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shared_ptr and global reset
by Matthieu Guillo 26 Feb '09

26 Feb '09

Hi Boosters Let's say that I have many shared_ptr<A> sharing ownership to the same A object. At some point, I would like all those shared_ptr to point to a new Object A. Is there an easy (and safe) way to accomplish that? I know how to do that for one shared_ptr using either "reset", either operator = but in order to do this for all shared_ptr sharing ownership, the only way I could think of is through a registration mechanism (like the Observer pattern) but this sounds an overkilling process to me. So basically, is there a "global" reset method? Thanks ------------------------------------------ Matthieu Guillo ------------------------------------------

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Re: [Boost-users] metafunction invocation performance
by Hicham Mouline 26 Feb '09

26 Feb '09

The solution to this one is provided by Joaquin, in his reply below: I tried compiling your code with MSVC++ 8.0 and it is indeed incredibly slow. After playing a little with the code I realized that MPL views are the culprit here: for some reason it is much faster to fold on a vector-based computation rather than a view: template<typename Sequence1,typename Sequence2> struct sequence_product : boost::mpl::fold< Sequence1, boost::mpl::vector0<>, boost::mpl::copy< boost::mpl::transform< Sequence2, pair_with<boost::mpl::_2> >, boost::mpl::back_inserter<boost::mpl::_1> > > {}; This transformation on sequence_product and seq_seqpair_product alone improved the performance tremendously. Additionally I've tried a small optimization: in seq_seqpair_product it is preumable better to fold on Sequence rather than SequencePair, since on average the first is expected to be shorter. Truth be said, I haven't detected any improvement with this, anyway. > Shouldn't there be a dot-product or cross-product of mpl sequences as > a general algorithm? and not just 2 sequences but N. I guess it is the O(n^2) behavior that deterred the author from including the algorithm (much as STL usually does not contain quadratic algorithms). It might be a worthy addition, nonetheless Joaquin --------- Interesting why a joint_view slower than the alternative. This result confirmed then on MSVC8 , gcc4.1, Intel10... regards, /Hicham

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Boost.IOStreams lzma support?
by anony 26 Feb '09

26 Feb '09

Is this going to be implemented? I might contribute some code if not. LZMA has amazing compression ratios.

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scoped_ptr::release (again)
by Yang Zhang 26 Feb '09

26 Feb '09

From http://www.boost.org/doc/libs/1_36_0/libs/smart_ptr/scoped_ptr.htm: "If scoped_ptr had a release() member, it would become possible to transfer ownership of the held pointer, weakening its role as a way of limiting resource lifetime to a given context. Use std::auto_ptr where transfer of ownership is required. (supplied by Dave Abrahams)" But there already is a way to escape the scope, via swap(). Would it make more sense to just provide release() and have users specify const if they want? (const scoped_ptr/scoped_array would effectively disallow swapping/releasing.) -- Yang Zhang http://www.mit.edu/~y_z/

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Boost; Default constructor work around.
by niranjan bangera 26 Feb '09

26 Feb '09

Hi, I need to know the information abt Constructor in my class to be serialized. What if i dont have defualt constructor in my class. Any other work around rather then putting the default construcor in my class, Pls Let me know if any workaround or doccumentaion. Boost: 1.38.0 ==== Compiler: ====== /_TOOLS_/dist/gnu-gcc-/4.1.1-binutils-2.16.1/x86_64-pc-linux2.4/bin/gcc class Myclass { Myclass (const string & a) { name=a; } private: int a; string name; //serialization code }; Thanks in Advance. Thanks, Niranjan

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[tuples][hash] How to make them work together ?
by Alexander 26 Feb '09

26 Feb '09

Is there an implementation of boost hash for tuples available in boost ?

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Boost.Thread annoyance
by anony 26 Feb '09

26 Feb '09

Just by including: "boost/thread.hpp", which includes "boost/bind.hpp" you pollute the namespace. If you also use Boost.Lambda, you must change _1 to boost::lambda::_1. Is this going to be fixed? Any workarounds?

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Archive reload
by Ferllings 26 Feb '09

26 Feb '09

Hello, I have a Class A with string attributes that I serialize in XML format: Class A { public: string _nom; string _prenom; template<class Archive> void serialize(Archive& ar, const unsigned in version){ ar & boost::serialization::make_nvp("Nom", _nom); ar & boost::serialization::make_nvp("Prenom", _prenom); } } The object is correctly saved using this code: A _a; void save() const { ... oTextArchive::xml_oarchive oTextArchive(ofile); oTextArchive << make_nvp("A", _a); ... } But I want to reload the object, the A attributes aren't updated and keep the previous values: void load() { ... iTextArchive::xml_oarchive iTextArchive(ifile); iTextArchive >> make_nvp("A", _a); ... } The only way I found to reload my object is to use an temporary object: void load() { ... A _tmp; iTextArchive::xml_oarchive iTextArchive(ifile); iTextArchive >> make_nvp("A", _tmp); _a = _tmp; ... } Why can't I update the object directly? Thanks for your help.

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ERROR: `boost::archive::ARCHIVE_VERSION'
by niranjan bangera 26 Feb '09

26 Feb '09

Yes steven, i have include these: -I /boost_1_36_0/include/boost-1_36 -L/boost_1_36_0/lib -lboost_serialization-gcc41-mt -lpthread in the make file, Let me know if am wrong. Thanks for Reply, Thanks, niranjan > > > Message: 8 > Date: Wed, 25 Feb 2009 07:50:08 -0800 > From: Steven Watanabe <watanabesj(a)gmail.com> > Subject: Re: [Boost-users] ERROR: `boost::archive::ARCHIVE_VERSION' > To: boost-users(a)lists.boost.org > Message-ID: <49A568B0.6000900(a)providere-consulting.com> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > AMDG > > niranjan bangera wrote: > > Hi all, > > > > Boost Version: 1.38.0 > > ========== > > > > > Compiler:/_TOOLS_/dist/gnu-gcc-/4.1.1-binutils-2.16.1/x86_64-pc-linux2.4/bin/gcc > > ====== > > > > > > While running my test case i am getting following ERROR, I know this > > is linking Error, Please Help me to remove this. > > Are you linking to the serialization library? > > In Christ, > Steven Watanabe > > > > ------------------------------ > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > > End of Boost-users Digest, Vol 1917, Issue 4 > ******************************************** >

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using Boost.Thread
by ayansinhas＠gmail.com 26 Feb '09

26 Feb '09

Hi All, I am new to boost library .. so apology if I am asking a silly question. We are planning to use boost thread in our project. We will like to know whether it is possible to use only Thread related files.. without installing the whole boost library?? Is there any way we can pull out only thread related files (some additional dependencies should be fine) in boost library and implement in our project. Please let us Know ASAP. Thanks in Advance Ayan.

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