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complexity of boost::num_vertices boost::num_edges
by Heiko Bauke 12 Aug '07

12 Aug '07

Hi, I wonder what is the time complexity of boost::num_vertices and boost::num_edges? Are these constant time operations? I could not find an answer to this question in BGL documentation. Regards, Heiko -- -- Never ascribe to malice, that which can -- be explained by incompetence. (Napoleon) -- Cluster Computing @ http://www.clustercomputing.de -- Heiko Bauke @ http://www.physics.ox.ac.uk/users/bauke

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Re: [Boost-users] cross compiling boost for ARM
by Hughes, James 12 Aug '07

12 Aug '07

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of remi > Sent: 05 January 2007 14:44 > To: boost-users(a)lists.boost.org > Subject: [Boost-users] cross compiling boost for ARM > > > hi! > > I want to cross compile boost for an ARM processor. > For a pxa 270. but when i try to cross compile boost with > arm-linux-g++ , it dosen't work ... a proble with jam... > > everyone can help me? > > Thank you > > BEST REGARDS > > Rémi bjam "-sGCC_ROOT_DIRECTORY=/opt/montavista/mobilinux/devkit/arm/iwmmxt_le" "-sGCC=iwmmxt_le-gcc" "-sGXX=iwmmxt_le-g++" <location for libs> Obviously you would need to change the location namd names of the compile tools to whatever you are using. James This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. If you are not the intended recipient, please notify the sender immediately by responding to this e-mail, and delete the message from your system. If you have any questions about this e-mail please notify the sender immediately.

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shared_ptr, pimpl, reference semantics, and const correctness
by Braddock Gaskill 11 Aug '07

11 Aug '07

I am continuing work on a futures library for boost. future objects (as currently considered by the C++ standards committee, in particular Peter Dimov's proposal) have reference semantics, like many pimpl types. I have some burning questions about const correctness. Hypothetical reference-semantic example: future f1; future f2 = f1; //f2 refers to the same underlying object as f1 f2.set(42); //do something assert(f1.get() == 42); // see, same underlying object This is roughly equivalent to: boost::shared_ptr<future_impl> f1; boost::shared_ptr<future_impl> f2 = f1; A std::vector<T>::iterator is an example of another type with reference semantics. So, say I have a simple future class: class future_impl { public: bool get() const {return value_;} void set(bool value) {value_ = value;} private: bool value_; }; class future { //not really a future, just example public: future() : impl_(new future_impl) {} future(const future &other) : impl_(other.impl_) {} bool get() const {return impl_->get();} // Set may not be const, but it does NOT really modify this class void set(bool value) {impl_->set(value);} private: boost::shared_ptr<future_impl> impl_; }; I have made the future::set() method non-const, but it does NOT really modify the underlying future class, only the future_impl class it refers to. This makes life very difficult when it comes to passing futures by reference: // alternative #1 - pass const future & void f1(const future &f) { bool v = f.get(); // no problem, get() is const f.set(!v); // cannot do this, set() is not const // BUT I can bypass the const-ness trivially, so it is pointless future f2(f); f2.set(!v); } // alternative #2 - pass future & // with #2, I can't do simple things like this: // f2(future(f)); //ERROR: non-const reference from a temporary - irritating void f2(future &f) { bool v = f.get(); // no problem, get() is const f.set(!v); } // alternative #3 - pass by value // Constructing shared_ptr's is VERY inefficient void f3(future f) { bool v = f.get(); // no problem, get() is const f.set(!v); // cannot do this, set() is not const } // alternative #4 - const_future base class with the subset of const methods? // kinda like a const_iterator? seems klunky. class const_future {bool get() const;}; class future : public const_future {void set(bool);} Does anyone have any advice or ideas? Oh, and then there is a possible need for something like a weak_ptr<future_impl>, like a weak_future class? And then a const_weak_future? I don't want to think about it... Thanks, Braddock Gaskill

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Installer for Boost 1.34.1
by Rusty Jones 11 Aug '07

11 Aug '07

Hi, Does anyone know if boost consulting is going to provide an installer for 1.34.1 and if so what time frame? Cheers, Rusty

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BOOST libraries still not part of BOOST dist
by dhruva 11 Aug '07

11 Aug '07

Hi, I am wondering if there is a list of all BOOST libraries which are under under review or accepted for future inclusions. Is "VAULT" the right place to look for such libraries? A list with a short writeup would be very useful. I know the interprocess and asio library existance and hence can google around to find their download locations. There may be many other libraries (I stumbled upon Channel and join) which is not listed in the BOOST site (in a comprehensive, single page manner). -dky -- Dhruva Krishnamurthy Contents reflect my personal views only!

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Serialization of infinite float
by Arnstein Ressem 11 Aug '07

11 Aug '07

Hi, I have run into a problem with the boost xml serialization of overflowing floats. On Linux these are being serialized as 'inf' into the xml files, but when reading the float back in it results in stream errors. I have searched the archives to find an answer to this, but without luck. The small program below has been compiled and run on 32-bit and 64-bit Linux (RedHat Enterprise Linux 4) with boost 1.33.1 and 1.34.1. In every case it results in a stream error and the float can not be read back in from the xml file. Does anyone know if this is supposed to work ? #include <fstream> #include <boost/archive/xml_iarchive.hpp> #include <boost/archive/xml_oarchive.hpp> int main() { const char fname[] = "float.xml"; float f = 1.0e+20*1.0e+20; { std::ofstream ofs(fname); assert(ofs.good()); boost::archive::xml_oarchive oa(ofs); oa << BOOST_SERIALIZATION_NVP(f); } { std::ifstream ifs(fname); assert(ifs.good()); boost::archive::xml_iarchive ia(ifs); ia >> BOOST_SERIALIZATION_NVP(f); } return 0; } Best regards, Arnstein Ressem

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Boost Math Toolkit: Compare simulation data
by NFarnsworth＠web.de 11 Aug '07

11 Aug '07

Hallo, I want to use the test function from the boost math toolkit library to compare simulation results of mechantronic systems with a reference solution. The test reads the reference solution from a file, and after the simulation the test compares the file data with the data from a double array. But if a value of a function is close to zero, I will get a gross relative error. Do you have any suggestion to solve this problem? Thanks for your help in advance Best regards Niklas _______________________________________________________________________ Jetzt neu! Schützen Sie Ihren PC mit McAfee und WEB.DE. 3 Monate kostenlos testen. http://www.pc-sicherheit.web.de/startseite/?mc=022220

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What happened to boost::thread priority?
by Graham Reitz 10 Aug '07

10 Aug '07

I was looking through the list archives and its looks like the a feature to set the thread priority fizzled out around 2003ish. Did this get tabled? This is really a curiosity question. Thanks, Graham

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[boost.python] can not export a union in VC2005sp1
by qiaozhiqiang＠datangmobile.cn 10 Aug '07

10 Aug '07

// Visual V++ 2005(8.0) sp1, boost 1.34.0 // union not is_class. // because there is BOOST_STATIC_ASSERT(is_class<T>::value) in make_instance_impl // can not export union. eg, class_<union my_u> // can not return_internal_reference<> when T not is_class, eg, return char*, char&, union u& // how to write return_internal_pointer: char* get(); // how to return_value_policy<return_by_value> work: char* get() // def_readwrite(union): default get() return by value ? // is_class<T> ? T& : T get() ?? // delete BOOST_STATIC_ASSERT(is_class<T>::value); of make_instance_impl, then compile OK, and work not all OK boost/python/object/make_instance.hpp template <class T, class Holder, class Derived> struct make_instance_impl { typedef objects::instance<Holder> instance_t; template <class Arg> static inline PyObject* execute(Arg& x) { // must is_class ?? to BOOST_STATIC_ASSERT(is_class<T>::value || is_union<T>::value)?? BOOST_STATIC_ASSERT(is_class<T>::value); /////////////////////////////// #include <boost/python.hpp> using namespace boost::python; union my_u { int a; char b; char& get_ref() { return b; } char* get_ptr() { return *b; } } struct my_s { my_u u; my_u& get_ref() { return u; } my_u* get_ptr() { return &u; } }; void my_module() { //1. compile ERROR: my_u not is_class, my_u is_union, I modify one line in make_instance.hpp // BOOST_STATIC_ASSERT(is_class<T>::value) to //BOOST_STATIC_ASSERT(is_class<T>::value || is_union<T>::value) // and the def_readwrite a, b work OK. // and work OK, why not export an union? class_<my_u > u_class("my_u", init< >()); u_class.def_readwrite("a", &my_u::a); u_class.def_readwrite("b", &my_u::b); //2. compile ERROR: char not is_class, delete BOOST_STATIC_ASSERT(is_class<T>::value), but run error u_class.def("get_ref", &my_u::get_ref, return_internal_reference< >()); //3. compile ERROR: char not is_class, delete BOOST_STATIC_ASSERT(is_class<T>::value), but run error, how to return_internal_reference a char? Use def_readwrite？ u_class.def("get_ptr", &my_u::get_ptr, return_internal_reference< >()); //4. compile OK, but run ERROR, I need it return a char .def("get_value", &my_u::get_ptr, return_value_policy<return_by_value>()); //5. compile ERROR, char* is not a reference, I need but have no copy_non_const_pointer, how to write copy_non_const_pointer? u_class.def("get_copy", &my_u::get_ptr, return_value_policy<copy_non_const_reference>()); class_<my_s > s_class("my_s", init< >()); //6. compile OK, buy run ERROR: // s = my_s() // s.u.a = 100 // print s.u.a // but output s.u.a != 100 !!! // s.u.a = 100 is s.get_u().set_a(100) and get_u() not return u(is_union) by ref ? s_class.def_readwrite("u", &my_s::u); // 7. compile ERROR: my_u not is_class, is_union, modify BOOST_STATIC_ASSERT(is_class<T>::value) to // BOOST_STATIC_ASSERT(is_class<T>::value || is_union<T>::value) s_class.def("get_ptr", &my_s::get_ptr, return_internal_reference<>()); s_class.def("get_ref", &my_s::get_ref, return_value_policy<return_by_value>());//compile ok } Best 　Regards ! Qiao Zhi Qiang

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Process for adding code to boost
by Hughes, James 10 Aug '07

10 Aug '07

Hello all, I was interested in knowing how to go about presenting new code for addition to boost. I'm not talking about a new library, but extensions to existing ones. For example, I have written some code to allow serialisation of the boost::filesystem::path class (not particularly exciting or complicated, but may be useful to someone), and would like to pass it on. James This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. If you are not the intended recipient, please notify the sender immediately by responding to this e-mail, and delete the message from your system. If you have any questions about this e-mail please notify the sender immediately.

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