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[BGL] how to build a hierarchy of graphs
by Shufei Fan 05 Apr '07

05 Apr '07

Hi, I need to build a hierarchy of graphs bottom up. Conceptually, every level(>1) of graph is a result of merging groups of nearest neighbors of its immediate lower level, according to some sort of criteria. My general question is, what is the best way of building this hierarchy using BGL?(or, BGL already has this kind of mechanism somewhere?) (I didnot read in detail concepts like subgraph, filter, etc. From the names, they seems to of help?) And Is it possible to effeciently retrieve information both within same level and across levels? Thanks in advance. Shufei

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[licensing] Proper way of quoting the license
by Ruediger Berlich 05 Apr '07

05 Apr '07

Hi there, while looking for a thread-safe buffer implementation, I discovered the upcoming circular_buffer library (with a thread-safe bounded_buffer implementation on top), and William E. Kempf's tutorial implementation of a bounded buffer (boost_1_33_1/libs/thread/tutorial/bounded_buffer.cpp in the 1.33.1 boost sources). The circular_buffer library is not yet officially available as part of Boost, but fortunately the tutorial implementaion does most of what I need. That is, with the notable exception that it covers Integers only. I have thus made a few small changes, including making it a template, so I can "plug in" any type I want, and I want to use it for the time being (until circular_buffer becomes officially available). ** My question now is, what the proper way is to refer to William and honour the license terms, while still excluding any "express or implied warranty" for my changes. ** Here is my current approach: /** * Note: This class was taken (with small modifications) * from the Boost.thread tutorials * ( boost_1_33_1/libs/thread/tutorial/bounded_buffer.cpp ). * The original code contained the following text: * *************************************************************** * Copyright (C) 2001-2003 * * William E. Kempf * * * * Permission to use, copy, modify, distribute and sell this * * software and its documentation for any purpose is hereby * * granted without fee, provided that the above copyright * * notice appear in all copies and that both that copyright * * notice and this permission notice appear in supporting * * documentation. William E. Kempf makes no representations * * about the suitability of this software for any purpose. * * It is provided "as is" without express or implied warranty. * *************************************************************** * * All modifications to William E. Kempf's original code, as shown * in this file, are covered by the same license as listed above, * and are Copyright (C) 2007 Ruediger Berlich. In particular, * please note that * *************************************************************** * Ruediger Berlich makes no representations * * about the suitability of this software for any purpose. * * It is provided "as is" without express or implied warranty. * *************************************************************** * / Is this sufficient ? And [do I have to / may I / should I] include an additional copyright statement for the modifications ? Or am I just paranoid ? ;-) Thanks and have a good easter time, Ruediger

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[MultiIndex] Resolving foreign keys
by Christian Henning 05 Apr '07

05 Apr '07

Hi there, beware I'm a new to Multiindex and haven't digested the whole capabilities of the library, yet. In my example I have two entities that are connected via a foreign key. In this case the key is type of an int. When retrieving the objects from a database I end up having two containers containing those objects. In the code below there are a customer_row and a order_row class. There is a one-to_many relationship between them. One customer can have several order but one order is can only one customer. So, my goal is to find an way to create order objects that are pointing to the correct row objects. So far, I don't really see how the MultiIndex lib can be of help for me. I have looked at the example six which I think came pretty close to my goal. So, taken this example, is it possible to use an key type instead of the car_manufacturer pointer? Please consider the following code: using namespace std; using namespace boost; using namespace boost::multi_index; struct primary {}; struct foreign {}; struct customer_row { int _id; string _name; customer_row( int id, const string& name ) : _id( id ), _name( name ) {} friend ostream& operator<<( ostream& os, const customer_row& c ) { os << c._id << " " << c._name << endl; return os; } }; typedef multi_index_container< customer_row, indexed_by< ordered_unique< tag< primary >, BOOST_MULTI_INDEX_MEMBER(customer_row,int,_id) > > > customer_table; struct order_row { int _id; int _customer_id; string _article; order_row( int id, int customer_id, const string& article ) : _id( id ), _customer_id( customer_id ), _article( article ) {} friend ostream& operator<<( ostream& os, const order_row& o ) { os << o._id << " " << o._customer_id << " " << o._article << endl; return os; } }; typedef multi_index_container< order_row, indexed_by< ordered_unique< tag< primary >, BOOST_MULTI_INDEX_MEMBER(order_row,int,_id) >, ordered_non_unique< tag< foreign >, BOOST_MULTI_INDEX_MEMBER(order_row,int,_customer_id) > > > order_table; struct order { const order_row* _order_row; const customer_row* _customer_row; }; int main() { customer_table ct; ct.insert( customer_row( 97, "Bon Jovi" )); ct.insert( customer_row( 98, "Billy Joel" )); ct.insert( customer_row( 99, "Morgan Freeman" )); order_table ot; ot.insert( order_row( 0, 97, "Book" )); ot.insert( order_row( 1, 97, "Car" )); ot.insert( order_row( 2, 97, "Dish Washer" )); order_table::iterator it = ot.get<primary>().begin(); order_table::iterator end = ot.get<primary>().end(); vector<order> orders; while( it != end ) { // find customer typedef customer_table::index<primary>::type customer_table_by_primary; customer_table_by_primary::iterator ic = ct.get<primary>().find( it->_customer_id ); order o; o._order_row = &( *it ); o._customer_row = &*ct.get<primary>().find( it->_customer_id ); orders.push_back( o ); ++it; } return 0; } Is there a more advanced way using the MultiIndex lib of combining two related objects so I can created my orders array? Or in different words can I structure my code more efficiently? Since this is a very simplified version it should be extensible to more entities with more than one foreign keys. Thanks ahead, Christian

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[BGL] re-indexing of vertices /or edges
by Shufei Fan 05 Apr '07

05 Apr '07

Hi, Can I disable re-indexing of vertices after one of them is removed? In one of the old thread: http://thread.gmane.org/gmane.comp.lib.boost.user/10551/focus=10552 Doug said: " Vertex and edge indices are a weak point in the BGL. It seems like they should be automatically updated, but that can't be done efficiently. We have a partial solution (a graph type that is reasonably good all-around and does automatic (re-)indexing), but it's not ready for release yet." I am using release 1.33.1. Is this re-indexing released?(I assume so, from my simple trial) But, is there any way of enabling /and disabling re-indexing? Interestingly, my application needs re-indexing disabled, even though some vertices or edges are removed. Thanks, Shufei

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to Jan gaspar : status of circular buffer
by Vincent Torri 05 Apr '07

05 Apr '07

Hello, I would like to know the status of the circular buffer library. The boost sandbox cvs shows regular commits, but is it close to a release (in boost 1.35, for example) ? thank you Vincent Torri

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Re: [Boost-users] [serialization] Serialization through pointer to baseclass
by Pfligersdorffer, Christian 05 Apr '07

05 Apr '07

Hey Ruediger, you simply need to make toString() virtual :-) Life can be that simple sometimes... Best wishes, DI Christian Pfligersdorffer Software Engineering EOS GmbH > -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org]On Behalf Of Ruediger > Berlich > Sent: Wednesday, April 04, 2007 5:28 PM > To: boost-users(a)lists.boost.org > Subject: [Boost-users] [serialization] Serialization through > pointer to > baseclass > > > Hi there, > I am trying to serialize an object through a pointer to its > base class. > > My application is in the field of distributed processing. I have > a "communicator" type of class, which receives pointers from > other objects, > serializes them, sends the generated string over a network > for further, > remote processing and then deals with the responses. It is > supposed to know > nothing about the objects it serializes, except that they contain a > method "toString()", which is contained in the base class. > > However, when I call that method, I only get a serialization > of that base > class, not of the derived class. > > Here is some code to illustrate the problem. The output of > the program is > listed at the end of this posting. > > How can I achieve serialization of the derived class (without explicit > casting), if it is stored in a pointer to a base class ? > > My assumption is that this has to do with the fact that the > "serialization" > method cannot be virtual, as it is a member function template. > > Any help is appreciated. > > Thanks and have a good day, > Ruediger > > /************************************************************* > ************/ > // headers and namespace statements removed ... > > class base > :public vector<int> > { > friend class boost::serialization::access; > > template<class Archive> > void serialize(Archive & ar, const unsigned int version){ > using boost::serialization::make_nvp; > ar & make_nvp("vector", > > boost::serialization::base_object<std::vector<int> >(*this)); > } > > public: > base(){ /* nothing */ } > virtual ~base() { /* nothing */ } > > virtual void appendValue(int val) = 0; > > string toString(void){ > ostringstream ofs; > boost::archive::xml_oarchive oa(ofs); > // this should point to derived objects > oa << make_nvp("myp",*this); > return ofs.str(); > } > > void printType(void){ > cout << typeid(*this).name() << endl; > } > }; > > BOOST_IS_ABSTRACT(base); > > /************************************************************* > ***************/ > > class derived > :public base > { > friend class boost::serialization::access; > > template<class Archive> > void serialize(Archive & ar, const unsigned int version){ > using boost::serialization::make_nvp; > ar & make_nvp("base", > boost::serialization::base_object<base>(*this)); > } > > public: > derived(){ /* nothing */ } > virtual ~derived() { /* nothing */ } > > void appendValue(int val){ > this->push_back(val); > } > }; > > > BOOST_CLASS_EXPORT(derived); > > /************************************************************* > ***************/ > > main() > { > base *myp = new derived(); > myp->appendValue(1); > > // only serializes class "base" > cout << myp->toString(); > > cout << "===========================" << endl; > > myp->printType(); > // this in printType points to the correct type > cout << "===========================" << endl; > > // Explicit casting to the derived class yields the > correct response > derived *mypp = (derived *)myp; > ostringstream ofs; > boost::archive::xml_oarchive oa(ofs); > oa << make_nvp("myp",*mypp); > cout << ofs.str() << endl; > } > > /************************************************************* > ***************/ > > Here is the output of the program: > > <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> > <!DOCTYPE boost_serialization> > <boost_serialization signature="serialization::archive" version="3"> > <myp class_id="0" tracking_level="0" version="0"> > <vector> > <count>1</count> > <item>1</item> > </vector> > </myp> > =========================== > 7derived > =========================== > <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> > <!DOCTYPE boost_serialization> > <boost_serialization signature="serialization::archive" version="3"> > <myp class_id="0" tracking_level="1" version="0" object_id="_0"> > <base class_id="1" tracking_level="0" version="0"> > <vector> > <count>1</count> > <item>1</item> > </vector> > </base> > </myp> > > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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nested containers with boost?
by nicola 05 Apr '07

05 Apr '07

Hi, I would like an arbitrarily nested data structure, e.g. similar to std::vector< std::list<int> >, giving access to the elements of any of its subcontainers, but, at the same time, being a model of Container - in particular, having an iterator over all the elements in the last nesting level (int's in the previous example). Space/time efficiency is very important in my application. My solution would be to build a container adaptor similar to // vector of lists of ... of int typedef my_nested_container<std::vector, std::list, ..., int> nc_type; nc_type nc; (with type lists?) with an iterator adaptor that allows me to write something like: for (nc_type::iterator i = nc.begin(); i != nc.end(); ++i) // do smth with integer *i The nested container should also allow the user to modify each subcontainer and to iterate over the elements of a subcontainer, possibly without (much) overhead, e.g. // Iteration over the elements of one subcontainer for (nc_type::inner_iterator j = nc.inner_begin(); j != nc.inner_end(); ++j) // ... I have started to implement a prototype from scratch, but I am wondering whether I am reinventing the wheel. I think I can use boost::iterator_facade for my_nested_container::iterator and/or boost::pointer_container to build the nested structure internally (to minimize reallocation overhead upon dynamical change of the structure). Is there any other boost library I could take advantage from? I find that operations on a nested container are not completely trivial to implement (or even to define properly, think of add/remove in subcontainers which may themselves be nested containers) given its recursive nature, so I would be very glad to know that something like that is available off-the-shelf. I have found myself in need for such a data structure more often than not. Nicola

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[serialization] Serialization through pointer to base class
by Ruediger Berlich 05 Apr '07

05 Apr '07

Hi there, I am trying to serialize an object through a pointer to its base class. My application is in the field of distributed processing. I have a "communicator" type of class, which receives pointers from other objects, serializes them, sends the generated string over a network for further, remote processing and then deals with the responses. It is supposed to know nothing about the objects it serializes, except that they contain a method "toString()", which is contained in the base class. However, when I call that method, I only get a serialization of that base class, not of the derived class. Here is some code to illustrate the problem. The output of the program is listed at the end of this posting. How can I achieve serialization of the derived class (without explicit casting), if it is stored in a pointer to a base class ? My assumption is that this has to do with the fact that the "serialization" method cannot be virtual, as it is a member function template. Any help is appreciated. Thanks and have a good day, Ruediger /*************************************************************************/ // headers and namespace statements removed ... class base :public vector<int> { friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version){ using boost::serialization::make_nvp; ar & make_nvp("vector", boost::serialization::base_object<std::vector<int> >(*this)); } public: base(){ /* nothing */ } virtual ~base() { /* nothing */ } virtual void appendValue(int val) = 0; string toString(void){ ostringstream ofs; boost::archive::xml_oarchive oa(ofs); // this should point to derived objects oa << make_nvp("myp",*this); return ofs.str(); } void printType(void){ cout << typeid(*this).name() << endl; } }; BOOST_IS_ABSTRACT(base); /****************************************************************************/ class derived :public base { friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version){ using boost::serialization::make_nvp; ar & make_nvp("base", boost::serialization::base_object<base>(*this)); } public: derived(){ /* nothing */ } virtual ~derived() { /* nothing */ } void appendValue(int val){ this->push_back(val); } }; BOOST_CLASS_EXPORT(derived); /****************************************************************************/ main() { base *myp = new derived(); myp->appendValue(1); // only serializes class "base" cout << myp->toString(); cout << "===========================" << endl; myp->printType(); // this in printType points to the correct type cout << "===========================" << endl; // Explicit casting to the derived class yields the correct response derived *mypp = (derived *)myp; ostringstream ofs; boost::archive::xml_oarchive oa(ofs); oa << make_nvp("myp",*mypp); cout << ofs.str() << endl; } /****************************************************************************/ Here is the output of the program: <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="3"> <myp class_id="0" tracking_level="0" version="0"> <vector> <count>1</count> <item>1</item> </vector> </myp> =========================== 7derived =========================== <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="3"> <myp class_id="0" tracking_level="1" version="0" object_id="_0"> <base class_id="1" tracking_level="0" version="0"> <vector> <count>1</count> <item>1</item> </vector> </base> </myp>

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[serialization] bug? serializing a vector resets ignored element members
by n.torrey.pines＠gmail.com 05 Apr '07

05 Apr '07

Hi If I serialize a struct, while ignoring one of its members, the member retains its value. I understand that this is the inteded serialization semantics - what you ignore for reading and writing remains intact. However, if I do this with a vector, the ingored members of its elements get reset to their "default" values. I'm too lazy to pore over the sources, but I'm guessing this might be happening because the implementation of vector serialization calls its constructor (and assignment?) where a resize could probably be better. Here is the specific code I boiled down the manifestation of this feature/bug to: // creates writes "remove_me" file #include <iostream> #include <fstream> #include <vector> #include <boost/filesystem/fstream.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/vector.hpp> struct s { s() : i(0), j(0) {} s(int i, int j) : i(i), j(j) {} int i, j; private: friend class boost::serialization::access; template<typename Archive> void serialize(Archive& ar, const unsigned version) { // ignore j ar & i; } }; struct v { v(const s& x) : data(5, x) {} std::vector<s> data; void write(const char* name) const { std::ofstream out(name); boost::archive::text_oarchive ar(out); ar << *this; } void read(const char* name) { std::ifstream in(name); boost::archive::text_iarchive ar(in); ar >> *this; } private: friend class boost::serialization::access; template<typename Archive> void serialize(Archive& ar, const unsigned version) { ar & data; } }; int main() { using namespace std; const char name[] = "remove_me"; s si(1, 2); // j == 2 v vi(si); vi.write(name); vi.read(name); std::cout << vi.data[0].j << std::endl; // j == 0 }

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[mpl] insert not inserting?
by Scott Meyers 04 Apr '07

04 Apr '07

In my continuing effort to demonstrate my inability to get much of anything working with the MPL, I'm having trouble inserting a type into an existing set of types. The code compiles and runs, but the revised type sequence is empty. Here's the code: #include <boost/mpl/set.hpp> #include <boost/mpl/for_each.hpp> #include <typeinfo> #include <iostream> namespace mpl = boost::mpl; struct Base { virtual ~Base(){} }; struct A { virtual ~A(){} }; struct B { virtual ~B(){} }; struct Print { template<typename T> void operator()(const T&) { std::cout << typeid(T).name() << ", "; } }; int main() { typedef mpl::set<A, B> Constraints; // print contents of Constraints (should be the equivalent // of "[A, B,]") std::cout << '['; mpl::for_each<Constraints>(Print()); std::cout << "]\n"; // add Base to Constraints, call result BaseClasses typedef mpl::insert<Constraints, mpl::end<Constraints>, Base> BaseClasses; // print contents of BaseClasses (should be the equivalent // of "[A, B, Base, ]") std::cout << '['; mpl::for_each<BaseClasses>(Print()); std::cout << "]\n"; } Can anybody spot what I'm doing wrong? I know that I could use the two-argument form of insert with a set, but I'm trying to write code that will work with a vector, too, and at any rate, I get the same results with the two-argument form of set. Thanks, Scott

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