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[graph] Efficiency of index map in dijkstra_shortest_paths
by Jan Hudec 18 Oct '12

18 Oct '12

Hello, The dijkstra_shortest_paths function requires an index map that maps vertices to index in range [0, num_vertices(g)). However there are several practially important algorithms that requite calculating shortest path trees with many times from each vertex, but each tree only spanning small fraction of an otherwise huge graph. I am somewhat concerned about allocating arrays of the size of the graph (that has millions of vertices) over and over (hundred million or more times) when many scans will stop after hundreds of vertices. Note that filtering the graph is not an option, because the stopping condition is given by radius or number of scanned vertices, but you obviously don't know which vertices will be scanned. Is there an option to use associative container for the queue indices? Or would it be useful to add it? Thanks Jan -- Jan 'Bulb' Hudec <bulb(a)ucw.cz>

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[pool2] Requests for comment
by DUPUIS Etienne 18 Oct '12

18 Oct '12

Greetings, I am currently working on a replacement for boost ::pool. I have a few questions regarding what would be an ideal implementation. Hopefully some members of the Boost mailing list will be able to help me answering these questions. The first question requires to look at the source code; my other questions are more general. First question : I have started by defining a pool object which manage fixed size buffers of a given object type. Documented code is found here : http://svn.boost.org/svn/boost/sandbox/pool2/boost/pool/pool.hpp. The code is short and hopefully well documented. Note that the 'ThreadSafe' template parameter is currently ignored; I have not implemented thread safety yet. My question is about the "pool growth policy". This policy defines how the pool grows when it needs to allocate more memory. This policy is given as a parameter to the pool constructor. Should this policy be a template argument instead ? Moreover, if the policy is a template argument, I could add a constant 'MaximumNumberOfTimesThePoolWillBeGrown' into the policy class. This constant would allow me to replace the std::vector() which holds allocated pointers with a static array. Is this the right solution ? Other questions : - I have defined a pool class which manage fixed sized buffers of some object T. Do we also need a pool class that can manage variable sized buffers of some object T ? - From a pool, I can implement a pool_allocator which inherits from std::allocator, exactly like it was done in the original boost::pool. Do we need something else ? Thank you for your valuable insights, Etienne Dupuis Ce message et toutes les pièces jointes sont confidentiels et établis à l'intention exclusive de ses destinataires. Toute modification, édition, utilisation ou diffusion non autorisée est interdite. Si vous avez reçu ce message par erreur, merci de nous en avertir immédiatement. ATEME décline toute responsabilité au titre de ce message s'il a été altéré, déformé, falsifié ou encore édité ou diffusé sans autorisation. This message and any attachments are confidential and intended solely for the addressees. Any unauthorized modification, edition, use or dissemination is prohibited. If you have received this message by mistake, please notify us immediately. ATEME decline all responsibility for this message if it has been altered, deformed, falsified or even edited or disseminated without authorization. Note: To protect against computer viruses, e-mail programs may prevent sending or receiving certain types of file attachments.

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[coroutine] final version?
by Oliver Kowalke 17 Oct '12

17 Oct '12

a final (?) version of boost.coroutine is available at http://ok73.ok.funpic.de/boost-coroutine.zip In contrast to the original concept coroutine<> is not similar to a function/functor. 1.) the coroutine-fn is started at construction of coroutine<> - helps to solve some problems related to the last 'yield'-operation - similar to the behaviour of boost::thread - arguments which have to be the first arguments of coroutine-fn must be applied to coroutine<>-ctor (arguments()) 2.) coroutine<>::operator() returns a reference to the coroutine instead the return-value 3.) return-values must be accessed via coroutine<>::get() regards, Oliver

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[smart_ptr] [shared_ptr] BOOST_NOEXCEPT patch
by Antony Polukhin 17 Oct '12

17 Oct '12

Hi, There is a trivial patch in ticket #7523 that marks some functions of Boost.SmartPtr library as noexcept. I'll test the patch for some more time and if there will be no objections, I'll commit it to trunk after boost_1_52_0 release. Any suggestions and comments are welcomed. -- Best regards, Antony Polukhin

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[lexical_cast] cast of int8_t
by Jochen Wilhelmy 16 Oct '12

16 Oct '12

Hi! In a previous message I asked if lexical_cast could throw boost::numeric::positive_overflow when the parsing is ok but the value too large for the target type. this turned out to be difficult because it breaks existing code, alternatively there could be another exception derived from bad_lexical_cast that indicates the overflow but this seems to be a lot of work. another question is why does lexical_cast treat int8_t and uint8_t like char? technically I see no reason for this as c++ has three types: char, signed char and unsigned char. in my code I use only char for characters and signed/unsigned char as numbers. I know that the standard stream operator << treats signed/unsigned char as char but I know no explanation for this (I consider it a bug ;-) -Jochen

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[type_erasure] any and shared_ptr
by Christophe Henry 16 Oct '12

16 Oct '12

Hi Steven, I need to use the associated types but don't get them to do what I need. Consider struct Pointee : public boost::enable_shared_from_this<Pointee> { void foo() { std::cout << "Pointee::foo called" << std::endl; //shared_from_this(); std::cout << "Pointee::foo end" << std::endl; } }; Pointee needs to be enable_shared_from_this for some reason, which forces me to use it in a shared_ptr. I reused your pointee / pointer structures: template<class T> struct pointee { typedef typename mpl::eval_if< boost::type_erasure::is_placeholder<T>, mpl::identity<void>, boost::pointee<T> >::type type; }; template<class T = _self> struct pointer : mpl::vector< copy_constructible<T>, dereferenceable<deduced<pointee<T> >&, T> > { typedef deduced<pointee<T> > element_type; }; I (naively) tried to define a pointee concept: typedef mpl::vector< pointer<>, same_type<pointer<>::element_type,_a >, relaxed_match, has_foo<void()> > PointeeConcept; // will not compile, shared_ptr<Pointee> has no foo... boost::shared_ptr<Pointee> p (new Pointee) ; any<PointeeConcept> ap (p); ap.foo(); So in the end I had to resort to a wrapper: struct PointeeWrap { PointeeWrap(boost::shared_ptr<Pointee>p):myPointee(p){} void foo() { std::cout << "PointeeWrap::foo called" << std::endl; myPointee->foo(); } boost::shared_ptr<Pointee> myPointee; }; BOOST_TYPE_ERASURE_MEMBER((has_foo), foo, 0); typedef any< mpl::vector< relaxed_match, copy_constructible<>, has_foo<void()> > > AnyPointee; boost::shared_ptr<Pointee> p (new Pointee); PointeeWrap wrap(p); AnyPointee ap(wrap); ap.foo(); But this will become tedious with an increasing number of members. Is there a better way? Thanks, Christophe

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[mpl] Nested BOOST_MPL_ASSERT fails on VC11
by Steven Watanabe 15 Oct '12

15 Oct '12

AMDG I just ran into the following bug: template<class T> struct test : T { BOOST_MPL_ASSERT((T)); }; BOOST_MPL_ASSERT((test<T>)); I've reworked BOOST_MPL_ASSERT to avoid the problem in the attached patch. Okay to commit? In Christ, Steven Watanabe

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[GIL] default_color_converter from float to integer should clamp
by Fabien Castan 15 Oct '12

15 Oct '12

Hi, The conversion from floating point image to 8 bits or 16 bits image should clamp instead of writing arbitrary values... // a floating point image, with some pixel values < 0.0 and > 1.0 boost::gil::rgba32f_view_t HDR; // use default_color_converter to convert this HDR image to 8 bits boost::gil::png_write_view( "LDR.png", boost::gil::color_converted_view<boost::gil::rgba8_pixel_t>( HDR ) ); The 8 bits LDR image contains arbitrary cast conversion values, that are not very nice. The conversion from floating point to integer values has no other valid solution than clamping. So I suggest this patch, for the file "boost/gil/channel_algorithm.hpp": @@ -272,7 +272,13 @@ template <typename DstChannelV> struct channel_converter_unsigned<bits32f,DstChannelV> : public std::unary_function<bits32f,DstChannelV> { DstChannelV operator()(bits32f x) const { typedef typename detail::unsigned_integral_max_value< DstChannelV >::value_type dst_integer_t; - return DstChannelV( static_cast< dst_integer_t >(x*channel_traits<DstChannelV>::max_value()+0.5f )); + + const bits32f convertedValue = x * channel_traits<DstChannelV>::max_value() + 0.5f; + const bits32f clampedValue = std::min( + (bits32f)channel_traits<DstChannelV>::max_value(), + std::max( (bits32f)channel_traits<DstChannelV>::min_value(), convertedValue ) ); + + return DstChannelV( static_cast< dst_integer_t >(clampedValue) ); } }; Regards, Fabien Castan

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[asio::ssl] TLS support
by ToBeKi＠gmx.de 15 Oct '12

15 Oct '12

Hello all, in asio::ssl context/context_base i couldn't find any TLS 1.1/1.2 method implementations. Is it missing/not supported yet? If so is there a roadmap supporting versions 1.1/1.2? Best, kito

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[config] call to destructor of temporary
by Vicente J. Botet Escriba 15 Oct '12

15 Oct '12

Hi, I have had some trouble debugging some code with clang-2.9 c++0x. The reason was a known bug on the compiler as it doesn't call the destructor of temporaries at the end of the expression. Is there a macro stating this missing feature? Best, Vicente

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