February 2019 - Boost-users - lists.preview.boost.org

[interprocess] Determine size of managed_shared_memory
by Kai Benndorf 12 Oct '19

12 Oct '19

Hi all, I want to create a managed_shared_memory in exactly the size I needed. Therefore I do something like this: size = sizeof( common_managed_shared_memory ); size += sizeof( MyClassInSharedMem ); managed_shared_memory segment(create_only, "name", size ); MyClassInSharedMem allocates itself some memory by segment->allocate(). I added this also to the size, but get a boost::interprocess::bad_alloc exception on allocating this additional memory. Are there some magic bytes I forgot to add? Many thanks in advance Kai

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boost::filtered_graph filtering on vertex color... if I only had a colormap
by Brian Davis 19 Jul '19

19 Jul '19

Lets say I have a graph g (of type graph_t) and a color map (boy I wish I had a colormap): typedef boost::property_map<graph_t, boost::vertex_color_t>::type color_map_t; or is it? auto indexmap = boost::get(boost::vertex_index, g); auto colors = boost::make_vector_property_map<boost::default_color_type>(indexmap); or maybe? auto indexmap = boost::get(boost::vertex_index, g); auto colors = boost::make_vector_property_map<boost::vertex_color_t>(indexmap); or possibly some goop found on the internet? boost::make_iterator_property_map(color_map.begin(), boost::get(boost::vertex_index, data_->g), color_map[0]) or other internet goop? typedef boost::property_map<GraphType, boost::vertex_color_t>::type color_map_t; color_map_t colorMap; boost::color_map(colorMap)) or other internet goop?? std::vector<int> colorMap(num_vertices(g), boost::white_color); so confused... (certainly not surprised why bgl is not a part of stl) Can someone help explain the various types and ways of specifying colormaps and the logic for each way and means? and a function (if I could get that far without VS syntax highlighter going bonkers and gobs of compiler errors.. you know the type): make_pretty(g, colormap ) which colors the graph colormap and a filter struct for boost::filtered_graph<Graph, EdgePredicate, VertexPredicate> (where I wonder why if I only want to filter vertices I have to set boost::keep_all for EdgePredicate... sigh... I know the answer... and also know how long it found me to find/figure out boost::keep_all - and if you are looking for boost::keep_all and found it here... your welcome ;-) ) and modifying (probably incorrectly) boost::filtered_graph example to: template <typename ColorMap> struct vertex_color_filter_eq { vertex_color_filter_eq() { } vertex_color_filter_eq(ColorMap colormap/*, boost::default_color_type c*/) : m_colormap(colormap)/*, m_c(c)*/ { } template <typename Vertex> bool operator()(const Vertex& v) const { return 0 < get(m_colormap, v); //return c < get(m_colormap, v); } ColorMap m_colormap; //boost::default_color_type m_c; }; auto indexmap = boost::get(boost::vertex_index, g); auto colors = boost::make_vector_property_map<boost::default_color_type>(indexmap); // some where here I would call make_pretty(g, colors) typedef property_map<graph_t, boost::vertex_color_t>::type ColorMap_t; vertex_color_filter<ColorMap_t> filter(colors); // boost::filtered_graph<graph_t, boost::keep_all, VertexPredicate> boost::filtered_graph<graph_t, boost::keep_all, vertex_color_filter> fg(g, filter); // Later say if I could get it compile and better if it compiled and worked I could move on and auto color = boost::red_color; typedef property_map<graph_t, boost::vertex_color_t>::type ColorMap_t; vertex_color_filter<ColorMap_t> filter(colors, color); boost::filtered_graph<graph_t, boost::keep_all, vertex_color_filter> fg(g, filter); Maybe if I color them yellow, I can then reach the wizard pull back the curtain and ask how to create a color map... If I only had a color map.

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Question on Posix timezone string
by Mats Webjörn/WIKAB 10 Mar '19

10 Mar '19

I'm using Boost 1.66 and use the following code to get a Posix string to set my uCLinux TZ environment variable to get a local time from an UTC time #include <boost/date_time/local_time/tz_database.hpp> #include <boost/date_time/local_time/local_time.hpp> tz_database tz_db; tz_db.load_from_file("./date_time_zonespec.csv"); time_zone_ptr nyc = tz_db.time_zone_from_region("Europe/Stockholm"); auto s = nyc->to_posix_string(); // "CET+01CEST+01,M3.5.0/02:00,M10.5.0/03:00" setenv("TZ", s.c_str(), 1); The odd thing is that my localtime becomes incorrect, and is actually 1 hr wrong on the opposite side of UTC. But, when I read https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html it says "The offset specifies the time value you must add to the local time to get a Coordinated Universal Time value". Not add to UTC time, which seems like the Boost Posix string assumes !!!!! Which explains why 16:00 UTC give 15:00 CET instead of 17:00 which is the correct value, when using localtime_r(). Am I missing something fundamentally, or what? Regards Mats Webjörn Webjörn IngenjörsKonsult AB Solhemsbackarna 75A SE-163 56 SPÅNGA Sweden

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Spatial search with boost r tree
by Bozo Vazic 01 Mar '19

01 Mar '19

Hi all, I'm trying to create a boost r tree with packing algorithm that will store 2D or 3D geometric points. This will be applied in side my peridynamic software for what we call "family search". Family search is basically a simple spatial search where each point of the peridynamic mesh (cloud of geometric points) needs to find all points inside it's horizon (horizon is for 2D a circle with a specific radius and for 3D it's a sphere with a specific radius). What I've found so far were examples for distance search using a random point (not the point that is a r-tree member). I did a distance and index check using bg::index::satisfies by passing a method that checks if the index is different and is distance smaller than radius. Also I use within(box) to constrain my search, but I'm not sure that is the correct way to use r tree spatial search for the point that is a member of the same r tree. Because as far as I understand the point in the r-tree knows has the information of boxes in which it is contained, so wouldn't there be a way to query the tree member using using only the horizon value? The reason why I'm asking this question is because I need to define most optimal spatial search so that query times don't take to long. This is important as I can have several million points that need to be constantly queried. Thnx in advance for all the help. Best Regads Bozo Here is my code for 2D search of only one point #include "stdafx.h" #include <boost/function_output_iterator.hpp> #include <boost/geometry/index/rtree.hpp> #include <boost/geometry.hpp> #include <boost/geometry/geometries/point.hpp> #include <boost/geometry/geometries/box.hpp> #include <vector> #include <iostream> namespace bg = boost::geometry; namespace bgi = bg::index; typedef bg::model::point <double, 2, bg::cs::cartesian> point; typedef std::pair<point, std::size_t> pointI; typedef bg::model::box<point> box; typedef std::pair<point, unsigned> value; bool CheckIndexAndDist(pointI i, pointI j, size_t dist); std::vector<uint64_t> res; struct StoreDataCallback { template <typename Value> void operator()(Value const& v) { res.push_back(v.second); } }; int _tmain(int argc, _TCHAR* argv[]) { std::vector<point> contourCenters; // has some value std::vector<pointI> cloud; double length = 2000; double width = 2000; double dX = length/1000.0; double horizon = 3.015*dX; for(int i = 0; i < length; i++) { for(int j = 0; j < width; j++) { point p; p.set<0>((-1.0 * length / 2.0) + dX + j * dX); p.set<1>((-1.0 * width / 2.0) + dX + i * dX); contourCenters.push_back(p); } } size_t id_gen = 0; std::transform( contourCenters.begin(), contourCenters.end(), back_inserter(cloud), [&](point const& p) { return std::make_pair(p, id_gen++); } ); bgi::rtree<pointI, bgi::quadratic<16> > rtree(cloud); // spatial search box query_box(point(cloud[10].first.get<0>() - 3.2*dX, cloud[10].first.get<1>() - 3.2*dX),point(cloud[10].first.get<0>() + 3.2*dX, cloud[10].first.get<1>() + 3.2*dX)); StoreDataCallback callback; rtree.query( bgi::within(query_box) && bgi::satisfies([&](value const& v) {return CheckIndexAndDist(v, cloud[10],3.015*dX);}), boost::make_function_output_iterator(callback)); return 0; } bool CheckIndexAndDist(pointI i, pointI j, size_t dist) { if( i.second != j.second && (bg::distance(i.first, j.first) < dist)) return true; else return false; }

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[Concept] Understanding Boost Concept library
by Robert Jones 28 Feb '19

28 Feb '19

This is a small excerpt from the Boost Concepts library, there's various rather unusual techniques employed in it, with preprocessor tricks and various compiler specific tweeks, but this one has defeated me! What is the purpose of "*********** Model:: ***********" ? Maybe it's just to generate a distinctive diagnostic, but it's very sensitive to exact numbers of asterisks! In general what's going on here is the compiler is checking that the destructor of the Model (which is a concept instantiated with a particular type), can be instantiated, but without ever running the destructor or creating an instance of the Model. struct failed {}; template <class Model> struct requirement<failed ************ Model::************> { static void failed() { ((Model*)0)->~Model(); } }; Any insight appreciated. Kind Regards Rob.

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Ambiguous symbols possibly caused by Boost 1.69.0
by tim＠raisedbar.net 28 Feb '19

28 Feb '19

Hi, I'm getting several instances of the following kind of error when I build my code, which does not use boost::thread, etc., as I use the STD versions: 1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.16.27023\include\condition_variable(1 24): error C2872: 'xtime': ambiguous symbol 1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.16.27023\include\thr\xtimec.h(18): note: could be 'xtime' 1>c:\program files\boost\boost\thread\lock_types.hpp(31): note: or 'boost::xtime' My research turned up: https://svn.boost.org/trac10/ticket/11477?cversion=0&cnum_hist=10 So I added the following value for Windows 10 to my preprocessor: _WIN32_WINNT=0x0601; Unfortunately, this makes no difference. Can anybody advise me of a way forward, please? Best wishes. Tim Burgess Raised Bar Ltd. E: <mailto:tim@raisedbar.net> tim(a)raisedbar.net M: +44 (0)7989 486976

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hi i am a beginner user, there are some problem when using the library, can anyone help me with that ? plz
by ching han 25 Feb '19

25 Feb '19

i am trying to use the boost polygon function for example boost::geometry::read_wkt("multipolygon(((0 0 , 3 0 , 3 2 , 0 2)))", q); however i want to use the changing input such as "multipolygon(((A B, 0 2, 0 0, 4 0, 4 0)))" and A, B are the parameters defined by my previous array, but it ends up with showing the bad lexical cast since the parameters A and B can not be used or read if there is any solution that i can use the changing parameters as my polygon input, i kept searching for the answer but still can not find it can anyone plz help me, and i will be so grateful with that. thanks again!

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[release] 1.70.0 closed for major changes
by Marshall Clow 23 Feb '19

23 Feb '19

The master branch is now closed for new libraries and breaking changes, and will be closing for the beta in one week. Also, if you're ready, you can also add your libraries' changes to the release notes at: < https://github.com/boostorg/website/blob/master/feed/history/boost_1_69_0.q… > After editing the release notes, you should get a form to create a pull request, remember to submit it, otherwise I won't see your change. As always, the calendar for the release cycle is available at: https://www.boost.org/development/ Thanks, -- The Boost Release Team

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Re: [Boost-users] [boost.test] Colors
by Raffi Enficiaud 23 Feb '19

23 Feb '19

On 21.02.19 17:22, Udo Steinbach via Boost-users wrote: > Am 2019-02-20 um 22:38 schrieb Raffi Enficiaud via Boost-users: >> and this was fixed in 1.69 > > I have read it, but was so far been too lazy to compile it. > I think that colors may help with many lines of output, and only then. But > the default output of boost::test should be OK, one line. Everything else > needs attention, also no colors needed. You can set an environment variable globally if you want to avoid the default behaviour. See https://www.boost.org/doc/libs/1_69_0/libs/test/doc/html/boost_test/utf_ref… The variable BOOST_TEST_COLOR_OUTPUT is there for your need. > If you want color, you have to handle colors complete, not only 'red here, > green that'. Maybe console setup or unsuitable combinations or color > blindness (system in high contrast mode) or remote console or whatever that > you have to take into account. Right, so your problem is rather the color scheme of Boost.Test that is not playing well with your color scheme. It is true that I did not adjusted the background and I made the hypothesis of the default one. > Because color is not needed for test AND handling colors is not easy, > default should be colorless mode. I respectfully disagree with this statement. I personally like having color outputs, and combining this with log levels let me parse a big amount of information/logs significantly faster. > That are my first two general thoughts. https://en.wikipedia.org/wiki/De_gustibus_non_est_disputandum > >> open an issue next time on GitHub > > I try to avoid registration on free services. > I am fine with that. I still consult this list, although in a less regular manner. If the variable BOOST_TEST_COLOR_OUTPUT is good enough for you, or if you want an improvement, let me know. Best, Raffi

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Re: [Boost-users] [boost.test] Colors
by Mateusz Loskot 21 Feb '19

21 Feb '19

On Thu, 21 Feb 2019 at 17:22, Udo Steinbach via Boost-users <boost-users(a)lists.boost.org> wrote: > Am 2019-02-20 um 22:38 schrieb Raffi Enficiaud via Boost-users: > > > open an issue next time on GitHub > > I try to avoid registration on free services. FYI, GitHub also offers paid account. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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