September 2009 - Boost-users

[Random] uniform_01
by Robert Patterson 01 Nov '09

01 Nov '09

Hi, I was looking at the docs for the uniform_01 distribution: http://www.boost.org/doc/libs/1_39_0/libs/random/random-distributions.html#… I read the following note "Note: The current implementation is buggy, because it may not fill all of the mantissa with random bits." I do not understand the problem. I looked at the code, which does what I expect. Why is it a problem if some of the mantissa bits are not 'random'? As I understand the requirement is the real numbers are uniformly distributed; the bit patterns should not matter provided they represent numbers with the right mathematical properties. Thanks Robert Patterson http://como.cheng.cam.ac.uk/index.php?Page=People&Section=riap2

3 2

[iterator] Automatic definition of transform_iterator reference_type
by Sebastian Theophil 28 Oct '09

28 Oct '09

[Posted once again with better subject] I've encountered a problem when using boost::mem_fn in transform_iterators. In the attached example, I've chained two transform_iterators. The first iterator returns an Obj by value and the second extracts a member of the temporary object. The example shows that the return value is not quite what is expected. boost::mem_fn(&Obj::m_member) returns an int const&. The transform_iterator uses the return value of the UnaryFunction template parameter to initialize his value_type. In the given example, this logic seems too simple. At least if the UnaryFunction is of type boost::_mfi::dm the transform_iterator could do better: If Reference is boost::use_default If UnaryFunction is boost::_mfi::dm && Iterator::value_type is not a reference itself reference = boost::remove_reference( result_of(UnaryFunction) ) Else reference = result_of(UnaryFunction) Else reference = Reference Is this too much of a special case to fix it in the transform_iterator? The same logic would apply to all (unknown) functors that returned references to member variables. In general, the transform_iterator can probably not decide if a reference returned from a UnaryFunction will cease to exist when the temporary is destroyed. It could have been a global object. On the other hand, transform_iterators should work correctly if only boost objects are used, shouldn't they? I'd like to hear what you think, Sebastian #include "boost/iterator/transform_iterator.hpp" #include <vector> struct Obj { Obj(int n) : m_member(n) {} Obj(Obj const& obj) : m_member(obj.m_member) {} ~Obj() { m_member=INT_MIN; } int m_member; }; static Obj GetObjByValue( int n ) { return Obj(n); } void main() { std::vector<int> v(1, 5); int n=*boost::make_transform_iterator( boost::make_transform_iterator( v.begin(), GetObjByValue ), boost::mem_fn(&Obj::m_member) ); _ASSERT(n==INT_MIN); } -- Sebastian Theophil . stheophil(a)think-cell.com Software Engineer think-cell Software GmbH . Invalidenstr. 34 . 10115 Berlin, Germany http://www.think-cell.com . phone +49-30-666473-10 . toll-free (US) +1-800-891-8091 Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl . Amtsgericht Berlin-Charlottenburg, HRB 85229

3 3

circular_buffer::erase in constant time
by Luca Cappa 26 Oct '09

26 Oct '09

Hello, is it possible to remove the first bunch of elements of a circular_buffer with constant complexity time? Unfortunately using any (r)erase function the complexity is linear. To give an idea, it could be implemented like this: /// Erase the first pCount element from the buffer void begin_erase (size_t pCount) { BOOST_ASSERT(pCount <= size ()); circular_buffer<Type>::add (m_first, pCount); m_size -= pCount;; } but this is not taking into account deletion of the deleted items (could they be deleted when they are overwritten? Or the stored type does not need to be destroyed at all), and many other details which are known to me. I am asking this 'cause I would like to make my circular_buffer class to be STL compliant container, but before doing it myself, I would like to evaluate if I could derive (or use aggregation) directly from circular_buffer and save me a lot of work. Thanks, Luca

2 3

[fusion] is there anything resembling a joint_view of 2 maps?
by er 22 Oct '09

22 Oct '09

Hi All, I am wondering if anyone knows of anything that resembles a joint_view of a pair of maps. typedef mpl::int_<1> key1_; typedef mpl::int_<2> key2_; typedef pair<key1_,int> pair1_; typedef pair<key2_,int> pair2_; typedef map<pair1_> map1_; typedef map<pair2_> map2_; map1_ m1( make_pair<key1_>(1) ); map2_ m2( make_pair<key2_>(2) ); typedef joint_view< map1_, map2_ > jv_; // not supposed to compile (?), yet it does: jv_ view(m1,m2); // but not this: // at_key<key1_>(view) // I have no choice (?) but create a new map, // although view helps a bit for initializing it: typedef map< pair1_, pair2_ > map3_; map3_ m3 = fusion::as_map(view); int n1 = fusion::at_key<key1_>(m3); BOOST_ASSERT(n1 == 1); int n2 = fusion::at_key<key2_>(m3); BOOST_ASSERT(n2 == 2);

3 6

[Boost.Test] [1.38] Automated test suie registration with muti-file-test-modules
by Greg Christopher 17 Oct '09

17 Oct '09

Hi, We are starting to expand the number of test modules and are having some growing pains. Originally we were using the "single header" variant included/unit_test.hpp file. Now we have switched to linking to the dynamic version of the boost test library and are including auto_unit_test.hpp. We have been counting on the Test Tools to automatically register suites and test cases. This still worked when we just included unit_test.hpp (instead of included/unit_test.hpp). However with multiple test modules, init_unit_test_suite is being defined in each module. I am looking for clear documentation on what to do. This seems like the closest thing: http://www.boost.org/doc/libs/1_31_0/libs/test/doc/components/unit_test_fra… However following those directions exactly when trying to use multiple test modules (in a single executable) and only one BOOST_AUTO_TEST_MAIN still results in init_unit_test_suite being multiply defined. I would like multiple test suites, although the documentation for this declares that there is a single global test suite. I apologize if this is well documented somewhere, but after an hour of googling I have to ask. Greg

4 15

1.40.0 - 32_64 broken on OS X 10.6 Snow Leopard
by JungleCat 15 Oct '09

15 Oct '09

Hi, 32_64 fat compilation is broken out of the box in 1.40.0 on OS X 10.6. Others reported this here: http://groups.google.com/group/boost-list/browse_thread/thread/06c7e1f93221… J

7 19

[asio] How to know if the io_service is runing
by Daniele Barzotti 14 Oct '09

14 Oct '09

In my library I have this code (yet used in another project) where pwork is assigned to a shared_ptr: -------------------------------------------------------------- typedef boost::shared_ptr<boost::asio::io_service::work> io_work_ptr; // Main io_service static boost::asio::io_service io_service; static boost::scoped_ptr<boost::thread> io_service_thread; static boost::asio::io_service::work* p_work; static bool thread_started; bool CreateMainThread() { if (!thread_started) { try { // create the work object on the heap p_work = new boost::asio::io_service::work(io_service); // run the IO service as a separate thread: io_service_thread.reset ( new boost::thread ( boost::bind ( &boost::asio::io_service::run, &io_service ) ) ); thread_started = !thread_started; return true; } catch (boost::thread_resource_error e) { // Failed to create the new thread return false; } } } -------------------------------------------------------------- WaveStream::WaveStream() : rx_timer_(io_service) { }; WaveStream::Test() { //Start a new timer or renew it rx_timer_.expires_from_now( boost::posix_time::milliseconds(500) ); // We managed to cancel the timer. Start new asynchronous wait. rx_timer_.async_wait( boost::bind(&WaveStream::handle_timeout, this, _1) ); } void WaveStream::handle_timeout(const boost::system::error_code& error) { .... } -------------------------------------------------------------- The timer callback is never called. Is there a way to know if the io_service is runing? Daniele.

2 2

New library for RPC-calls using only boost and C++0x
by Siegfried Kettlitz 13 Oct '09

13 Oct '09

Hello boost users and developers, i'm currently writing a library for making remote procedure calls to C++ objects. The library is based on the variadic templates extension coming with C++0x (already present in GCC 4.3) in conjunction with the boost library (threads, serialization, asio). The aim is to have a library, that is easy to integrate and doesn't require additional tools. Writing it, so far, has thaught me a lot about C++, templates, variadic templates, threading, networking etc.. I post this message, because i think that this library is quite handy in situations, where a developer already uses boost libraries and wants to add some networking functionality to his/her project and the usage of variadic templates instead of additional tools is quite new. One example would be remote monitoring an application by adding a "std::string get_status()"-function to some object. Implemented as example is a chat-system with a server and clients interacting by remote calls. This example is tested with a x64-linux and win32 using the portable boost-text-serialization. Multiple clients can connect to the server via the TCP/IP-acceptor (and disconnect without crashing the system). Implemented is a console-client for text input and display and a morse client, that interacts via a digital output device (relais card), which is connected via a serial port. The serial port and the digital output driver are both also connected via the rpc-system and can be physically located on separate computers. At this point, i have the basic bits together and a working rpc-library, that needs to be cleaned, refined and extended to match the practical needs. This means, that some programs and libraries have to be written, which use the rpc-library and show its bugs and limitations. The downside of it is, that the interface of the rpc-library may change one more time until it can be considered stable. Therefore it would not be good to test it widely in libraries posing similar requirements, but to test it with a variety of possible applications and provide the implementations as examples and (regression-/unit-)tests. - One library for Measurement/Automation is already in development. - The chat-server/client exists. - A transaction based game server is under consideration. - Some distributed parallel computing application with dynamic joining/leaving of clients. Can you give me some more ideas of different applications, which are easy to implement but yet useful? What would you like to have implemented and accessible by an rpc-library? One speed measurement using local (shared memory) channels resulted in 20000 calls/s and 60000 messages/s on a 1.8GHz Opteron. Do you know how this compares to other implementations on similar hardware? The TCP/IP-channel implementation using ASIO resulted in only about 100 synchronous calls/second regardless of the payload and almost no CPU load, which suggests that ASIO somewhere "sleeps" on linux systems for a few milliseconds. This would be fixed in some future implementation. Using asynchronous calls (1000 open calls) again leads to about 10000 calls/s. I'll have a closer look on what can be merged with "channels" from the boost vault[1], but from the first look it seems that "channels" targets a much more general approach. After the first tries, i realized, that my implemention has to be very specific (e.g. templates only where necessary). So, the design approaches might be too different. After the refinement, cleanup, some testing and documenting, i'd like to publish the rpc-library (and libraries based on it) under GPL- or boost-license. Then you'll hear from me again. In future i'll probably work 2-8 hours per week on the library and use it in some projects, but there's plenty of work left to do in various regions. This will leave space for other developers who might want to use and modify it to fit their needs. Some of the harder parts that would need implementation are redundant parallel connections and advanced routing, authentication of nodes, signing of messages, encryption of payload, access restriction to objects. Please let me know if * you are interested in this library in some way * have comments * know very similar libraries or * are interested in serialization using variadic function templates. Regards, Siegfried Kettlitz --- A short introduction on the library: * "nodes" are the central parts. They contain a factory for objects, store objects and forward "messages" to objects or other nodes in the network and contain a "scheduler" for executing function calls. The nodes are connected by "channels", which forward messages between the two connected nodes. Currently there is a TCP/IPv4 implementation using ASIO and direct forwarding. * Nodes connected by channels form a network, create and monitor virtual connections between each other. The network map is used to route messages between connected nodes. * An object has to supply a template for a class name (only if it can be constructed by the factory) and a template for registering the callable functions (also for abstract base classes which can't be constructed). * A function call is executed asynchronously (wrapper for synchronous call exists). The call to node.call(...) returns a "link_caller"-object. The function to be executed itself can optionally have "link_callee" as the first argument (which is invisible for the caller). The "link_caller"/"link_callee" is used for synchronization (wait for call to begin/finish execution), message forwarding (push/pop strings at caller/callee) and transfer/extraction of the return value. * Objects of class hierarchies with abstract base classes are possible and handled transparently. * Objects can be constructed by the factory of a node or an existing (externally constructed) object can be registered by the node. * Objects don't necessarily need to know (be modified, inherit something etc.) that they are part of the RPC-system and some of their functions are called remotely. * Objects can be aware that they are constructed by the factory and can, on construction be informed about their identity and get a reference to the node to make remote calls themselves. * An object is identified by a "reference" consisting of the "node_id" and the "object_id". * Parameters are passed (serialized, deserialized) by value. All function parameters must have the possibility to be serialized. Modifying referenced parameters won't affect the parameter at the caller. Pointers obviously won't work between nodes not sharing the same memory-address-space. * Called functions can use "link_callee" to make remote calls themselves, regardless of the object. * Priorities are assigned to calls and affect message forwarding and scheduling. * Calls to objects can be transformed into a boost::function using node.bind(...). * If a called function throws, the exception is forwarded as rpc::exception or a more specialized exception class. The exception is thrown at the caller, when waiting for interaction with the callee (e.g. wait for return value). * Template functions as targets are possible when specifying the template parameters of the function pointer when registering the function. * There is no need to use macros at all, although macros could be used to simplify some things. ---------- // Example for creating and calling an object. // Create a service. boost::asio::io_service node_io_service; // Create a node. rpc::node node_s(node_io_service, config); // Register the builder in order to build the server object later. node_s.register_builder<devicelib::chat_server_impl>(); // Register the interface of the client to be able to make calls to it. node_s.register_interface<devicelib::chat_client>(); // Create the server object. rpc::reference cs( node_s.get_id(), node_s.allocate_object_template<devicelib::chat_server_impl>() ); // Store the server in name server. // rpc::reference( node_s.get_id(), rpc::oid_simple_object_name_server ) -> A reference to the object_name_server. // rpc::sched_default() -> Default scheduling parameters. // &rpc::simple_object_name_server::store, cs -> function to call. // cs, "chat_server_object" -> function parameters. node_s.wrap_call( rpc::reference( node_s.get_id(), rpc::oid_simple_object_name_server ), rpc::sched_default(), &rpc::simple_object_name_server::store, cs, "chat_server_object" ); ---------- // Example for abstract base class. namespace devicelib { class chat_server : public chat_types { public: virtual void receive( std::string xml_message ) = 0; virtual user_id_t connect_user( rpc::reference a_client, std::string xml_user_info ) = 0; virtual std::string query_user( user_id_t id ) = 0; virtual void disconnect_user( user_id_t user ) = 0; virtual void join_room( user_id_t user, room_id_t room ) = 0; virtual std::list<user_id_t> list_users( ) = 0; virtual std::list<room_id_t> list_rooms( ) = 0; }; } --------------- // Example for registering the interface of the server object. // The template is declared in namespace rpc, therefore we need to define it there. namespace rpc { // For the base object. template<> void register_proxy_functions<devicelib::chat_server>( function_call_proxy<devicelib::chat_server>& ar_proxy ) { // Register the functions of the abstract base object using unique strings. ar_proxy.register_interface( &devicelib::chat_server::connect_user, "&chat_server::connect_user" ); ar_proxy.register_interface( &devicelib::chat_server::query_user, "&chat_server::query_user" ); ar_proxy.register_interface( &devicelib::chat_server::disconnect_user, "&chat_server::disconnect_user" ); ar_proxy.register_interface( &devicelib::chat_server::join_room, "&chat_server::join_room" ); ar_proxy.register_interface( &devicelib::chat_server::list_users, "&chat_server::list_users" ); ar_proxy.register_interface( &devicelib::chat_server::list_rooms, "&chat_server::list_rooms" ); } // For each implementation. template<> void register_proxy_functions<devicelib::chat_server_impl>( function_call_proxy<devicelib::chat_server_impl>& ar_proxy ) { // Register the functions of the base object. register_proxy_functions<devicelib::chat_server>( (function_call_proxy<devicelib::chat_server>&) ar_proxy ); // Make the functions of this object available. ar_proxy.register_interface( &devicelib::chat_server_impl::connect_user, &devicelib::chat_server::connect_user ); ar_proxy.register_interface( &devicelib::chat_server_impl::disconnect_user, &devicelib::chat_server::disconnect_user ); ar_proxy.register_interface( &devicelib::chat_server_impl::join_room, &devicelib::chat_server::join_room ); ar_proxy.register_interface( &devicelib::chat_server_impl::list_users, &devicelib::chat_server::list_users ); ar_proxy.register_interface( &devicelib::chat_server_impl::list_rooms, &devicelib::chat_server::list_rooms ); } // The implementation can be built, the base object not. template<> std::string class_builder_name<devicelib::chat_server_impl>() { // Give it an unique name here. return "chat_server_impl"; } } ----------------- 1: http://www.boostpro.com/vault/index.php?&direction=0&order=&directory=Distr…

8 12

Formal Review of Boost.Polygon extended one more week: until September 9, 2009
by Fernando Cacciola 13 Oct '09

13 Oct '09

Dear boost users, The review of Boost.Polygon was initially scheduled to end today. However, the discussions are in their best moment only now so the review period was extended by one week, until September 9, 2009 (that is next Wednesday). Best Fernando Cacciola Review Manager

9 12

How to use the shared region in append mode
by manish4gupta 02 Oct '09

02 Oct '09

First of all i would like to thank for previous answers. Now i am able to use the shared region to create a map, insert value into shared map and use the shared map. Now moving one step ahead. I am planning to use the shared region in append mode. For instance 1. create shared region if it is not used before // how to check this ? managed_shared_memory segment(create_only,MySharedMemory, 999999999); 2. create map in the region // done 3. open the map and use the map for retrieving and inserting values //done How i can that the given region already allocated to map so that i can insert the value in it otherwise i can create the that region and create tha map and insert the value in the map. Thanks in advance. -- View this message in context: http://www.nabble.com/How-to-use-the-shared-region-in-append-mode-tp2567740… Sent from the Boost - Users mailing list archive at Nabble.com.

2 5