November 2015 - Boost - lists.preview.boost.org

Status of the CMake-ification
by Louis Dionne 02 Jan '16

02 Jan '16

Dear Boost, I'd like to inquire about the status of the CMake-ification of Boost that had been started a while ago. AFAICT, the effort is completely stopped now; is this correct? Also, I'd like to poll the community to gauge interest in the rebirth of such an effort. __I'm not proposing myself to work on such a rebirth__, but I'm just curious to know what the community thinks about it. I, for one, would love to see it happen. Regards, Louis -- View this message in context: http://boost.2283326.n4.nabble.com/Status-of-the-CMake-ification-tp4681599.… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[smart_ptr] Moving cast for unique_ptr
by Karolin Varner 21 Dec '15

21 Dec '15

Hi all! There is the family of boost pointer cast (boost::static_pointer_cast, boost::dynamic_pointer_cast, ...) that allow a developer to write generic code by casting pointers regardless of whether they are some smart pointer (e.g. shared_ptr) or plain pointers. However, those functions have not been implemented for unique_ptr, because they create a copy of their pointer and unique_pointers can not be copied. In my case I still needed to cast some unique_ptr and since it's ok to move unique_ptrs I wrote a function that does exactly that. The code is below – Comments are very, very welcome. It works for my case, but I am sure it is not as generic and safe as it should be ;) . Specifically, for a library, it should be made to work on any kind of smart/plain pointer. Not just unique_ptr. Is there any interest to include a boost::static_moving_pointer_cast and the other types of casts in boost? Best, Karolin /// Dynamic cast a unique_ptr. /// /// This function shall move the pointer in in_ptr, into /// a new unique_pointer of the desire type, dynamic_casting /// it in the process. /// In given pointer shall contain a NULL pointer afterwards. /// /// If unsuccessful, function shall throw an error and leave /// in_ptr unmodified. /// /// This behaviour contrasts a bit with the behaviour of the /// normal dynamic_cast: /// 1. dynamic_cast copies objects, this moves them since /// unique_pointers can not be copied. /// 2. dynamic_cast returns a NULL pointer if the pointer to /// cast is of an incomplete type, this throws /// incomplete_cast instead, to ease error handling. /// /// @tparam T The type to convert to (as non-pointer) /// @tparam F The type to convert from (as non-pointer) /// @param in_ptr The unique_ptr to cast /// @return in_ptr, cast to the desired type template<typename T, typename F> std::unique_ptr<T> dynamic_moving_pointer_cast(std::unique_ptr<F> &in_ptr) { // Exception safety: If The dynamic cast throws an error, // or of we throw incomplete_cast, in_ptr will still be // unmodified T *plain_out_ptr = dynamic_cast<F*>(in_ptr.get()); if (plain_out_ptr == NULL && in_ptr.get() != NULL) throw incomplete_cast(); // Exception safety: Both operations are noexcept in_ptr.release(); return std::unique_ptr<T>(plain_out_ptr); }

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[variant] Opinion on boost::safe_get<> and default boost::get<> behavior
by Antony Polukhin 18 Dec '15

18 Dec '15

Hi all, I'm in doubt and would like to hear opinions on the following issue. boost::get for boost::variant was not making any compile time checks, resulting in runtime errors where a compile time error must be: boost::variant<int, string> v(100); boost::get<bool>(&v); // returns NULL instead of compile time error boost::get<bool>(v); // throws exception on runtime instead of compile time error Now we have an implementation of compile time checked get in a separate branch at git: boost::variant<int, string> v(100); boost::safe_get<bool>(&v); // compile time error boost::safe_get<bool>(v); // compile time error boost::unsafe_get<bool>(&v); // returns NULL instead of compile time error boost::unsafe_get<bool>(v); // throws exception on runtime instead of compile time error I'm in doubt, what the default behavior of boost::get must be: * safe_get behavior is much closer to Standard Library behavior (just like std::get for tuples) and allows to avoid errors in user code * unsafe_get behavior is same as behavior of old boost::get and won't break user's code if boost::get is used in some generic contexs What's your opinion? -- Best regards, Antony Polukhin

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[LOG] formatting_ostream API change
by Andrew Hundt 09 Dec '15

09 Dec '15

I had the following code, which worked in 1.58: #include <boost/log/trivial.hpp> #include <boost/exception/all.hpp> #include <boost/algorithm/string.hpp> /// @todo move elsewhere, because it will conflict with others' implementations of outputting vectors template<typename T> inline boost::log::formatting_ostream& operator<<(boost::log:: formatting_ostream& out, std::vector<T>& v) { out << "["; size_t last = v.size() - 1; for(size_t i = 0; i < v.size(); ++i) { out << v[i]; if (i != last) out << ", "; } out << "]"; return out; } I used it to output a std::vector<float> as follows: BOOST_LOG_TRIVIAL(trace) << “Real joint angles from FRI: " << realJointPosition << "\n"; However this now seems to fail in 1.59. I’ve created a github gist with the compiler output <https://gist.github.com/ahundt/5869dbd09e889b7153c3> in case that’s helpful as well. I see that the update recently had some breaking changes, what is the new way to provide the desired functionality? Thanks for your help. Cheers! Andrew Hundt

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interest in an asynchronous linear algebra library?
by Oswin Krause 07 Dec '15

07 Dec '15

Hi list, Disclaimer: What I am proposing here does not exist (yet). But it will in the near future and if there is interest i would like to give something back to the boost community. I would like to propose a new library to boost: asynchronous blas. What is it and what can I do with it? It is a linear algebra library where all computations are carried out in an asynchronous manner on GPU and CPU. Computing a matrix-matrix product does not block the current thread but instead launches a task which at some point returns with a result, allowing the main thread to continue until the result is needed. GPU and CPU tasks can be started at the same time depending on each other (e.g. a CPU computation waits until the GPU returned some needed result and vice-versa) Why is this important? Which problems does it solve? Many linear algebra libraries are target towards either a) solving a few large linear algebra problems b) solving many small similar problems This library is targeted towards the middle ground: a medium amount of decently sized problems. Here the problem is that it is often hard to use all the computing resources available as a single problem will not exhaust the device resources and there is no easy way to launch several similar tasks in parallel. This problem occurs often in GPU computing where out-of-order execution of kernels is used to fill up the device. Similarly, it is often hard to make CPU and GPU work together as GPU tasks are asynchronous while CPU tasks are often synchronous and it is not straight forward to couple both without blocking either CPU or GPU. How does it work? Expression templates similar to boost::ublas are used to create a dependency graph: which object is used in which computations and which tasks have to wait to ensure a correct outcome? a simple case would be two independent computations like matrix A=prod(B,trans(B)); matrix C=prod(trans(B),B); a normal library like ublas would wait until A is computed before C is evaluated. Instead, it can be more efficient to just add the two tasks to a list and let worker threads execute them as soon as resources are available. First the computation of A is put into the graph and A is marked as "being written to" while B is marked as "being read". When C is added to the list, it does not depend on the first computation as several tasks can read from B at the same time. So another worker thread can grab the task and execute it. If we now add the task B += prod(D,prod(C,trans(D)); the library computes it as matrix temp = prod(C,trans(D); B += prod(D,temp). temp can be computed as soon as C is computed. But B can only be computed after A and temp are computed as we can only write to B after all previous tasks using B are finished. Are you qualified? I am main contributor to https://github.com/Shark-ML/Shark/ and as part of it I forked ublas https://github.com/Shark-ML/Shark/tree/master/include/shark/LinAlg/BLAS which now uses several linear algebra libraries as possible backends (ATLAS, openBLAS...). What is the timeline? I would start developing a minimal example ASAP based on the rewrite of ublas above. I would use a minimum set of features (only dense square matrices) and basic GPU support. Opinions? Best, Oswin

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Boost 1.60.0 beta 1 Release Candidate 2 available for testing
by Marshall Clow 04 Dec '15

04 Dec '15

Release candidate files for 1.60.0 beta 1 are available at http://boost.cowic.de/rc/ As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. This helps ensure the candidates build OK before we push them out to SourceForge. Changes since rc1: * Boost.Sprit has been updated and Boost.Log now builds. * Boost.Math has been updated and now builds. Known issues: * Errors when building libraries for visual studio: test and type_erasure. * Boost.Test fails when building on Darwin with gcc 4.9.2 The files (and associated md5s) are: MD5 (boost_1_60_0_b1_rc2.7z) = dd38daa9378a6002fc12da0cab695511 MD5 (boost_1_60_0_b1_rc2.tar.bz2) = f3c9ffc14db3b2e55c7c5c703e69883d MD5 (boost_1_60_0_b1_rc2.tar.gz) = 89365262443cc16990b69f8e4b8b47ab MD5 (boost_1_60_0_b1_rc2.zip) = 3389bd4595a989fe95966440cbe45ca9 Thanks! -- The release managers

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compilation errors with ublas / cppad
by Peter Caspers 30 Nov '15

30 Nov '15

Hi, I think this has been asked before, but since I am not aware of any answer, I would like to bring up the topic again: When using CppAD::AD<double> with boost ublas, certain compilation errors show up. I attach a small example (ublas_cppad.cpp) and the (start of the) error messages I get (compilation_errors.txt, produced with boost 1.59.0, g++ 4.9.3, CppAD-20151124). The problem is in matrix_assign.hpp; when changing template<class E1, class E2, class S> BOOST_UBLAS_INLINE bool equals (const matrix_expression<E1> &e1, const matrix_expression<E2> &e2, S epsilon, S min_norm) { return norm_inf (e1 - e2) < epsilon * std::max<S> (std::max<S> (norm_inf (e1), norm_inf (e2)), min_norm); } to template<class E1, class E2, class S> BOOST_UBLAS_INLINE bool equals (const matrix_expression<E1> &e1, const matrix_expression<E2> &e2, S epsilon, S min_norm) { S tmp = norm_inf (e1 - e2); return tmp < epsilon * std::max<S> (std::max<S> (norm_inf (e1), norm_inf (e2)), min_norm); } the example code compiles without errors. Can someone point out, how this should be fixed (either on boost or CppAD side)? In general, are there requirements for a type T to cooperate with ublas matrices one should be aware of? Thank you Peter

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Is master branch open for bug fixes?
by Vicente J. Botet Escriba 30 Nov '15

30 Nov '15

Hi, the calendar says that master branch is open for bug fixes, but not mail has been sent to to notify it. Could some release manager confirm that? Best, Vicente

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[program_options] empty string argument
by Benedek Thaler 30 Nov '15

30 Nov '15

Hi, I have the exact same problem: http://boost.2283326.n4.nabble.com/ProgramOptions-explicit-empty-string-arg… --compression '' gave me a specified, empty compression switch value, as expected, on boost 1.58. However, on 1.59, the empty string counts against the positional arguments, and causes regressions. Also, --compression='' gives: The argument for option '--compression' should follow immediately after the equal sign. What is the recommended workaround? Is it planned to be fixed/changed? Thanks, Benedek

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[Boost.LLVM] Synopsis now available
by Andy Jost 29 Nov '15

29 Nov '15

I've created a new GitHub repository for this project and uploaded a synopsis of the proposed interface. I redesigned the interface, so it differs slightly from the prototype code and examples I gave before. Please take a look and provide feedback if you can! https://github.com/andyjost/Boost.LLVM/blob/master/boost_llvm.cpp -Andy

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