May 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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Downloads of boost from Bintray.com are temporarily unavailable
by Marshall Clow 30 May '19

30 May '19

Apparently, Boost is being downloaded over 6000 times/day from Bintray, and we've reached the limits of their bandwidth for the month. We're trying to get them to increase our quota (and see if there's someone who is downloading boost over and over again), but at the present time, downloads from bintray are being rejected. Hopefully this will be a temporary situation. -- Marshall (boost release manager)

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Re: [Boost-users] catmull_rom splines
by Nick Thompson 30 May '19

30 May '19

Yes, the Catmull-Rom curve is confusing for scientific application developers because it *creates* a parametrization. For example, if you solved by stepper an ODE y' = f(t,y) and got a solution skeleton {t_i, y_i}, the Catmull-Rom curve *wouldn't accept the time points t_i*. It's only interested in the y_i. Since the Catmull-Rom curve is used in computer graphics, you can kinda see why those guys don't care what the parametrization is. I'm currently working on extending the barycentric rational interpolator into higher dimensions; mathematically it's trivial but getting the interface right is (as always) the real problem. Nick ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Thursday, May 30, 2019 8:52 AM, Giorgino R <giorginor21(a)gmail.com> wrote: > Dear Nick/all, > > That was my bad. > > I though that the parametrisation should be in the range [0-1] or [x_min-x_max]. I debugged my program and I saw that Catmull-Rom class internally change the parametrisation from 0 to m_max_s (for normal range 0 -1). Actually, it is explicitly mentioned in the documentation, as well. For some reason, I didn't interpret it properly. I attach my normal spline that now look as expected. > > Apologies for the trouble. It's because I have never had any previous experience with these type of splines. > > Many thanks > Giorgio > > On Thu, May 30, 2019 at 11:07 AM Giorgino R <giorginor21(a)gmail.com> wrote: > >> Dear Nick, >> >> Many thanks for your prompt reply along with your valuable suggestions. >> >> I have now added two ghost points at each end as you described; however, the curve looks (see the attached) more disappointing (always for my objectives :) ). >> To clarify, what I am trying to achieve is to get a (interpolation) line that passes through all the knots/points. Then, for a set of discrete x values (within the space of the line) I want to evaluate the corresponding points and pass them to a boost::linestring. I tried also with both [Cubic B-spline interpolation](https://www.boost.org/doc/libs/1_70_0/libs/math/doc/html/mat… and [Barycentric Rational Interpolation](https://www.boost.org/doc/libs/1_70_0/libs/math/doc/html/mat…. However, my sample points are not equally spaced and non-monotonic (x values). Therefore, I found that Catmull-Rom may be of better use here. >> >> The other issue that is unclear to myself is that the evaluation of a Catmull-Rom spline looks dependent on the parametrisation (see the two images in my first email), as well. >> >> Since in my application I am going to use Boost geometry, I would really like to find a solution on how to interpolate such data point sets with functionality available in Boost. >> >> Once again, many thanks for your support. >> >> Giorgio >> >> On Wed, May 29, 2019 at 6:32 PM Nick Thompson via Boost-users <boost-users(a)lists.boost.org> wrote: >> >>> Hi Giorgino, >>> >>> The strange behavior at the end of the Catmull-Rom splines is a deficiency of the method. However, we are fortunate that this is not a big deficiency. This is because the Catmull-Rom splines are interpolated by functions of compact support, so a point can influence at most four segments (only two, if the point is on the boundary). Looking at your images, I personally don't think they look bad. But presumably since you are writing this, you want better! >>> >>> I would recommend adding two ghost points. Draw a line between point 0 and point 1, and put the ghost point "in the mirror", i.e., place it where point 1 would appear if a mirror sat in the plane passing through P0 and orthogonal to the line joining point zero and point one. You might contend that this is an arbitrary choice, and it is! But the compact support of the basis functions means that the decision is not super important, and this choice will at least give reasonable-looking tangent vectors. >>> >>> Nick >>> >>> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ >>> On Wednesday, May 29, 2019 12:08 PM, Giorgino R via Boost-users <boost-users(a)lists.boost.org> wrote: >>> >>>> Hi all, >>>> >>>> I am trying to interpolate some data with a catmull_rom spline available in boost math (interpolation). However, the resulting spline has a strange behavior; especially, at its ends (see the attached image). >>>> Just out of curiosity, I also tried to normalise my data to [0-1] range. However, the line has had even worse behavior (see the attached image). >>>> Below, the c++ code segment of the interpolation is depicted: >>>> >>>> std::vector<std::array<double, 2>> points_intr(16); >>>> >>>> points_intr[0] = { 1.263270, 0.774614 }; >>>> points_intr[1] = { 1.876, 2.480 }; >>>> points_intr[2] = { 1.651110, 4.550 }; >>>> points_intr[3] = { 1.426340, 5.688 }; >>>> points_intr[4] = { 1.429, 7.054 }; >>>> points_intr[5] = { 2.073220, 8.377020 }; >>>> points_intr[6] = { 3.910, 9.140 }; >>>> points_intr[7] = { 6.430, 9.537 }; >>>> points_intr[8] = { 8.950, 9.859 }; >>>> points_intr[9] = { 11.470, 10.317 }; >>>> points_intr[10] = { 12.730, 10.6456 }; >>>> points_intr[11] = { 13.990, 11.0741 }; >>>> points_intr[12] = { 15.335, 11.6928 }; >>>> points_intr[13] = { 16.680, 12.5661 }; >>>> points_intr[14] = { 18.3538, 14.830 }; >>>> points_intr[15] = { 18.700, 16.056 }; >>>> >>>> bm::catmull_rom<std::array<double, 2>> >>>> interpolator_cr(std::move(points_intr)); >>>> >>>> std::vector<double> x_linspace_cr(100); >>>> std::vector<std::array<double, 2>> inter_points(100); >>>> linspace(1.263270, 18.700, 100, x_linspace_cr); // evaluation points along the line >>>> >>>> for (std::size_t i{0}; i < x_linspace_cr.size(); ++i) >>>> { >>>> inter_points[i] = interpolator_cr(x_linspace_cr[i]); >>>> } >>>> >>>> Should I have to add additional (ghost) points at both ends? If yes, is there any optimum way to calculate where exactly to poisition these points? I understand if I get the derivatives at both end I can calculate a straight line that the additional points should lie within. However, how should I calculate the distance from the end points? >>>> >>>> I hope I am not doing anything fundamentally wrong. Any help would be much appreciated. >>>> >>>> Many thanks! >>> >>> _______________________________________________ >>> Boost-users mailing list >>> Boost-users(a)lists.boost.org >>> https://lists.boost.org/mailman/listinfo.cgi/boost-users

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catmull_rom splines
by Giorgino R 29 May '19

29 May '19

Hi all, I am trying to interpolate some data with a catmull_rom spline available in boost math (interpolation). However, the resulting spline has a strange behavior; especially, at its ends (see the attached image). Just out of curiosity, I also tried to normalise my data to [0-1] range. However, the line has had even worse behavior (see the attached image). Below, the c++ code segment of the interpolation is depicted: std::vector<std::array<double, 2>> points_intr(16); points_intr[0] = { 1.263270, 0.774614 }; points_intr[1] = { 1.876, 2.480 }; points_intr[2] = { 1.651110, 4.550 }; points_intr[3] = { 1.426340, 5.688 }; points_intr[4] = { 1.429, 7.054 }; points_intr[5] = { 2.073220, 8.377020 }; points_intr[6] = { 3.910, 9.140 }; points_intr[7] = { 6.430, 9.537 }; points_intr[8] = { 8.950, 9.859 }; points_intr[9] = { 11.470, 10.317 }; points_intr[10] = { 12.730, 10.6456 }; points_intr[11] = { 13.990, 11.0741 }; points_intr[12] = { 15.335, 11.6928 }; points_intr[13] = { 16.680, 12.5661 }; points_intr[14] = { 18.3538, 14.830 }; points_intr[15] = { 18.700, 16.056 }; bm::catmull_rom<std::array<double, 2>> interpolator_cr(std::move(points_intr)); std::vector<double> x_linspace_cr(100); std::vector<std::array<double, 2>> inter_points(100); linspace(1.263270, 18.700, 100, x_linspace_cr); // evaluation points along the line for (std::size_t i{0}; i < x_linspace_cr.size(); ++i) { inter_points[i] = interpolator_cr(x_linspace_cr[i]); } Should I have to add additional (ghost) points at both ends? If yes, is there any optimum way to calculate where exactly to poisition these points? I understand if I get the derivatives at both end I can calculate a straight line that the additional points should lie within. However, how should I calculate the distance from the end points? I hope I am not doing anything fundamentally wrong. Any help would be much appreciated. Many thanks!

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bug or documentation missing boost posix_time time_duration not_a_date_time
by Erik Thiele 27 May '19

27 May '19

hi please compile this program: #include <boost/date_time/posix_time/ptime.hpp> #include <iostream> #include <vector> using namespace boost::posix_time; using namespace std; #define x(v) cout << #v << " : " << (v) << '\n'; int main(int argc, char *argv[]) { time_duration a(not_a_date_time); time_duration b; x(a<b); x(a>b); x(a<=b); x(a>=b); x(b<a); x(b>a); x(b<=a); x(b>=a); x(a==b); x(b==a); x(a.is_special()); x(b.is_special()); vector<time_duration> v0, v1; v0.push_back(time_duration()); v0.push_back(time_duration(not_a_date_time)); sort(v0.begin(), v0.end()); v1.push_back(time_duration(not_a_date_time)); v1.push_back(time_duration()); sort(v1.begin(), v1.end()); x(v0==v1); return 0; } the output is: a<b : 0 a>b : 0 a<=b : 1 a>=b : 1 b<a : 0 b>a : 0 b<=a : 1 b>=a : 1 a==b : 0 b==a : 0 a.is_special() : 1 b.is_special() : 0 v0==v1 : 0 if the time_duration datatype is a complete partial order which is for example needed for it to be able to be sorted, then the above output is partly illegal: if not a<b and not b<a then must be a=b. but this is not the case. if a<=b and b<=a then must be a=b. but this is not the case. so as expected the two vectors v0 and v1 are not equal after being sorted even though they certainly should be! i do not understand why time_duration is behaving in such a strange way here. I am using time_duration(not_a_date_time) as a SQL-NULL value just like i am using date(not_a_date_time) and ptime(not_a_date_time) as SQL-NULL values. obviously I should not use time_duration(not_a_date_time). maybe this is the reason why time_duration() != time_duration(not_a_date_time)? I don't understand the design here. for example date()==date(not_a_date_time) and also ptime()==ptime(not_a_date_time) but not with time_duration. why??? why is there no documentation that time_duration is not a complete partial order and thus not sortable - at least when using not_a_date_time? cya erik

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[Boost.Build] configure.builds and check-target-builds always build in debug mode
by David Callu 25 May '19

25 May '19

Hi, I try to add icu support in boost conan package, but on windows with msvc, the build never use icu. During icu detection in boost.locale, the has_icu.exe never build because configure.builds try to build in debug mode when I use property "variant=release" in b2 command line. I can see that in config.log written by b2 during build : b2 use icuucd.lib and icuind.lib instead of icuuc.lib and icuin.lib. So icu is not correctly detected, and so never used. If I bypass the has_icu test, boost locale build fine and have icu backend as expected. This behaviors only fail builds that use different library in release and debug mode, like icu build with msvc. Is it the correct behaviors ? - If yes this is a bad news for library with different library name in release and debug mode. - If no ... houston, we have a problem Best regards David

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[asio] example link dead
by Stephan Menzel 21 May '19

21 May '19

This is just a quick heads up. The website link to a file example in asio: https://www.boost.org/doc/libs/1_70_0/doc/html/boost_asio/example/cpp11/non… ... appears to be dead. 404. HTH... Stephan

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Re: [Boost-users] linker error boost with 1.69 and 1.70
by Danny K 21 May '19

21 May '19

I figured out my problem so please disregard my question. My problem was that zlib and bzip2 support was not being included. I developed a perl script that builds everything for me for Windows & Linux and somehow when the Linux script builds 1.69 or 1.70, it turns off zlib and bzip2 support. Not sure the cause but taking the command my perl script executes and running it the shell outside of perl, boost builds with the proper support for zlib/bzip2 in iostreams. Not sure what the change would be but I have a workaround. wr, Danny

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linker error boost with 1.69 and 1.70
by Danny K 20 May '19

20 May '19

So I have been using boost for awhile. I compile boost the same way for all the versions and have been since 1.48. My platforms are CentOS 6 & 7 and Windows 10 vs2017. My code has compiled on all 3 platforms with Boost without a problem. My current version is 1.66 and I wanted to upgrade to 1.69. Under Windows, I build 1.69 with ZLIB & BZIP and my applications have no problems. I use zlib & bzip in the IOstreams library to read & write compressed files. So I built 1.69 under Linux the same way as I always have but I am now getting a linker error that I don't understand and I am stuck. The error starts with: API_utiltyFunctions.cpp:(.text+0x154): undefined reference to `boost::iostreams::detail::zlib_base::before(char const*&, char const*, char*&, char*)' API_utiltyFunctions.cpp:(.text+0x15b): undefined reference to `boost::iostreams::zlib::sync_flush' API_utiltyFunctions.cpp:(.text+0x165): undefined reference to `boost::iostreams::detail::zlib_base::xinflate(int)' API_utiltyFunctions.cpp:(.text+0x177): undefined reference to `boost::iostreams::detail::zlib_base::after(char const*&, char*&, bool)' API_utiltyFunctions.cpp:(.text+0x17e): undefined reference to `boost::iostreams::zlib_error::check(int)' API_utiltyFunctions.cpp:(.text+0x185): undefined reference to `boost::iostreams::zlib::stream_end' The boost portion of my linker line is: -L[ path to boost 1.69] \ -lboost_random-1_69 \ -lboost_program_options-1_69 \ -lboost_date_time-1_69 \ -lboost_chrono-1_69 \ -lboost_regex-1_69 \ -lboost_thread-1_69 \ -lboost_exception-1_69 \ -lboost_filesystem-1_69 \ -lboost_system-1_69 \ -lboost_iostreams-1_69 -lrt -lbz2 -lz -lm Any help would be appreciate. Weirdly if I revert back to boost 1.66, I don't have a problem. I also tested this compilation against boost 1.70 and I get the same problem. I do compile boost statically with shared runtime libraries and threads. Respectfully, Danny K

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