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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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Why my program always complains: cannot open file 'libboost_thread-vc80-mt-sgd-1_35.lib'?
by Bill David 25 Dec '08

25 Dec '08

I have no 'libboost_thread-vc80-mt-sgd-1_35.lib' but 'libboost_thread-vc80-mt-gd-1_35.lib' in the link path. But my console program always automatically links to 'libboost_thread-vc80-mt-sgd-1_35.lib'. I have checked boost document, -s means statically linking to C++ standard library. Question: How could I modify the project settings and make it link to 'libboost_thread-vc80-mt-gd-1_35.lib'? I am using VS2005 + boost1.35.0.

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Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max)
by Max 25 Dec '08

25 Dec '08

seconded. But could you tell me where I can find the temple version of AbsoluteValue function you mentioned? Thanks B/Rgds Max ----- Original Message ----- From: Deane Yang To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max) Date: 2008-12-23 23:28:08 Scott McMurray wrote: > On Mon, Dec 22, 2008 at 21:06, Max wrote: >> What I need is a template version of abs, not the >> int abs(int) function, to make use of it genericly. >> > > Do you really need a template of it? I can't see why using ADL > wouldn't be enough (with a using declaration for std::abs, to catch > the overloads for scalars from and ). I certainly use template versions of Max, Min, and AbsoluteValue, because I need them for user-defined classes (that represent real numbers) and not just for built-in types. ------------------------------------------------------------------- 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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Re: [Boost-users] [boost] [test] Runtime parameter handling subsystem updated
by David Abrahams 25 Dec '08

25 Dec '08

on Tue Dec 23 2008, Gennadiy Rozental <rogeeff-AT-gmail.com> wrote: > Hi, > > I've checked in an update to the runtime parameters handling > subsystem. It's not completely up to my liking yet, but should fare > better than old one. > > From usage prospective you will see major differences in features > supported by command line argument parser (don't worry - everything is > backward compatible). Are these new features documented? -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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Re: [Boost-users] [iterator] transform_iterator
by Max 25 Dec '08

25 Dec '08

But another minor thing that I don't understand is why the template parameters of the transform_iterator and the parameters of its constructor are in the different order. If I were the author, I would feel keeping them in the same order be more natural and more straightforward. Perhaps letting Function be the 1st template parameter make it clearer the behavior of the class? :-) If this is a too stupid question, just ignore. :-) Thanks. B/Rgds Max ----- Original Message ----- From: Steven Watanabe To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [iterator] transform_iterator Date: 2008-12-25 00:47:36 AMDG Max wrote: > I just came across transform_iterator and found it a useful generic tool. > But is it possible for it to go further to make the following code get > compiled and run as expected? > No. > struct A > { > int i_; > A() : i_(0) {} > explicit A(int i) : i_(i) {} > }; > > const int N = 5; > A a_list[N] = { A(-3), A(1), A(3), A(2), A(-4) }; > > typedef boost::function fn_t; > > // sorting a_list according to the elements' i_ member > std::stable_sort(boost::make_transform_iterator(a_list, fn_t(boost::bind(&A::i_, _1))), > boost::make_transform_iterator(a_list+N, fn_t(boost::bind(&A::i_, _1))), > std::less()); > stable_sort assumes that the sort keys are the same as the objects that it is moving around. In Christ, Steven Watanabe ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ ) ------------------------------------------------------------------- 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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Re: [Boost-users] [iterator] transform_iterator
by Max 25 Dec '08

25 Dec '08

Thank you, Watanabe. B/Rgds Max ----- Original Message ----- From: Steven Watanabe To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [iterator] transform_iterator Date: 2008-12-25 00:47:36 AMDG Max wrote: > I just came across transform_iterator and found it a useful generic tool. > But is it possible for it to go further to make the following code get > compiled and run as expected? > No. > struct A > { > int i_; > A() : i_(0) {} > explicit A(int i) : i_(i) {} > }; > > const int N = 5; > A a_list[N] = { A(-3), A(1), A(3), A(2), A(-4) }; > > typedef boost::function fn_t; > > // sorting a_list according to the elements' i_ member > std::stable_sort(boost::make_transform_iterator(a_list, fn_t(boost::bind(&A::i_, _1))), > boost::make_transform_iterator(a_list+N, fn_t(boost::bind(&A::i_, _1))), > std::less()); > stable_sort assumes that the sort keys are the same as the objects that it is moving around. In Christ, Steven Watanabe ------------------------------------------------------------------- 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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