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Random library, discrete distribution
by Kevin Martin 18 Aug '09

18 Aug '09

I made a post sometime last year about requiring a distribution that could generate enums with specified probabilities. I find I am regularly requiring a discrete distribution like this - where I specify the probabilities. Am I the only one who requires it, or would it be useful to a wider audience? I'm just wondering whether to submit a feature request for it or not? Thanks, Kevin Martin This is what I'm using at the moment: template<class IntType = int> class discrete_distribution { public: typedef boost::uniform_int<>::input_type input_type; typedef IntType result_type; template<size_t N> discrete_distribution(const boost::array<int, N> &outputs, const boost::array<int, N> &weights) : outputs_(outputs.begin(), outputs.end()), weights_(weights.begin(), weights.end()) { for(int i=1;i!=weights_.size();++i) weights_[i] += weights_[i-1]; } inline void reset() {} template<class Engine> result_type operator()(Engine& eng) { boost::uniform_int<> ui(0, weights_.back()-1); boost::variate_generator<Engine&, boost::uniform_int<> > vg(eng, ui); int idx = std::lower_bound(weights_.begin(), weights_.end(), vg()) - weights_.begin(); return outputs_[idx]; } private: std::vector<int> outputs_; std::vector<int> weights_; };

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Re: [Boost-users] Iterating over the seconds of a list of pairs
by Hicham Mouline 17 Aug '09

17 Aug '09

> > -----Original Message----- > > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > > bounces(a)lists.boost.org] On Behalf Of Björn Karlsson > > Sent: 08 August 2009 18:12 > > To: boost-users(a)lists.boost.org > > Subject: Re: [Boost-users] Iterating over the seconds of a list of pairs > > > > You're right -- transform_iterator is the right tool for the job. Try > > something like this. > > > > 1) Write a function object that extracts the second element of the pair. > > 2) Use the transform iterator adaptor to provide you with the type of > > the iterators for your class. > > 3) Use the helper function make_transform_iterator in your begin() and > > end() methods to create the iterators. > > > > Here's an example that does the above: > > > > #include <iostream> > > #include <list> > > #include <utility> > > > > #include "boost/iterator/transform_iterator.hpp" > > > > // Extract the second element of a pair > > template <typename T> class pair_second_t { > > public: > > typedef T result_type; > > > > template <typename U> T operator()(const std::pair<U,T>& element) > > const > > { > > return element.second; > > } > > }; > > > > class some_class > > { > > public: > > typedef std::list<std::pair<double,float> > container_type; > > typedef boost::transform_iterator<pair_second_t<float>, > > container_type::iterator> iterator_type; > > Bjorn Karlsson Hello bjorn, I have a similar problem. I have a vector< pair<LeftT, RightT> >. I'm very happy to use vector< pair<LeftT, RightT> >::iterator The only extra is I'd like to name the functions GetLeft() and GetRight() and make them callable as: typedef vector< pair<LeftT, RightT> >::iterator stl_iterator; stl_iterator i = ...; i->GetLeft() and i->GetRight() // I can't do this obviously so: typedef boost::transform_iterator<functor, stl_iterator> my_iterator_type; Should functor provide GetLeft() and GetRight()? or should my_iterator_type derive from the result of transform_iterator<functor, stl_iterator> ? regards,

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Help in using smart (double) pointers
by Sundaram 17 Aug '09

17 Aug '09

Howdy I'm very new to Boost libraries, and this is my first try in using it, so pardon my naive questions. Now for the question: I'm trying to port a Java module to C++, as in a J2ME game to Windows Mobile. I've re-written all the classes that the game code depends on the J2ME packages using Windows Mobile's native methods. Now for the last difference between the two: memory. The game code has lots of new and obviously no deletes, since Java has automatic garbage collection. So for the C++ equivalent , I thought of going for smart pointers, so that I needn't bother about memory leaks and to call delete for all news. I've no problem in using smart pointers for normal dumb pointers. While it is the double pointers that I'm confused of. Say if I have: int **palette = new int* [5]; palette[0] = new int[10]; palette[1] = new int[7]; ... ... what is the boost equivalent that I can use, so that when all references to palette's are released, all memory allocated in the name of palette should be freed i.e. both the single (palette[0], etc.) and double pointer (**palette) should be freed. If yes, can you please show me how? Thanks! Sundaram

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[1.40.0] Beta 1 available
by Beman Dawes 17 Aug '09

17 Aug '09

Boost release 1.40.0 beta 1 is available from SourceForge: http://sourceforge.net/projects/boost/files/ This release contains no new libraries, but contains numerous bug fixes for existing libraries. Boost source files with types .bz2 and .gz are created with POSIX-style (\n) line endings. Source files with types .7z and .zip are created with Windows-style (\r\n) line endings. The content is otherwise identical. Be sure to download a file with the appropriate line endings for your platform. If you are new to Boost, be sure to read the Getting Started Guide. See www.boost.org There are three known issues with beta 1: * boost/detail/scoped_enum_emulation.hpp, used by Boost.Filesystem, has a name conflict (enum_t) with Unix header rpc/types.h. Fixed in trunk, but not yet merged into the release. * Boost.Python has fixes in trunk not yet merged into to the release. * Boost.Signals has has fixes in trunk not yet merged into to the release. These issues will be resolved for the final 1.40.0 release. Other than these three known issues, please report any problems with the beta on the developers or users mailing lists. Unless unexpected problems arise, the plan is to ship the final 1.40.0 release in a week to ten days. Thanks, --The Boost release team

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[random] Singleton engine
by Diederick C. Niehorster 17 Aug '09

17 Aug '09

Hi All, I have been writing a wrapper around the variate_generator as I always want to use the same number generator, but do want to use different distributions. As I want to use only one instance of the engine instance for all instanced of my random number generator class, I used a singleton pattern. as is my first time using it, I decided to test it generously, to try and see if the same instance of the enigine is used. So not only did i check if the engine pointer for different instances of my random class is the same, but i also checked if the destructor for the engine (does not) get called (i've added a constructor to the boost header file temporarily) and whether the random numbers generated are indeed not the same. It seems my code does not work, the destructor gets called weirdly often, e.g., 4 times every time i initialize my random class. Also, the numbers generated by the two generators are the same, indicating the engine is reinitialized for every instance of my random class. Yet, the pointer to the engine is the same (note that it is also the same if i dont call the destructor in between). I am using MSVC 2008 on windows XP 32 bit. What am I doing wrong? As I am learning, any other feedback is also very welcome. Best, Diederick ---- output of run of code below: check 0 00000000 ctor 1 destructor destructor destructor destructor after ctor 1 003462E0 random: 8148 dtor 1 destructor ctor 2 destructor destructor destructor destructor after ctor 2 003462E0 random: 8148 destructor destructor ---- code // includes #include <boost/random.hpp> #include <time.h> #include <iostream> using namespace std; // declaration template<class Dist> class CRandom { public: /** use for Dist: CRandomI Ci(min,max); uses uniform_int<int> - integral types CRandomR Cr(min,max); uses uniform_real<double> - floating point types for other ditributions or types, use: CRandom<distribution<optional type>> Cr(0--3 params, depending on distribution); for distributions and params, see: http://www.boost.org/doc/libs/1_39_0/libs/random/random-distributions.html */ // forwarding constructors explicit CRandom() : Gen(*EngineSingleton::Eng(), Dist()) { } template<class P> explicit CRandom(const P & p1) : Gen(*EngineSingleton::Eng(), Dist(p1)) { } template<class P> explicit CRandom(const P & p1, const P & p2) : Gen(*EngineSingleton::Eng(), Dist(p1, p2)) { } template<class P> explicit CRandom(const P & p1, const P & p2, const P & p3) : Gen(*EngineSingleton::Eng(), Dist(p1, p2, p3)) { } ~CRandom(void) {}; typedef typename Dist::result_type result_type; result_type operator()() { return Gen(); } template<class T> result_type operator()(T value) { return Gen(value); } private: boost::variate_generator<boost::mt19937,Dist> Gen; }; // end declaration // shorthand typedefs typedef CRandom<boost::uniform_int<int>> CRandomI; // even int is default type , specify it in case it ever changes typedef CRandom<boost::uniform_real<double>> CRandomR; // even double is default type, specify it in case it ever changes /** engine wrapper class following singleton pattern, so every instantiation of CRandom uses the same engine based on: http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf */ // declaration class EngineSingleton { public: static boost::mt19937* Eng(); static boost::mt19937* GetEngPoint() {return pEng;}; // for test only protected: // disallow (copy) construction and assignment operator EngineSingleton(); EngineSingleton(const EngineSingleton&); EngineSingleton& operator=(const EngineSingleton&); private: static boost::mt19937* pEng; }; // end declaration // implementation boost::mt19937* EngineSingleton::pEng = NULL; boost::mt19937* EngineSingleton::Eng() { if (pEng == NULL) { pEng = new boost::mt19937(/*unsigned int(time(NULL))*/); // initialize with same seed always, for test only } return pEng; } // end implementation //main int main(int argc, char* argv[]) { cout << "check 0" << endl; cout << EngineSingleton::GetEngPoint() << endl; cout << "ctor 1" << endl; CRandomI Cr(1,10000); cout << "after ctor 1" << endl; cout << EngineSingleton::GetEngPoint() << endl; int test = Cr(); cout << "random: " << test << endl; cout << "dtor 1" << endl; Cr.~CRandom(); cout << "ctor 2" << endl; CRandomI Cr2(1,10000); cout << "after ctor 2" << endl; cout << EngineSingleton::GetEngPoint() << endl; int test2 = Cr2(); cout << "random: " << test2 << endl; // exit return 1; }

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Re: [Boost-users] Boost interprocess named mutexes
by Mike Spertus 17 Aug '09

17 Aug '09

Ion Gaztanaga wrote: > Mike Spertus escribió: > > I am seeing the following problems with Boost interprocess named > > mutexes on Windows. > > > 3. Although the documentation says that mutexes have process > > persistence, they appear to have filesystem persistence. This means that > > is a process or system crashes while the mutex is held, the mutex is > > permanently unavailable (without deleting it). > > The documentation says kernel or filesystem persistence for "named mutex": > http://www.boost.org/doc/libs/1_39_0/doc/html/interprocess/some_basic_expla… > > Hi Ion, Sorry, I misread that doc page. You are of course correct. What do you think of my suggestion to use a Windows mutex to back a boost interprocess named mutex? Since "abandoned Windows mutexes" are automatically released by Windows, we see substantially fewer hangs when we use Windows mutexes. Thanks, Mike > Best, > > Ion >

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[mpl, units] rational and static_rational
by alfC 17 Aug '09

17 Aug '09

Hi, I am looking for a template library that can handle compile time rationals, ideally with a similar interface to mpl::int_ and that plays well with boost::rational (the dynamic type). First I found boost/mpl/math/rational_c.hpp but soon I realized that it doesn't work with basic operations like mpl::plus, it doesn't even simplify reducible fractions (i.e. 2/4 -> 1/2), in fact it looks like it is just the storage of two (static) integers. Is this something that will be developed in the future or am I using it in the wrong way? Then I found boost::units::static_rational which is more promising, because it simplifies fractions and works with mpl::plus, but it is not integrated with boost::rational nor has an interface similar to that of mpl metatypes. Is there a way of extending mpl::math::rational_c with the existing libraries in boost, or a simple way to make boost::units::static_rational have an interface similar to mpl and also have a value type that returns it runtime boost::rational value? Thank you, Alfredo

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Runtime properties in BGL
by Andre de Leiradella 17 Aug '09

17 Aug '09

Hi All, I've recently discovered BGL and am considering using it to replace some graph classes and algorithms I use in an application. One thing that I need is the ability of adding properties to nodes at runtime. In my application each node represents an operation to be performed upon a set of inputs and generating one or more outputs. The properties of the nodes are defined in an external file and depend on the node's operation. Does BGL support it? Both bundled properties and the property map seem to required the definition of the properties at compile-time, and they seem to required that all nodes have the same set of properties. While I could hold each node's properties in an external structure (i.e. std::map), I also want to use read_graphml/write_graphml to load/save the graph along with the node's properties. Thanks in advance, Andre de Leiradella

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Need help in install boost 1.39 on Mac OSX
by n179911 16 Aug '09

16 Aug '09

Hi, I am following the step here to install boost 1.39 on Mac OSX: http://www.boost.org/doc/libs/1_39_0/more/getting_started/unix-variants.htm… I did: $ ./bootstrap.sh $ ./bjam install After the build is done. I do see boost-1_39 under /usr/local/include But, i don't see any boost related stuff in /usr/local/lib? So can you please tell me how to link to boost library? Where are the .a/.so files for boost libraries? Thank you.

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Program using boost asio crashes on MacOSX
by n179911 16 Aug '09

16 Aug '09

Hi, I am trying to run blocking_udp_echo_server.cpp from Boost asio on MacOSX 10.5. But it crashes: >From the console: /Developer/SDKs/MacOSX10.5.sdk/usr/include/c++/4.0.0/debug/safe_iterator.h:127: error: attempt to copy-construct an iterator from a singular iterator. Objects involved in the operation: iterator "this" @ 0x0x100420 { type = N11__gnu_debug14_Safe_iteratorIN10__gnu_norm14_List_iteratorISt4pairIiPN5boost4asio6detail16reactor_op_queueIiE7op_baseEEEEN15__gnu_debug_def4listISB_SaISB_EEEEE (mutable iterator); state = singular; } iterator "other" @ 0x0xbfffee64 { type = N11__gnu_debug14_Safe_iteratorIN10__gnu_norm14_List_iteratorISt4pairIiPN5boost4asio6detail16reactor_op_queueIiE7op_baseEEEEN15__gnu_debug_def4listISB_SaISB_EEEEE (mutable iterator); state = singular; } Program received signal: “SIGABRT”. >From backtrace: (gdb) bt #0 0x918c3e42 in __kill () #1 0x918c3e34 in kill$UNIX2003 () #2 0x9193623a in raise () #3 0x91942679 in abort () #4 0x940d96f9 in __gnu_debug::_Error_formatter::_M_error () #5 0x0000ada6 in __gnu_debug::_Safe_iterator<__gnu_norm::_List_iterator<std::pair<int, boost::asio::detail::reactor_op_queue<int>::op_base*> >, __gnu_debug_def::list<std::pair<int, boost::asio::detail::reactor_op_queue<int>::op_base*>, std::allocator<std::pair<int, boost::asio::detail::reactor_op_queue<int>::op_base*> > > >::_Safe_iterator (this=0x100420, __x=@0xbfffee64) at debug/safe_iterator.h:124 #6 0x00010195 in boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type::bucket_type (this=0x100420) at hash_map.hpp:277 #7 0x0001291d in std::_Construct<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> (__p=0x100420, __value=@0xbfffee64) at stl_construct.h:81 #8 0x00012edd in std::__uninitialized_fill_n_aux<__gnu_cxx::__normal_iterator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type*, __gnu_norm::vector<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, std::allocator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> > >, unsigned long, boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> (__first={_M_current = 0x100420}, __n=3, __x=@0xbfffee64) at stl_uninitialized.h:194 #9 0x00012f67 in std::uninitialized_fill_n<__gnu_cxx::__normal_iterator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type*, __gnu_norm::vector<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, std::allocator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> > >, unsigned long, boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> (__first={_M_current = 0x100420}, __n=3, __x=@0xbfffee64) at stl_uninitialized.h:218 #10 0x00012f8f in std::__uninitialized_fill_n_a<__gnu_cxx::__normal_iterator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type*, __gnu_norm::vector<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, std::allocator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> > >, unsigned long, boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> (__first={_M_current = 0x100420}, __n=3, __x=@0xbfffee64) at stl_uninitialized.h:310 #11 0x000134ba in __gnu_norm::vector<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, std::allocator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> >::_M_fill_insert (this=0x1002f0, __position={_M_current = 0x0}, __n=3, __x=@0xbfffee64) at vector.tcc:365 #12 0x00013760 in __gnu_norm::vector<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, std::allocator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> >::insert (this=0x1002f0, __position={_M_current = 0x0}, __n=3, __x=@0xbfffee64) at stl_vector.h:658 #13 0x00013807 in __gnu_norm::vector<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, std::allocator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> >::resize (this=0x1002f0, __new_size=3, __x=@0xbfffee64) at stl_vector.h:427 #14 0x000138c0 in __gnu_debug_def::vector<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type, std::allocator<boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::bucket_type> >::resize (this=0x1002f0, __sz=3, __c=@0xbfffee64) at debug/vector:169 #15 0x0001400e in boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::rehash (this=0x1002c4, num_buckets=3) at hash_map.hpp:221 #16 0x0001443b in boost::asio::detail::hash_map<int, boost::asio::detail::reactor_op_queue<int>::op_base*>::hash_map (this=0x1002c4) at hash_map.hpp:67 #17 0x000144c4 in boost::asio::detail::reactor_op_queue<int>::reactor_op_queue (this=0x1002c0) at reactor_op_queue.hpp:42 #18 0x00014574 in boost::asio::detail::kqueue_reactor<false>::kqueue_reactor (this=0x100270, io_service=@0xbffff7a4) at kqueue_reactor.hpp:86 #19 0x00014850 in boost::asio::detail::service_registry::use_service<boost::asio::detail::kqueue_reactor<false> > (this=0x100180) at service_registry.hpp:109 #20 0x0001499d in boost::asio::use_service<boost::asio::detail::kqueue_reactor<false> > (ios=@0xbffff7a4) at impl/io_service.ipp:195 #21 0x00014abd in boost::asio::detail::reactive_socket_service<boost::asio::ip::udp, boost::asio::detail::kqueue_reactor<false> >::reactive_socket_service (this=0x100250, io_service=@0xbffff7a4) at reactive_socket_service.hpp:111 #22 0x00014b94 in boost::asio::detail::service_registry::use_service<boost::asio::detail::reactive_socket_service<boost::asio::ip::udp, boost::asio::detail::kqueue_reactor<false> > > (this=0x100180) at service_registry.hpp:109 #23 0x00014ce1 in boost::asio::use_service<boost::asio::detail::reactive_socket_service<boost::asio::ip::udp, boost::asio::detail::kqueue_reactor<false> > > (ios=@0xbffff7a4) at impl/io_service.ipp:195 #24 0x00014d25 in boost::asio::datagram_socket_service<boost::asio::ip::udp>::datagram_socket_service (this=0x100230, io_service=@0xbffff7a4) at datagram_socket_service.hpp:95 #25 0x00014dee in boost::asio::detail::service_registry::use_service<boost::asio::datagram_socket_service<boost::asio::ip::udp> > (this=0x100180) at service_registry.hpp:109 #26 0x00014f3b in boost::asio::use_service<boost::asio::datagram_socket_service<boost::asio::ip::udp> > (ios=@0xbffff7a4) at impl/io_service.ipp:195 #27 0x00014f61 in boost::asio::basic_io_object<boost::asio::datagram_socket_service<boost::asio::ip::udp> >::basic_io_object (this=0xbffff6a4, io_service=@0xbffff7a4) at basic_io_object.hpp:72 #28 0x00014fd3 in boost::asio::basic_socket<boost::asio::ip::udp, boost::asio::datagram_socket_service<boost::asio::ip::udp> >::basic_socket (this=0xbffff6a4, io_service=@0xbffff7a4, endpoint=@0xbffff6b8) at basic_socket.hpp:108 #29 0x000150b5 in boost::asio::basic_datagram_socket<boost::asio::ip::udp, boost::asio::datagram_socket_service<boost::asio::ip::udp> >::basic_datagram_socket (this=0xbffff6a4, io_service=@0xbffff7a4, endpoint=@0xbffff6b8) at basic_datagram_socket.hpp:107 #30 0x00002022 in server (io_service=@0xbffff7a4, port=8090) at /Users/n179911/Documents/ServerXCode/main.cpp:21 #31 0x0000217a in main (argc=2, argv=0xbffff7e8) at /Users/n179911/Documents/ServerXCode/main.cpp:47 (gdb) Any one has any idea?

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