November 2021 - Boost-users - lists.preview.boost.org

Clarification on statechart post_event vs process_event within react()
by John McCabe 10 Jan '22

10 Jan '22

Hi, Apologies if this has already been answered/clarified, but my search of the internet to try to get a definitive answer, at least one I recognised as being definitive, was unsuccessful. Below I have posted some source code, based on the stopwatch example from the tutorial, but using an 'external' object to delegate the actual handling of event stuff to and using the state, rather than simple_state base class, and some other tweaks. This is a cut down version of something that someone I work with has devised, but I just wanted to get a clear answer on whether process_event() should be getting called in cases like this. I think it probably should not since, in the code below, you change state (with a state object's destructor being executed) whilst you're executing that state's react(EvStartStop) function. If someone can confirm this is the correct interpretation that would be very much appreciated. Any questions, feel free to ask (BTW - I'm compiling for C++17) John PS - In case it's of any use, the output from running this code is: ------ Entered Active Entered Stopped Stopped - payload2 m_charValue: a Exited ~Stopped <<<--- This is the bit I don't like the look of because... Entered Running Active - payload2 m_charValue: a <<<--- ... this happens from the forward_event() call payload1 value1: 20 payload1 value2: 200.2 Exited ~Running Entered Stopped Exiting Program Exited ~Stopped Exited ~Active ------ If I swap the //*** comments to the doProcess() lines instead of doPost(), the output seems more sensible ------ Entered Active Entered Stopped Stopped - payload2 m_charValue: a Exited ~Stopped Entered Running Active - payload2 m_charValue: a payload1 value1: 20 payload1 value2: 200.2 Exited ~Running Entered Stopped Exiting Program Exited ~Stopped Exited ~Active ------ ========== code =========== #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/state.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/custom_reaction.hpp> #include <boost/mpl/list.hpp> #include <iostream> #include <string> namespace sc = boost::statechart; namespace mpl = boost::mpl; // Forward declare a handler 'class' that's going to have activity delegated to it struct Handler; // Normal example start/stop and reset events struct EvStartStop : sc::event<EvStartStop> {}; struct EvReset : sc::event<EvReset> {}; // A couple of events that carry data with them struct EvPayload1 : sc::event<EvPayload1> { EvPayload1(int value1, double value2) : m_value1 { value1 }, m_value2 { value2 } {}; int m_value1 { 0 }; double m_value2 { 0.0 }; }; struct EvPayload2 : sc::event<EvPayload2> { EvPayload2(const char& charValue) : m_charValue { charValue } {}; char m_charValue { false }; }; // Back to the example bits struct Active; struct StopWatch : sc::state_machine<StopWatch, Active> { typedef sc::transition<EvReset, Active> reactions; // The extra 'handler' stuff void setHandler(Handler* handler) { m_handler = handler; }; Handler* getHandler() const { return m_handler; }; Handler* m_handler { nullptr }; // Used to make post_event() accessible from an external class...seems unpleasant, but... using sc::state_machine<StopWatch, Active>::post_event; }; // The implementation of the Handler class; created with a reference to a StopWatch object struct Handler { Handler(StopWatch& stopWatch) : m_stopWatch { stopWatch } {}; void doPost() { m_stopWatch.post_event(EvStartStop()); } void doProcess() { m_stopWatch.process_event(EvStartStop()); } StopWatch& m_stopWatch; }; struct Stopped; struct Active : sc::state<Active, StopWatch, Stopped> { Active(my_context ctx) : my_base { ctx } { std::cout << "Entered Active" << std::endl; }; ~Active() { std::cout << "Exited ~Active" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload1>, sc::custom_reaction<EvPayload2>, sc::transition<EvReset, Active>> reactions; sc::result react(const EvPayload1& payload1) { std::cout << "payload1 Event NOT HANDLED" << std::endl; return discard_event(); } sc::result react(const EvPayload2& payload2) { std::cout << "Active - payload2 m_charValue: " << payload2.m_charValue << std::endl; return discard_event(); } }; struct Running : sc::state<Running, Active> { Running(my_context ctx) : my_base { ctx } { std::cout << "Entered Running" << std::endl; }; ~Running() { std::cout << "Exited ~Running" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload1>, sc::transition<EvStartStop, Stopped>> reactions; sc::result react(const EvPayload1& payload1) { std::cout << "payload1 value1: " << payload1.m_value1 << std::endl; std::cout << "payload1 value2: " << payload1.m_value2 << std::endl; //***context<StopWatch>().getHandler()->doPost(); context<StopWatch>().getHandler()->doProcess(); return discard_event(); } }; struct Stopped : sc::state<Stopped, Active> { Stopped(my_context ctx) : my_base { ctx } { std::cout << "Entered Stopped" << std::endl; }; ~Stopped() { std::cout << "Exited ~Stopped" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload2>, sc::transition<EvStartStop, Running>> reactions; sc::result react(const EvPayload2& payload2) { std::cout << "Stopped - payload2 m_charValue: " << payload2.m_charValue << std::endl; //***context<StopWatch>().getHandler()->doPost(); context<StopWatch>().getHandler()->doProcess(); return forward_event(); } }; int main() { StopWatch myWatch; Handler myHandler(myWatch); myWatch.setHandler(&myHandler); myWatch.initiate(); myWatch.process_event(EvPayload2 { 'a' }); myWatch.process_event(EvPayload1 { 20, 200.2 }); std::cout << "Exiting Program" << std::endl; return 0; }

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[Graph] Occasional crash when removing a vertex
by Anne van de Graaf 29 Nov '21

29 Nov '21

Hello all, When I remove a vertex from a graph, I occasionally experience a crash (on a system running Red Hat Enterprise Linux 8.5). I have been able to replicate the behavior with the following test program: #include <boost/graph/adjacency_list.hpp> int main() { using MyGraph = boost::adjacency_list<boost::setS, boost::vecS, boost::undirectedS>; using MyVertexDescriptor = boost::graph_traits<MyGraph>::vertex_descriptor; using MyVertexDescriptorVec = std::vector<MyVertexDescriptor>; MyGraph g; MyVertexDescriptorVec vertices{ boost::add_vertex( g ), boost::add_vertex( g ), boost::add_vertex( g ) }; boost::add_edge( vertices[0], vertices[1], g ); boost::add_edge( vertices[1], vertices[2], g ); boost::clear_vertex( vertices[0], g ); boost::remove_vertex( vertices[0], g ); return 0; } Also on a Windows platform, I observe similar behavior. When I build the above code with Microsoft Visual Studio 2019 (MSVC 14.27.29110) and run it with a debugger, a debug assertion is triggered ("cannot increment value-initialized map/set iterator"). In both cases (on Linux and Windows platforms), the debugger reveals that the problem is at line 2071 of boost/graph/detail/adjacency_list.hpp. For clarity, I have copied the involved template function below: template < class EdgeList, class vertex_descriptor > inline void reindex_edge_list( EdgeList& el, vertex_descriptor u, boost::disallow_parallel_edge_tag) { for (typename EdgeList::iterator ei = el.begin(); ei != el.end(); ++ei) // line 2071: increment operator fails { if (ei->get_target() > u) { typename EdgeList::value_type ce = *ei; el.erase(ce); --ce.get_target(); el.insert(ce); } } } While I was searching for a proper place to post my question, I found the following issue at GitHub (which was opened on July 1 of this year): https://github.com/boostorg/graph/issues/268. This appears to be the exact same issue. So last week, I added a comment saying that I am facing the exact same problem. Unfortunately, so far no one has responded yet. To me, it seems that the problem is well-understood. Also, some have proposed a bug fix to resolve the issue (including a pull request). Nevertheless, no progress has been made over the past months. So I was just wondering what is the best way to proceed if we want to fix the issue in Boost itself? Is there anything that I can do (apart from starting this thread) to help in resolving the issue? Any feedback is greatly appreciated. Kind regards, Anne van de Graaf

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assigning a "float128" variable with a regular "double" variable
by Jacques Mequin 27 Nov '21

27 Nov '21

I am a fresh new user ( I need to extend some EIGEN library feature by using your float128 ) How to assign a "float128" variable with a regular "double" variable ? With my source code in attachement double double_pi = 3.141592653589793 ; float128 float128_pi = 3.141592653589793Q ; produces the output that looks fine to me double_pi = 3.141592653589793e+00 float128_pi = 3.141592653589793000000000000000000e+00 but thestatement float128_pi = double_pi ; produces float128_pi = 3.141592653589793115997963468544185e+00 How to get 3.141592653589793000000000000000000e+00 also from an assigment ??? What am I doing wrong ? Thanks for any help Regards, Jacques

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Fw: How to access global fixture class member
by Ming Cheng 21 Nov '21

21 Nov '21

________________________________ From: Ming Cheng Sent: Thursday, November 18, 2021 6:52 AM To: Boost-interest(a)lists.boost.org <Boost-interest(a)lists.boost.org> Subject: How to access global fixture class member Hi struct Myconfig{ int m_any; }; BOOST_GLOBAL_FIXTURE(Myconfig) How to access m_any?

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boost units and single-precision floats
by Carel Combrink 19 Nov '21

19 Nov '21

Hi, I have aliases for radians and degrees that use float as the storage type. When I convert between these two units I see the assembly promote the values to doubles and then back to floats. How can I make sure that all operations and conversions stay in floats? PS: I would not be surprised if I have defined my aliases or/and my conversion functions incorrectly. My Code: === using radians_f = boost::units::quantity<boost::units::si::plane_angle, float>; using degrees_f = boost::units::quantity<boost::units::degree::plane_angle, float>; degrees_f to_degrees(const radians_f& angle) { return static_cast<degrees_f>(angle); } radians_f to_radians(const degrees_f& angle) { return static_cast<radians_f>(angle); } === >From compiler explorer I see the following assembly instructions: https://godbolt.org/z/Gnjr54dn6 cvtss2sd - Converts a single-precision floating-point value in the “convert-from” source operand to a double-precision floating-point value in the destination operand. mulsd - Multiplies the low double-precision floating-point value in the second source operand by the low double-precision floating-point value in the first source operand. cvtsd2ss - Converts a double-precision floating-point value in the “convert-from” source operand to a single-precision floating-point value Any help will be appreciated. Regards, Carel

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Using Boost Compute with ArrayFire
by Muhammad Hassan Khan 17 Nov '21

17 Nov '21

Hi, I am trying to run a code which uses functions from both boost compute library and arrayfire library. I am getting the following errors when I try to build the code: Scanning dependencies of target hello [ 50%] Building CXX object CMakeFiles/hello.dir/hello.cpp.o In file included from /opt/arrayfire/include/CL/cl.h:32, from /usr/include/boost/compute/cl.hpp:19, from /usr/include/boost/compute/system.hpp:20, from /usr/include/boost/compute/algorithm/accumulate.hpp:17, from /usr/include/boost/compute/algorithm.hpp:18, from /usr/include/boost/compute.hpp:14, from /home/rcms/debruijn/arrayfire/hello.cpp:2: /opt/arrayfire/include/CL/cl_version.h:34:104: note: #pragma message: cl_version.h: CL_TARGET_OPENCL_VERSION is not defined. Defaulting to 220 (OpenCL 2.2) 34 | #pragma message("cl_version.h: CL_TARGET_OPENCL_VERSION is not defined. Defaulting to 220 (OpenCL 2.2)") | ^ [100%] Linking CXX executable hello /usr/bin/ld: CMakeFiles/hello.dir/hello.cpp.o: undefined reference to symbol 'clGetDeviceIDs@@OPENCL_1.0' /usr/bin/ld: /opt/arrayfire/lib64/libOpenCL.so.1: error adding symbols: DSO missing from command line collect2: error: ld returned 1 exit status make[2]: *** [CMakeFiles/hello.dir/build.make:85: hello] Error 1 make[1]: *** [CMakeFiles/Makefile2:76: CMakeFiles/hello.dir/all] Error 2 make: *** [Makefile:84: all] Error 2 The code I am using is a very simple helloworld using functions from both libraries. #include <iostream> #include <boost/compute.hpp> #include <arrayfire.h> namespace compute = boost::compute; using namespace af; int main() { // Boost Compute Part // get the default device compute::device device = compute::system::default_device(); // print the device's name and platform std::cout << "hello from " << device.name(); std::cout << " (platform: " << device.platform().name() << ")" << std::endl; // Array Fire Part std::cout<< "ArrayFire Part:" << std::endl; af::setDevice(0); af::info(); return 0; } The CMakeList used to build the project is: cmake_minimum_required(VERSION 3.0) project(deBruijn_Graph) find_package(ArrayFire) add_executable(hello hello.cpp) target_link_libraries(hello ArrayFire::afopencl) I do not have a programming background. Please guide me on what I am doing wrong. Regards, Hassan <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campai…> Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campai…> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

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pgRouting use BGL
by Vicky Vergara 12 Nov '21

12 Nov '21

Hello, First of all, I want to congratulate you for the amazing job you are doing. I am the main developer of pgRouting, and the project is part of the OSGeo Foundation [2] community projects. pgRouting extends the PostGIS / PostgreSQL geospatial database to provide geospatial routing functionality. I would like pgRouting [1] to be added on the list of "Boost Graph Library Users" The Boost license is on the projects repository [3] and we document when a boost graph function is used for example in [4] [1] https://pgrouting.org/ [2] https://www.osgeo.org [3] https://github.com/pgRouting/pgrouting [4] https://docs.pgrouting.org/latest/en/pgr_aStar.html Thanks Vicky Vergara -- Georepublic UG (haftungsbeschränkt) Salzmannstraße 44, 81739 München, Germany Vicky Vergara Operations Research eMail: vicky(a)georepublic.de Web: https://georepublic.info Tel: +49 (089) 4161 7698-1 Fax: +49 (089) 4161 7698-9 Commercial register: Amtsgericht München, HRB 181428 CEO: Daniel Kastl

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[release] Boost 1.7.0 beta 1 released
by Marshall Clow 11 Nov '21

11 Nov '21

Boost release 1.77.0 beta 1 is now available at: <https://boostorg.jfrog.io/artifactory/main/beta/1.78.0.beta1/source/> The SHA256 checksums are as follows: 7a3a025451dfa2923129214eef7d16b03c02310a353d02158a549f6caa4284b0 boost_1_78_0_b1.tar.bz2 c491b1dcb916195598aa6581d6708d57fcc750516641c22511c088d572de9c07 boost_1_78_0_b1.tar.gz 35e7a3b0eb412a3933e57c72ba96374eb7d88ff1f89dbec62a16d67ffea2105a boost_1_78_0_b1.7z e6b68feb2f63401c96ca9fe25e939b409189fbe526a6e784e4bd69832c8f09cb boost_1_78_0_b1.zip For details of what's in the release, see <https://www.boost.org/users/history/version_1_78_0.html>. Please download the beta, give it a try, and report any problems you encounter. Thanks, -- The Boost Release Team

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Boost.asio. Crash in Tutorial Timer.5, "Synchronizing handlers in multithreaded programs"
by Senthil Cheetancheri 11 Nov '21

11 Nov '21

Hi, I'm learning to use Boost.asio by going through the tutorials at [1]. However, the listing for "Synchronizing handlers in multithreaded programs" crashes on my Ubuntu. Source listing (about 70 lines) is at [2]. I have given my compilation steps, stack trace from gdb, and boost information below. Can you please advise how I can get this working right? [1] https://www.boost.org/doc/libs/1_77_0/doc/html/boost_asio/tutorial.html [2] https://www.boost.org/doc/libs/1_77_0/doc/html/boost_asio/tutorial/tuttimer… I compiled and ran as follows: $ g++ -g -o timer_5.1 timer_5.1.cpp -lpthread -lboost_thread $ ./timer_5.1 Timer 1: 0 Timer 2: 1 Timer 1: 2 Timer 2: 3 Timer 1: 4 Timer 2: 5 Timer 1: 6 Timer 2: 7 Timer 1: 8 Timer 2: 9 Segmentation fault (core dumped) The backtrace from gdb is: $ cat gdb_log.txt #0 0x00007ffff799f88b in ?? () from /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.65.1 #1 0x00007ffff79a0bd5 in ?? () from /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.65.1 #2 0x00007ffff7bbb6db in start_thread (arg=0x7ffff6851700) at pthread_create.c:463 #3 0x00007ffff711e71f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 I have the following boost library installed: $ sudo apt show libboost-all-dev Package: libboost-all-dev Version: 1.65.1.0ubuntu1 Priority: optional Section: universe/libdevel Source: boost-defaults Origin: Ubuntu Maintainer: Ubuntu Developers <ubuntu-devel-discuss(a)lists.ubuntu.com> Original-Maintainer: Debian Boost Team <pkg-boost-devel(a)lists.alioth.debian.org> Bugs: https://bugs.launchpad.net/ubuntu/+filebug Installed-Size: 10.2 kB Depends: libboost-dev, libboost-tools-dev, libboost-atomic-dev, libboost-chrono-dev, libboost-container-dev, libboost-context-dev, libboost-coroutine-dev, libboost-date-time-dev, libboost-exception-dev, libboost-fiber-dev, libboost-filesystem-dev, libboost-graph-dev, libboost-graph-parallel-dev, libboost-iostreams-dev, libboost-locale-dev, libboost-log-dev, libboost-math-dev, libboost-mpi-dev, libboost-mpi-python-dev, libboost-numpy-dev, libboost-program-options-dev, libboost-python-dev, libboost-random-dev, libboost-regex-dev, libboost-serialization-dev, libboost-signals-dev, libboost-stacktrace-dev, libboost-system-dev, libboost-test-dev, libboost-thread-dev, libboost-timer-dev, libboost-type-erasure-dev, libboost-wave-dev Homepage: http://www.boost.org/ Download-Size: 2,340 B APT-Manual-Installed: yes . . . Thanks in advance. Thanks, Senthil.

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[release] Boost 1.78.0 Beta 1 Release Candidate 1 is available
by Marshall Clow 09 Nov '21

09 Nov '21

The first release candidates for the 1.78.0 beta release are now available at: <https://boostorg.jfrog.io/ui/native/main/beta/1.78.0.beta1/source <https://boostorg.jfrog.io/ui/native/main/beta/1.78.0.beta1/source>> The SHA256 checksums are as follows: 7a3a025451dfa2923129214eef7d16b03c02310a353d02158a549f6caa4284b0 boost_1_78_0_b1_rc1.tar.bz2 c491b1dcb916195598aa6581d6708d57fcc750516641c22511c088d572de9c07 boost_1_78_0_b1_rc1.tar.gz 35e7a3b0eb412a3933e57c72ba96374eb7d88ff1f89dbec62a16d67ffea2105a boost_1_78_0_b1_rc1.7z e6b68feb2f63401c96ca9fe25e939b409189fbe526a6e784e4bd69832c8f09cb boost_1_78_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 Release managers

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