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[Graph] Unable to get the edge_color in depth_first_search
by Ashish Kumar 27 Jul '20

27 Jul '20

Hello, First of all, I am new to Boost Graph Library. So, there might be a simpler or easier fix to the problem I am facing. I am trying to get the edge color after executing the boost::depth_first_search algorithm on the graph. For that, I created an edge color map and passed it to the function. Also, to log the colors of the edges, I made a visitor class, passed the color of the edge to it, and printed it to the standard output stream, for the tree_edge, back_edge, etc. But, for every edge, the value of color comes out to be 0. So, I am not able to get the color of every edge. A small snippet of how I am calling the depth_first_search function: depth_first_search(graph, visitor(dfs_visitor(root, visited_order, colors, graph)) .edge_color_map(&colors) .root_vertex(root)); The complete code along with the visitor class can be found here: https://gist.github.com/krashish8/5f8d8e613e189857bd2b0fd46dd02b29 Please suggest any possible solution to this problem. Thank you, Ashish Kumar.

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[boost] Clang on Windows - No Autolink?
by Klaim - Joël Lamotte 27 Jul '20

27 Jul '20

Hi, am I correct that autolinking is not supported by Boost when using Clang on Windows? To be clear, I'm talking about both clang++ and clang-cl drivers. The behavior I observe suggests that I am correct but looking at the autolink.hpp header I didn't understand how it decides if it should work or not. A. Joël Lamotte

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Two Graphs Common Spanning Trees Issue [GSoC]
by Prakash Tiwari 24 Jul '20

24 Jul '20

Hello, Community Members and developers, I'm student of Google Summer Of Code and contributing to the pgRouting <https://github.com/pgRouting/pgrouting/>[1]. I need to use boost algorithm boost::two_graphs_common_spanning_trees. I have gone through the documentation and try to use it (with help of example.cpp) But I found that this algorithm is not returning the expected results. I have mentioned the example that I have used and explained the expected and given results <https://github.com/prakashupes/ProposalCodes/issues/1>.[2] So, please try to figure out that is it a bug implemented algorithm or It might be possible that I'm using the algorithm in the wrong way. Thanks Prakash Tiwari [1].https://github.com/pgRouting/pgrouting/ [2]. https://github.com/prakashupes/ProposalCodes/issues/1

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jpeg resize - file size increases
by Lloyd 24 Jul '20

24 Jul '20

Hi, We tried boost gil resize example to experiment with scaling down a jpeg image file. For some images, this causes the size of the file to increase. We are using bilinear_sampler algorithm. Our aim to reduce the input image size so as to save storage/network bandwidth. Quality can be compromised to a certain extent. Which algorithm/method should we use? The code fragment is given below:- boost::gil::rgb8_image_t img; boost::gil::read_and_convert_image(InStream, img, T()); float width = (float)(img.width() * Ratio) / 100; float height = (float)(img.height() * Ratio) / 100; boost::gil::rgb8_image_t resizedImg(width, height); boost::gil::resize_view(const_view(img), view(resizedImg), boost::gil::bilinear_sampler()); boost::gil::write_view(OutStream, boost::gil::const_view(resizedImg), T()); Thanks, Lloyd

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bjam resources
by Antonis Polykratis 18 Jul '20

18 Jul '20

Hello, are there any bjam tutorials documentation about how I could create a project using bjam? Thanks

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Boost ABI/Linkage of clang vs g++
by DV Henkel-Wallace 17 Jul '20

17 Jul '20

boost-users(a)lists.boost.org We build with clang++-10 w/libc++.a and g++-10 w/libstdc++.a, so build a copy of boost in each configuration as well. This works great on the Mac development machines but the clang case doesn't generate the correct linkage on the Linux deployment machines. The correct clang linkage is std::__1::basic_string... but boost builds with std::__cxx11::basic_string Here's the linkage of libc++: $ objdump -T /usr/lib/llvm-10/lib/libc++.so.1|c++filt|grep ::basic_string|head -1 0000000000057450 g DF .text 0000000000000048 Base std::__1::locale::locale(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) Notice: std::__1::basic_string< ... When compiling my own code with clang++-10 the correct symbol is generated: $ nm options.cc.o |c++filt |fgrep __ |fgrep ::set_option_name |head -1 0000000000000000 W fmt::v6::basic_format_context<std::__1::back_insert_iterator<fmt::v6::internal::buffer<char> >, char>::iterator... Notice std::__1:: ... However the boost object have the wrong symbol name: $ nm 3P/llvm/lib/libboost_program_options.a |c++filt |fgrep __ |fgrep ::basic_string |head -1 0000000000000000 W boost::program_options::unknown_option::unknown_option(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) Notice std::__cxx11::basic_string< ... I'm compiling boost this way: export CC=clang CXX="clang++ -stdlib=libc++" CXXSTD=c++20 ; ./b2 stdlib=libc++ toolset=clang boost.locale.icu=off boost.locale.std=off --with-atomic --with-chrono --with-date_time --with-headers --with-locale --with-log --with-program_options --with-random --with-regex --with-system --with-thread threading=multi -sNO_COMPRESSION=1 link=static install It's 1.73.0

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[release] Boost 1.74.0 beta 1 released
by Marshall Clow 16 Jul '20

16 Jul '20

Boost release 1.74.0 beta 1 is now available at: <https://dl.bintray.com/boostorg/beta/1.74.0.beta.1/source/> The SHA256 checksums are as follows: 577a6b575ff2c227e14cce1b929c73d969475e58f3d2ab2901ad234f773bbd12 boost_1_74_0_b1.7z ba09c72dc848e7c0904922967014d853897b5a634926c910cc3b1fd627c31605 boost_1_74_0_b1.tar.bz2 2ccdc39efa076822cf1b359f9449f9d07707f3e27a18b393297b25885a9ff45b boost_1_74_0_b1.tar.gz c267c450166e040a374eaddab5e583cef09f6c3fe96a4db826172d0315c38dd5 boost_1_74_0_b1.zip For details of what's in the release, see < https://www.boost.org/users/history/version_1_74_0.html>. Please download the beta, give it a try, and report any problems you encounter. Issues that were found during the beta release process and will be fixed for the final 1.74.0 release: * The Boost.STLInterfaces documentation was left out of the beta. * Some of the Boost.Geometry documentation files have very long names; this could cause problems on platforms (like Windows) with shorter limits on path lengths. * There is a compile error in Boost.ASIO when compiling with 32-bit MSVC-14.2 with BOOST_BEAST_NO_TS_EXECUTORS. Thanks, -- The Boost Release Team

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[release] Boost 1.74.0 Beta 1 Release Candidate 1
by Marshall Clow 14 Jul '20

14 Jul '20

The release candidates for the first 1.74.0 beta release are now available at: https://dl.bintray.com/boostorg/beta/1.74.0.beta.1/source/ The release notes are not yet available. The SHA256 checksums are as follows: 577a6b575ff2c227e14cce1b929c73d969475e58f3d2ab2901ad234f773bbd12 boost_1_74_0_b1_rc1.7z ba09c72dc848e7c0904922967014d853897b5a634926c910cc3b1fd627c31605 boost_1_74_0_b1_rc1.tar.bz2 2ccdc39efa076822cf1b359f9449f9d07707f3e27a18b393297b25885a9ff45b boost_1_74_0_b1_rc1.tar.gz c267c450166e040a374eaddab5e583cef09f6c3fe96a4db826172d0315c38dd5 boost_1_74_0_b1_rc1.zip As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Boost Release Managers

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bjam using boost-1.77
by Cho-Kuen Ng 11 Jul '20

11 Jul '20

I used to use a very old version of bjam and wanted to switch to the most recent version 1.77. When I use the new bjam, I encounter the following problems. o I have 2 projects with the same id, the error message is error: at nml/unit_test/Jamfile:1 error: Attempt to redeclare already registered project id '/test'. error: Original project: error: Name: Jamfile</Users/cho/work/distmesh/unit_test> error: Module: Jamfile</Users/cho/work/distmesh/unit_test> error: Main id: /test error: File: distmesh/unit_test/Jamfile error: Location: distmesh/unit_test error: New project: error: Module: Jamfile</Users/cho/work//nml/unit_test> error: File: nml/unit_test/Jamfile error: Location: nml/unit_test After I changed the id in one project, the errors disappeared. o I do bjam again, I have this error /Users/cho//doc/boost/boost_1_73_0/tools/build/src/build/generators.jam:1127: in ensure-type from module generators error: target { PNCDF_Variable.C. } has no type Once I changed the C extension to cpp, the error disappeared. I don't have these problems using the old bjam. Are there syntax changes in the Jamfile? Please help. Thanks, Cho

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[InterProcess] receiving notification when an item is added to the message queue
by Sean Farrow 11 Jul '20

11 Jul '20

Good afternoon, I am looking to use the message queue in the Interprocess library to communicate between two Windows processes. I was wondering whether there was an in-built mechanism to signal to the process reading from the queue that a message is available for consumption. If there isn't anything in-built, I was wondering what the best way to do this is and whether anybody has any working sample code they would be willing to share? Any help appreciated as always. Kind regards Sean.

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