- Boost-users - lists.boost.org

equals() from boost/algorithm/string.hpp in top namespace?
by Olaf van der Spek 10 Mar '07

10 Mar '07

Hi, Why is equals() in the top namespace in 1.33.1? #include <boost/algorithm/string.hpp> #include <boost/array.hpp> int main() { boost::array<char, 4> a = { 1, 2, 3, 4 }; equals(a, a); return 0; }

3 3

[Serialization] How to restore ref-counted strings
by Bill Lear 10 Mar '07

10 Mar '07

We have a massive amount of data to serialize, on the order of several gigabytes. Lots of strings involved, maybe hundreds of millions. We discovered that the data structure in memory would bloat enormously when read back in from disk (say, from 2 gig to 3.1 gig). We think we have tracked this down to (gcc implementation) string reference counts not being "restored". I think a solution for us is to do something like the following: static map<string, bool> string_map; template <class Archive> void read_string(Archive ar, string& a_string) { string s; ar >> s; // read from disk map<string, bool>::iterator i = string_map.find(s); if (i == string_map.end()) { i = string_map.insert(make_pair(s, true)); } a_string = i->first; } void destroy_map() { string_map.clear(); } Then, when the data structures have all been read, invoke the destroy_map() method to clear the string_map object, thus decremented all refcounts of strings by one. Has anyone else encountered this and found a solution? Also, if anyone has bright ideas on a better data structure than std::map to use for storing hundreds of millions of strings at once for the above purpose, that also might be nice. Thanks. Bill

2 8

[MPL?] generating functions for all fields in a struct
by Christoph Duelli 10 Mar '07

10 Mar '07

Given a struct like struct X { int a; char b; float c; } and some function-'template' f is it possible to 'generate' - preferably by means of templates, MPL or something of the kind - variations of some function f for each of X's fields? E.g. I'd like to have functions like int getA() { return a; } char getB() { return b; } float getC() { return c; } ... (The functions I have in mind are more complex, obviously, but the idea is to generate one such function for all the fields of X.) I would like to avoid writing a macro call or something per field, as I would like the code to work (after recompiling it) even if the definition of X is changed and some fields are added. So, is there some generic 'iterator' over the fields of a struct? Thank you and best regards Christoph

4 4

Problem with iterator_property_map
by Jens Müller 10 Mar '07

10 Mar '07

I have a problem with the iterator property map adapter ... I have the following call in my program: bucket_sort(out_edges(*vi,g).first, out_edges(*vi,g).second, make_iterator_property_map(ord.begin(), get(edge_index, g)), std::back_inserter(sorted_edge_lists[get(get(vertex_index, g), *vi)].first) Bucket sort is a function written by me: /** Bucket sort algorithm. Accepts a range of object with a pair of ForwardIterators and outputs the elements in ascending order with an OutputIterator. \todo Maybe adding a sort order parameter is useful? \param begin Iterator pointing to the first element to be sorted. \param end Iterator pointing after the last element to be sorted. \param values ReadablePropertyMap with values of type int and keys having the type of *begin. \param out output iterator for the sorted elements. */ template<class ForwardIterator, class ValueMap, class OutputIterator> void bucket_sort(ForwardIterator begin, ForwardIterator end, ValueMap values, OutputIterator out) { int max = get(values, *begin); int min = get(values, *begin); for(ForwardIterator i = begin; i!=end; ++i) { if(get(values, *i)>max) max = get(values, *i); if(get(values, *i)<min) min = get(values, *i); } int n = (max - min)+1; std::cout << "max: " << max << ", min: " << min << std::endl; typedef typename std::iterator_traits<ForwardIterator>::value_type value_type; std::vector< std::list<value_type> > bucket(n); for(ForwardIterator i = begin; i!=end; ++i) { int index = get(values, *i); bucket[index-min].push_back(*i); } for(int i=0;i<n;++i) { typedef typename std::list<value_type>::iterator iter; for(iter b = bucket[i].begin(), e = bucket[i].end(); b!=e; ++b) { *out = *b; } } // for } // bucket_sort My graph is a LEDA graph, the edge_index property map is created by this code in leda_graph.hpp: class leda_graph_id_map : public put_get_helper<int, leda_graph_id_map> { public: typedef readable_property_map_tag category; typedef int value_type; typedef int reference; typedef leda::node key_type; leda_graph_id_map() { } template <class T> long operator[](T x) const { return x->id(); } }; template <class vtype, class etype> inline leda_graph_id_map get(vertex_index_t, const leda::GRAPH<vtype, etype>& g) { return leda_graph_id_map(); } template <class vtype, class etype> inline leda_graph_id_map get(edge_index_t, const leda::GRAPH<vtype, etype>& g) { return leda_graph_id_map(); } template <class Tag> struct leda_property_map { }; template <> struct leda_property_map<vertex_index_t> { template <class vtype, class etype> struct bind_ { typedef leda_graph_id_map type; typedef leda_graph_id_map const_type; }; }; template <> struct leda_property_map<edge_index_t> { template <class vtype, class etype> struct bind_ { typedef leda_graph_id_map type; typedef leda_graph_id_map const_type; }; }; (The edge_index part of this is new, I think). Well, when I try to compile it, I get: /home/jmueller/software-gcc34/boost/include/boost-1_33_1/boost/property_map.hpp: In function `Reference boost::get(const boost::put_get_helper<Reference, PropertyMap>&, const K&) [with PropertyMap = boost::iterator_property_map<__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, boost::leda_graph_id_map, int, int&>, Reference = int&, K = leda::edge_struct*]': bucket_sort.hpp:27: instantiated from `void separator::bucket_sort(ForwardIterator, ForwardIterator, ValueMap, OutputIterator) [with ForwardIterator = boost::graph_traits<leda::GRAPH<int, int> >::out_edge_iterator, ValueMap = boost::iterator_property_map<__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, boost::leda_graph_id_map, int, int&>, OutputIterator = std::back_insert_iterator<std::list<leda::edge_struct*, std::allocator<leda::edge_struct*> > >]' special_bfs.hpp:323: instantiated from `void separator::balanced_breadth_first_visit(const EdgeListGraph&, const typename boost::graph_traits<G>::vertex_descriptor&, BFSVisitor, ColorMap) [with EdgeListGraph = leda::GRAPH<int, int>, BFSVisitor = boost::bfs_visitor<boost::distance_recorder<boost::leda_node_property_map<int, int&, leda::node_map<int, leda::graph, -0x000000001>*>, boost::on_tree_edge> >, ColorMap = MapAsColorMap<boost::leda_node_property_map<int, int&, leda::node_map<int, leda::graph, -0x000000001>*>, boost::default_color_type>]' [...] /home/jmueller/software-gcc34/boost/include/boost-1_33_1/boost/property_map.hpp:312: error: no match for 'operator[]' in '(const boost::iterator_property_map<__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, boost::leda_graph_id_map, int, int&>&)((const boost::iterator_property_map<__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, boost::leda_graph_id_map, int, int&>*)(&pa))[k]' /home/jmueller/software-gcc34/boost/include/boost-1_33_1/boost/property_map.hpp:349: note: candidates are: R boost::iterator_property_map<RandomAccessIterator, IndexMap, T, R>::operator[](typename boost::property_traits<IndexMap>::key_type) const [with RandomAccessIterator = __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, IndexMap = boost::leda_graph_id_map, T = int, R = int&] Does anyone have any suggestions what I am doing wrong here?

1 2

Use boost on AIX 5.2L?
by Aaron Tan 10 Mar '07

10 Mar '07

Hi, Does anyone know how to use boost libraries with VisualAge C++ 6 on AIX 5.2L? Regards, Aaron ____________________________________________________ Yahoo! Singapore Answers Real people. Real questions. Real answers. Share what you know at http://answers.yahoo.com.sg

4 3

another problem with bind
by Christian Henning 09 Mar '07

09 Mar '07

Hi there, for whatever reason the compiler cannot decide the right call to "make". Please consider the following code: using namespace std; using namespace boost; template< typename T > void make( const T& t ) {} template< typename T > void make( const T& t, int i ) {} template< typename T > void make( const T& t, int i, int j ) {} struct a {}; struct b {}; void foo( string& s, a ) {} void foo( string& s, b ) {} int _tmain(int argc, _TCHAR* argv[]) { string str( "Hello" ); make( ( bind( static_cast<void(*)(string&, a )>( &foo ), _1, _2)( ref( str ) , a() )) ); return 0; } I want to make a call to the first make taking just on parameter, the bind object. But the compiler thinks something else: test.cpp(29) : error C2780: 'void make(const T &,int,int)' : expects 3 arguments - 1 provided test.cpp(16) : see declaration of 'make' test.cpp(29) : error C2780: 'void make(const T &,int)' : expects 2 arguments - 1 provided test.cpp(13) : see declaration of 'make' test.cpp(29) : error C2784: 'void make(const T &)' : could not deduce template argument for 'const T1 &' from 'boost::_bi::bind_t<R,F,L>::result_type' with [ R=void, F=void (__cdecl *)(std::string &,a), L=boost::_bi::list2<boost::_bi::list_av_2<boost::arg<1>,boost::arg<2>>::B1,boost::_bi::list_av_2<boost::arg<1>,boost::arg<2>>::B2> ] test.cpp(10) : see declaration of 'make' How can I make that clear to the compiler? Thanks ahead, Christian

1 0

problem with bind and non-member function
by Christian Henning 09 Mar '07

09 Mar '07

Hi there, I'm using MSVC 7.1 and cannot get the following program to compile. I have tried the mailing list but couldn't find anything related. I'm sure it's a trivial problem but I cannot see right now. Anyone any idea? using namespace std; using namespace boost; struct a {}; struct b {}; void foo( string& s, a ) {} void foo( string& s, b ) {} int _tmain(int argc, _TCHAR* argv[]) { string str( "Hello" ); bind( static_cast<void(*)(string&, a )>( &foo ), ( ref( str ), a() )); return 0; } The error message is: c:\boost\boost\bind.hpp(63) : error C2825: 'F::result_type': cannot form a qualified name c:\boost\boost\bind\bind_template.hpp(15) : see reference to class template instantiation 'boost::_bi::result_traits<R,F>' being compiled with [ R=boost::_bi::unspecified, F=void (__cdecl *)(std::string &,a) ] test.cpp(18) : see reference to class template instantiation 'boost::_bi::bind_t<R,F,L>' being compiled with [ R=boost::_bi::unspecified, F=void (__cdecl *)(std::string &,a), L=boost::_bi::list1<boost::_bi::list_av_1<a>::B1> ] c:\boost\boost\bind.hpp(63) : error C2039: 'result_type' : is not a member of 'operator``global namespace''' c:\boost\boost\bind.hpp(63) : error C2146: syntax error : missing ';' before identifier 'type' c:\boost\boost\bind.hpp(63) : error C2955: 'boost::_bi::type' : use of class template requires template argument list c:\boost\boost\bind.hpp(112) : see declaration of 'boost::_bi::type' c:\boost\boost\bind.hpp(63) : fatal error C1903: unable to recover from previous error(s); stopping compilation

2 4

iostream large file - performance
by Aljaz 09 Mar '07

09 Mar '07

Hello.. I've been testing fstream libary to read a huge text file (45 megabytes), which has around 2 million lines.. When I do (using fstream): Code: int line = 0; string str; ifstream is("file.txt"); while (!is.eof()) { getline(is, str); line++; }It takes about 9 seconds to read the whole file.. If I open file it with any 'good' text editor (editplus, notepad++ for instance) it takes a few seconds to read/load the whole file.. So I'm wondering.. What am I doing wrong? What should I do to achieve that speed - better preformance? Can boost::iostream do any better? Another thing: I tried writing data to deque (deque.pushback(str)) and was shocked on what happened.. It took ages to process the file, cpu constant at 99% so I closed the program after around 3 minutes.. Whats the 'proper' way to read files to memory? How do text editors do this? They load the same file in 4 seconds! I need a fastest way to read about 10 000 lines from text file at once.. Any help highly appreciated! Best regards A

7 7

[BGL] Visitor events
by Anton A. Patrushev 09 Mar '07

09 Mar '07

Hi, I want to implement my own edge-based visitor. I need to implement new visitor events (for example on_initialize_edge or on_finish_edge). So, what should I do? Do I need to redefine entire visitor concept? Regards, Anton.

2 2

Circular buffer library in boost
by Meryl Silverburgh 09 Mar '07

09 Mar '07

Hi, Is there a Circular buffer library in boost? If not, can you please tell me if there is a circular buffer library in c++? Thank you.

2 1