December 2008 - Boost-users - lists.preview.boost.org

Re: [Boost-users] [shared_ptr] Is it possible for a shared_ptr to hand over it ownership
by Alan M. Carroll 27 Dec '08

27 Dec '08

I don't see why you would ever want to do that. Why not hand over ownership to another shared_ptr? Why can B in your example not be of type shared_ptr<>? Then you can hand over ownership by b = p1; p1 = 0; Or, if B must be a class, why not have a member that's a shared_ptr and have getOwnership(shared_ptr& src) do _member = src; src = 0; The object can be explicitly destroyed by assigning 0 to _member. I would recommend against using auto_ptr, as it is just so _odd_. I used it once when Boost.scoped_ptr wasn't quite what I wanted, but that was a mistake (although I did find a nifty bug in the Microsoft compiler implemementation of auto_ptr). At 06:57 AM 12/25/2008, Max wrote: >Suppose I have a shared_ptr which is the only owner of the pointee. >I hope there is a way to hand over its ownership to another object >without rendering the pointee being deleted. > >Or, if the answer is no, is there an alternative class that has >this feature? > >The use case is like this: > >B b; >{ >shared_ptr p1(A()), p2(A()); > >b.GetOwnership(p1.HandOver()); >// now p1 is empty >} >// p2 is deleted here > >// but the A obj p1 used to be pointing to >// has been handed over to b and is still >// alive here > >b.DestroyA(); >// the A obj holded by b is destroyed by b >// explicitly

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Re: [Boost-users] [ASIO] design question, multiple listenning sockets vs. one
by Jose Martinez 27 Dec '08

27 Dec '08

Overmind, Etienne, Thank you very much for your advice. I switched over to one socket design, one thread doing all the recving. I setup some worker threads to deal with the parsing and processing. I am putting the final touches on the new code now (integrating the new and altered classes into main() ). So hopefully if I have the stamina I should be testing it tonight. Also, the UDP buffers have been moved up to 16megs to deal with the onslaught. thanks again. jose

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Is there a portable way to determine whether a type is functor ?
by ancode tran 26 Dec '08

26 Dec '08

Hi all, The following code only works under g++ 4.x: #include <boost/type_traits.hpp> template <class T> struct is_functor_helper { static boost::type_traits::no_type test (...); template <class U> static boost::type_traits::yes_type test (U*, typeof(&U::operator()) dummy = NULL); BOOST_STATIC_CONSTANT (bool, value = sizeof(test((T*)NULL)) == sizeof(boost::type_traits::yes_type)); }; template <class T> struct is_functor: public boost::integral_constant<bool, is_functor_helper<T>::value> { }; Can anyone give me a hint to make it work under other toolset, please ? Thanks in advance. Regards, Trung An Tran --------------------------------- Hãy cùng chat với bạn bè trên Yahoo! Pingbox mới toanh! Tạo một không gian riêng để chat trên blog là chuyện nhỏ.

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what is boost "jam"?
by Robert P. J. Day 26 Dec '08

26 Dec '08

i admit that this is inevitably a dumb question but what is boost "jam" as opposed to the generic boost library? thanks. rday p.s. i want to install boost on a fedora 9 (soon to be fedora 10) system, and i just want to know what's essential and what isn't. ======================================================================== Robert P. J. Day Linux Consulting, Training and Annoying Kernel Pedantry: Have classroom, will lecture. http://crashcourse.ca Waterloo, Ontario, CANADA ========================================================================

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Why does not ublas overload operators?
by Allen Chen 26 Dec '08

26 Dec '08

Six years ago, I design my own matrix library like matlab. I overload operators, it make it conveninent to do matrix manupulations. For example matrix A, B, C, D; A = B*C +D; It is easy to use and read. Why does not ublas overload such operators as +, -, *, /, ^, [], (),... Allen

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Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max)
by Max 26 Dec '08

26 Dec '08

In my opinion, the self-made version in my initial post is probably superior than yours. :-P which is repeated as follows: #include <boost/utility/value_init.hpp> // my abs function // it works not only for POD types, but also for // user types that are default constructible and // support operator<() and unary operator-() template<class T> T abs(const T & x) { static boost::value_initialized<T> zero; return (x < zero? -x : x); } Max ----- Original Message ----- From: Deane Yang <deane.yang(a)yahoo.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max) Date: 2008-12-25 18:09:26 I just made up my own naive version. Improvements would be welcome: template<typename T> inline T AbsoluteValue(const T& x) { if (x < T(0)) { return -x; } else { return x; } } Max wrote: > seconded. > > But could you tell me where I can find the temple version of > AbsoluteValue function you mentioned? > > Thanks > B/Rgds > Max > ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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[ASIO] design question, multiple listenning sockets vs. one
by Jose Martinez 25 Dec '08

25 Dec '08

Hello, I am creating a SIP load tester. The load tester will mimic thousands of SIP end-points registering and making phone calls to a SIP proxy. Originally I have created one udp::socket object for each mimic'd SIP end-point. Each listening and executing async_receive_from() on its own port. So if I have 1000 SIP end-points, I have 1000 udp::sockets listening, receiving, and writing. I am expecting to go up to 20,000 SIP end-points in production. The reason I did this is because when packets arrive to the udp::sockets, I know exactly which SIP end-point it belongs to... which saves the app the hassle of having to parse through the new SIP packet to figure out which SIP end-point it should go through. But I did not take into account any back-end context switching that boost::asio::io_service might be doing or other overhead it might do. I cannot find much information about this. The alternative would be to have one udp::socket (or maybe a few, one on its own thread for example) and parse the incoming packets to figure out which SIP end-point it belongs to. So this comes down to parsing incoming SIP messages and using one (or a few) udp::sockets on its (their) own thread, versus using many udp::sockets but no SIP message parsing. Does anyone have any insight into the back-end context switching that boost::asio uses to work its magic? Does 20,000 udp::sockets each listenning and receiving scream out 'NO DO NOT DO THIS'? Any insight is welcomed. thanks jose

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[review][constrained_value] Review of Constrained Value Library begins today
by Jeff Garland 25 Dec '08

25 Dec '08

Hi all, The review of the Robert Kawulak's Constrained Value library begins today December 1, 2008, and will end on December 10th -- I will be the review manager. Please post reviews to the developer list. Here's the library synopsis: The Boost Constrained Value library contains class templates useful for creating constrained objects. A simple example is an object representing an hour of a day, for which only integers from the range [0, 23] are valid values. bounded_int<int, 0, 23>::type hour; hour = 20; // OK hour = 26; // exception! Behavior in case of assignment of an invalid value can be customized. The library has a policy-based design to allow for flexibility in defining constraints and behavior in case of assignment of invalid values. Policies may be configured at compile-time for maximum efficiency or may be changeable at runtime if such dynamic functionality is needed. The library can be downloaded from the here: http://rk.go.pl/f/constrained_value.zip The documentation is also available online here: http://rk.go.pl/r/constrained_value --------------------------------------------------- Please state in your review, whether you think the library should be accepted as a Boost library. Additionally, please consider the following aspects in your review of the library: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Thanks, Jeff

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[shared_ptr] Is it possible for a shared_ptr to hand over it ownership
by Max 25 Dec '08

25 Dec '08

hello all I hope this is not a stupid question. Suppose I have a shared_ptr which is the only owner of the pointee. I hope there is a way to hand over its ownership to another object without rendering the pointee being deleted. Or, if the answer is no, is there an alternative class that has this feature? The use case is like this: B b; { shared_ptr p1(A()), p2(A()); b.GetOwnership(p1.HandOver()); // now p1 is empty } // p2 is deleted here // but the A obj p1 used to be pointing to // has been handed over to b and is still // alive here b.DestroyA(); // the A obj holded by b is destroyed by b // explicitly Thanks in advance B/Rgds Max ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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How to do svd for a complex matrix using ublas & lapack bindings?
by Allen Chen 25 Dec '08

25 Dec '08

Hi, Today I begin to learn to use boost ublas. And I have successfully done svd for a real matrix. To do svd for a complex matrix, I simply change codes from double to std::complex like the following. But it does not work. #include <boost/numeric/bindings/lapack/gesdd.hpp> #include<boost/numeric/bindings/traits/ublas_matrix.hpp> #include<boost/numeric/bindings/traits/ublas_vector.hpp> #include <boost/numeric/ublas/matrix.hpp> #include <boost/numeric/ublas/vector.hpp> int main() { using namespace boost::numeric::bindings::lapack; using namespace boost::numeric::ublas; matrix<std::complex<double>, column_major> A (4,2); A(0,0)=std::complex<double>(2, 5); A(0,1)=4; A(1,0)=1; A(1,1)=3; A(2,0)=0; A(2,1)=0; A(3,0)=0; A(3,1)=0; std::cout << A << std::endl; matrix<std::complex<double>, column_major> U(4,4); matrix<std::complex<double>, column_major> V(2,2); vector<std::complex<double>> S(2); gesdd(A, S, U, V); std::cout << U << std::endl; std::cout << S << std::endl; std::cout << V << std::endl; return 0; } When compiles the program, MSVC8 will tell that it found no gesdd method for complex type arguments. Please help me. Thanks Allen

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