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a thread pool that allows recursive calls
by Frédéric Bron 13 Jun '15

13 Jun '15

Dear boosters, I need to perform some tasks in parallel and want to control the number of CPUs that are used. A threadpool seems to be what I want and http://threadpool.sourceforge.net/ looks good. However, my tasks may also want to launch some parallel sub-tasks and the sub-tasks may also want to launch tome parallel sub-sub-tasks... and this is not possible with this implementation of threadpool. I have programmed something that works and I wonder if anyone had also already done that because my implementation is very rudimental for now and if something already exists I do not want to reinvent the wheel. Having said that, if there is nothing publicly available (I mean open-source), do you think it would be valuable I share what I did and make it available to boost as a library? This would require some advices/reviews from thread experts and a lot of work from me but I would be happy to contribute. Kind regards, Frédéric

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Heterogeneous Container Library (HCL) Feedback and Testing
by James Armstrong 13 Jun '15

13 Jun '15

I send out a little feeler about a month ago for interest in a container library which natively allows users to insert a heterogeneous set of types. After getting some really good feedback, I think I have settled into something that is efficient, has a nice clean interface, and provides some useful capabilities. I am hoping people can take a look at the code, test it out, and provide an additional feedback in terms of interface, implementation, bugs, or additional features/classes that would be useful. I have implemented a set of containers which mimic the capabilities of the STL containers. These are (so far) * heterovector * heterostack * heteroqueue * heterolist * heteroforward_list * heterodeque These containers were implemented using variadic templates and were somewhat inspired from the posts of Joaquín Muñoz. http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections.html http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections-with.html In addition, I have an adaptor class which provides a simple interface for accessing data of a specific type from a container of type_erased objects (boost::any, boost::variant, etc). The code is hosted at https://github.com/armstrhu/HCL and the directory structure there should be simple to navigate. There is an include directory which contains the header files needed, and an examples directory which provides examples for using the containers and the adaptors. As they mimic the STL containers, once you see how to use them (basically just provide an additional template parameter) you should be able to use them smoothly. One note is I focused mainly on developing the heterovector class, and the remainders are primarily copies of that class where std::vector has been replaced with std::deque, std::list, etc, and associated methods added/removed as needed. I have primarily tested with the heterovector, so having people check out the other classes would be nice :) Any and all feedback is much appreciated. Thanks! -- James Armstrong

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[Geometry] Wrong results for dissolve Polygon
by Andreas Wimmer 12 Jun '15

12 Jun '15

Dear Boost Geometry Contributors, I am testing the boost::geometry::dissolve function upon some invalid polygons that are produced by a certain in-house segmentation alg. The fact that the algorithm is producing possibly invalid polygons cannot be changed easily so I thought I will fix them afterwards using dissolve from “geometry/extensions/algorithms/dissolve.hpp” for the latest boost 1.58 version. Unfortunately I stumbled over the following polygons for which dissolve produces wrong results. The following code illustrates the result using namespace boost::geometry; using namespace boost::geometry::model; using namespace boost::geometry::model::d2; int main(int argc, _TCHAR* argv[]) { polygon< point_xy<float> > Poly; read_wkt("POLYGON((10 10, 10 20, 20 20, 15 12, 15 18, 20 10, 10 10))", Poly); multi_polygon< polygon< point_xy< float > > > Dissolved; boost::geometry::dissolve(Poly, Dissolved); } Which results in a polygon including the small intersection part which should be excluded from the polygon And even more problematic the following example (same polygon with and additional self-touching outer ring) results in missing the entire main part of the polygon int main(int argc, _TCHAR* argv[]) { polygon< point_xy<float> > Poly; read_wkt("POLYGON((10 10, 10 20, 20 20, 20 25, 22 25, 20 20, 15 12, 15 18, 20 10, 10 10))", Poly); multi_polygon< polygon< point_xy< float > > > Dissolved; boost::geometry::dissolve(Poly, Dissolved); } I hope somebody can show me what I did wrong or what I can to too work around this problem. Best regards, Andreas Wimmer

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Appveyor
by Mathieu Champlon 12 Jun '15

12 Jun '15

Hello, I've seen it mentioned a few times on the mailing list. Can anyone point me to a boost library (or a library which makes use of boost) which builds on appveyor ? A find for appveyor.xml in the boost/libs directory does not yield anything and I couldn't find a way to search for projects on appveyor itself... Thank you ! MAT.

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[status] How should boost/status master be updated?
by Adam Wulkiewicz 11 Jun '15

11 Jun '15

Hi, Some time ago I prepared a PR for develop version of boost/status. Now I'd like to propagate the changes to master. How should I do that? I saw that there are some changes made only in develop and other only in master. Some commits were cherry-picked. What should be the practice in this case? Shouldn't status be made a separate module? It'd greately simplify the synchronization of branches. Regards, Adam

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[boost.lockfree] spsc_queue read/write_available
by Philip Bennefall 11 Jun '15

11 Jun '15

Hi all, I am debugging a crash that I am getting inside of the pop method in spsc_queue from boost.lockfree. I am not sure exactly what is happening yet, but I do have one question. I call read_available and write_available a few times, and am wondering why read_available can only be called from the producer thread and why write_available can only be called from the consumer thread? Wouldn't it make sense to call read_available from the consumer, and write_available from the producer? Why is it the other way around? Currently I call write_available from the thread that pops, and read_available from the thread that pushes. Did I interpret the documentation correctly? If so, some clarifications would be much appreciated. Thanks! Kind regards, Philip Bennefall

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sourceforge and release hosting
by Adam Walling 11 Jun '15

11 Jun '15

Should releases be hosted somewhere other than sourceforge? I've ran across this regarding boost twice this week, and I'm sure we are all well aware of the history of problems that sourceforge has been accumulating. Personally I think twice now every time I happen upon sourceforge, and despite being a source target than binary release, I can't help but be disturbed by these recent events. And I certainly don't want boost associated. Are there any strong feelings among us here regarding this?

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[BestPracticeHandbook] Try the library online
by Krzysztof Jusiak 10 Jun '15

10 Jun '15

Hi, I've recently added a new badge (try boost.di | online) to proposed boost.di library. It uses Wandbox (awesome) facilities to check the library using online compiler (Wandbox supports newest gcc/clang). IMHO this approach is really useful for reviews and new users, since they don't have to install anything, just click the link and its done. They can experiment and then if they like it, clone the library and explore it more. You can check the badge here: http://krzysztof-jusiak.github.io/di/cpp14/boost/libs/di/doc/html And, for inpatients, direct link to online compiler with the library: http://melpon.org/wandbox/permlink/O3ABWKU3VBV3WG8J Let me know, what do you think. Cheers, Kris

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[Config] Support for switching between std:: and boost:: equivalents.
by John Maddock 10 Jun '15

10 Jun '15

There is a pull-request for Config to provide support for switching between boost:: and std:: library equivalents: https://github.com/boostorg/config/pull/63 My questions are: * Is this the right approach? And, * Is Boost.Config the right place for it? Thanks for your comments, John.

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Interest in B-Tree and B+-Tree Implementation?
by Timo Bingmann 10 Jun '15

10 Jun '15

Hello people, I want to ask if there is an interest in adding an in-memory B+-Tree container implementation that I wrote some time ago: https://github.com/bingmann/stx-btree http://panthema.net/2007/stx-btree/ It emulates the std::set/map/multiset/multimap interfaces as far as possible (there are some unavoidable minor exceptions). And since I keep telling my collegues to stop using std::map for bigger instances, I think adding it to Boost would be a good idea. So ... I could clean up my old implementation, add C++11/Boost move semantics, use of uninitialized objects, boostify various things, etc, etc, and then things should be pretty fine. I also have an idea to modify/fork the implementation to create a B-tree (non-plus) container, which should be a bit slower, but provide an interface even closer to std::map (only remaining unavoidable incompatibility would be with iterator invalidation). My main question before starting this is whether it is a better idea to add it to Ion's existing Container library, or to add it as a separate "library" under Boost like the existing circular_buffer, which is pretty old. Apparently libraries have gotten bigger over Boost's life. So which variant would be better? The "Container" library seems to be more targeted at reimplementing STL containers with new features, and simple new containers, not complexer ones? But it should still be a good match. In the incubator I found the "STL Extensions" submission, which appears to be dead. It aims to provide "augmented array based B+ trees", which is different from the usual trees where nodes are dynamically allocated. Best Regards, Timo Bingmann

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