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[random] A much faster Poisson variate generation
by Ross Levine 21 Jan '09

21 Jan '09

Hello, I have modified the poisson_distribution class to use an updated version of Ahrens and Dieter's PD algorithm for generating Poisson variates, as described in "Computer Generation of Poisson Deviates from Modified Normal Distributions." Is this allowed in Boost, and is there interest? The current algorithm is O(mean), while PD is bounded time. In addition, the current implementation fails for mean >> 750. PD does, however, use a lookup table and thus has a non-trivial constructor and needs 36 * sizeof(RealType) + 1 * sizeof(IntType) bytes per poisson_distribution object. Please let me know if this is desired. Ross

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Re: [boost] A PP trick to define a synchronized block java-like macro
by JOAQUIN M. LOPEZ MUÑOZ 21 Jan '09

21 Jan '09

________________________________________ De: boost-bounces(a)lists.boost.org [boost-bounces(a)lists.boost.org] En nombre de Sebastian Redl [sebastian.redl(a)getdesigned.at] Enviado el: martes, 20 de enero de 2009 22:39 Para: boost(a)lists.boost.org Asunto: Re: [boost] A PP trick to define a synchronized block java-like macro > vicente.botet wrote: > > for (VARS DECLARATION, bool __continue=true; > > __continue; > > __continue=false) > > > > > I'm afraid this is not valid syntax. The first clause of the > for-statement is a for-init-statement, which can be either an expression > with a semicolon, or a simple-declaration. A simple-declaration lets you > declare any number of variables, but they must all have the same > declspec, i.e. the same fundamental type (with variations like "pointer > to", "array of" or "function returning"). The following variation would do: for (VARS DECLARATION, *continue_hlp_,**continue_=&continue_hlp_; continue_; continue_=0) Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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[1.38.0][Spirit] char_class test failing on both trunk and release, all platforms
by Beman Dawes 21 Jan '09

21 Jan '09

The Spirit char_class test is failing on both trunk and release, all platforms. Any progress on fixing this? --Beman

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[1.38.0] [config] Linux release branch link failures
by Beman Dawes 20 Jan '09

20 Jan '09

config_test is failing with link errors on both Linux testers. Any ideas? --Beman "g++" -o "/home/steve/Packages/boost/upstream/testing/release/results/boost/bin.v2/libs/config/test/config_test.test/gcc-4.3.3/debug/config_test" -Wl,--start-group "/home/steve/Packages/boost/upstream/testing/release/results/boost/bin.v2/libs/config/test/config_test.test/gcc-4.3.3/debug/config_test.o" -Wl,-Bstatic -Wl,-Bdynamic -Wl,--end-group -g /home/steve/Packages/boost/upstream/testing/release/results/boost/bin.v2/libs/config/test/config_test.test/gcc-4.3.3/debug/config_test.o: In function `boost_has_pthread_mutexattr_settype::f()': /home/steve/Packages/boost/upstream/testing/release/boost/status/../libs/config/test/boost_has_pthread_ma_st.ipp:21: undefined reference to `pthread_mutexattr_init' /home/steve/Packages/boost/upstream/testing/release/boost/status/../libs/config/test/boost_has_pthread_ma_st.ipp:23: undefined reference to `pthread_mutexattr_settype' /home/steve/Packages/boost/upstream/testing/release/results/boost/bin.v2/libs/config/test/config_test.test/gcc-4.3.3/debug/config_test.o: In function `boost_has_pthreads::test()': /home/steve/Packages/boost/upstream/testing/release/boost/status/../libs/config/test/boost_has_pthreads.ipp:35: undefined reference to `pthread_mutex_trylock' /home/steve/Packages/boost/upstream/testing/release/boost/status/../libs/config/test/boost_has_pthreads.ipp:44: undefined reference to `pthread_create' /home/steve/Packages/boost/upstream/testing/release/boost/status/../libs/config/test/boost_has_pthreads.ipp:52: undefined reference to `pthread_join' /home/steve/Packages/boost/upstream/testing/release/results/boost/bin.v2/libs/config/test/config_test.test/gcc-4.3.3/debug/config_test.o: In function `boost_has_clock_gettime::f()': /home/steve/Packages/boost/upstream/testing/release/boost/status/../libs/config/test/boost_has_clock_gettime.ipp:21: undefined reference to `clock_gettime' collect2: ld returned 1 exit status

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A PP trick to define a synchronized block java-like macro
by vicente.botet 20 Jan '09

20 Jan '09

In Boost.Log we can see how to define a macro that preserv the osream syntax but that logs conditionally. LOG << "Ah" << std::end; We use here the following trick: let the sentence generated by the macro is unterminated and form a correct sentence together with what follows the macro call. #define LOG if (!log::enabled()); else log::os I have recently see in [1] a trick allowing the declaration of a variable local to a block scope but OUT OF THE SCOPE!!!. This will allows to write things like synchronized(mtx_) { // block protected by a scoped lock } or atomic(tr) { // atomic block managed by a transaction } The idea is to place the declaration of the needed variables on the init declaration of a for. So these variables are accessible by the next sentence or block. The condition will let executes its body only once. A variable __continue variable is used to this goal; it initialized to true and set to false on the next part of the for. for (VARS DECLARATION, bool __continue=true; __continue; __continue=false) The definition of the synchronized macro can be #define synchronized(MUTEX) \ for (boost::mutex::scoped_lock __lock(MUTEX), bool __continue=true; \ __continue; \ __continue=false) In order to help when debuging we can define the __lock and _cont variables as macros generating symbols including the line number. #define __concat(a,b) a##b #define _concat(a,b) __concat(a,b) #define __lock _concat(__lock_, __LINE__) #define __continue _concat(__continue _, __LINE__) As the variables are local to the scope, we can use the macro twice on the same line as synchronized(mtx_1) synchronized(mtx_2){ // block protected by a scoped lock on mtx_1 and mtx_2 // ... } See how we can nest the synchronized blocks: synchronized(mtx_1) { // block protected by a scoped lock on mtx_1 // ... 1 synchronized(mtx_2) { // Embeeded block protected by a scoped lock on mtx_2 // ... 2 synchronized(mtx_3) unique_sentence_protected_by_mtx_3(); // ... 2 } // ... 1 } I know that most of the participants to this ML do not like macros too much, even less when we can do without them. { // block protected by a scoped lock on mtx_1 boost::mutex::scoped_lock lock1(mtx_1) ; // ... 1 { // Embeeded block protected by a scoped lock on mtx_2 boost::mutex::scoped_lock lock1(mtx_2) ; // ... 2 { // Artificial Embeeded block protected by a scoped lock on mtx_3 boost::mutex::scoped_lock lock1(mtx_3) ; unique_sentence_protected_by_mtx_3(); } // ... 2 } // ... 1 } But I think that in these cases the language-like macros make the code realy more readable, specially in the case of software transactional memory (STM), see (http://en.wikipedia.org/wiki/Software_transactional_memory) // language-like transaction with retry. try_atomic(t) { transaction_ptr(x) = val; } before_retry {} I wanted simply to share this trick with you, maybe someone wants to use something like that in its own application. Let me know however what do you think. Thanks to the authors of this excelent paper and the DracoSTM library. Hoping this would inspire some of you, Vicente ___________________________________ P.S. the exception based timed locks post http://www.nabble.com/-thread--Exception-based-timed-locks-tp21554444p21554… is also inspired from this article. [1] Toward Simplified Parallel Support in C++ Justin E. Gottschlich, Jeremy G. Siek, Paul J. Rogers and Manish Vachharajani

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filesystem::remove_all error handling
by Zachary Turner 20 Jan '09

20 Jan '09

Has there been any discussion regarding the possibility of filesystem::remove_all allowing a second parameter, a functor or function, to be specified which on any file system error is called with the filename that was attempted to be removed as well as the error code? My application, for example, would like to log every single occurence of failure with a warning, but still delete every possible file that it can, but I see no way to handle this without rolling my own implementation of remove_all. Which is fine if that's what I have to do, but at the same time it doesn't seem that uncommon a case where someone would want to know about every single error, yet still attempt every deletion possible. I guess one tricky aspect of this is that you probably would not want to invoke the error callback if the error code means "directory not empty" and the reason it is not empty is because a file was unable to be deleted below the directory. Side note, but the implementation of remove_all does not appear to be tail recursive either, so even the best compiler will not be able to optimize this into a loop, leading to the potential for a stack overflow in deeply nested directory hierarchies. (Now that I think about it, I'm not even sure what, if any, C++ compilers optimize tail recursive calls). Apologies if either of these two issues has been addressed (I'm using 1.35.0), did not find anything in the archives. Thoughts?

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[Serialization] Improving performance
by Hartmut Kaiser 20 Jan '09

20 Jan '09

Hi all, in one of my projects I have a lot of types (>1000) to be serialized using a pointer to a single base class. At some point we found the serialization/deserialzation time to be O(N*M), where N is the number of types and M the number of classes in the derivation hierarchy. Wondering why this is so significant I started digging and measuring. I found the type information registry used for the void_upcast() to be the culprit. It's a plain std::vector<const void_caster *> ($BOOST_ROOT_1_37/libs/serialization/src/void_cast.cpp:37) which is searched sequentially a lot (once for each derived/base pair for each serialization call). Moreover, this vector isn't even kept sorted. it = std::find_if( s.begin(), s.end(), void_cast_detail::match(& ca) ); ($BOOST_ROOT_1_37/libs/serialization/src/void_cast.cpp:180). Changing this to be a std::set improves the picture significantly! What's the reasoning behind using a std::vector<> instead of a std::set<> or a similar indexed structure? Regards Hartmut

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[thread] Exception based timed locks
by vicente.botet 20 Jan '09

20 Jan '09

Hi, I've read recently about timed locks throwing an exception when there is a timeout. What do you think about this behaviour? Could the thread library provide both? Next follows a piece of code without exceptions while (polling) { t=now()+100; boost::unique_lock<boost::mutex> l1(m1, t); if (l1.has_lock() { boost::unique_lock<boost::mutex> l2(m2, t); if (l2.has_lock() { boost::unique_lock<boost::mutex> l3(m3, t); if (l2.has_lock() { foo(); polling = false; } else execute_on_failed(); } else execute_on_failed(); } else execute_on_failed(); } and now with exceptions while (polling) try { t=now()+100; boost::exception_unique_lock<boost::mutex> l1(m1, t); boost::exception_unique_lock<boost::mutex> l2(m2, t); boost::exception_unique_lock<boost::mutex> l3(m3, t); foo(); polling = false; } catch (timeout_exception& ex) {execute_on_failed(); } What do you think about a try_lock_until, try_lock_for functions while (polling) try { boost::try_lock_for(100, m1, m2, m3); foo(); polling = false; } catch (timeout_exception& ex) {execute_on_failed(); } Best, Vicente

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[Fwd: [ublas] why is there no constructor that fills the matrix with a default value]
by Thorsten Ottosen 20 Jan '09

20 Jan '09

I didn't get any response to this, so I'll try again. Thanks -Thorsten

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[test] Warnings and EDG compiler error patch.
by John Maddock 20 Jan '09

20 Jan '09

Geniydi, I hope you don't mind, but I'm about to apply the attached trivial patch to Boost.Test in Trunk to: 1) Quieten a minor blizzard of msvc warnings. 2) Get the code compiling with Intel C++. Regards, John.

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How to structurate libraries ?
by Joel Falcou 20 Jan '09

20 Jan '09

I may have a few components to propose as library. They mostly deals with low-level, architecture-dependant problems that get homogeneized across compiler/platform. Things like class for padding a type to a given boundary, SIMD computation DSEL, traits concerning low-level properties of types and/or compilers and some more. What's the best way to handle this ? A series of small-scale libraries or a larger framework like boost::architecture or something ? -- ___________________________________________ Joel Falcou - Assistant Professor PARALL Team - LRI - Universite Paris Sud XI Tel : (+33)1 69 15 66 35

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Futures - Reviews Needed (January 5, 2009)
by Tom Brinkman 19 Jan '09

19 Jan '09

Futures Join the review and discussion starting January 5, 2009. I need commitments for reviews from threading experts on the two Futures library candidates. Braddock Gaskill - http://braddock.com/~braddock/future Anthony Williams - http://www.justsoftwaresolutions.co.uk/files/n2561_future.hpp Early comments are welcome.

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Lazy list
by Zachary Turner 19 Jan '09

19 Jan '09

It occured to me that boost is lacking a true lazy list. I feel like this should be possible to implement on most compilers, although I doubt I have the metaprogramming expertise to be able to implement such a data structure myself. But nonetheless I think this would be extremely useful. Lazy lists are basically lists that don't store the actual values of the list, instead they store a -function- that is called each time the next element of the list is requested, and the result of that list is returned. Most likely there is a caching mechanism as well, so that accessing recently accessed (or preceding) elements would return a cached value if it had already been accessed. I guess it would not cache arbitrarily large amounts of elements though for memory usage reasons, otherwise it would defeat the whole purpose, which is the ability to expose truly infinite sequences to the user in the form of a list. Has this been considered before, and can anyone think of any technical limitations that would prevent such a class to be written?

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[filesystem] operator == performance
by Konstantin Litvinenko 19 Jan '09

19 Jan '09

Hi! I am developing an application with very intensive boost::filesystem::path usage. At certain moment application start to be slowly and I start profiler. Profiler shows me that std::map<fs:path, ....> is painfully slow due path::operator <() that do lexicographical compare , that do void iterator_helper<Path>::do_increment( iterator & itr ) that is really slow. So I have replaced std::map on boost::unordered_map.. and didn't get expected performance gain. Profiles show me that path::operator <() hit count 200000 and now only 100000. That tooooo much. Further investigation shows that problem was path::operator ==() used in unordered_map. I understand that operator == can be implemented using strict weak ordering concept, but for filesystem::path. Why not implement it as: bool path::operator == (const path& lhs, const path& rhs) const { return lhs.string() == rhs.string(); } ?

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Re: [boost] [SVN Configuration] Request an additional MIME type to support Scalable Vector Graphics (SVG)
by Jeroen N. Witmond 19 Jan '09

19 Jan '09

Peter Foley wrote on 2007-08-23 11:52:25 GMT: > Should I simply update my local configuration file to include the line: > > *.svg = svn:eol-style=native; svn:mime-type=image/svg+xml > > Any advice would be greatly appreciated. With this autoprop set, `svn add` gets into trouble (at least for me) adding a file with extension .svg. I had to change the svn:mime-type to text/svg+xml to get it to work. Regards, Jeroen.

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utility class: lazy data type
by Zachary Turner 19 Jan '09

19 Jan '09

I wrote this class to support lazy evaluation and caching of values. It seems like it would be useful for inclusion as a miscellaneous class in boost. It seems like this pattern occurs pretty often in practice, it's even the fundamental implementation method for singletons, and at least I often have tons of boost::optionals in my code, with get accessors on the classes that check if there's a value, if not call a fetch function, and then return the value. It's cleaner to just call get every single time and not worry about it. I don't consider myself a guru, so suggestions on how to make it better are, of course, appreciated. template<class T> class lazy { public: explicit lazy(function<T ()> fetch) : _fetch(fetch) { } T get() { if (!_cached) _cached = _fetch(); return _cached.get(); } private: optional<T> _cached; function<T ()> _fetch; }; Perhaps such a class is too trivial to be included, but here it is nonetheless.

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[interthreads] Library under development v0.3
by vicente.botet 19 Jan '09

19 Jan '09

Hi, I have add the fork_after function to Boost.InterThreads. The prototype allows to execute asynchronously N functions and execute asynchronously a function that depends on the completion of N functions. bith::shared_launcher ae; BOOST_AUTO(actT, bith::fork_all(ae, fct1, fct2)); BOOST_AUTO(act, bith::fork_after(ae, fct3, actT)); act.wait(); bith::shared_launcher is an asynchronous executor (AE) that executes asynchronously a function on a new thread. bith::fork_all request the AE to execute asynchronously each function. It returns a fusion tuple of the asynchronous completion token (ACT) associated the the ae. bith::fork_after request the AE to execute a function asynchronously once each one of ACTs in the dependency tuple parameter are ready. It is similar to the async_with_dependencies proposed Peter Dimov. I have used for that Boost.Future (Anthony proposal). I've added also some act traits, as value type, is movable, has_future_if, has_thread_if. The library is available at Boost Sandbox: https://svn.boost.org/svn/boost/sandbox/interthreads and Boost Vault: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=intert… Includes every thing on the Sandbox + Html documentation + Boost.Futures + Boost.ThreadPool adaptations I'd appreciate it if people could take a look, test it on their compiler and give me some feedback. Best regrads, Vicente _____________________ Vicente Juan Botet Escribá

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BoostCon'09 Registration Now Open
by David Abrahams 18 Jan '09

18 Jan '09

Greetings, Boosters and former BoostCon attendees The third annual Boost conference (BoostCon), featuring a keynote address by Andrei Alexandrescu, will take place May 3-8 2009 in Aspen, Colorado. The conference is now open for registration! Please go to http://www.boostcon.com/registration and reserve your place at the year's premier C++ event today. -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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Boost Library Authors: BoostCon submission deadline approaching
by Hartmut Kaiser 18 Jan '09

18 Jan '09

Hi all, at last year's BoostCon, one of the highlights was the authors corner track. These were 20-30 minute sessions held by Boost library authors talking about their libraries. Most of the attendees of those sessions found them to be very interesting and useful. At this year's BoostCon we would like to have a similar track again. Unfortunately by now we don't have any related submissions. So I thought I explicitly encourage boost authors who are planning to be in Austin this year to consider giving a 30 minute introductory talk about their libraries. This is not a huge effort in terms of preparation, but adds a lot to the conference. You can find the details about BoostCon and the submission process here: http://www.boostcon.com/program/call-for-sessions. Please spread the word! Regards Hartmut Program Chair

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[uitility/result_of] CodeGear support of result_of
by joaquin＠tid.es 18 Jan '09

18 Jan '09

Hi, Seemingly, CodeGear does not support boost::result_of http://tinyurl.com/8onbjj I propose that this is officially recognized so that including <boost/utility/result_of.hpp> results in BOOST_NO_RESULT_OF being defined rather than the current compile error. This will benefit those result_of-dependent libraries honoring BOOST_NO_RESULT_OF (vg. Boost.Parameter). Joaquín M López Muñoz Telefónica, Investigación y Desarrollo||* *

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[any] Will it be in C++0x?
by Andrey Semashev 17 Jan '09

17 Jan '09

Suddenly, it occurred to me that STL does not provide an instrument for dynamic typed variables (or variants). I didn't see such a tool in TR1 either. So, are there any plans to include such a tool in C++0x? Boost.Any seems to me a very simple, yet very useful example of utility of that kind. It would be great if STL provided a similar instrument out of box.

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[smart_ptr] make_shared performance
by Frank Mori Hess 17 Jan '09

17 Jan '09

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I've been doing a little benchmarking (trivial benchmark program attached) of boost::make_shared performance. With svn trunk, I don't see much improvement from using make_shared, in fact for large objects it is much slower. I would guess this is due to the increased overhead of copying sp_ms_deleter for large types. I wonder if anyone has any ideas for improving the situation? -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFJcP7d5vihyNWuA4URApVPAJ9EfS6MtkNHTUgb/gOTD/nRngPiUQCeL6K0 MtkmtRAmzKlN1m0eXO9t5k0= =LpQ1 -----END PGP SIGNATURE-----

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[interprocess] Arithmetic error
by Henrik Sundberg 17 Jan '09

17 Jan '09

Disclaimer: I have no minimal reproducing program. The problem occurs at line 458 in mapped_region.hpp: 456 //We calculate the difference between demanded and valid offset 457 std::size_t page_size = this->get_page_size(); 458 m_extra_offset = (offset - (offset / page_size) * page_size); I've found out that page_size gets the value 0. It only seems to happen in my single core computer. It works for other Kubuntu 8.10 systems. The code is needed during so-load. The library is used from two other libraries that are loaded by the program (like a diamond library load). I've been discussing the problem in this forum: http://www.safirsdk.com/forum/phpBB3/viewtopic.php?f=4&t=61 The code is open (available from the site of the forum). It is a whole framework though, not just a small program. I don't know if this is a compiler bug, a Boost bug or a bug in the program. I think that the page size is supposed to be cached, but that this somehow doesn't happen in this setup. I get the error every time. Preloading the library avoids the problem. I.e. starting like this works: LD_PRELOAD=libdots_kernel.so dobexplorer /$

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Mixing protocol
by Joel Falcou 17 Jan '09

17 Jan '09

So far BOOST proposes various prtocols for meta-function : - the result_of protocol - the apply<> protocol of MPL - the ::type protocol of traits Can those protocols be mixed somehow without any side-effects when used with the various aforementionned protocol ? -- ___________________________________________ Joel Falcou - Assistant Professor PARALL Team - LRI - Universite Paris Sud XI Tel : (+33)1 69 15 66 35

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[scope_exit] capture list syntax for scope_exit and local_function
by Alexander Nasonov 16 Jan '09

16 Jan '09

gmane wrote: > The following errors were found. Fix them, and submit again: > You seem to be top-posting. Don't do that. apparently gmane bug. Hi, My current implementation uses ref/cref/val prefixes to pass arguments. It's not consistent with C++0x lambda capture list syntax. scope_exit: (ref a)(cref b)(val c) c++0x: [&a, &b, c] I have a proof-of-concept implementation for BOOST_SCOPE_EXIT( (&a)(&b)(c) ) { std::cout << a << '\n' << b << '\n' << c << '\n'; } BOOST_SCOPE_EXIT_END It does not support passing by reference of classes with overloaded unary operator& but they are rather rare and we can tell users to use reference_wrapper to pass them. Also, it does indirect function call. Gcc 3.4 and 4.2 don't optimize it away even with -O3 but Intel 10.1 does (though, it generates a body of the function even with -Os). What do you think? #include <iostream> #include <boost/mpl/if.hpp> #include <boost/call_traits.hpp> #include <boost/type_traits/is_function.hpp> template<class T> inline T& deref(T* p, boost::false_type) { return *p; } template<class T> inline T& deref(T& r, boost::true_type) { return r; } void foo(int a, long const b, char const c) { int &a_ref_test(); int &b_ref_test(); int c_ref_test(); typedef boost::is_function<typeof(&a_ref_test)> is_not_ref_0; typedef boost::is_function<typeof(&b_ref_test)> is_not_ref_1; typedef boost::is_function<typeof( c_ref_test)> is_not_ref_2; typedef typeof(deref(&a, is_not_ref_0())) value_t_0; typedef typeof(deref(&b, is_not_ref_1())) value_t_1; typedef typeof(deref( c, is_not_ref_2())) value_t_2; typedef boost::mpl::if_< is_not_ref_0, boost::call_traits<value_t_0>::param_type, value_t_0 >::type param_t_0; typedef boost::mpl::if_< is_not_ref_1, boost::call_traits<value_t_1>::param_type, value_t_1 >::type param_t_1; typedef boost::mpl::if_< is_not_ref_2, boost::call_traits<value_t_2>::param_type, value_t_2 >::type param_t_2; struct params_t { value_t_0 &a; value_t_1 &b; value_t_2 c; params_t(param_t_0 &a, param_t_1 &b, param_t_2 c) : a(a), b(b), c(c) {} void invoke(void (*f)(param_t_0 &a, param_t_1 &b, param_t_2 c)) { f( deref(&a, is_not_ref_0()), deref(&b, is_not_ref_1()), deref( c, is_not_ref_2()) ); } }; params_t params( deref(&a, is_not_ref_0()), deref(&b, is_not_ref_1()), deref( c, is_not_ref_2()) ); void* p = ¶ms; struct guard_t { params_t* params; guard_t(void* p) : params((params_t*)p) {} ~guard_t() { params->invoke(&guard_t::body); } static void body(param_t_0 &a, param_t_1 &b, param_t_2 c) { std::cout << a << '\n' << b << '\n' << c << '\n'; } } guard(p); } int main() { foo(0, 1, '2'); } Thanks, Alex

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