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Threads, condition variables, and signals
by Scott Gifford 08 Oct '07

08 Oct '07

Hello, I'm writing a multithreaded server on Unix using boost::thread. The basic operation is fairly straightforward; a master thread starts up worker threads, and coordinates various management tasks using condition variables. As with most Unix servers, the server is shut down with an OS signal telling the server to shut down. The server catches this signal, then simply calls exit(1). Any important cleanup happens in the destructors of global variables, so it will happen properly no matter how the server exits. One object which is always cleaned up is the object for the master thread. The master thread sets a flag, then does a notify_all() on some condition variables to tell the other threads to shut down, The problem I'm having is that if the master thread is waiting on a condition variable when the signal arrives, and the destructor does a notify_all() on that condition variable, then the destructor for the boost::condition variable hangs. For example, if I run the included code and hit CTRL-C after a short bit, I get this output: Waiting... ^C Caught signal 2 Destroyed ThreadTest Running destructor 1 [ ... hangs ... ] Here is the program: #include <iostream> #include <signal.h> #include <boost/thread.hpp> #include <boost/thread/mutex.hpp> #include <boost/thread/condition.hpp> template<int n> struct PrintOnDestruct { ~PrintOnDestruct() { std::cout << "Running destructor " << n<< std::endl; } }; class ThreadTest { public: void doSomething() { boost::mutex::scoped_lock lock(myMutex); while(true) { std::cout << "Waiting..." << std::endl; myCond.wait(lock); } } ~ThreadTest() { boost::mutex::scoped_lock lock(myMutex); myCond.notify_all(); std::cout << "Destroyed ThreadTest" << std::endl; } private: PrintOnDestruct<2> d2; boost::mutex myMutex; boost::condition myCond; PrintOnDestruct<1> d1; }; // Exit properly on signal void sighandle(int sig) { std::cerr << "Caught signal " << sig << std::endl; exit(1); } ThreadTest tt; int main() { // Get ready to handle signals signal(SIGINT,sighandle); tt.doSomething(); } Does anybody have any suggestions for a straightforward way to handle this properly? Thanks! ----ScottG.

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[preprocessor] using __FILE__ with BOOST_PP_FILENAME_x
by Server Levent Yilmaz 08 Oct '07

08 Oct '07

Hi all, Please take a look as this trivial example of file iteration: // trivial.h #if !BOOST_PP_IS_ITERATING #ifndef TRIVIAL_H #define TRIVIAL_H #include <boost/preprocessor/iteration/iterate.hpp> #define BOOST_PP_FILENAME_1 "trivial.h" //!!! #define BOOST_PP_ITERATION_LIMITS (1, 3) ??=include BOOST_PP_ITERATE() #endif // TRIVIAL_H #else BOOST_PP_ITERATION() #endif Perhaps not so obvious many (wasn't to me), that #define BOOST_PP_FILENAME_1 __FILE__ doesn't work. One has to specify (kind of like hardcode) the file's name in there.. Is there some, possibly contrived, way to achieve automation of this? regards, - Levent PS: What an AMAZING library this Boost.Preprocessor is!? -- Server Levent Yilmaz Mechanical Engineering University of Pittsburgh

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exp functions with interval
by Mark Beinker 08 Oct '07

08 Oct '07

Hi, I was trying to use the boost interval class using g++ under cygwin and ubuntu, but unfortunately, I have trouble to use the exp function. The following code: #include <iostream> #include <cmath> #include <boost/numeric/interval.hpp> #define DOUBLE boost::numeric::interval<double> int main(int argc, char** argv) { DOUBLE x(4,5); std::cout.precision(19); DOUBLE res = exp(x); std::cout<<'['<<res.lower()<<", "<<res.upper()<<']'<<std::endl; return 0; } generates the following compile error: /usr/include/boost/numeric/interval/transc.hpp: In function `boost::numeric::interval<T, Policies> boost::numeric::exp(const boost::numeric::interval<T, Policies>&) [with T = double, Policies = boost::numeric::interval_lib::policies<boost::numeric::interval_lib::rounded_math<double>, boost::numeric::interval_lib::checking_strict<double> >]': itest.cpp:14: instantiated from here /usr/include/boost/numeric/interval/transc.hpp:34: error: 'struct boost::numeric::interval_lib::rounded_math<double>' has no member named 'exp_down' itest.cpp:14: instantiated from here /usr/include/boost/numeric/interval/transc.hpp:34: error: 'struct boost::numeric::interval_lib::rounded_math<double>' has no member named 'exp_up' I use boost version 1.34.1. Any idea why this doesn't work? Regards, Mark

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[string_algo] Case-insensitive keys in map with is_iless?
by Boris 07 Oct '07

07 Oct '07

Am I supposed to be able to use boost::algorithm::is_iless (see http://www.boost.org/doc/html/boost/algorithm/is_iless.html) to create a map with case-insensitive keys? I wonder as either it is broken in VS2005 or I do something wrong: #include <boost/algorithm/string.hpp> #include <string> #include <map> int main() { std::map<std::string, int, boost::algorithm::is_iless> m; m["test"] = 1; } C:\Program Files\Microsoft Visual Studio 8\VC\include\xlocale(583) : error C2440: 'type cast' : cannot convert from 'unsigned char' to 'std::basic_string<_Elem,_Traits,_Ax>' ... C:\Program Files\Microsoft Visual Studio 8\VC\include\xlocale(561) : error C2440: 'type cast' : cannot convert from 'std::basic_string<_Elem,_Traits,_Ax>' to 'unsigned char' The assignment causes the problem. If you use insert() you get the same compiler error. Without the assignment the code compiles fine. Boris

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"Missing" lib for 1_34_1 using MSVC-71
by Larry 07 Oct '07

07 Oct '07

I had a program that I had built with Boost 1_34 and it worked well (built with MSVC 7.1). I downloaded 1_34_1 and built 1_34_1 for VC8 and VC7.1 using bjam 3.1.14. bjam --toolset=msvc-7.1 install I switched the program build to use Boost 1_34_1 and the build fails looking for libboost_date_time-vc71-mt-sgd-1_34_1.lib as part of the link. Going back to the Boost build I find msvc.archive bin.v2\libs\date_time\build\msvc-71\debug\link-static\runtime-link-static\libboost_date_time-vc-sgd-1_34_1.lib common.copy C:\Boost\lib\libboost_date_time-vc-sgd-1_34_1.lib 1 file(s) copied. The only thing I changed was the include list entry from c:\boost\include\boost_1_34 to c:\boost\include\boost_1_34_1. The lib directory is the same in both cases. I didn't find anything looking through the boost.user group or in the doc but perhaps I looked at it and just didn't realize the answer was there. Perhaps I didn't do something I should have or did something I shouldn't have. Any ideas? I got surprised (probably again) when building Boost because I had run vcvars32.bat for MSVC 7.1 and then did bjam --toolset=msvc install and the surprise was it built for MSVC 8.0. The doc does say the build will find the VC compiler but I had sort of assumed it would use what was in the environment before searching elsewhere for a compiler version. But after that I ran bjam --toolset=msvc-71 install and it ran without complaint. I did several iterations of the 7.1 build including a build with -a and also did a --clean followed by a Boost build and neither altered the outcome of the Boost build (that I could see) and did not alter the outcome of the program build with VC 7.1. The program build was done via VS. Moving the include back to 1_34 works. Larry

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[thread] example to delegtate jobs to threads
by Torsten Mohr 07 Oct '07

07 Oct '07

Hi, i wrote a small test project that makes use of boost::thread to split jobs into parts that are delegated to threads. A class "Job" contains a state machine (IDLE, EXECUTING, ABORTED, ...). That class can be derived from and methods "execute" and "report" can be overwritten. A class JobProvider can be derived from to feed new data to a Job. A Template "Foreman" can then start several threads and delegate Jobs that get their data from "JobProvider" to the Jobs and they report when they are done. In the example, MyJobProvider provides numbers from 3 to 100. MyJob::execute calculates if these numbers are prime. MyJob::report prints out the numbers that are prime. All the methods "report" are protected, only one of them at a time is ever called, methods "execute" are run in parallel. The performance is poor, can anybody give me a hint why? Best regards, Torsten. ######## job.h: #ifndef JOB_H #define JOB_H 1 #include <boost/thread.hpp> extern boost::mutex io_mutex; #define QWE { boost::mutex::scoped_lock lck(io_mutex); printf("file %s line %i\n", __FILE__, __LINE__); } class Job { boost::mutex job_mutex; boost::mutex cond_mutex; boost::mutex* m_report_mutex; boost::condition* m_condition; boost::thread* thr; bool m_stopped; int m_state; void setState(int state); protected: bool is_stopped(void); public: enum { CMD_IDLE = 212, CMD_EXEC, CMD_KILL }; enum { STATE_IDLE = 37, STATE_EXEC_PREPARE, STATE_EXEC, STATE_EXEC_ABORTED, STATE_REPORT_PREPARE, STATE_REPORT, STATE_DEAD }; void set_foreman_data(boost::mutex* report_mutex, boost::condition* condition); void init(void); virtual void execute_handler(void); void report_handler(void); void fork(void); int getState(void); void doCommand(int command); virtual void execute(void); virtual void report(void); }; class JobProvider { public: bool provide(Job& j); }; #endif ######## job.cc: #include <boost/thread.hpp> #include <boost/bind.hpp> #include "job.h" int Job::getState(void) { boost::mutex::scoped_lock lock(job_mutex); return m_state; } void Job::setState(int state) { boost::mutex::scoped_lock lock(job_mutex); m_state = state; } void Job::doCommand(int cmd) { boost::mutex::scoped_lock lock(job_mutex); // sparse transitions if((m_state == STATE_EXEC || m_state == STATE_EXEC_PREPARE) && cmd == CMD_KILL) { m_state = STATE_EXEC_ABORTED; m_stopped = true; } else if(m_state == STATE_IDLE && cmd == CMD_EXEC) { m_state = STATE_EXEC_PREPARE; } else if(m_state == STATE_IDLE && cmd == CMD_KILL) { m_state = STATE_DEAD; m_stopped = true; } } bool Job::is_stopped(void) { boost::mutex::scoped_lock lock(job_mutex); return m_stopped; } void Job::execute_handler(void) { int state; do { state = getState(); switch(state) { case STATE_EXEC_PREPARE: execute(); state = getState(); if(state != STATE_EXEC_ABORTED) { boost::mutex::scoped_lock lock(*m_report_mutex); report(); m_condition->notify_one(); setState(STATE_IDLE); } break; case STATE_DEAD: case STATE_EXEC_ABORTED: return; } } while(1); } void Job::init(void) { m_state = STATE_IDLE; } void Job::fork(void) { thr = new boost::thread(boost::bind(execute_handler, this)); } void Job::report_handler(void) { boost::mutex::scoped_lock lock(*m_report_mutex); report(); } void Job::set_foreman_data(boost::mutex* report_mutex, boost::condition* condition) { m_report_mutex = report_mutex; m_condition = condition; } void Job::execute(void) { } void Job::report(void) { } ######## foreman.h: #ifndef FOREMAN_H #define FOREMAN_H 1 #include <boost/thread.hpp> #include <boost/bind.hpp> #include "job.h" template<class JOBB, class JOBB_PROVIDER> class Foreman { JOBB* jb; JOBB_PROVIDER* m_provider; int m_threads; bool m_finished; boost::mutex report_mutex; boost::mutex m_cond_mutex; boost::condition m_condition; boost::thread* me; void handler(void); public: Foreman(int threads, JOBB_PROVIDER* provider); ~Foreman(); void spawn(void); void cleanup(void); void abort(void); bool is_finished(void); }; template<class JOBB, class JOBB_PROVIDER> Foreman<JOBB, JOBB_PROVIDER>::Foreman(int threads, JOBB_PROVIDER* provider) : m_threads(threads), m_provider(provider) { jb = new JOBB[m_threads]; } template<class JOBB, class JOBB_PROVIDER> Foreman<JOBB, JOBB_PROVIDER>::~Foreman() { delete[] jb; } template<class JOBB, class JOBB_PROVIDER> void Foreman<JOBB, JOBB_PROVIDER>::handler(void) { bool all_done; do { boost::mutex::scoped_lock lock(m_cond_mutex); all_done = true; for(int i = 0; i < m_threads; ++i) { int state = jb[i].getState(); if(state == Job::STATE_IDLE) { if(m_provider->provide(jb[i])) { jb[i].doCommand(Job::CMD_EXEC); all_done = false; } else { m_finished = true; } } else { all_done = false; } } if(m_finished || all_done) { return; } m_condition.wait(lock); } while(1); // (!m_finished || !all_done); } template<class JOBB, class JOBB_PROVIDER> void Foreman<JOBB, JOBB_PROVIDER>::spawn(void) { for(int i = 0; i < m_threads; ++i) { jb[i].set_foreman_data(&report_mutex, &m_condition); jb[i].init(); jb[i].fork(); } m_finished = false; // me = new boost::thread(boost::bind(handler, this)); handler(); } template<class JOBB, class JOBB_PROVIDER> void Foreman<JOBB, JOBB_PROVIDER>::cleanup(void) { // me->join(); } template<class JOBB, class JOBB_PROVIDER> void Foreman<JOBB, JOBB_PROVIDER>::abort(void) { } template<class JOBB, class JOBB_PROVIDER> bool Foreman<JOBB, JOBB_PROVIDER>::is_finished(void) { return m_finished; } #endif ######## my_job.h: #ifndef MY_JOB_H #define MY_JOB_H 1 #include "job.h" class MyJob : public Job { int m_suspect; bool is_prime; public: MyJob(); virtual void execute(void); virtual void report(void); void setJobStuff(int suspect); }; class MyJobProvider : public JobProvider { int m_actual; public: MyJobProvider(); bool provide(MyJob& j); }; #endif ######## my_job.cc: #include <iostream> #include <math.h> #include "my_job.h" #include "job.h" MyJob::MyJob() { m_suspect = 0; } void MyJob::setJobStuff(int suspect) { m_suspect = suspect; } void MyJob::execute(void) { int root = (int)sqrt((double)m_suspect); for(int j = 2; j <= root; j++) { if(is_stopped()) { return; } if((m_suspect % j) == 0) { is_prime = false; return; } } is_prime = true; } void MyJob::report(void) { if(is_prime) { std::cout << m_suspect << " is prime" << std::endl; } } MyJobProvider::MyJobProvider() : m_actual(3) {} #define NN 100 bool MyJobProvider::provide(MyJob& j) { j.setJobStuff(m_actual); m_actual++; if(m_actual > NN) return false; return true; } ######## qwe.cc: #include <iostream> #include "job.h" #include "my_job.h" #include "foreman.h" boost::mutex io_mutex; void test1(void) { MyJobProvider p; MyJob j; while(p.provide(j)) { j.execute(); j.report(); } } void test2(void) { MyJobProvider p; Foreman<MyJob, MyJobProvider> fm(7, &p); fm.spawn(); do { } while(!fm.is_finished()); fm.cleanup(); } int main(int argc, char** argv) { test2(); return 0; }

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Serializing a Method
by at forum 07 Oct '07

07 Oct '07

Hi to all I am new to the boost library, I downloaded it and I am doing some tests. I was using MFC serialization. I want to do something like this : template<class _CReceiver, class _CMemberType> class CASetMemberCommand { friend class boost::serialization::access; public: typedef void (_CReceiver::* Action)(_CMemberType) ; protected: _CReceiver *m_pReceiver; _CMemberType m_Property; Action m_fnAction; public: CASetMemberCommand() { m_pReceiver = NULL; } CASetMemberCommand(_CReceiver *pReceiver, Action fnAction, _CMemberType memberProperty) { m_pReceiver = pReceiver; m_fnAction = fnAction; m_Property = memberProperty; } ~CASetMemberCommand() { } virtual void Execute() { if(m_pReceiver) (m_pReceiver->*m_fnAction)(m_Property); } template<class Archive> void serialize(Archive & ar, const unsigned int /* file_version */){ ar & BOOST_SERIALIZATION_NVP(m_pReceiver) //& BOOST_SERIALIZATION_NVP(m_fnAction) & BOOST_SERIALIZATION_NVP(m_Property); } void Save(const char * filename) { std::ofstream ofs(filename); assert(ofs.good()); boost::archive::xml_oarchive oa(ofs); oa << BOOST_SERIALIZATION_NVP(this); } void Load( const char * filename) { std::ifstream ifs(filename); assert(ifs.good()); boost::archive::xml_iarchive ia(ifs); ia >> BOOST_SERIALIZATION_NVP(*this); } }; int main(int argc, char *argv[]) { gps_position pos(32,52,25.0f); CASetMemberCommand<gps_position,int> cmd(&pos,&gps_position::SetMinutes,25); CASetMemberCommand<gps_position,int> cmd4(&pos,&gps_position::SetDegrees,25); cmd.Execute(); SaveCommand(cmd,"D:/test.xml"); cmd.Save("D:/Test2.xml"); CASetMemberCommand<gps_position,int> cmd2; cmd2.Load("D:/Test2.xml"); return 0; } the problem is that BOOST_SERIALIZATION_NVP(m_fnAction) is not working (compile errors); Is there any way to save a methode of w class, so it can be loaded and used later? Thank you

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Allocator and smart_ptrs
by Seweryn Habdank-Wojewódzki 06 Oct '07

06 Oct '07

Dears I found that only shared_ptr can use allocator. Is there any possibility to join the existing allocator and the other smart_ptrs. Why the rest smart_ptrs can not use allocators? Regards. -- |\/\/| Seweryn Habdank-Wojewódzki \/\/

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Need a help about boost.thread
by Steven Woody 06 Oct '07

06 Oct '07

hi, i am doing a job and considering if boost.thread can help. what i am doing is writing some code for other one's use. my code will be called by many threads, and accessing some shared data. my problem is how to keep my code thread-safe. i have no way to control how those other threads were created ( actually, those had already done by another team using windows MFC, and, for some reasons, my code can not use MFC, is has to be portable bwteen Linux and Windows ). in breif, you can think my code in a way of producer/consumer pattern. the producer is a rouine which will be called by many threads ( which are actaully connected sockets created by a listening socket ), and the consumer routine will be called by another thread ( which is actually GUI's main thread ). what i expected is: 1, only one producer can write to the shared data; 2, when a producer is writting, other producers have to busy waiting; and the GUI thread should immediately exit; 3, when GUI thread is reading, no producer can write to the shared data; to my problem, does the boost.thread can help? thanks in advance. -- woody then sun rose thinly from the sea and the old man could see the other boats, low on the water and well in toward the shore, spread out across the current.

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Boost/C++ group on facebook
by Jan Stetka 06 Oct '07

06 Oct '07

Boost/C++ group on facebook: Already have 47 members! Show your support for boost (unofficially) http://www.facebook.com/group.php?gid=4200526117

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