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what can you get from boost::thread?
by Kim Kuen tang 27 May '08

27 May '08

Hi all, i've written a small code for estimating the mean from a series of random numbers. The random numbers are generated with and without boost::thread. The simulation shows me that with boost::thread you only get a small performance. So my question is, how much performance can you get for simulation with boost::thread? with best regards, Kim Tang My code is shown below: #include <iostream> #include <fstream> #include <ctime> // std::time #include <climits> #include <boost/timer.hpp> #include <boost/random/linear_congruential.hpp> #include <boost/random/uniform_int.hpp> #include <boost/random/uniform_real.hpp> #include <boost/random/variate_generator.hpp> #include <boost/random/normal_distribution.hpp> #include <boost/thread/thread.hpp> // Sun CC doesn't handle boost::iterator_adaptor yet #if !defined(__SUNPRO_CC) || (__SUNPRO_CC > 0x530) #include <boost/generator_iterator.hpp> #endif #ifdef BOOST_NO_STDC_NAMESPACE namespace std { using ::time; } #endif typedef boost::minstd_rand base_generator_type; typedef boost::variate_generator<base_generator_type&, boost::normal_distribution<> > NormalRandomNumber; class SimClass { public: SimClass(double& data,NormalRandomNumber & generator, std::size_t number) : data_(data), generator_(generator), number_(number) {}; void operator()() { data_=0.0; for(std::size_t i = 0; i < number_; i++) data_+=generator_(); }; private: double& data_; NormalRandomNumber generator_; std::size_t number_; }; int main() { double mean=0.0; const std::size_t NUM_OF_THREADS=4; const std::size_t NUM_CALCS=10000000; const std::size_t NSIMULATION=NUM_CALCS*NUM_OF_THREADS; base_generator_type generator(42u); std::cout <<NSIMULATION <<" samples of a normal distribution :\n"; boost::normal_distribution<> norm_dist(0,1); NormalRandomNumber normalRN(generator, norm_dist); std::cout.setf(std::ios::fixed); // You can now retrieve random numbers from that distribution by means // of a STL Generator interface, i.e. calling the generator as a zero- // argument function. boost::timer cTime; for(int i = 0; i < NSIMULATION; i++) mean+=normalRN(); std::cout <<"estimated mean is: " <<mean/NSIMULATION << '\n'; std::cout<<"time to elapsed:"<<cTime.elapsed()<<"\n"; std::cout <<NSIMULATION <<" samples of a normal distribution with "<<NUM_OF_THREADS<<" threads:\n"; cTime.restart(); double results[NUM_OF_THREADS]; boost::thread_group thrds; for (int i=0; i < NUM_OF_THREADS; ++i) thrds.create_thread(SimClass(results[i],normalRN,NUM_CALCS)); thrds.join_all(); double result=0.0; for(std::size_t i=0;i<NUM_OF_THREADS;++i) result+=results[i]; std::cout<<"estimated mean is: "<<result/NSIMULATION<<"\n"; std::cout<<"time to elapsed:"<<cTime.elapsed()<<"\n"; return 0; }

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Pool
by Ta-Cheng Lin 27 May '08

27 May '08

Hi All: Could anyone kindly point to me where I can get some examples of using Boost Pool library? I read the document and there is no examaples. Thanks! Todd

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how to turn off wide char i/o?
by Longyu Mei 27 May '08

27 May '08

We cannot build boost 1.35 under Cygwin because Cygwin doesn't support wide char i/o yet. I heard boost 1.35 has a flag to turn off wide char. Anybody can tell me how to do it? thanks, James

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lexical_cast question
by Hansi 27 May '08

27 May '08

Hello, I have implemented the following template: template<typename Value> struct Validator { typedef bool result_type; bool operator()(const std::wstring& newVal)const { boost::lexical_cast<typename Value>(newVal); return true; } }; now here is the problem that for pointers the lexical cast doesn't work. I have now made the following declaration: boost::lexical_cast<boost::mpl::if_< boost::is_pointer<typename Value>, boost::remove_pointer<typename Value>::type, typename Value>>::type>(newVal); It works now for pointers too, but now I have the problem with the char type. First I have made a specialization for this type. Is it here also possible to make only one specialization or have I to provide both for pointer and value? Is there another way to solve that problem? best regards Hansjörg

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Deprecated methods in boost - filesystem/{canonize, normalize}
by Martin Knapp-Cordes 27 May '08

27 May '08

Hi, In boost/filesystem/path.hpp there are a set of methods controlled by: # ifndef BOOST_FILESYSTEM_NO_DEPRECATED public: typedef bool (*name_check)( const std::string & name ); basic_path( const string_type & str, name_check ) { operator/=( str ); } basic_path( const typename string_type::value_type * s, name_check ) { operator/=( s );} string_type native_file_string() const { return file_string(); } string_type native_directory_string() const { return directory_string(); } static bool default_name_check_writable() { return false; } static void default_name_check( name_check ) {} static name_check default_name_check() { return 0; } basic_path & canonize(); basic_path & normalize(); # endif I have been using normalize for several releases of boost, but I am very concerned that it is no longer part of the officially supported spec and may disappear in some future release. normalize is a very very useful routine and one of the reasons for using boost was to let smarter people produce routines that could become standards. Our local version of 'normalize' did a poor job and I went to boost to fix this version hopefully once and for all. So if it is going away, what are my options? Sincerely, Martin Knapp-Cordes --------------------------------------------------------------- | Martin Knapp-Cordes martin(a)mathworks.com | | The MathWorks, Inc. http://www.mathworks.com | | 3 Apple Hill Drive Natick, MA 01760 | | Tel: (508) 647-7321 Fax: (508) 647-7015 | ---------------------------------------------------------------

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BOOST documentation in PDF/PS format
by dhruva 27 May '08

27 May '08

Hello, I am looking for the BOOST library in either PDF/PS formats so that I can print the ones I need and read them offline (which I generally prefer). Reading though the boost documenting link, it appears quite a daunting task to setup boost doc build to generate PDF files (it has a bunch of dependencies). Is there any location from where I can download the PDF files for the current release version of BOOST or any plans for providing the same in the near future? with best regards, dhruva -- Contents reflect my personal views only!

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How to disable memory leak test
by Selçuk Giray Özdamar 27 May '08

27 May '08

Hello, Is there any way to disable memory leak test while running unit tests. Thanks...

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[boost-users][StateChart]
by Igor R 26 May '08

26 May '08

Hello, Just a few more questions about the subj :) 1. IIUC, in async_state_machine it's impossible to post an "internal" event from a state by calling queue_event(), as noone will actually call process_event(). Instead, it should be always done through the processor queue, like this: outermost_context_type &machine = outermost_context(); machine.my_scheduler().queue_event(machine.my_handle(), MyEvent()); Am I right? 2. Deferred events in async.machine. Say, we've got the following states (simplified code): struct State1 : simple_state<...> { typedef transition<EvGotoState2, State2> reactions; }; struct State2 : simple_state<...> { typedef mpl::list < transition<EvGotoState1, State1>, deferral<EvGotoState2> > reactions; }; Both events are queued to the machine from the "outer world". * We're already in State2. * We get a bunch of EvGotoState2 posted (eg., 10 events). All of them are queued to the state's deferred events queue. * EvGotoState1 comes. The machine goes to State1 and then immediately consumes 1 deferred EvGotoState2 and move to State2. What happens to the rest of the deferred events? Are they queued again to the deferral queue of State2? 3. Is it possible to clear all the deferred events? Is it possible to clear deferred events of a specific type? Eg., in State2 I'd like to alway defer only the *last* EvGotoState2, discarding all the previous deferred events of this type. Is it possible? Thanks a lot! Igor'.

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[Boost users] [interprocess] enable_shared_from_this in boost interprocess?
by Lars Hagström 26 May '08

26 May '08

Hi, I just tried to use enable_shared_from_this in boost interprocess, but it did not seem to work. I only got a bad_weak_ptr exception. Looking a little bit in shared_ptr.hpp (comparing the interprocess one and the "normal" one) it appears that calls to sp_enable_shared_from_this are not made in the constructors as they ought to be. Is this a known bug, or am I doing something wrong? Cheers Lars

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Recommend Unix Compiler and Unix Platform?
by Jeff Dunlap 26 May '08

26 May '08

Dear Boost Users: I have developed a number of reliable web based applications and ISAPI filters for Windows in C++ using several of the Boost libraries. Although I have no experience in Unix, I am very interested in doing similar web development in C++ on Unix. Can someone recommend a good compiler and platform (Unix Variant)? I've noticed that the following seem to be pretty popular for web servers. To keep things easy, I guess that I'd be using a specific variant for both development and web server: FreeBSD, Fedora, Ubantu, and CentOS. Please Advise, Jeff

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