February 2017 - Boost-users - lists.preview.boost.org

[accumulator] std::chrono::duration in boost::accumulator
by georg＠schorsch-tech.de 12 Feb '17

12 Feb '17

I want to build a histogram of `std::chrono::high_resolution_clock::duration` object. For this issue i wanted to use boost::accumulators as the framework. As it did not compile in my project i teared it down and based it on a running example with `double` as a data type. My general goal on my project is to do use for everything united types. Time and all measured stuff. I would want to avoid to use `.count()` on the duration. Is there any known workaround around this? it is not dependent on the compiler as it seems. With gcc 6.3 it failes too. It compiles when i use clang++-3.9 --std=c++14 -g -O0 main.cpp But when i set the define USE_CHRONO it failes with the error: clang++-3.9 --std=c++14 -g -O0 -DUSE_CHRONO main.cpp In file included from main.cpp:7: /usr/include/boost/accumulators/statistics/density.hpp:75:15: error: no matching constructor for initialization of 'array_type' (aka 'vector<std::chrono::duration<unsigned long, std::ratio<1, 1000000000> > >') , samples_in_bin(num_bins + 2, 0.) ^ ~~~~~~~~~~~~~~~~ and here is my teared down example. I used this site as a base and exhanged double to data_t. http://programmingexamples.net/wiki/CPP/Boost/Histogram #include <vector> #include <algorithm> #include <iostream> #include <chrono> #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/density.hpp> #include <boost/accumulators/statistics/stats.hpp> using namespace boost; using namespace boost::accumulators; using duration_t = std::chrono::high_resolution_clock::duration; #ifdef USE_CHRONO using data_t = duration_t; data_t construct(double d) { return std::chrono::milliseconds(0); } #else using data_t = double; data_t construct(double d) { return d; } #endif using acc = accumulator_set<data_t, features<tag::density> >; using histogram_type = iterator_range<std::vector<std::pair<data_t, data_t> >::iterator >; template <typename T> class data_filler { public: data_filler(){} T operator()() { return rand()/(T)RAND_MAX; } }; template <> class data_filler<duration_t> { public: data_filler(){} duration_t operator()() { return std::chrono::milliseconds(rand()/RAND_MAX); } }; int main(int argc, char** argv) { //create some random data std::vector<data_t> data(100); std::generate(data.begin(), data.end(), data_filler<data_t>()); int c = data.size();//cache size for histogramm. //create an accumulator acc myAccumulator( tag::density::num_bins = 20, tag::density::cache_size = 10); //fill accumulator for (int j = 0; j < c; ++j) { myAccumulator(data[j]); } auto hist = density(myAccumulator); data_t total = construct(0.0); for( int i = 0; i < hist.size(); i++ ) { // std::cout << "Bin lower bound: " << hist[i].first << ", Value: " << hist[i].second << std::endl; total += hist[i].second; } //std::cout << "Total: " << total << std::endl; //should be 1 (and it is) return 0; }

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boost::icl::contains question
by Sanchay Harneja 09 Feb '17

09 Feb '17

Hi, boost::icl::interval_map<int, boost::icl::interval_map<int, boost::icl::interval_set<int>>> larger, smaller; larger.add(make_pair(boost::icl::discrete_interval<int>::closed(102,104), boost::icl::interval_map<int, boost::icl::interval_set<int>>{ make_pair(boost::icl::discrete_interval<int>::closed(0,0), boost::icl::interval_set<int>{boost::icl::discrete_interval<int>::closed(2,4)})})); smaller.add(make_pair(boost::icl::discrete_interval<int>::closed(103,103), boost::icl::interval_map<int, boost::icl::interval_set<int>>{ make_pair(boost::icl::discrete_interval<int>::closed(0,0), boost::icl::interval_set<int>{boost::icl::discrete_interval<int>::closed(3,3)})})); cout << larger << endl; cout << smaller << endl; cout << boost::icl::contains(larger, smaller) << endl; cout << ((smaller & larger) == smaller) << endl; As given above, I'm trying to check if smaller is subset of larger. But I get following output: {([102,104]->{([0,0]->{[2,4]})})} {([103,103]->{([0,0]->{[3,3]})})} 0 1 Any reason why boost::icl::contains(larger, smaller) doesn't work but ((smaller & larger) == smaller) works? Thanks.

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Thread safe full duplex sockets
by Christi258 08 Feb '17

08 Feb '17

This question has been asked many times, but I'm still not satisfied with the answers. I want to use a socket in full duplex: 1. asynchronously: with async_read, async_write (multiple threads running io_service.run()) 2. synchronously: with read and write in two distinct threads I am pretty sure that 1. is thread safe using strands. But I can find no information about 2. Please refere to any official documents of boost. -- View this message in context: http://boost.2283326.n4.nabble.com/Thread-safe-full-duplex-sockets-tp469155… Sent from the Boost - Users mailing list archive at Nabble.com.

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[serialization] Object reference tracking on instances bug?
by Robert P 07 Feb '17

07 Feb '17

In my serialize function I am exporting a class which is a template wrapper around std:vector. template <typename E> class MyArray { public: vector<E> array; ... template <typename Archive> void MyArray::serialize(Archive & ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(array); } } When I add unique class instance variables to this array and then serialize it to XML... ... MyArray<Color> colorsArray; Color a; a.name = "one"; colorsArray.add(a); Color b; b.name = "two"; colorsArray.add(b); ... template <typename Archive> void MyColorsObject::serialize(Archive & ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(colorsArray); } Sometimes the XML comes out using object_id_reference instead of the unique values, and this then gets improperly unserialized with incorrect values, i.e. both colors will have "one" as the name. I was able to disable object tracking and it works now, but I don't think it should be doing object reference tracking on instance variables. Is it because of the template wrapper around vector?

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[gsoc17] Attn: We need 2017 mentors and project ideas for Boost!
by Niall Douglas 07 Feb '17

07 Feb '17

Dear Boost community, We are now a few weeks from the beginning of Google Summer of Code 2017! Last year we had the big surprise of being rejected by Google as an org, the second time ever, on the basis that Google felt we needed a year off. Thanks to the quick actions of the Boost Steering Committee and IMC Financial Markets we managed to put together a "Boost Summer of Code" so the students with projects in progress would not be left stranded. Despite a fair few teething problems, I think that worked out okay. As part of filling in our application for 2017, we must supply to Google a list of potential GSoC mentors and potential GSoC projects for summer 2017 in order to be approved as an organisation this year. Therefore a lengthy page of awesome project ideas at https://svn.boost.org/trac/boost/wiki/SoC2017 before *February 9th* would be an enormous help to getting us approved again this year and bringing to Boost another US$35,000 of Google funding. If you think yourself able to mentor a student doing some work on Boost this summer, *please* consider adding a description of the proposed work item and your name to the list. The year before last we had more slots awarded to us by Google than we had good combinations of student and mentor, so we had to return slots which I believe has not happened here at Boost GSoC in at least a decade. That means that your project ideas have a better chance than ever of receiving funding if you can find a good student, and that is best done by getting project ideas floated *early*. If you want to know more about mentoring a Google Summer of Code funded student work before you nominate yourself, please feel free to ask on the main Boost developers mailing list boost(a)lists.boost.org or via gsoc-admin(a)boost.org. Thank you in advance for your time.

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[MultiIndex] Prevent automatic re-indexing after "modify"?
by Deniz Bahadir 06 Feb '17

06 Feb '17

Hi guys, Hi Joaquín, I have a question concerning the automatic re-indexing of Boost.MultiIndex indexes. Is it somehow possible to modify a member of the element-type that is used as key for (another) index without triggering automatic re-indexing? (Of course, I want to be able to trigger manual re-indexing later.) Or is it at least possible to adjust the code so that this can be achieved? To understand my question, here is my use-case and why I need it. I have a boost::multi_index_container with multiple indexes (one hashed_unique and four hashed_non_unique). I am accessing a range of elements through a hashed_non_unique index 'A'. Then I am iterating through these elements and want to modify the value of a member 'M' of each element. However, that member is used when calculating the key for another hashed_non_unique index 'B'. Therefore, I must use the "modify" function of index 'A'. The problem is now that it takes forever to modify the entire range. (We are talking about 100 thousands if not millions of entries that need to be modified.) Probably because re-indexing is triggered after each call to "modify". However, in my case it should be perfectly fine to postpone the re-indexing after I modified the entire range, because I am not going to access any element through index 'B' until I finished modifying the entire range. As a workaround I removed index 'B' from the container and declared the element-member 'M' as mutable. This allows me to directly change the value of 'M'. The speedup is astonishing. It now finishes almost in no time. But this workaround is not really feasible as it requires reimplementing index 'B' by somehow tracking the information outside of the multi_index_container. Therefore, my question really is: Is it possible to provide an "unsafe_modify" function, which does the same as "modify" but does not trigger automatic re-indexing, and an "refresh_index" function, which (manually) triggers the re-indexing? Thanks, Deniz

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Re: [Boost-users] Boost iostreams for binary data
by Bjorn Reese 06 Feb '17

06 Feb '17

On 01/31/2017 09:25 PM, Robert Dailey wrote: > I have my own BinaryInputStream and BinaryOutputStream classes that > simply take a reference to some container that meets the requirements > of random access and contiguous internal memory. It doesn't own this > container, but rather serves as an adapter to the container to allow > stream operators to be used for streaming out data. For example, you > can stream a `std::uint32_t` to the binary stream, and it will insert > 4 elements into an internal byte vector which is just > `std::vector<std::uint8_t>`. Do they work with arrays?

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[clang-win][bjam][context] '-c' is not recognized as an internal or external command
by Mikhail Strelnikov 06 Feb '17

06 Feb '17

Hello Boost, I'd like to build Boost.Context with clang on Windows with BB. There are my files: site-config.jam: using clang-win : : "C:/Program Files/LLVM/bin/clang-cl.exe" : <compatibility>vc14 <cxxflags>-Xclang <cxxflags>-std=c++1z <cxxflags>-DBOOST_USE_WINDOWS_H <cxxflags>-DNOMINMAX <cxxflags>-DWIN32_LEAN_AND_MEAN <cxxflags>-D_HAS_AUTO_PTR_ETC=1 ; Jamroot: local BOOST_ROOT = [ modules.peek : BOOST_ROOT ] ; project main : source-location . : requirements <include>$(BOOST_ROOT) <define>BOOST_ALL_NO_LIB=1 ; use-project /boost : $(BOOST_ROOT) ; exe main : main.cpp /boost//coroutine /boost//date_time ; main.cpp int main() {} I run the command: b2.exe -d+2 toolset=clang-win address-model=64 link=static runtime-link=static release -sBOOST_ROOT=D:\path\to\boost This gives me following error: clang-win.compile.asm D:\path\to\boost\bin.v2\libs\context\build\clang-vc14-win\release\link-static\runtime-link-static\threading-multi\asm\make_x86_64_ms_pe_gas.obj -c -Zp4 -Cp -Cx -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_SOURCE -DBOOST_DISABLE_ASSERTS -DNDEBUG -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_SOURCE -DBOOST_DISABLE_ASSERTS -DNDEBUG /W3 -Fo "D:\path\to\boost\bin.v2\libs\context\build\clang-vc14-win\release\link-static\runtime-link-static\threading-multi\asm\make_x86_64_ms_pe_gas.obj" "D:\path\to\boost\libs\context\src\asm\make_x86_64_ms_pe_gas.asm" '-c' is not recognized as an internal or external command, Am I doing something wrong? Thanks.

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[mpl] Working with map, copy and back_inserter
by ☂Josh Chia (謝任中) 05 Feb '17

05 Feb '17

I'm trying to implement a compile-time topological sort of the DAG representing a certain dependency relationship between my classes. One of the data structures I can use to implement topological sort is a map, so I'm trying to use mpl::map using mpl::size_t<> as key. The documentation doesn't define key equality for mpl::map, but I assume it's effectively std::is_same<>. If so, I think I have a problem. In the following code, the last two lines fail static_assert(). The essence of the problem is that my attempt to construct/build my keys using copy with back_inserter does not give me a mpl::vector<> of mpl::size_t<> that is_same to Count, the expected value. It does give me a sequence, and the elements have the right value and value_type but they are not is_same to the expected size_t<> types. So, if I use the elements together with the size_t<> in an mpl::map, won't they be considered to be different keys? Josh #include <type_traits> #include <boost/mpl/at.hpp> #include <boost/mpl/back_inserter.hpp> #include <boost/mpl/copy.hpp> #include <boost/mpl/equal.hpp> #include <boost/mpl/equal_to.hpp> #include <boost/mpl/range_c.hpp> #include <boost/mpl/size_t.hpp> #include <boost/mpl/vector.hpp> using namespace std; namespace mpl = boost::mpl; using Empty = typename mpl::vector<>; using Count = mpl::vector<mpl::size_t<0>, mpl::size_t<1>>; using ConstructedCount = typename mpl::copy< typename mpl::range_c<size_t, 0, 2>, mpl::back_inserter<Empty>>::type; using The0 = typename mpl::at<ConstructedCount, mpl::size_t<0>>::type; using The1 = typename mpl::at<ConstructedCount, mpl::size_t<1>>::type; static_assert(mpl::equal<Count, ConstructedCount, mpl::equal_to<mpl::_1, mpl::_2>>::value, "succeeds"); static_assert(The1::value == 1, "succeeds"); static_assert(std::is_same<typename The1::value_type, size_t>::value, "succeeds"); static_assert(std::is_same<Count, ConstructedCount>::value, "fails"); static_assert(std::is_same<The1, mpl::size_t<1>>::value, "fails");

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[mpl] at<> behaves differently for vector_c<> and vector<>
by ☂Josh Chia (謝任中) 05 Feb '17

05 Feb '17

I asked earlier in a post "[mpl] Working with map, copy and back_inserter". This is a related question. The common question is: What does compile-time equality means in MPL, particularly for map and set key equality? Does it mean std::is_same? The following code works whether USE_VECTOR_C is defined as 0 or 1 -- the last 2 lines are static_asserts that have conditions determined by USE_VECTOR_C so that they succeed, highlighting the difference in behavior between USE_VECTOR_C == 0 and USE_VECTOR_C == 1. USE_VECTOR_C == 0 is the normal case where everything is working as I expect. USE_VECTOR_C == 1 is the unexpected case where the static_asserts in the last 2 lines have conditions altered so that they succeed. Why do vector_c and vector give me different "element values"? In general, what should I be careful about when trying to use the "compile-time values" as keys to avoid the situation elucidated by the last line, where I expect two "compile-time values" to be the same but they are not, resulting in two set/map items instead of one? To clarify, I'm using boost 1.63 with gcc 6.3.1 and -std=c++14 on Arch Linux. Josh #include <type_traits> #include <boost/mpl/at.hpp> #include <boost/mpl/insert.hpp> #include <boost/mpl/set.hpp> #include <boost/mpl/size.hpp> #include <boost/mpl/size_t.hpp> #include <boost/mpl/vector.hpp> #include <boost/mpl/vector_c.hpp> using namespace std; namespace mpl = boost::mpl; #define USE_VECTOR_C 0 using Zero = mpl::size_t<0>; #if USE_VECTOR_C == 1 using Vector = mpl::vector_c<size_t, 0>; #else using Vector = mpl::vector<Zero>; #endif using ZeroElt = typename mpl::at<Vector, Zero>::type; using EmptySet = mpl::set<>; using NonEmptySet = typename mpl::insert<typename mpl::insert<EmptySet, Zero>::type, ZeroElt>::type; static_assert(ZeroElt::value == 0, ""); static_assert(is_same<ZeroElt::value_type, size_t>::value, ""); static_assert(is_same<ZeroElt, Zero>::value == !USE_VECTOR_C, ""); static_assert(mpl::size<NonEmptySet>::value == USE_VECTOR_C + 1, "");

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