January 2013 - Boost - lists.boost.org

Re: [boost] [non-instrusive move] interest in new library?
by Joseph Gauterin 10 Jan '13

10 Jan '13

Out of curiosity, how are you detecting if a member function swap exists? >it detects at compile-time if the type of the >argument(s) has a member swap function In general, there's no way of knowing if a member swap function is more efficient than a single assignment. It isn't even for all the examples you gave - boost::array<T,N>::swap performs N boost::swaps, which, if T doesn't provide an efficient swap, results in N calls to std::swap, and 3*N assignments. In general I'm wary of using swap in a generic context unless the intent is to swap (i.e. not as a potential optimization of assignment). >The library is non-intrusive and generic, it will perform an efficient move >in terms of swap for any type providing a member >swap operation, e.g, std::vector, boost::array, user-defined types etc.

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Re: [boost] (Boost) QVM update
by Shakti Misra 09 Jan '13

09 Jan '13

Hi Emil, I also am waiting to try it out. My environment doesn't allow me to use boost completely. I may be getting little greedy, but any chance of using vectorization? :) ~Thanks Shakti On Wed, Jan 9, 2013 at 11:30 AM, Nathan Crookston < nathan.crookston(a)gmail.com> wrote: > Hi Emil, > > Emil Dotchevski wrote: > > > Boost QVM has been updated. Note, this library has not been reviewed > > yet and it is not part of Boost. > > > > Comments and bug reports are appreciated. > > > > I've been looking forward to this library. I often need something like > this in my work (mixture of graphics programming, image processing, and > geospatial applications). I wasn't happy with what ublas offered in the > static-sized 3-8 dimensions, so I rolled my own -- I'd be much happier to > have something like this, though. > > The documentation seem especially complete. A few questions and comments > that occurred to me as I was reading through (and occasionally glancing at > the code): > > * I'm sure [qvms]_traits is used all over the place, but I'd still rather > see scalar_traits, vector_traits, etc., especially as those may be > specialized by the user. > > * I thought s_traits was hard to find in the 'Generic programming > utilities' section. Should it be in the 'Type traits' section instead? > > * It looks like matrix types (probably vectors and quaternions too) must be > default constructible (for both make and the template conversion operator > of mat), though I didn't see that particular requirement noted -- am I > mistaken? > > * The SFINAE page seems to reference itself: > > sfinae > The boost::qvm::sfinae namespace contains only function names that use > SFINAE <circular link>. The boost::qvm namespace contains all Boost QVM > type and function names. > > I would have expected it to link to an explanation of sfinae -- not > necessarily part of QVM's docs. > > * inverse: I was surprised to see that you're inverting using the matrix > of cofactors. For my personal education, why do you use that method -- is > it more stable or efficient than others? A home-rolled implementation I > did something like the following: > > //Solving Ax = b > matrix<float> A; > vector<float> b; > inverse_matrix<float> inverse_m = invert(m);//actually perform lu > decomposition > vector<float> x = inverse_m * b;//actually back-substitutes from lu matrix. > > In that case, I knew that I'd only ever multiply by a vector -- which > allowed me to use a method which is at least as efficient as matrix > inversion and more numerically stable. I'm not sure if an inverse_matrix > type would allow something like: > > matrix<float> A = ...; > inverse_matrix<float> B = ...; > auto C = A * B; > auto D = B * A; > to be computed as efficiently as if B were really just a matrix type. I > could look that up tomorrow, when I have a reference on the material. If > it is, I think it would be interesting to have inverse return a view_proxy. > > * I haven't looked, but I assume QVM is targeting cases where both matrices > fit into cache? Meaning, it doesn't worry about things like cache > blocking? > > * I think the swizzling code is interesting. The Accessing * Elements > pages aren't too informative, though. It would help me if those pages, in > the 'See also:' section, were to link to examples of their usage. > > * Further on swizzling -- when I'm dealing with OpenGL texture coordinates, > the canonical names for them are s, t, r and q. Is there an interface > whereby I could allow writing something like this? > > TexCoord tc1(1, 2, 0, .5); > TexCoord tc2 = tc1 % TSRQ; > > I don't know that I'll ever need such a thing -- this is mostly out of > curiosity. > > I haven't had a chance to try QVM out -- I'd like to work up examples with > e.g., std::array<float,4>, then something with boost::units types as the > scalar types. In fact, working with the latter would be a killer feature > from this library for me. I'll let you know what I find. > > Thanks again for making this library available! > > Nate > > _______________________________________________ > Unsubscribe & other changes: > http://lists.boost.org/mailman/listinfo.cgi/boost >

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(Boost) QVM update
by Emil Dotchevski 09 Jan '13

09 Jan '13

Boost QVM has been updated. Note, this library has not been reviewed yet and it is not part of Boost. Boost QVM provides a set of generic functions for working with quaternions, and vector and matrix types of static size. All operations use a type-traits system, which enables types from other vector/matrix libraries to be integrated in a common type-safe interface. The current source code and documentation is available at http://www.revergestudios.com/boost-qvm. It contains minor bug fixes, and the following new features: - view proxies that negate matrix rows and columns (negr/negc) - view proxies that swap two rows or columns in a matrix (swapr/swapc) - functions for indexing at run-time of any vector or matrix object of arbitrary size. Comments and bug reports are appreciated. Thanks! Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode

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[non-instrusive move] interest in new library?
by THOMAS JORDAN 09 Jan '13

09 Jan '13

Apologies, my previous email I sent incomplete by mistake, please ignore that in favour of the following: Hi, Would there be interest for Boost in a small library providing a simple, non-instrusive emulation of basic move semantics for C++03 (though one which could also be used without harm in a C++11 environment)? The library currently consists of a small number of 'move' function overloads, plus a trait class. It can be used to facilitate move semantics/efficient value-orientated software design in environments which lack, or forbid C++11 or other, more intrusive C++03-aware move libraries (e.g., old/buggy compiler, learning curve prohibitive, etc.). In conjunction it facilitates/forces copy-elision and return-value (RVO) optimisations in certain situations where they might otherwise not be feasible. It works as follows: it detects at compile-time if the type of the argument(s) has a member swap function, and if so, it performs a swap, otherwise it calls the regular assignment operator ('move if possible, copy otherwise'). It can be used to provide an emulation of: - move-assignment between lvalues - moving an rvalue to an lvalue - moving an lvalue to a temporary It also supports moving between built-in arrays. Example use-cases are (ignoring namespace): #include "non_intrusive_move.h" //returning a value std::string foo(std::string s) { //e.g., append something to s //... //compiler can perform rvo (compiler would likely not perform nrvo if just used 'return s;') return move(s); } //moving a value to a function/ctor, when the value is not required by the calling code after the //function/ctor call std::string s("hello"); void bar(std::string s){...} bar(s); //copy bar(move(s)); //move //moving a value into place void MyClass::MyClass(std::string s) { //move value from s into default constructed member s_ move(s, s_); } Note that the combination of both moving a value to a function/ctor and then moving it into place e.g., std::string lv; //... MyClass mc(move(lv)); //lv no longer needed effectively results in a zero-copy invocation, with just a small number of fixed size swap, default ctor and shallow dtor calls, so this is pretty efficient. //moving a temporary into an lvalue std:: string lv; move(foo(), lv); //nicer than foo().swap(lv) The moved-from value is left in a 'valid' but undefined state, i.e., it can be destructed, assigned/moved to, swapped, etc. The library is non-intrusive and generic, it will perform an efficient move in terms of swap for any type providing a member swap operation, e.g, std::vector, boost::array, user-defined types etc. It also performs an efficient move for built-in arrays. The library is header-only and currently depends only on boost::enable_if and boost::swap as external dependencies. It is portable between C++03 and C++11 and has a gentle learning curve - the code is brief and easy to understand (with possible exception of the traits class) - I think that is quite an important feature of the library. It might be feasible to add a few other things, e.g., move, move_backward algorithms. The library is not intended to be standard-compliant (though similar where possible), and is not intended to compete with a much richer, but 'intrusive' library like Boost.Move. I've called it 'non-intrusive move' for the moment but it could of course be called something else (e.g., simple_move). Regards, Tom

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Boost.Logging 1.51 Using VS2012.
by syvyi 09 Jan '13

09 Jan '13

Hello, my application which was successfully compiled on VS2010 brings the next errors using VS2012 c:\program files (x86)\boost\boost_1_51_0\boost\log\sources\basic_logger.hpp(227): error C2664: 'std::pair<_Ty1,_Ty2> boost::log_mt_nt5::basic_attribute_set<CharT>::insert(const std::pair<const boost::log_mt_nt5::basic_slim_string<CharT>,boost::log_mt_nt5::basic_attribute_set<CharT>::mapped_type> )' : cannot convert parameter 1 from 'std::pair<_Ty1,_Ty2>' to 'const std::pair<_Ty1,_Ty2> &' 4> with 4> [ 4> _Ty1=boost::log_mt_nt5::basic_attribute_set<char>::iter<false>, 4> _Ty2=bool, 4> CharT=char 4> ] 4> and 4> [ 4> _Ty1=std::basic_string<char,std::char_traits<char>,std::allocator<char>>, 4> _Ty2=boost::shared_ptr<boost::log_mt_nt5::attribute> 4> ] 4> and 4> [ 4> _Ty1=const boost::log_mt_nt5::basic_slim_string<char>, 4> _Ty2=boost::log_mt_nt5::basic_attribute_set<char>::mapped_type 4> ] 4> Reason: cannot convert from 'std::pair<_Ty1,_Ty2>' to 'const std::pair<_Ty1,_Ty2>' 4> with 4> [ 4> _Ty1=std::basic_string<char,std::char_traits<char>,std::allocator<char>>, 4> _Ty2=boost::shared_ptr<boost::log_mt_nt5::attribute> 4> ] 4> and 4> [ 4> _Ty1=const boost::log_mt_nt5::basic_slim_string<char>, 4> _Ty2=boost::log_mt_nt5::basic_attribute_set<char>::mapped_type 4> ] 4> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 4> c:\program files (x86)\boost\boost_1_51_0\boost\log\sources\basic_logger.hpp(226) : while compiling class template member function 'std::pair<_Ty1,_Ty2> boost::log_mt_nt5::sources::basic_logger<CharT,FinalT,ThreadingModelT>::add_attribute_unlocked(const std::basic_string<_Elem,_Traits,_Alloc> &,const boost::shared_ptr<T> &)' 4> with 4> [ 4> _Ty1=boost::log_mt_nt5::basic_attribute_set<char>::iter<false>, 4> _Ty2=bool, 4> CharT=char, 4> FinalT=manster::logger::manster_logger_mt, 4> ThreadingModelT=boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>, 4> _Elem=char, 4> _Traits=std::char_traits<char>, 4> _Alloc=std::allocator<char>, 4> T=boost::log_mt_nt5::attribute 4> ] 4> c:\program files (x86)\boost\boost_1_51_0\boost\log\sources\severity_feature.hpp(188) : see reference to function template instantiation 'std::pair<_Ty1,_Ty2> boost::log_mt_nt5::sources::basic_logger<CharT,FinalT,ThreadingModelT>::add_attribute_unlocked(const std::basic_string<_Elem,_Traits,_Alloc> &,const boost::shared_ptr<T> &)' being compiled 4> with 4> [ 4> _Ty1=boost::log_mt_nt5::basic_attribute_set<char>::iter<false>, 4> _Ty2=bool, 4> CharT=char, 4> FinalT=manster::logger::manster_logger_mt, 4> ThreadingModelT=boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>, 4> _Elem=char, 4> _Traits=std::char_traits<char>, 4> _Alloc=std::allocator<char>, 4> T=boost::log_mt_nt5::attribute 4> ] 4> c:\program files (x86)\boost\boost_1_51_0\boost\log\sources\channel_feature.hpp(212) : see reference to class template instantiation 'boost::log_mt_nt5::sources::basic_logger<CharT,FinalT,ThreadingModelT>' being compiled 4> with 4> [ 4> CharT=char, 4> FinalT=manster::logger::manster_logger_mt, 4> ThreadingModelT=boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex> 4> ] 4> c:\program files (x86)\boost\boost_1_51_0\boost\log\sources\basic_logger.hpp(315) : see reference to class template instantiation 'boost::log_mt_nt5::sources::channel<ChannelT>::apply<BaseT>' being compiled 4> with 4> [ 4> ChannelT=std::string, 4> BaseT=boost::log_mt_nt5::sources::basic_logger<char,manster::logger::manster_logger_mt,boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>> 4> ] 4> c:\program files (x86)\boost\boost_1_51_0\boost\mpl\aux_\preprocessed\plain\apply_wrap.hpp(49) : see reference to class template instantiation 'boost::log_mt_nt5::sources::aux::inherit_logger_features::apply<PrevT,T>' being compiled 4> with 4> [ 4> PrevT=boost::log_mt_nt5::sources::basic_logger<char,manster::logger::manster_logger_mt,boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>>, 4> T=boost::log_mt_nt5::sources::channel<std::string> 4> ] 4> c:\program files (x86)\boost\boost_1_51_0\boost\mpl\aux_\preprocessed\plain\apply.hpp(63) : see reference to class template instantiation 'boost::mpl::apply_wrap2<F,T1,T2>' being compiled 4> with 4> [ 4> F=boost::log_mt_nt5::sources::aux::inherit_logger_features, 4> T1=boost::log_mt_nt5::sources::basic_logger<char,manster::logger::manster_logger_mt,boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>>, 4> T2=boost::log_mt_nt5::sources::channel<std::string> 4> ] 4> c:\program files (x86)\boost\boost_1_51_0\boost\mpl\aux_\preprocessed\plain\reverse_fold_impl.hpp(81) : see reference to class template instantiation 'boost::mpl::apply2<F,T1,T2>' being compiled 4> with 4> [ 4> F=boost::log_mt_nt5::sources::aux::inherit_logger_features, 4> T1=boost::log_mt_nt5::sources::basic_logger<char,manster::logger::manster_logger_mt,boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>>, 4> T2=boost::log_mt_nt5::sources::channel<std::string> 4> ] 4> c:\program files (x86)\boost\boost_1_51_0\boost\mpl\reverse_fold.hpp(41) : see reference to class template instantiation 'boost::mpl::aux::reverse_fold_impl<N,First,Last,State,BackwardOp,ForwardOp>' being compiled 4> with 4> [ 4> N=2, 4> First=boost::mpl::v_iter<boost::mpl::vector2<boost::log_mt_nt5::sources::severity<severity_level>,boost::log_mt_nt5::sources::channel<std::string>>,0>, 4> Last=boost::mpl::v_iter<boost::mpl::vector2<boost::log_mt_nt5::sources::severity<severity_level>,boost::log_mt_nt5::sources::channel<std::string>>,2>, 4> State=boost::log_mt_nt5::sources::basic_logger<char,manster::logger::manster_logger_mt,boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>>, 4> BackwardOp=boost::log_mt_nt5::sources::aux::inherit_logger_features, 4> ForwardOp=boost::mpl::arg<1> 4> ] 4> c:\program files (x86)\boost\boost_1_51_0\boost\log\sources\basic_logger.hpp(338) : see reference to class template instantiation 'boost::mpl::reverse_fold<Sequence,State,BackwardOp>' being compiled 4> with 4> [ 4> Sequence=boost::log_mt_nt5::sources::features<boost::log_mt_nt5::sources::severity<severity_level>,boost::log_mt_nt5::sources::channel<std::string>>, 4> State=boost::log_mt_nt5::sources::basic_logger<char,manster::logger::manster_logger_mt,boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>>, 4> BackwardOp=boost::log_mt_nt5::sources::aux::inherit_logger_features 4> ] 4> d:\sankom\manster\manster\manster\manster_logger.h(160) : see reference to class template instantiation 'boost::log_mt_nt5::sources::basic_composite_logger<CharT,FinalT,ThreadingModelT,FeaturesT>' being compiled 4> with 4> [ 4> CharT=char, 4> FinalT=manster::logger::manster_logger_mt, 4> ThreadingModelT=boost::log_mt_nt5::sources::multi_thread_model<boost::log_mt_nt5::aux::light_rw_mutex>, 4> FeaturesT=boost::log_mt_nt5::sources::features<boost::log_mt_nt5::sources::severity<severity_level>,boost::log_mt_nt5::sources::channel<std::string>> 4> ] What is the solution ? -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-Logging-1-51-Using-VS2012-tp464114… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Requesting permission to merge 82408 to release
by Glen Fernandes 09 Jan '13

09 Jan '13

82408 is a fix for #7867 (found by Mathias) where BOOST_NO_EXCEPTIONS was not honored. Glen

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[non-instrusive move] interest in new library?
by THOMAS JORDAN 09 Jan '13

09 Jan '13

Hi, Would there be interest for Boost in a small library providing a simple, non-instrusive emulation of move semantics for C++03 (though it could also be used in a C++11 environment)? It consists of a small number of 'move' function overloads, plus a trait class. It can be used facilitate move semantics/value-orientated programming in environments which lack/forbid C++11 or intrusive move libraries, and facilitate/force copy-elision and RVO optimisations in certain situations where they might otherwise not occur. Its mechanism is as follows: it detects at compile-time if the type of the argument(s) has a member swap function, and if so, it performs a swap, otherwise is calls the regular assignment operator. It can be used to provide an emulation of: move-assignment between lvalues moving an rvalue to an lvalue moving an lvalue to a temporary. It also supports moving between built-in arrays. Example use-cases are: //returning a value std::string foo(std::string s) { //append something to s //... //compiler can perform rvo, if just used 'return s;' compiler would not perform nrvo return move(s); } //passing a value std::string s("hello"); void bar(std::string s) {...} foo(s); //copy foo(move(s)); //move //moving a value into place void MyClass::MyClass(std::string s) { //move value into default constructed member move(s, s_); }

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[log] v2 beta 1 mini-review request
by Andrey Semashev 09 Jan '13

09 Jan '13

Hi, It's been a while since Boost.Log v1 was reviewed back in 2010. Here is the review result: http://lists.boost.org/boost-announce/2010/03/0256.php But the time was spent for purpose as the library took substantial changes. I've just uploaded the v2 beta 1 to the SourceForge project page: Code: http://sourceforge.net/projects/boost-log/files/boost-log-2.0-beta1-r800.zi… Docs: http://boost-log.sourceforge.net/libs/log/doc/html/index.html SVN: svn co https://boost-log.svn.sourceforge.net/svnroot/boost-log/trunk/boost-log I must say this is not the final release; the docs are not quite complete (in particular, the Extending the library section has not been updated yet) and the code may have rough edges here and there. But it is good enough to review the changes, or the whole library if you haven't got acquainted with v1. The change log is quite big, you can see it here: http://boost-log.sourceforge.net/libs/log/doc/html/log/changelog.html I'll just mention the most significant highlights here: - Character type support unified. Log records, core, filters and most sinks have been made character type agnostic. It is possible now to emit log records with messages with different character types in a single application. Character code conversion will be performed as needed when formatting log records. - Filters and formatters were rewritten and are now based on Boost.Phoenix. Unified attribute value placeholders in filters and formatters. The template expressions now reside in the common namespace "expressions". - Added support for attribute keywords in filters and formatters. Attribute keywords identify particular attribute values within log records; their use significantly simplify template expressions syntax. - Reworked attribute value extraction. In fact, the old extraction API has been split into visitation and the new extraction APIs. In conjunction with attribute keywords this makes extracting attribute values very simple. - Introduced a concept of a default sink which is used when no sinks are registered in the logging core. The sink outputs formatted log records to the console. - Trivial logging now outputs to console by default. Actually, trivial logging logs to the default sink by default. - Asynchronous sink now supports customizing record queueing strategies. New bounded queue strategies solve the problem of log records piling in the queue. - Attributes are now implemented following the pimpl pattern; it is no longer needed to create attributes using make_shared or new. This simplified attribute registration code. - Channel logger now allows changing channel name after construction. I don't plan any major changes to the code until the final release, unless something critical comes up during the review. I will keep updating the docs in the coming days and will request permission to merge to Boost when done. Comments are welcome.

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[interprocess] (OS X) waiting on condition variable = CPU 100% + fans running loud
by Francisco Lopes 08 Jan '13

08 Jan '13

Hi, I was implementing a kind of server using shared memory. The server should keep idle, waiting for a request and I do this by waiting on a condition variable, of course. I then noticed my fans running high when I let the server waiting a little longer while testing and discovered this happens simply because of some busy loop implementation for condition waiting. Is there any reason for that? Given the interprocess library age, there's no way for implementing a non-busy interprocess condition variable waiting available? https://svn.boost.org/trac/boost/ticket/6108 Regards, Francisco Lopes

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Re: [boost] [interprocess] (OS X) waiting on condition variable = CPU 100% + fans running loud
by Peter Dimov 08 Jan '13

08 Jan '13

> > Clang has std::atomic though, doesn't it? It probably supports the > > __sync intrinsics as well. > > Actually, it seems to support the even better __atomic intrinsics: > > http://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html Also here: http://libcxx.llvm.org/atomic_design_a.html

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