March 2010 - Boost-users - lists.boost.org

Re: [Boost-users] ranking of ublas vector
by Kraus Philipp 14 Mar '10

14 Mar '10

> Oops. I guess I didn't understand exactly what you wanted. The > temp vector, should contain the result you want. > > In Christ, > Steven Watanabe There is an error: I create a random vector like: [4](0.405121, 0.943918, 0.887914, 0.338921) I think it's clear that: 0.338921 < 0.405121 < 0.887914 < 0.943918 The code returns: [4](2,0,1,3) and that's wrong because the 2nd element is not the smallest value. The (mathematical) rank is: 3, 0, 2, 1 because the 3rd element is the smallest and the first the largest in the original vector. I hope that's clearer Thanks Phil

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Clever simultaneous iteration over multiple containers
by Joseph Wakeling 14 Mar '10

14 Mar '10

Dear Boost users, A (possibly naïve) question, as I'm a reasonably competent C programmer but only a relative novice with C++, and just starting to get used to concepts from libraries like Boost. The BOOST_FOREACH macro provides a nice way to iterate over all the contents of a container like a vector, list, etc. But what about when several containers are involved? I'll give a concrete-ish example from a problem I'm working on. I have two vectors, vector<myClass *> v1 and vector<double> v2 where myClass is a base class and v1.size()==v2.size(). Then, what I want to do is, for(unsigned int i=0;i<v1.size();++i) v1.at(i)->func(v2.at(i)); That works, of course; I'm just wondering if there is a more elegant or compiler-friendly way of writing this along the lines of the BOOST_FOREACH macro. Initialising separate iterators for both v1 and v2 seems ugly/lots of boilerplate. I have seen the solution here: http://permalink.gmane.org/gmane.comp.lib.boost.user/31954 ... but that seems less desirable because it involves using an extra library which I don't think is standard in Linux distros. I have the impression that the zip_iterator boost lib is useful here, but did not fully understand if or how. Can anyone advise? Thanks & best wishes, -- Joe

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serialization error for a struct
by alev mutlu 14 Mar '10

14 Mar '10

Hi all, I am very new to boost. I am getting a serialization error, and I have no idea about what to do #include <boost/serialization/string.hpp> //some other headers struct field { std::string field_name; std::string field_type; std::string field_ref; std::string field_colType; }; int main(int argc, char* argv[]){ vector<field> C; // other definitions // populating the C vector scatter(world, C, relMyValues, w_mySize, 0); } and I got error: struct field has no member named serialize what should I do? thank you in advance

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Compilation problems with MinGW
by Benjamin Lau 14 Mar '10

14 Mar '10

Hello everyone, I successfully compiled Boost with MinGW (GCC 4.4.0 - it came installed with the Qt SDK) with all the settings on, so it has generated both dynamic and static libraries, debug and release versions, multithreaded and non-multithreaded runtimes etc. I tried to compile a small program that uses the serialization library (http://www.boost.org/doc/libs/1_42_0/libs/serialization/doc/tutorial.html#s…) and tried to link it statically with these libraries (in different compilations): libboost_serialization-mgw34-1_40.lib libboost_serialization-mgw34-mt-1_40.lib libboost_serialization-mgw34-mt-s-1_40.lib libboost_serialization-mgw34-mt-s.lib libboost_serialization-mgw34-mt.lib libboost_serialization-mgw34-s-1_40.lib libboost_serialization-mgw34-s.lib libboost_serialization-mgw34.lib Each time I compiled, it would always give me linker errors like so: undefined reference to `__gxx_personality_sj0' undefined reference to `_Unwind_SjLj_Register' undefined reference to `_Unwind_SjLj_Unregister' undefined reference to `_Unwind_SjLj_Resume' These are repeated over and over again. The compiler command and flags that I use are g++ test.cpp -o test -Ipath/to/boost/include path/to/static/library However, if I compile it with an import library like boost_serialization-mgw34.lib I don't get such errors. Searching online seems to suggest I am missing a compiler flag, but I cannot determine which one I am missing. Perhaps my Google-Fu isn't strong enough, so if I did miss out something patently obvious that could have been found online I offer my due apologies. Thanks a lot anyway! Benjamin

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[serialization] installed documentation bug and suggestions.
by Mostafa 14 Mar '10

14 Mar '10

Bugs: I've had bad internet connection so I had to resort to using the installed boost docs and noticed some bugs. 1) /share/doc/boost/libs/serialization/doc/index.html has broken links in the left frame. 2) /share/doc/boost/libs/serialization/doc/archive_reference.html has broken links in the following paragraph: //Start As a convenience, small header files have been included which contain typedef for polymorphic implementation for each corresponding templated one. For example, the headers polymorphic_text_iarchive.hpp and polymorphic_text_oarchive.hpp. contain the typedef for the polymorphic implementation of the standard text archive classes text_iarchive.hpp and text_oarchive.hpp respectively. All included polymorphic archives use the same naming scheme. //End Suggestion: 1) It's not readily apparent that there's a polymorphic implementation of the serialization classes, may be this should be mentioned in the tutorial? 2) Or have a section in the Overview page categorizing the available categories of serializors as intrusive, non-intrusive, polymorphic, giving a short definition of each type, and their pros/cons. Basically what is missing is an eye-ball summary of the available serializors that this library offers, and why one would choose one over the other and vice versa. The information is there, but it is scattered and it took some digging to get to it. For example, from the overview page one cannot deduce that there exists an intrusive, or polymorphic version. It is only from Tutorials page can one immediately deduce that there is an intrusive version, and to figure out there is a polymorphic version one has to navigate the following path: Reference link in left frame -> Archive Class Reference. Also, best practices/potential pitfalls like the following suggestion: //Start // /share/doc/boost/libs/serialization/doc/tutorial.html#nonintrusiveversion Note the serialization of the base classes from the derived class. Do NOT directly call the base class serialize functions. Doing so might seem to work but will bypass the code that tracks instances written to storage to eliminate redundancies. It will also bypass the writing of class version information into the archive. For this reason, it is advisable to always make member serialize functions private. //End should be made more eye grabbing. It's very easy to accidentally skip over such information. Thanks, - Mostafa

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Boost.Thread idiom
by anony 14 Mar '10

14 Mar '10

Is is possible to inherit from boost::thread and then store pointers to instantiated objects of such classes in say ptr_vector<>? I need to interrupt() a specific thread now and then and once you commit a thread to thread_group you can only interrupt them all at once.

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[boost] [chrono] v0.4 New thread_clock
by vicente.botet 14 Mar '10

14 Mar '10

Hi, I'm pleased to announce the version 0.4 of the Boost.Chrono library. The implementaton is stable, I don't plan to add more features before review. I'll concentrate in improving the documentation and the tests. I know that review managers are hard to find, so if you are interested in the library, please contact me or the Review Wizards. The library can be downloaded from http://www.boostpro.com/vault/index.php?action=downloadfile&filename=chrono… and the documentation is online on the sandbox http://svn.boost.org/svn/boost/sandbox/chrono/libs/chrono/doc/html/index.ht…. New Features since v0.3.2: * Suspendible Clock concept + template class suspendible_clock<> * Added scope_suspend which do suspend/resume if the Clock is a model of Suspendible Clock concept, and nothing otherwise. * thread_clock support on platforms providing it natively. * Added support for wide character for stopwatch_reporter, stopclock, and stopclock_accumulator. * digital_time renamed t24_hours Perf * Added performances measures. Bug Fixes * Bug on timeval_demo. time_point t(duration(xtime(0))); // this was taken as a function declaration gettimeofday((timeval*)&t, 0); return t; time_point t(duration(xtime(0))); // this was taken as a function declaration gettimeofday((timeval*)&t, 0); return t; by timeval tv; gettimeofday(&tv, 0); xtime xt( tv.tv_sec, tv.tv_usec); return time_point(duration(xt)); * Bug on run_timer_test (add a global variable to avoid optimization that removes completely the code to be measured Best regards, _____________________ Vicente Juan Botet Escribá

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ranking of ublas vector
by Kraus Philipp 14 Mar '10

14 Mar '10

Hello, I have a very large non sparse ublas vector (most long double content). I would like to sort this vector without change the vector content, but I know the rank of the elements like the smalest element in the vector is the 312 element in the original vector (for example). Is there a boost implementation for create ranking of elements? Thanks Phil

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boost.units converting double tp SI prefix
by Olaf Peter 13 Mar '10

13 Mar '10

Hi, is there a way to use boost.units to convert a double automatically to a SI unit prefix, e.g. 10e-3 to 10m or 10e3 to 10k ?? The value isn't know at compile time, so the decision has to be done on runtime. Thanks, Olaf

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[Boost.Intrusive] Compilation error with Visual Studio 2008
by info-tibo 13 Mar '10

13 Mar '10

Hello, For a project, I created a class allowing to reference some objects, and I use Boost.Intrusive. I started coding this class using Code::Blocks and gcc 3.4.5 . But now I want to use Visual Studio 9, and I simply added the class to the project. And then... it doesn't compile... The code is here : ----------------------------------------------------------------------------------------------------------------------------------------- #ifndef _BASE_EQUALREFSYSTEM_H_ #define _BASE_EQUALREFSYSTEM_H_ #include <boost/intrusive/list.hpp> namespace base { //! Convenient typedef typedef boost::intrusive::list_member_hook< boost::intrusive::link_mode<boost::intrusive::normal_link> > EqualRefSysHook; //! A class to handle self referencing systems /** Each object can point to a target, in order to interact with it. How to use: \code // First, you have to derivate this class class MyClass : public EqualRefSystem { // code... } // Then you can, in your main function, create these objects: MyClass* myClassPointer = new MyClass; // for example: repeated 200 times // Afterthat, you can point each object to another. When you have finished // you can simply call: delete myClassPointer; \endcode **/ class EqualRefSystem { public: //! The hook used by the intrusive list ReferencedBy EqualRefSysHook ERSMemberHook; public: //! Constructor EqualRefSystem() :Target(0),RefCount(0) {} //! Destructor /** Safe destructor : all references and target are reseted. **/ virtual ~EqualRefSystem() { resetTarget(); unlink(); } //! Returns the targeted object /** \return A pointer to the object targeted by this EqualRefSystem. **/ inline EqualRefSystem* getTarget() const { return Target; } //! Sets the target /** \param tgt : The new target. 0 means 'no target'. If tgt == this, the target is set to 0. This function is stable and very fast, you can use it without any restriction. **/ inline void setTarget(EqualRefSystem* tgt) { if(tgt == Target) return; if(tgt == this) tgt = 0; if(Target) Target->dereference(this); Target = tgt; if(Target) Target->reference(this); } //! Resets the target /** This function is a synonym for setTarget(0). **/ inline void resetTarget() { if(Target) Target->dereference(this); Target = 0; } //! Returns whether a target is set or not /** This function is a synonym for (getTarget() != 0). \return True if a target is set, else false. **/ inline bool hasTarget() const { return Target != 0; } //! Unlink from all objects which targets this one /** This function resets the target of all objects targeting this EqualRefSystem. **/ inline void unlink() { while(!ReferencedBy.empty()) ReferencedBy.begin()->resetTarget(); RefCount = 0; } //! Returns the number of objects targeting this one /** \return The number of objects targeting this EqualRefSystem. Constant-time. **/ inline unsigned int getNumberOfReferences() const { return RefCount; } private: //! Reference an object in this EqualRefSystem inline void reference(EqualRefSystem* toRef) { if(!toRef || toRef == this) return; ReferencedBy.push_back(*toRef); RefCount++; } //! Dereference an object from this EqualRefSystem inline void dereference(const EqualRefSystem* toDeref) { if(!toDeref || toDeref == this) return; ReferencedBy.erase(ReferencedBy.iterator_to(*toDeref)); RefCount--; } //! Targeted object EqualRefSystem* Target; //! Objects that reference this EqualRefSystem boost::intrusive::list< EqualRefSystem, boost::intrusive::member_hook<EqualRefSystem,EqualRefSysHook,&EqualRefSystem::ERSMemberHook>, boost::intrusive::constant_time_size<false> > ReferencedBy; //! Number of references unsigned int RefCount; }; } #endif // _BASE_EQUALREFSYSTEM_H_ ----------------------------------------------------------------------------------------------------------------------------------------- VCC told me 42 errors, all related to the first one: line 112 : C2327: 'base::EqualRefSystem::ERSMemberHook' : is not a type name, static, or enumerator I searched the doc about the C2327, but it doesn't helped me. Thanks in advance, Darktib PS: I apologize for my english, I'm french.

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