December 2010 - Boost-users

MSVC Visualizers Update
by Filip Konvička 28 Jul '11

28 Jul '11

Hi all, I've just updated the Boost visualizers wiki page at https://svn.boost.org/trac/boost/wiki/DebuggerVisualizers I updated the visualizer for Boost.MultiIndex, which did not work since Boost 1.35. I also added new visualizers for Boost.DateTime (ptime and time_duration) and a simple boost::shared_ptr visualizer. The visualizers are available for checkout via SVN at https://svn.boost.org/svn/boost/sandbox/boost_docs/subprojects/DebuggerVisu… Cheers, Filip

6 7

[multi-array] Extracting dimension information from a multi-array
by Ryan McConnehey 15 Jul '11

15 Jul '11

4 7

Asio unhandled exception
by Łukasz Majewski 20 May '11

20 May '11

Hello, I created a server single thread async (linux) and clinet (win). Every time client is close while server is writing to the socket connected to this client exception appears: terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::system::system_error>>' what(): Transport endpoint is not connected Aborted and server is terminated. I dont know why this exception is unhandled. int main( int argc, char** argv ) { try { boost::asio::io_service io_service; quotation_server server( io_service ); while ( true ) { try { io_service.run(); } catch( ... ){} } } catch ( std::exception& e ) { LOG << e.what() << std::endl; } catch( ... ) { LOG << "Unexpected exception" << std::endl; } return 0; }

2 1

distributed breadth first search doesn't work properly?
by Mattia Lambertini 04 May '11

04 May '11

Hi, i am new to boost and i'm using the PBGL to write a software that compute some graph analysis. I've installed boost 1.44.0 and openmpi 1.5 I tried to run the breadth first search example located in $BOOST_ROOT/libs/graph_parallel/example with the graph $BOOST_ROOT/libs/graph/test/weighted_graph.gr All went well since i figure out that the result is different if i run the algorithm with a different number of processors. Only with one processor the values are corrected. here's what happens: mpirun -np 1 ./breadth_first_search.out graph g { subgraph cluster_0 { label="p0"; n0[label=0]; n1[label=2]; n2[label=1]; n3[label=2]; n4[label=1]; } n0 -- n2; n1 -- n1; n1 -- n3; n1 -- n4; n2 -- n1; n2 -- n3; n3 -- n4; n4 -- n0; n4 -- n1; } --------------------- mpirun -np 2 ./breadth_first_search.out graph g { subgraph cluster_0 { label="p0"; n0[label=0]; n1[label=1]; n2[label=1]; } n0 -- n2; n1 -- n1; n1 -- n3; n1 -- n4; n2 -- n1; n2 -- n3; subgraph cluster_1 { label="p1"; n3[label=1]; n4[label=0]; } n3 -- n4; n4 -- n0; n4 -- n1; } Is that correct? From the doc i can't figure out why.. -- Cordiali saluti, Mattia Lambertini

2 11

Request for conditional index feature in boost multi-index
by Gokulakannan Somasundaram 28 Apr '11

28 Apr '11

Hi, First of all thanks for the great library, which had reduced our development time by a lot. In boost multi-index, we currently have almost all the indexing concepts integrated. Hence i am requesting for a new feature called conditional indexes, where in an index/view inside multi-index will only index a portion of the entries inside the entire multi-index(Say something that satisfies a functor). This is in resemblance to the partial indexes in Postgresql. I feel that would provide elegant solutions to lot of issues without forming round about solutions. For example i have a requirement where in there are two sets of data with the same search criteria, but different eviction criteria Say i have two sets of data with same search condition, but one set needs a MRU(Most Recently Used) list of 100 and the other set requires a MRU of 200. Say the entry is like this class Student { int student_no; char sex; std::string address; }; The search criteria is student_no, but for sex='m', we need MRU of 200 and for sex='f', we need a MRU of 100. Now i have a solution where in i introduce a new ordered index to maintain ordering. For example the IndexSpecifierList will be something like this typedef multi_index_container< Student, indexed_by< ordered_unique< member<Student, int, &Student::student_no> >, ordered_unique< composite_key< member<Student, char, &Student::sex>, member<Student, int, &Student::sex_specific_student_counter> > > > > student_set Here i have to introduce a new counter called sex_specific_student_counter, and during the eviction time, i need a logn search. Insertion also involves a extra logn complexity. Now instead if i have two sequenced indexes (like mentioned in the MRU example) in the place of second ordered index, but both with a condition on indexing only a few items, this would have looked more elegant and with better performance. Thanks in advance, Gokul.

3 3

vs 2010 can't find correct boost lib version?
by Li, Tieniu 30 Mar '11

30 Mar '11

I built boost with visual studio 2010. Libraries of *-vc100-* are generated correctly. When trying to using boost.thread, VS 2010 generated error message: can't find *-vc90-*.lib. Any idea and fixing? Thanks a lot.

4 4

[BGL] Separating twin vertices
by Shaun Jackman 18 Mar '11

18 Mar '11

Hi, I have a directed graph where every vertex has a twin vertex. It is known ahead of time which pairs of vertices are twins. I want to remove as few vertices as possible from the graph such that no vertex and its twin is in the same connected component. Could someone suggest an appropriate algorithm? I've just started delving into the BGL. So far I'm suitably impressed! Cheers, Shaun

2 5

[GIL] gray pixel iterator in generic algorithm
by Curtis Gehman 17 Feb '11

17 Feb '11

I'm trying to use GIL pixel iterators in a generic STL-style algorithm. I'm primarily using GIL for the generic 2D iterators. And in my context, I'm only interested in grayscale images. The value_type associated with GIL iterators is a pixel type, which typically is an object representing multiple channels (e.g., colors). It makes sense that comparison operators (e.g., <) are not defined for general color pixel types. For grayscale images, however, it makes sense that common arithmetic and comparison operators would be defined for the pixel type. This seems to be the case for the 8-bit grayscale GIL type (gray8_view_t). The iterator's value_type appears to be seamlessly evaluated to an unsigned char, exactly as I would expect. When I try to use a float image view type, however, the same magic doesn't seem to happen. Below is some toy code that demonstrates the issue. When the last line is knocked out with "//", the code compiles. But with that second template instantiation (for floats) there, the compiler (gcc 4.2 and VC++2010) exits when it does not find an operator< for the iterator's value_type when instantiating for gray32fc_view_t. I suppose that I can roll my own less<iterator_traits<SrcView::x_iterator>::value_type> functors. But I just started using GIL, and I'm hoping that there is a simpler solution. Any ideas? #include <algorithm> #include <iterator> #include <vector> #include <boost/gil/gil_all.hpp> namespace g = boost::gil; using std::vector; using std::iterator_traits; template <typename SrcView> inline vector<typename iterator_traits<typename SrcView::x_iterator>::value_type> row_min(const SrcView& src) { typedef typename iterator_traits<typename SrcView::x_iterator>::value_type value_t; vector<value_t> result; for (int y = 0; y < src.height(); ++y) { result.push_back(*std::min_element(src.row_begin(y), src.row_end(y))); } return result; } // Explicit template instantiation // Works for gray8c_view_t. template vector<iterator_traits<g::gray8c_view_t::x_iterator>::value_type> row_min(const g::gray8c_view_t& src); // Compile error for gray32fc_view_t. // No operator< for iterator_traits<g::gray32fc_view_t::x_iterator>::value_type. template vector<iterator_traits<g::gray32fc_view_t::x_iterator>::value_type> row_min(const g::gray32fc_view_t& src);

3 7

Re: [Boost-users] multi_array and variants
by Alle Meije Wink 07 Feb '11

07 Feb '11

Dear Kris, thanks for your reply. > > What I now have is a class bisArray: > > ... > > template<typename T> > > class bisArray: public bisObject { > > typedef boost::variant > > < boost::multi_array_ref<T, 1>, > > boost::multi_array_ref<T, 2>, > > boost::multi_array_ref<T, 3>, > > boost::multi_array_ref<T, 4>, > > boost::multi_array_ref<T, 5>, > > boost::multi_array_ref<T, 6>, > > boost::multi_array_ref<T, 7>, > > boost::multi_array_ref<T, 8>, > > boost::multi_array_ref<T, 9> > > > bisArray_t; > > bisArray_t _bisArray; > > ... > > > > and a class bisImage, which has a bisArray as well as a pointer to the > > data as read from file (1-dimensional structure): > > ... > > > > template<typename T> > > > > class bisImage: public bisObject { > > > > public: > > > > /** Constructor using existing array data > > Reformats array as bisImage > > */ > > bisImage ( T* _data, size_t _dimensions, std::vector<size_t> _sizes > > ): > > data(_data), dimensions(_dimensions) { > > > > This code (or You) comes from java or C#, doesn't it? ;-) In C++ it is > supposed to be this->[...] instead of this.[...] No, it's C (which doesn't use any of this -not properly at least). The whole this[...] business was not supposed to be there anyway I realised. The reason that I went to boost:: is that I was hoping to get one class for all data types (using T) and dimensionalities (using multi_array) > Second thing: the member storage is initialized with the default constructor > (which in this case does not exist => error ), and then assigned (below). > > I suggest a change to: > bisImage([...]) : [...], storage( _data, _dimensions, _size ) { [...] > and remove the assignment from the body of the constructor > > Note also: I have read in many places, that you should not use names > beginning with an underscore (_), because they are reserved for > compiler/library implementation. One of those places was Herb Sutter's gotw > series. Ah! The underscore names come from a library that I tried to imitate which has successfully incorporated some aspects of boost(it is called MIMAS). Have not reached the stage of 'nicifying' the code yet... I moved the storage thing to where you suggested (1 line up) and that does get rid of lots of errors. However what I am stuck with seems to be, in essence, still the same thing: >>> /home/amwink/programs/cpp/bis/src/bisniftiimage.cpp||In function ‘void bis::bisReadNifti(std::string)’:| >>> /home/amwink/programs/cpp/bis/src/bisniftiimage.cpp|102|warning: unused variable ‘testimage’| >>> /usr/include/boost/variant/variant.hpp||In constructor ‘boost::variant<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19>::variant() [with T0_ = boost::multi_array_ref<unsigned char, 1ul>, T1 = boost::multi_array_ref<unsigned char, 2ul>, T2 = boost::multi_array_ref<unsigned char, 3ul>, T3 = boost::multi_array_ref<unsigned char, 4ul>, T4 = boost::multi_array_ref<unsigned char, 5ul>, T5 = boost::multi_array_ref<unsigned char, 6ul>, T6 = boost::multi_array_ref<unsigned char, 7ul>, T7 = boost::multi_array_ref<unsigned char, 8ul>, T8 = boost::multi_array_ref<unsigned char, 9ul>, T9 = boost::detail::variant::void_, T10 = boost::detail::variant::void_, T11 = boost::detail::variant::void_, T12 = boost::detail::variant::void_, T13 = boost::detail::variant::void_, T14 = boost::detail::variant::void_, T15 = boost::detail::variant::void_, T16 = boost::detail::variant::void_, T17 = boost::detail::variant::void_, T18 = boost::detail::variant::void_, T19 = boost::detail::variant::void_]’:| >>> /home/amwink/programs/cpp/bis/src/bisarray.hpp|52|instantiated from ‘bis::bisArray<T>::bisArray(T*, size_t, std::vector<long unsigned int, std::allocator<long unsigned int> >) [with T = unsigned char]’| >>> /home/amwink/programs/cpp/bis/src/bisimage.hpp|33|instantiated from ‘bis::bisImage<T>::bisImage(T*, size_t, std::vector<long unsigned int, std::allocator<long unsigned int> >) [with T = unsigned char]’| >>> /home/amwink/programs/cpp/bis/src/bisniftiimage.cpp|126|instantiated from here| >>> /usr/include/boost/variant/variant.hpp|1198|error: no matching function for call to ‘boost::multi_array_ref<unsigned char, 1ul>::multi_array_ref()’| >>> /usr/include/boost/multi_array/multi_array_ref.hpp|623|note: candidates are: boost::multi_array_ref<T, NumDims>::multi_array_ref(T*, const typename boost::const_multi_array_ref<T, NumDims, T*>::storage_order_type&, const typename boost::const_multi_array_ref<T, NumDims, T*>::index*, const typename boost::const_multi_array_ref<T, NumDims, T*>::size_type*) [with T = unsigned char, long unsigned int NumDims = 1ul]| >>> /usr/include/boost/multi_array/multi_array_ref.hpp|469|note: boost::multi_array_ref<T, NumDims>::multi_array_ref(T*, const boost::detail::multi_array::extent_gen<NumDims>&, const boost::general_storage_order<NumDims>&) [with T = unsigned char, long unsigned int NumDims = 1ul]| >>> /usr/include/boost/multi_array/multi_array_ref.hpp|463|note: boost::multi_array_ref<T, NumDims>::multi_array_ref(T*, const boost::detail::multi_array::extent_gen<NumDims>&) [with T = unsigned char, long unsigned int NumDims = 1ul]| >>> /usr/include/boost/multi_array/multi_array_ref.hpp|417|note: boost::multi_array_ref<unsigned char, 1ul>::multi_array_ref(const boost::multi_array_ref<unsigned char, 1ul>&)| >>> ||=== Build finished: 1 errors, 1 warnings ===| So boost.variant now sugegsts that multi_array_ref() is called, a constructor with no arguments! I don't use that, and I don't even think it exists (because it produces a multi_array view of an *existing* C-style array! The only way I knew to initialise a bisArray was with using a switch statement -proper C: switch dims{ case 1: _bisarray=multi_array_ref<T,1> (data, sizes); break; case 2: _bisarray=multi_array_ref<T,2> (data, sizes); break; ... } That is the only way multi_array_ref is called! Any idea why a problem with the *default* constructor would turn up? Thanks for your suggestions! My error list already fits on one screen :) Alle Meije

3 3

Simple serial port demonstration with boost asio asynchronous I/O
by Jeff Gray 25 Jan '11

25 Jan '11

A couple of weeks ago I posted a simple asynchronous demonstration of a telnet client using boost asio TCP network code. I have changed this code to turn it into a simple serial terminal application using the serial port support in the new version of boost asio. It required no changes at all the the read or write code. I just altered the initialization to use a serial port instead of a socket. Note that this is not intended to show how a fully functional application would work. There are plenty of areas that are not handled in this code. But it shows the idea and it's easy to build on this once you've got it working. Hope this helps someone else get started... Jeff

3 2