April 2012 - Boost - lists.preview.boost.org

Review request: extended complex number library
by Matthieu Schaller 02 May '12

02 May '12

Dear all, Following the comments from V. Escriba, I formally propose my complex number library for review. The library is an extension of the std::complex class addressing two issues: - The standard does not guaranty the behaviour of the complex class if instantiated with types other than float/double/long double. - Some calculation where pure imaginary numbers (i.e. multiples of sqrt(-1)) appear are unnecessarily slowed down due to the lack of support for these numbers. The code I submit contains two interleaved classes boost::complex and boost::imaginary which can be instantiated with any type T provided T overloads the usual arithmetic operators and some basic (real) mathematical functions depending on which complex function will be used. It is thus an extended version of Thorsten Ottosen's n1869 proposal (http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2005/n1869.html) Performance tests show some non-negligible speed-ups compared to std::complex for calculations where pure imaginary numbers are involved. A speed-up of 25% has been observed when solving the Schroedinger equation explicitly on a regular mesh and some comparable figures can be observed when computing the Mandelbrot set (the two examples snippets provided in the archive). Furthermore, the functions (sin(), exp(), log(),...) involving boost::imaginary numbers are more precise than their equivalent using a std::complex with the real part set to 0. The code and (doxygen) documentation is available in the repository http://code.google.com/p/cpp-imaginary-numbers/ A comprehensive zip archive can be found in the "download" and the code can also be checked-out via the SVN repository. The archive contains the class header, two examples, a comprehensive precision test, a brute-force performance test and the documentation. I'd be happy to answer any question from your side and to provide more detailed information if required. Regards, Matthieu -- Matthieu Schaller PhD student - Durham University

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Array in Unordered Map
by Olaf van der Spek 01 May '12

01 May '12

Hi, What's the right way to get an array into an unordered map? This one works on VC10, but GCC appears to look for the hash_value function in namespace std. What's the right way to do this? Olaf #include <array> #include <boost/unordered_map.hpp> namespace boost { template<class T, size_t N> size_t hash_value(const std::array<T, N>& v) { return boost::hash_range(v.begin(), v.end()); } } int main() { boost::unordered_map<std::array<char, 20>, int> c; c[std::array<char, 20>()] = 0; return 0; } -- Olaf

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Re: [boost] [exception] warning about non-virtual destructor - resolution?
by Hite, Christopher 30 Apr '12

30 Apr '12

This is annoying me too: boost_1_49_0/boost/checked_delete.hpp:34:5: warning: deleting object of polymorphic class type 'boost::error_info<boost::tag_original_exception_type, const std::type_info*>' which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor] A) easy solution /boost_1_49_0/boost/exception/detail/error_info_impl.hpp It's probably easiest to just make ~error_info_base() virtual. It doesn't cost much since there's already a virtual table. B) harder solution The other cooler C++11 alternative is declare error_info final. I tried it on gcc-4.7.0 and it works wonderfully. Since the compiler knows you can not derive a class from that type it knows a that deconstructor is complete. struct base{ virtual void foo(); }; struct derived final : base { }; //struct illegal : derived {}; // error: cannot derive from 'final' base 'derived' in derived type 'illegal' void kill(derived* d){ delete d; // no complaint } I vote for A, because you'd anyway have to detect support for final. Chris

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Re: [boost] [type_traits] has_equal_to< std::vector<T> > always true_
by Frédéric Bron 30 Apr '12

30 Apr '12

> We could use <boost/detail/container_fwd.hpp> here (rather like Boost.Hash > does, which has a similar issue) and get the best of both worlds? My > concern about making it a separate header, is that it runs the risk of ADL > errors if the #includes are inconsistent across translation units. I assume > that only forward declarations are needed for the containers? This looks a very good idea. It is a pity that the standard does not provide such header as it does for iostreams (iosfwd). However, I see that <boost/detail/container_fwd.hpp> has some troubles with many compilers, in particular with g++. // GNU libstdc++ 3 // Disable forwarding for all recent versions, as the library has a // versioned namespace mode, and I don't know how to detect it. This is a major drawback but maybe we can do something for it. I see also that with the new standard, this header is now not exhaustive; we have to include all of these: * <array> - <deque> * <forward_list> - <list> - <vector> - <map> - <set> * <unordered_map> * <unordered_set> - <queue> - <stack> - <string> - <bitset> *: missing headers in <boost/detail/container_fwd.hpp> Frédéric

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Exception visibility and non-GCC compilers
by Mathias Gaunard 30 Apr '12

30 Apr '12

Exceptions types need to be exported so that shared libraries work correctly. Currently, the only code I see that does this is in Boost.Exception : #if defined(__GNUC__) # if (__GNUC__ == 4 && __GNUC_MINOR__ >= 1) || (__GNUC__ > 4) # pragma GCC visibility push (default) # endif #endif ... some exception type being declared or defined #if defined(__GNUC__) # if (__GNUC__ == 4 && __GNUC_MINOR__ >= 1) || (__GNUC__ > 4) # pragma GCC visibility pop # endif #endif But shouldn't we have macros to make this work with other compilers too? I'm not sure all unix-like compilers pretend to be GCC 4.1+.

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[pool] Definition of a static_pool ?
by DUPUIS Etienne 30 Apr '12

30 Apr '12

Greetings, The Boost.Pool class describes a pool of buffer, pool whose size grows as needed. This is very convenient but there usage cases where the pool should not perform any dynamic memory allocation, i.e. the maximum number of simultaneously required buffers is known at initialization. I have hence defined a simple class 'static_pool' (see below), which (i) allocate all requested buffers at initialization; (ii) fails (returns null) if more buffers are being asked for at runtime. Does such a class has its place within the Boost Pool library ? Regards, Étienne #ifndef BOOST_STATIC_POOL_HPP #define BOOST_STATIC_POOL_HPP #include <boost/pool/pool.hpp> namespace boost { template<typename UserAllocator> class static_pool : protected pool<UserAllocator> { public : // Overridden functions explicit static_pool(const size_type nrequested_size) : pool<UserAllocator>(nrequested_size, nrequested_size) { free(malloc()); } void * malloc() { return store().empty() ? NULL : store().malloc(); } public : // Inherited functions void free(void * const chunk) { return pool<UserAllocator>::free(chunk); } size_type get_requested_size() const { return pool<UserAllocator>::get_requestedSize(); } bool is_from(void * const chunk) const { return pool<UserAllocator>::is_from(chunk); } }; } #endif 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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[filesystem] [system] Suddenly, dynamic linking by default
by Lars Viklund 30 Apr '12

30 Apr '12

Hello list. I have a habit of tracking trunk to find out if there's any strangeness or mistakes done on the platforms I target. A while ago I encountered some strange linking errors on some of my projects, which in the end turned out to be because for some reason, Boost.Filesystem and Boost.System now attempt to be dynamically linked by default, both symbol-decoration-wise and auto-link filename-wise. I happened to have some older shared libraries from an older trunk version lying around, so they were suddenly and unexpectedly picked up instead of my fresh static libraries. Even without my library hygiene deficiencies, the decision (which I have yet to see a rationale or announcement about) will cause a lot of problems. Why is it that System/Filesystem suddenly default to dynamic linking? Are there problems about linking statically? Why are there then static libraries built at all? Is this just some personal preference of the author that goes contrary to the general approach of Boost? Such choices have _massive_ impacts on consumers of the code, they should not be made lightly and if there is a really concrete need to do so, why is it not documented and thoroughly explained? Linking dynamically requires you to deploy the Boost DLLs to the end user, which prevents any plugin-like deployment, as they tend to require a single self-contained shared library with no dependencies, which implies linking to a static language runtime of choice. Dynamic linking of Boost means that you need to share a CRT between the project and Boost, which implies that the only CRT choice is the dynamic one, which prevents many deployment scenarios, as you have to deploy _that_ as well to the end user, either as a redistributable install or as a private deployment. This also has an impact on code size, as there is no dead-code elimination possible when the code resides in a DLL, you have to ship _all_ of the library even if you use a few convenience functions. For one of my projects (an extension to a popular music player), this would inflate its size many times for each and every download, as the software is deployed as a single ZIP archive through automatic update services. Additionally, the autolink macros to force symbol decoration and linking for a static link are undocumented in the Boost.Config table [1], which explicitly states that all libraries that can be statically linked will be statically linked. There is no mention of libraries that arbitrarily decide to go dynamic, just that some libraries are only available in dynamic form. For future reference for anyone finding this in archives, the undocumented, and in this case required, macros to force a static link and symbol decoration are: BOOST_<WHATEVER>_STATIC_LINK or BOOST_ALL_STATIC_LINK [1] http://www.boost.org/doc/libs/1_49_0/libs/config/doc/html/index.html#boost_… -- Lars Viklund | zao(a)acc.umu.se

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[iostream] tests broken due to dependency on removed filesystem internals
by Jürgen Hunold 30 Apr '12

30 Apr '12

Hi, almost all Boost.Iostreams test fail with: bin.v2/libs/iostreams/test/array_test.test/gcc-4.6/debug/array_test.o In file included from ../array_test.cpp:14:0: ../detail/temp_file.hpp:16:46: fatal error: boost/filesystem/v3/operations.hpp: No such file or directory compilation terminated. The v3/ was removed recently as v2 was finally dropped. Patch to fix this attached. This gets a lot of the tests running. Okay to commit? There are some remaining failures. Yours, Jürgen -- * Dipl.-Math. Jürgen Hunold ! * voice: ++49 4257 300 ! Fährstraße 1 * fax : ++49 4257 300 ! 31609 Balge/Sebbenhausen * jhunold(a)gmx.eu !

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[multiprecision] Looking for a review manager
by John Maddock 29 Apr '12

29 Apr '12

Just a quick line to remind/hassle you all that I'm still looking for a review manager for the multiprecision library: http://svn.boost.org/svn/boost/sandbox/big_number/libs/multiprecision/doc/h… All volunteers/victims gratefully accepted ;-) Many thanks in advance, John.

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Re: [boost] Slow Bugs Tracker
by Olaf van der Spek 29 Apr '12

29 Apr '12

Hi, A few months ago there seemed to be plans to improve Trac. What's the status of those plans? Trac is still slow as hell. http://lists.boost.org/Archives/boost/2011/12/188639.php http://lists.boost.org/Archives/boost/2011/12/188937.php -- Olaf

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