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[asio] skipping data in tcp stream
by Roman Shmelev 30 Mar '09

30 Mar '09

HI! What we have: tcp connection, from which we read messages. each message = header(fixed len) + body(random len) header contains the length of body and crc to check if the header is not corrupted. Reading is done in two async steps - first the header is read, then memory for body is allocated and the body is read. Questions are: 1) if header is corrupted under some cases (header crc says body len could be wrong) then as I understand we must skip all body data and read the next message. How to skip? async_read_until seemed to be the solution, but manual told that it may read surplus data into streambuf - it will be hard to deal with that data because I am reading directly from socket to some allocated memory (as was told above) 2) actually, can it be that in tcp stream data will be corrupted? I guess, yes - so header contains bodylen and crc for body and for header? is such solution an overhead? 3) maybe I do some global design mistakes? Thank you!

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String processing algorithms
by Aggelidis Nikos 30 Mar '09

30 Mar '09

hi to all,i am interested in implementing some string processing algorithms{eg boyer-moore , knuth morris prat} for educational purposes. This is the first "real" exposure i will have with boost. I've done a bit of searching and i think Xpressive is the corresponding library of boost, for string processing. From what i read Xpressive is a header-only template library, so i will have to study xpressive.hpp . Any other directions i should follow? thanks in advance for your trouble, nicolas

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[boost][system] Linking problems with C++0x, boost 1.38, Intel C++ 11.0 on windows
by Jesse Perla 30 Mar '09

30 Mar '09

Just to see if it was possible and if I could use "auto", I tried to compile my program with /Qstd:C++0x on Intel Windows 11.0. I am using boost::filesystem (which I assume uses boost::system). I did not recompile these binaries with this flag turned on (partially because I don't know how to mess with bjam or if I needed to mess with settings). The only thing that appears to be failing is linking to boost system. I get the following unresolved externals: 1>sandbox.obj : error LNK2019: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::get_system_category(void)" (?get_system_category@system @boost@@YAABVerror_category@12@XZ) referenced in function ___sti__$E 1>sandbox.obj : error LNK2019: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::get_generic_category(void)" (?get_generic_category@system @boost@@YAABVerror_category@12@XZ) referenced in function ___sti__$E I thought maybe automatic linking was buggy, so I tried to add the following to linker inputs, but no luck: libboost_system-iw-mt-gd-1_38.lib Any ideas? Thanks, -Jesse

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[boost] Any experiences with C++0x features with Intel C++ 11.0 on windows and boost?
by Jesse Perla 29 Mar '09

29 Mar '09

Has anyone tried messing around with the /Qstd:C++0x setting on Intel C++ 11.0 and used boost in the same project? I would love to use "auto" and simple "decltype" if possible, but I don't want to waste a bunch of time if this isn't likely to work with boost or is known to cause incomprehensible errors when mixed with older style generic programming. What about really simple use of the new lambdas? In practice, do you think this is premature and likely to cause major regressions in the future? I can't see how "auto" or "decltype" would change, but is simple lambda usage fairly stable in the converging C++0x specs? -Jesse

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[parameter]Boost Parameter and template template arguments
by Jesse Perla 29 Mar '09

29 Mar '09

I have a class template with a large number of potential template parameters where I would like to use boost parameter. I understand that I can use integers with the int_<> wrapper, but is there any trick or design pattern to allow template template's? The problem is that I have class templates such as an interpolator which will take in a type and a dimension size, and a variety of function objects of the same type. If I can't use template templates, I am not sure how to make the design sane. For example, right now I have something like: template<int Dimension, class T = double, template <int Dim2, class T> template Interpolator = cubic_spline> class DPP; I don't think I can write a free function to solve the instantiation difficulty since many of the types are only used internally and I couldn't use function template argument deduction. -Jesse

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Boost.lamba compile errror....
by Joost Kraaijeveld 29 Mar '09

29 Mar '09

Hi, I want to sort a Matrix of Vectors according to their difference in length to some arbitrary Vector. e.g: template< typename T> struct MatrixVector : std::vector< T > { ... double length() const; MatrixVector<T> difference(const MatrixVector< T>& rhs) const; ... } template< typename T > MatrixVector< T > operator-(const MatrixVector< T >& lhs, const MatrixVector< T >& rhs) { return lhs.difference(rhs); } typedef MatrixVector< double > Vector; typedef std::vector< Vector > Matrix; ... Matrix matrix; matrix.push_back(some vectors); // multiple! std::sort( matrix.begin(), matrix.end(), boost::lambda::bind(&Vector::difference, boost::lambda::_1, observation).length() < boost::lambda::bind(&Vector::difference, boost::lambda::_2, observation).length() ); Compiling this gives (GCC 4.3.2, Debian Lenny, Boost 1.35): g++ -DHAVE_CONFIG_H -I. -I../../src -I/usr/include -g -O2 -MT Main.o -MD -MP -MF .deps/Main.Tpo -c -o Main.o ../../src/Main.cpp ../../src/Main.cpp: In function ‘int main(int, char**)’: ../../src/Main.cpp:101: error: ‘const class boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, boost::tuples::tuple<MatrixVector<double> (MatrixVector<double>::* const)(const MatrixVector<double>&)const, const boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, const MatrixVector<double>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >’ has no member named ‘length’ The error "has no member named ‘length’" is unexpected: a MatrixVector , the return value of the global operator is a MatrixVector, has a member length() . I have tried several syntax possibilities but with no luck. Does anyone has any suggestions? TIA -- Groeten, Joost Kraaijeveld Askesis B.V. Molukkenstraat 14 6524NB Nijmegen tel: 024-3888063 / 06-51855277 fax: 024-3608416 web: www.askesis.nl

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Djikstra Algo
by madhav rao 29 Mar '09

29 Mar '09

I want the source code of djikstra algorithm.I also want to know how to contact the mentors. Can any one please help.I have written a too much optimized version of djikstra algorithm using a priority queue. Please do tell me How to contact the mentor's for this

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Implementing matrix_as_graph to convert a boost::numeric::ublas::matrix to a "graph"
by John Burgoon 29 Mar '09

29 Mar '09

Hi all, I wrote a small program in C++ using boost to read a neural network file (directional graph of a feedforward multilayer perceptron) into boost::numeric::ublas::matrix. The typical file size creates matrices of various sizes, anywhere from a 36x36 to a 130x130 matrix (of floats - edge weights between 0 and 1 to four sig figs). About half to two-thirds of the values are 0 in a typical graph, so I think of them as sparse. There are thousands of such files, so I have been really thrilled with the speed of boost. (I was doing this work with Perl last year. Ahem.) Now I want to implement the boost matrix_as_graph library so that I can convert my matrix into a graph and then implement various network metrics on the graph (such as betweenness_centrality.hpp). However, when I looked in the docs at http://www.boost.org/doc/libs/1_38_0/boost/graph/matrix_as_graph.hpp I was dismayed to find only a code listing: no explanation, no examples. I'm not the strongest C++ coder. Can someone point me to an example or tutorial of how to implement matrix_as_graph to turn a ublas::matrix into a graph? I think I could puzzle it out if I could find an example to emulate. I'll repay the community with a simple blog tutorial of how I did it, if someone can only help me get started. Thanks in advance, John -- John Burgoon Indiana University Bloomington, IN, USA -- >>Insight without implementation is worthless. Get to work.

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Error In undirected subgraph with no parallel edges
by Sandeep Gupta 28 Mar '09

28 Mar '09

Hi, I am using following declaration to define subgraphs over undirected graph such that parallel edges are disallowed: typedef boost::adjacency_list<vecS, setS, undirectedS, property<vertex_index_t,int>, property<edge_index_t,int> > ImplGraph_t; typedef boost::subgraph<ImplGraph_t> embeddedGraph_t; that is use setS for EdgeList instead of listS. However when I call the function local_to_global over the subgraph i end up following errors: /home/sandeep/Computing/boost_1_38_0/boost/graph/subgraph.hpp:147: error: passing ‘const std::vector<void*, std::allocator<void*> >’ as ‘this’ argument of ‘typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::reference std::vector<_Tp, _Alloc>::operator[](size_t) [with _Tp = void*, _Alloc = std::allocator<void*>]’ discards qualifiers /home/sandeep/Computing/boost_1_38_0/boost/graph/subgraph.hpp:147: error: invalid conversion from ‘void*’ to ‘unsigned int’ /home/sandeep/Computing/boost_1_38_0/boost/graph/subgraph.hpp:147: error: initializing argument 1 of ‘typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::reference std::vector<_Tp, _Alloc>::operator[](size_t) [with _Tp = void*, _Alloc = std::allocator<void*>]’ Please find the full code that creates the above scenario. Appreciate any help. -Thanks sandeep ///////////////-----------------------Undirected_Subgraph.cpp----------------------------- #include <boost/graph/subgraph.hpp> #include <boost/graph/adjacency_list.hpp> using namespace boost; typedef boost::adjacency_list<vecS, hash, undirectedS, property<vertex_index_t,int>, property<edge_index_t,int> > ImplGraph_t; typedef boost::subgraph<ImplGraph_t> embeddedGraph_t; int main() { embeddedGraph_t G; typedef graph_traits<embeddedGraph_t>::vertex_descriptor vertex_t; vertex_t v; embeddedGraph_t& G1 = G.create_subgraph(); G.local_to_global(v); return 0; }

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MacOSX: problems linking with "universal binary" Boost and libstdc++-static.a
by FFT 28 Mar '09

28 Mar '09

I'm trying to link my "universal binary" program statically with both Boost and libstdc++-static.a to make the distribution easier, because, as I understand, /usr/lib/libstdc++.6.dylib isn't always there, especially, in versions prior to OSX-10.4 I can build Boost apparently successfully, but linking the regex example statically with libstdc++ causes errors. Perhaps someone here could point out what I'm doing wrong (if anything). Here's what I did to build "universal binary" Boost and compile the example (Btw, the documentation could use some clarity about the recipe): (1) Make sure "g++ --version" says i686-apple-darwin8-g++-4.0.1 (symlinks and PATH adjustments to avoid v3.3) (2) ../../bjam --prefix=~/local --build-dir=~/boost_build toolset=darwin link=static \ threading=multi architecture=combined stage install (I also tried adding runtime-link=static with similar results, see below) (3) g++ -static-libgcc -I ~/local/include/boost-1_38 example.cpp \ -o example /usr/lib/libstdc++-static.a ~/local/lib/libboost_regex-xgcc40-mt.a (I tried skipping /usr/lib/libstdc++-static.a, in which case the binary builds, but is linked with /usr/lib/libstdc++.6.dylib) The errors I get here take up many pages and start like this: /usr/libexec/gcc/i686-apple-darwin8/4.0.1/ld: warning multiple definitions of symbol std::codecvt<char, char, __mbstate_t>::~codecvt() /usr/lib/libstdc++-static.a(codecvt.o) private external definition of std::codecvt<char, char, __mbstate_t>::~codecvt()in section (__TEXT,__tex t) /usr/lib/gcc/i686-apple-darwin8/4.0.1/libstdc++.dylib(single module) definition of std::codecvt<char, char, __mbstate_t>::~codecvt() /usr/libexec/gcc/i686-apple-darwin8/4.0.1/ld: warning multiple definitions of symbol std::codecvt<char, char, __mbstate_t>::~codecvt() /usr/lib/libstdc++-static.a(codecvt.o) private external definition of std::codecvt<char, char, __mbstate_t>::~codecvt()in section (__TEXT,__tex t) /usr/lib/gcc/i686-apple-darwin8/4.0.1/libstdc++.dylib(single module) definition of std::codecvt<char, char, __mbstate_t>::~codecvt() When I use Boost built with "runtime-link=static", the errors look like this instead: /usr/libexec/gcc/i686-apple-darwin8/4.0.1/ld: warning multiple definitions of symbol std::codecvt<char, char, __mbstate_t>::~codecvt() /usr/lib/libstdc++-static.a(codecvt.o) private external definition of std::codecvt<char, char, __mbstate_t>::~codecvt()in section (__TEXT,__tex t) /usr/lib/gcc/i686-apple-darwin8/4.0.1/libstdc++.dylib(single module) definition of std::codecvt<char, char, __mbstate_t>::~codecvt() /usr/libexec/gcc/i686-apple-darwin8/4.0.1/ld: warning multiple definitions of symbol std::codecvt<char, char, __mbstate_t>::~codecvt() /usr/lib/libstdc++-static.a(codecvt.o) private external definition of std::codecvt<char, char, __mbstate_t>::~codecvt()in section (__TEXT,__tex t) Any suggestions?

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