April 2011 - Boost-users - lists.preview.boost.org

Seeking to particular array element while deserializing
by rajiv82 11 Apr '11

11 Apr '11

I have a structure like: struct Header { vector foo; vector bar; }; I have created an array of above structure: Header *ptr = new Header[1000]; Now doing serialization/deserialization works fine with binary_oarchive. But, in some situation, I want to just deserialize particular element of array(say element at index 80). Is it possible using binary archive ? I have a work around of writing each element one by one & while de-serialization, ignore irrelevant data(in our case index 0-79) & then use proper data. But it is not optimum solution. I even tried xml archive with name as index & value as binary object by using make_binary_object. Doing something like: for(int i = 0 ; i<1000; i++) { stringstream ss ; ss << i; ar << make_nvp(ss.str().c_str(), make_binary_object(&ptr[i], 1)) ; } And deserializing 80th index object like: ar >> make_nvp("80", make_binary_object(&ptr[80], 1)) ; Program compiles fine, but result is inconsistent. Please suggest is there any better way to read(deserialize) just one element of an array. -- View this message in context: http://boost.2283326.n4.nabble.com/Seeking-to-particular-array-element-whil… Sent from the Boost - Users mailing list archive at Nabble.com.

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Monitoring thread liveness using multiple threads with a single asio io_service
by Krajnak, Mike (GE Healthcare) 11 Apr '11

11 Apr '11

We have a server implemented with boost::asio that uses a vector of threads with a single io_service as in the asio http server 3 sample program. We want to check on the liveness of threads by having each thread periodically call back to a thread manager so that we can confirm it is still running. To do that we have an inner loop that uses run_one() so we can call our heartbeat function after each action is completed (pseudo code): do { num_ops = io_svc.run_one(ec) heartbeat_to_thread_manager(); } while (num_ops > 0); However, asio makes no garantees on how work is dispatched to threads. In our testing work seems to go prefentially to one thread for several iterations before going to another thread with no pattern that we can find. Is there some way we can change this solution so that we can be reasonably sure each thread will be called at least once in a some period of time or some other mechanism for monitoring thread liveness? Thanks, Mike

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Re: [Boost-users] Compiling Boost with 4 byte packing...
by Brian Nantz 11 Apr '11

11 Apr '11

I finally got boost to build with visual studio 2008 and 4-byte packing. Here is what I had to do: 1. Edit the tools\build\v2\user-config.jam and add: using msvc : vc9 : "D:/Program Files/Microsoft Visual Studio 9.0/VC/bin/cl.exe" : <compileflags>-DBOOST_HAS_ABI_HEADERS <compileflags>-DBOOST_PROTO_MAX_ARITY=10 <compileflags>-DBOOST_MPL_CFG_NO_PREPROCESSED_HEADERS <compileflags>-DBOOST_MPL_LIMIT_METAFUNCTION_ARITY=10 <compileflags>-DWIN32 <compileflags>-D_DEBUG <compileflags>-D_LIB <compileflags>-D_WIN32_WINNT=0x0501 <compileflags>-D_UNICODE <compileflags>-DUNICODE <compileflags>-DBOOST_ASIO_ENABLE_BUFFER_DEBUGGING <compileflags>-Gm <compileflags>-EHsc <compileflags>-RTC1 <compileflags>-MTd <compileflags>-Zp4 <compileflags>-W4 <compileflags>-c <compileflags>-ZI <compileflags>-TP <linkflags>/MACHINE:X86 ; 2. On the bjam command line use the options: --toolset=msvc-9.0 cxxflags=-Zp4 3. Edit boost/config/user.hpp: // BOOST_ABI_PREFIX: A prefix header to include in place of whatever // boost.config would normally select, any replacement should set up // struct packing and alignment options as required. #define BOOST_ABI_PREFIX <boost/config/abi/saplib_prefix.hpp> // BOOST_ABI_SUFFIX: A suffix header to include in place of whatever // boost.config would normally select, any replacement should undo // the effects of the prefix header. #define BOOST_ABI_SUFFIX <boost/config/abi/saplib_suffix.hpp> The prefix header just contains #pragma pack(push,4) and the suffix just has #pragma pack(pop) 4. For some reason ASIO does not use the boost ABI header prefix and suffix. It has its own. Edit boost/asio/detail/push_options.hpp to use #pragma pack(push,4). The boost build now completes cleanly (with no errors or warnings) on boost 1.43. There seems to be some room for simplification or improvement here?

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[boost-users][parameter] ArgumentPack Documentation Best Practices
by Christoph Heindl 11 Apr '11

11 Apr '11

Hi, I wonder if anyone could share his best practices as far as documenting Boost.Parameter enabled constructors is concerned. I'm currently doing something along the lines of /** Construct from named parameters and use defaults where parameters are empty * * * \tparam Opts ArgumentPack of options. The following options are supported * - \a min_group_size minimum number of supporting correspondences to form a group. * - \a ntrials number of times to form basis from two randomly selected correspondences. * - \a bin_size_pos quantization size for transformed point coordinates. * - \a bin_size_orientation quantization in radians for surface orientation angles. * */ template<class Opts> group_geo_hash(const Opts &opts) { this->init( opts[Keywords::_min_group_size | 10], opts[Keywords::_bin_size_pos | LibFundament::rasFloat(10)], opts[Keywords::_orientation_rad | LibFundament::rasFloat(0.2)], opts[Keywords::_ntrials | 0]); } } which is sub-optimal, because default values for options and option types are missing. Doxygen can deduce types for regular parameters as well as default values. Ideally this should work for boost.parameters as well :) Even better, Doxygen could warn about undocumented parameters. Any thoughts? Best regards, Christoph

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Re: [Boost-users] [Boost.Thread] Multithreaded Multithreaded Server (Ian Mallett)
by Marat Abrarov 11 Apr '11

11 Apr '11

> Hi, > > Fairly new to Boost. Bear with me. > > I'm trying to write a multithreaded multithreaded server (two multithreaded > operations): ideally, there should be a single process, containing at least two threads. The first > thread handles various tasks (and can start other threads to help it as well). The other thread waits > for incoming connections, and adds a new thread for each one: http://sourceforge.net/projects/asio-samples/ Look at projects "echo_server" and "qt_echo_server". They use 2 thread pools among main (GUI) thread. One thread pool (size is 1-2 threads) executes session management loop: acceptance (with limited number of active sessions), start of accepted session, end of all sessions. Second thread pool (by default is CPU number bounded) executes sessions' loops: start of asynchronous read, start of asynchronous write, IO operation completion handling. Regards, Marat Abrarov.

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Re: [Boost-users] [MSM] problem compiling a functor-guard using a flaginside.
by Christophe Henry 11 Apr '11

11 Apr '11

>while developing I want to use functors for a guard. The state machine compiles well until I added a >function call to the FSM which has a template parameter. Then I always got the following error message >while compiling it with gcc 4.4.1. >SubtractionControllerNew.cpp: In member function ‘bool<unnamed>::player_::isCDLoaded::operator()(const EVT&, FSM&, SourceState&, TargetState&)’: >SubtractionControllerNew.cpp:175: error: expected primary-expression before ‘>’ token >SubtractionControllerNew.cpp:175: error: expected primary-expression before ‘)’ token >Does anybody know why this happens and how to circumvent it? I admit C++ is sometimes full of hard-to-get rules :( Try adding a template keyword: struct isCDLoaded { template <class EVT,class FSM,class SourceState,class TargetState> bool operator()(EVT const& ,FSM& fsm,SourceState& ,TargetState& ) { //return fsm.is_contained(); // this works well return fsm.template is_flag_active<CDLoaded>(); // Line 175 } }; HTH, Christophe

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[Fusion] Output of adapted ADT
by Tore Halvorsen 11 Apr '11

11 Apr '11

Hi, I'm trying to output a string from an adapted class, but I'm getting 1>main.cpp(33): error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'boost::fusion::extension::adt_attribute_proxy<foo,0,false>' (or there is no acceptable conversion) for the following code (boost 1_46_1, msvc2010) Is there a header I'm missing? Very similar code works for BOOST_FUSION_DEFINE_STRUCT - and using ints or doubles also work... #include <iostream> #include <string> #include <ostream> #include <boost/fusion/include/adapted.hpp> #include <boost/fusion/sequence.hpp> class foo { public: foo(std::string const& str) : s(str) { } std::string const& get_s() const { return s; } void set_s(std::string const& str) { s = str; } private: std::string s; }; BOOST_FUSION_ADAPT_ADT( foo, (std::string const&, std::string const&, obj.get_s(), obj.set_s(val)) ); int main(int argc, char* argv[]) { foo f("foo"); std::cout << boost::fusion::front(f) << std::endl; return EXIT_SUCCESS; } -- Eld på åren og sol på eng gjer mannen fegen og fjåg. [Jøtul] <demo> 2011 Tore Halvorsen || +052 0553034554

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[Boost.Thread] Multithreaded Multithreaded Server
by Ian Mallett 10 Apr '11

10 Apr '11

Hi, Fairly new to Boost. Bear with me. I'm trying to write a multithreaded multithreaded server (two multithreaded operations): ideally, there should be a single process, containing at least two threads. The first thread handles various tasks (and can start other threads to help it as well). The other thread waits for incoming connections, and adds a new thread for each one: Server process: -Thread 1 (Handle background server operations, etc.) -helper thread 1 -helper thread 2 ... -helper thread *n* -Thread 2 (Listen for incoming connections. When found, make a new connection thread to handle it) -connection thread 1 -connection thread 2 ... -connection thread *n* I began by making heavy use of the example here<http://www.boost.org/doc/libs/1_36_0/doc/html/boost_asio/example/echo/async…>. Please see my attached files for my implementation. The classes "mMindThreadServerListener" and "mMindServerHandlerClient" correspond to "server" and "session", respectively. "mMindServer" is the highest level (server process). In it, there's a thread group that contains "Thread 1" ("_thread_connection_pruner", which kills unused connections, and represents a background server operation) and "Thread 2" ("_thread_listener", which listens for incoming connections). Thread 2's need to make other threads seems to be handled by boost::asio::io_service. Unfortunately, when a connection is found, Thread 1 stops. I can only attribute this to a lock boost::asio::io_service puts, although I have no idea. Can someone explain what's going on, and possibly a better way to do this? Thanks, Ian

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BOOST and Android
by Claude 10 Apr '11

10 Apr '11

Hi! It is possible compile/use BOOST with Android (3.0?) NDK? -- View this message in context: http://boost.2283326.n4.nabble.com/BOOST-and-Android-tp3439871p3439871.html Sent from the Boost - Users mailing list archive at Nabble.com.

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Re: [Boost-users] [MSM] Use events twice
by Christophe Henry 10 Apr '11

10 Apr '11

> I'm using MSM to implement a client for a simple network application. Basically, the server sends messages and the client changes state and responds to them as appropriate. > > One of these messages is THROW. THROW gets two arguments: an identifier (0-3) and a value. My client is supposed to sum up the values for consecutive THROW events with the same identifier, and on a change of identifier, store the sum somewhere and start over for the new identifier. > > So I have three states (id0, id1, id2 - there's some special handling, which is why they're separate states) and an event Throw(id, value). The transitions for idN are: > Throw(my id, value) -> no switch, state.sum += value > Throw(other id, value) -> switch to state of other id, reprocess event, storing the sum is handled by the exit action > > In other words, I want the next state to immediately handle the event as well, because there's a value there I need to store. The question is, how do I do this? > > Here's a sequence of events and actions that could occur: > E1: [init] Throw(0, 4) -> [id0: ?] > Entry [id0: ?] -> [id0: 0] > [id0: 0] reprocess E1 -> [id0: 4] > E2: [id0: 4] Throw(0, 8) -> [id0: 12] > E3: [id0: 12] Throw(1, 7) -> [id1: ?] > Exit [id0: 12] -> save 12 > Entry [id1: ?] -> [id1: 0] > [id1: 0] reprocess E3 -> [id1: 7] Hi Sebastian, Let's see if I get it. Reprocessing is not going to be the problem, I suppose. An action reprocessing an event untouched would be: struct reprocess { template <class Fsm,class Evt,class SourceState,class TargetState> void operator()(Evt const& evt,Fsm& fsm,SourceState& ,TargetState& ) { fsm.process_event(evt); } }; MSM has a message queue by default so you have no risk of deadlocking yourself. Actually you might not even need to reprocess if you use internal actions and transition conflicts, so I suggest a different version. For every Throw event, sou create a conflict between a state internal transition (not necessary but more elegant and with more reuse, see below) and an external one, leading to another state if the id contained in Throw is not the one from the current state. If it is the one from the current state, we add the value from the event. I also added an Init state to make it simpler. Now, all I need to do is make the states template classes and write just one. I attach an example. Please tell me if that's what you're looking for. Christophe

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