page: http://cppcon.org/submissions/ Hope to hear you speak! Boris

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