June 2010 - Boost-users - lists.preview.boost.org

[BGL] graphviz example
by Adam Spargo 09 Jun '10

09 Jun '10

Hi, I am trying to run Dijkstra example from the BGL book (chapter 5). I have built libbgl-viz.a and I am trying to link it like this: CPP = g++ CFLAGS = -O2 IFLAGS = -I ~/src/boost_1_42_0 LFLAGS = -L ~/src/boost_1_42_0/libs/graph/src ospf: ospf.o $(CPP) -o $@ $(LFLAGS) -l bgl-viz ospf.o ospf.o: ospf.cpp $(CPP) $(CFLAGS) $(IFLAGS) -c -o $@ ospf.cpp it seems to find the lib okay, but I get an error like this: ospf.cpp:(.text+0xa2): undefined reference to `boost::read_graphviz(std::basic_s ... Is there some obvious pitfall, or maybe someone could help me work it out? Thanks, Adam. -- Dr Adam Spargo High Performance Assembly Group email: aws(a)sanger.ac.uk Wellcome Trust Sanger Institute Tel: +44 (0)1223 834244 x7728 Hinxton, Cambridge CB10 1SA Fax: +44 (0)1223 494919 -- The Wellcome Trust Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1 2BE.

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boost::format help to format doubles.
by Mauricio Gomes 09 Jun '10

09 Jun '10

Hi I read the documentation and looked for some examples but I was not able to come up with a format string to do this: Format a double using desired grouping char and decimal separator. So 1234567.89 should print 1,234,567.89 First, how can I specify the usage of the grouping char ? sprintf uses the ' char but it gave me invalid format string every time I tried to use it. Also how can I specify the grouping char and decimal separator ? By setting the locale ? An example would be great. std::stringstream ss2; ss2 << boost::format ("%|.2f|") % src.get_valor_total (); String svalor_total = ss2.str (); Thank you in advance for your attention, Mau.

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passing a shared pointer
by Lloyd 09 Jun '10

09 Jun '10

Hi, I have a shared pointer like this class a { }; boost::shared_ptr<a> Ptr(new a()); I need to pass this pointer as an argument to function (MyFunc) which access this as a reference void MyFunc(a& ref) { } Now I am calling the function like this MyFunc(*Ptr); But this causes the "Ptr" to destroy early (I am using this for an asynchronous-ASIO- operation) How can I do this right? Thanks a lot, Lloyd ______________________________________ Scanned and protected by Email scanner

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contiguous Boost.Multimap?
by anony 09 Jun '10

09 Jun '10

Is it somehow possible to coax boost::multimap to store data contiguously, i.e. that all multimap elements are stored contiguously, without gaps between them, and all in the same memory block?

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[Property Tree] Replace RapidXML with pugiXML?
by Brent Arias 09 Jun '10

09 Jun '10

How difficult is it to replace the RapidXML XML parser with another parser, such as pugiXML? Is this a change-case that has been planned and streamlined, and therefore a straight-forward effort, or is it a lengthy and detailed affair that requires intimate knowledge of PropertyTree internal workings? I ask because my organization predicts we likely will change back-and-forth between competing implementations (RapdidXML, Kranf xmlParser, pugiXML) as time goes by, which implies that we should have some kind of wrapper around the XML parser. I am investigating how well boost's "property tree" could server as that wrapper. And, in fact, we currently want pugiXML because of it's wide-char support<http://code.google.com/p/pugixml/source/browse/#svn/branches/unicode>, and because it has XPath support (granted PropertyTree assuredly won't "wrap" the XPath capability, but we'll deal with that separately). Brent Arias Software Architect Lumension Security(tm) Tel ~ (480) 444-1607 Fax ~ (480) 970-6323 brent.arias(a)lumension.com<mailto:brent.arias@lumension.com>

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initialization of boost::thread::id object
by Boost lzw 09 Jun '10

09 Jun '10

Hi, I have a class (for illustrative purpose only): class X { public: X() : id_(0) // does not compile { } void f() { if (operation_failed) id_ = 0; // does not compile else id_ = boost::this_thread::get_id(); // get which thread is sucessfully executing f() } bool compare() { // compare current thread with the one that has sucessfully executed f() return id_ == boost::this_thread::get_id(); } private: boost::thread::id id_; }; My questions are: How can I set the id_ to an initial value (e.g., 0 here) for compare() function to get correct result, assuming multiple threads might be executing f() and compare() at the same time? Is there a way to do this: atomic<boost::thread::id> id_; to make them thread-safe? Thanks a lot in advance, Robert

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Serialization of polymorphic types defined by plugins loaded at runtime
by Sam Spilsbury 09 Jun '10

09 Jun '10

Hi Everyone, I'm working on a project called "compiz" which is a plugin-based compositing window manager for X11 written in C++[1]. Recently, I've been adding serialization through the use of a wrapper class such that plugin class inherits this wrapper class, which automatically loads serialized data when instantiated and saves it when destroyed (by using a function that is called at the beginning of the plugin class destructor. My main problem at the moment is that I have a boost::ptr_vector of a class called "Element", which is a base for which other plugins derive and add their own "move" "start" "stop" functions as well as any additional properties they wish to attach to the "Element". So for example, this is where the ptr_vector is kept: class PrivateElementAnimation { public: PrivateElementAnimation (CompString type, int nElement, int size, int speed, int iter, bool rotate); PrivateElementAnimation () {}; template <class Archive> void serialize (Archive &ar, const unsigned int version) { ar & mElements; // Exception unregistered_type is raised here } boost::ptr_vector<Element> mElements; }; This is the definition of the class "Element" class Element { public: Element (); ElementAnimation *anim; float x, y, z; float dx, dy, dz; float rSpeed; int rDirection; int rAngle; float opacity; template <class Archive> void serialize (Archive &ar, const unsigned int version) { fprintf (stderr, "saving an element\n"); ar & x; ar & y; ar & z; ar & dx; ar & dy; ar & dz; ar & rSpeed; ar & rDirection; ar & rAngle; ar & opacity; } virtual bool init (); virtual void move (); virtual void fini (); private: void defaultInit (); void regenerateOffscreen (); friend class ElementAnimation; friend class PrivateElementScreen; }; And this is the definition of a derived class, FireflyElement, which is stored in a separate library loaded at runtime. (E.g, boost::serialization doesn't know this type exists at compile time of Element and PrivateElementAnimation. class FireflyElement : public Element { public: float lifespan; float age; float lifecycle; float dx[4], dy[4], dz[4]; bool init (); void move (); void fini (); template <class Archive> void serialize (Archive &ar, const unsigned int version) { boost::serialization::base_object <Element> (*this); ar & lifespan; ar & age; ar & lifecycle; ar & dx; ar & dy; ar & dz; } static Element * create (); ~FireflyElement (); FireflyElement (); friend class boost::serialization::access; private: }; BOOST_CLASS_EXPORT_GUID (FireflyElement, "FireflyElement"); // this class has a default constructor BOOST_SERIALIZATION_FACTORY_0 (FireflyElement); Of course, at this point, when I try to run the program, boost raises an exception unregistered_type, which as far as I know means that it doesn't know about the type relationship between FireflyElement and Element when trying to serialize Element *. I had a look at the documentation, and it appears that this is the way to register such type relationships (by using EXPORT_GUID, SERIALIZATION_FACTORY_0 and boost::serialization::base_object <Element> (*this); in the serialize function. I also had a look at the documentation for "plugins" and "dll's"[2] and couldn't find anything of use there. Does anybody know how to resolve this? Kind Regards, Sam [1] http://www.compiz.org [2] http://www.boost.org/doc/libs/1_38_0/libs/serialization/doc/special.html#de… -- Sam Spilsbury

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Serialization Question
by Paul Dugas 08 Jun '10

08 Jun '10

I'm looking into recording some data collected by one of my programs into rotating files. Something like so: ofstream ofs; boost::archive::text_oarchive oa(ofs) size_t rotate = 0; for(;;) { foo_t foo = get_some_foo(); if (!rotate) { ofs.open(some_clever_new_filename); // attach oa again? rotate = 1000; } oa << foo; if (!--rotate) { ofs.close(); // detach oa? } } Do I need to do anything to detach or re-attach the oarchive? Paul

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Boost documentation simple example fails
by hmiller＠hiwaay.net 08 Jun '10

08 Jun '10

I know I must be doing something wrong. I am trying to use the very simple example at: http://www.boost.org/doc/libs/1_43_0/libs/test/doc/html/tutorials/hello-the… #include <my_class.hpp> #define BOOST_TEST_MODULE MyTest #include <boost/test/unit_test.hpp> BOOST_AUTO_TEST_CASE( my_test ) { my_class test_object( "qwerty" ); BOOST_CHECK( test_object.is_valid() ); } I constructed and compiled a very simple class to use, but I get a compile error using the simple test above. I am using gcc version 4.1.2 on SUSE_linux. The compile error I get is: test_my_class.cpp:5: error: expected constructor, destructor, or type conversion before '(' token It is as if the compiler does not recognize BOOST_AUTO_TEST_CASE. Here is the my_class.hpp file: //==================== #include <string> using namespace std; class my_class { public: my_class( string str ); ~my_class(); private: bool valid; public: bool is_valid(); }; Here is my_class.cpp file: //==================== #include "my_class.hpp" my_class::my_class( string str ) { valid = false; } my_class::~my_class() { } bool my_class::is_valid() { return valid; } I may have made some typos while entering this code, but it does compile, and it does function properly when I instantiate it with another test program. What am I doing wrong? Thanks, Herb Miller

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boost.mpi possible bug with mpi::scatter
by raj 08 Jun '10

08 Jun '10

Ok I'm new to mpi so maybe this is expected behaviour. But when using scatter, if number the of threads running is greater than number of elements in the array\vector sent to scatter, then there are the following issues 1) if the array contains a user-defined data then an out-of-bounds error will occur 2) otherwise (if is_mpi_datatype is true) the recieved data for threads that are "out-of-bound", will contain garbage and as such validity of the data cannot be tested. I assume this not correct behaviour? Raj

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