January 2013 - Boost - lists.boost.org

[thread] thread::join() + thread::interrupt() not reliable?
by Oliver Kowalke 14 Jan '13

14 Jan '13

Hi, following code does not work reliable - sometimes the output is thread_interrupted thrown by t1 in main(): false thread_interrupted thrown by t1 in fn2(): false done and sometimes I get an exception terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::thread_resource_error> >' what(): boost thread: thread not joinable: Invalid argument I would expect that thread_interrupted will be catched in main() and fn2() as the documentation describes. Oliver #include <iostream> #include <boost/assert.hpp> #include <boost/bind.hpp> #include <boost/thread.hpp> void fn1( boost::barrier * b) { b->wait(); boost::this_thread::interruption_point(); } void fn2( boost::thread * t1, boost::barrier * b, bool * interrupted) { t1->interrupt(); b->wait(); try { t1->join(); } catch ( boost::thread_interrupted const&) { * interrupted = true; } } int main() { bool interrupted1 = false, interrupted2 = false; boost::barrier b( 2); boost::thread t1( boost::bind( fn1, & b) ); boost::thread t2( boost::bind( fn2, & t1, & b, & interrupted2) ); try { t1.join(); } catch ( boost::thread_interrupted const&) { interrupted1 = true; } t2.join(); std::cout << "thread_interrupted thrown by t1 in main(): " << std::boolalpha << interrupted1 << "\n"; std::cout << "thread_interrupted thrown by t1 in fn2(): " << std::boolalpha << interrupted2 << "\n"; std::cout << "done\n"; }

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[1.53.0] Beta1 release available
by Marshall Clow 14 Jan '13

14 Jan '13

Boost release 1.53.0 beta 1 is now available from SourceForge. See https://sourceforge.net/projects/boost/files/boost/1.53.0.beta.1/ This release contains numerous enhancements and bug fixes for existing libraries. For details of what's in the release, see http://www.boost.org/users/history/version_1_53_0.html. Please download the beta, give it a try, and report any problems you encounter. Thank you, -- The Boost Release Team Beman Dawes, Eric Niebler, Rene Rivera, Daniel James, Vladimir Prus and Marshall Clow.

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Boost.iostreams on Android - Fails on multichar input filters
by Sukender 14 Jan '13

14 Jan '13

Hi, I found iostreams "filtering_stream_test" to fail under Android (32 bits, gcc 4.6, boost 1.52.0) : " Running 18 test cases... read_input_filter_test.hpp(88): error in "read_input_filter_test": failed reading from a filtering_istream in chars with a multichar input filter read_input_filter_test.hpp(101): error in "read_input_filter_test": failed reading from a filtering_istream in chunks with a multichar input filter " Note : I ran some tests by compiling on the host machine (64-bits Linux), then manually copying/running on the (emulator) device (using "adb push" / "adb shell"). I know Android is not actively maintained, but I need multichar filters (gzip_compressor & gzip_decompressor are multichar and thus fail). And I wonder why this test fails. I could not run the regression test on iOS, but my original code (using gzip_decompressor) works as expected under iOS, and Windows, and MacOSX. I have no clue about how to solve the issue. Any idea? Thank you. Cheers, Sukender

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Re: [boost] Flow-based programming library for Boost?
by Marcus Tomlinson 13 Jan '13

13 Jan '13

>> * You use a bus of input/output untyped signals. Why the signals are not >> typed? 1. Flexibility - inputs and outputs can dynamically accept changing signal types. E.g. Varying sample size in an audio stream. 2. Less coding, more expandability - the component designer need not specify the types required at each input / output when configuring IO, only how many. Consider the situation where you would like to update a component to accept int instead of bool for one of its inputs. This would (in your implementation) require you to edit multiple sections of code. With DSPatch, you need only edit / add to the process method. 3. Allow for generic virtual base process method (explained below). >> * Why do you need that the process function be virtual? This is due to the way the circuit works in DSPatch. When a component is required to process, the circuit needs a way of triggering it without having to know anything about the specifics (input / output count, types etc.) of that particular component. A generic inherited virtual method guarantees this kind of catch-all interface. >> // 1. Derive component class from DspComponent >> // =========================================== >> class DspAnd : public DspComponent<DspAnd, InPort<bool>,InPort<bool>, >> OutPort<bool>> >> { >> typedef DspComponent<DspAnd, InPort<bool>,InPort<bool>, OutPort<bool>> >> base_type; >> public: >> // 2. Configure component IO buses >> // =============================== >> DspAnd(DspComponentBase& parent, Signal<bool>& x, Signal<bool>& y, >> Signal<bool>& o) >> : base_type(parent, x, y, o) >> { >> } These requirements for component construction are quite overwhelming. There is a lot to remember (and type) every time you need to create / edit a component. Besides, as mentioned before, flexibility is paramount with DSPatch. This kind of static IO configuration goes against DSPatch's design (more on this later). >> protected: >> // 3. Implement a non-virtual operator() method >> // ====================================== >> bool operator()(bool x, bool y) >> { >> return x && y; >> } >> }; Having to keep track of every component input and output (count, types, etc) in multiple places (constructor, operator(), and in external use) seems overly complex and difficult to expand on / maintain. And again, static IO configuration is quite limiting. >> void main() >> { >> // 1. Create a DspCircuit where we can route our components >> // ======================================================== >> DspCircuit circuit; >> // 2. Create the internal signals >> DspSignal<bool> i1, i2, o; >> // ======================================================== >> // 3. Create instances of the components needed for our circuit and >> connect the signals and the ports >> // ============================================================ >> DspRandBool randBoolGen1(circuit, i1); >> DspRandBool randBoolGen2(circuit, i2); >> DspAnd logicAnd(circuit, i1,i2,o); >> DspPrintBool boolPrinter(circuit, o); Firstly, I like how the signals are referenced externally and are common between all components. This is something I need to improve on in the circuit class. ATM there is a fair amount of data copying going on. I assume that in your idea of this type of implementation, there is still a means of disconnecting and reconnecting signals at a later point? Wiring and rewiring at runtime is a large emphasis of the DSPatch design. I'm not sure wiring at construction is all that important though -I especially don't think it should be mandatory. This looks like the kind of code you'd find in other dataflow libraries. However, this is exactly why I designed DSPatch, and why I designed it the way I did. In my opinion, the code is convoluted (doesn't read well). But alas, I fear that most people actually prefer this kind of syntax over mine. >> Components with several outputs should define a operator() returning the >> tuple of outputs. Much like your implementation of input configuration, tuples have to be defined at compile time and hence can't be adjusted at a later point. By design, DSPatch avoids static IO, in fact it tries to avoid anything that is static. Not only does DSPatch allow you to adjust IO types and runtime, you can add / remove IO dynamically too. E.g. An AI minimax tree where each node dynamically creates a new output, and a feedback input for each possible player move from current position. It may be worth mentioning (again) that DSPatch was originally designed for audio DSP applications (hence the name). Therefore runtime features like branch synchronization, dynamic routing, and adaptive IO signal types are all part of the core design requirements. These features then subsequently cover a very large range of applications, allowing for small, simple static circuits, to large, complex dynamic circuits. I hope this helps you understand why DSPatch is designed the way it is.

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[1.53] [multiprecision] Still time for bug fixes?
by John Maddock 12 Jan '13

12 Jan '13

If there's still time (and the test results need to cycle first), I'd like to merge this bug fix: https://svn.boost.org/trac/boost/changeset/82460 for this bug: https://svn.boost.org/trac/boost/ticket/7878 Which causes integer division to fail in some cases. Thanks, John.

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Re: [boost] [non-instrusive move] interest in new library?
by THOMAS JORDAN 11 Jan '13

11 Jan '13

Thomas Jordan wrote: >Jeffrey Lee Hellrung, Jr. wrote >> You didn't really expound on the implementation, but, if I had to guess, >> you'd also require your types to be default constructible, and it would >> perform suboptimally (worse than leaving the move call out) if the swap >> member function was equivalent to std::swap. I think this might preclude >> its use in generic contexts and limit its use to situations where you >> *know* the type is std::vector-like. Let me know if I'm presuming >> incorrectly :) >> > >Yes, it certainly requires the types to be default constructible. > ><snip> > >The alternative would be to have just the single, default, template move >function: > >//pseudo-code >move(T& left, T& right) > >plus a pair of template functions to move to and from temporaries >respectively: > >T move(T& x) >void move(const T& from, T& to) > >then have optimised move functions defined on a per-type basis, e.g., > >MyClass >{ > void swap(MyClass& other) > { > //efficient swap member > } > > friend void swap(MyClass& lhs, MyClass& rhs){} > > friend void move(MyClass& lhs, MyClass& rhs) > { > lhs.swap(rhs); > } >} > >as well as overloads defined for any cheap-to-swap library types >interested in: > >void move(std::vector& lhs, std::vector& rhs){} >void move(boost::function& lhs, boost::function& rhs){} >etc. > >Although this is safer in that it should ensure optimality - and is >actually where I started - it requires more boilerplate to be written, >though there may be way(s) to automate the generation of the the >user-type's move function. Also, with the library move functions >implemented like this, you could still write algorithms like >move()/move_backwards() (and helper functions >such as iter_move() to move the values between two iterators) generically. Also generic overloads of the move() function would be provided for built in arrays and e.g., boost::array //pseudocode void move(boost::array<T,N>& from, boost::array<T,N>& to){} void move(T (& left)[N], T (& right)[N]){} which would be implemented with a call to move(left[i], right[i]) for each element, in which case the elements would be swapped if a move overload has been defined for the element type, copied otherwise, thereby preserving optimality. It would work for multi-dimensional (boost) arrays in a recursive fashion. >So I guess the new question is, would this even smaller library be of >any interest? >Its use-cases would be the same as described in my original post, just >to reiterate: > >//use-case: returning a argument directly from a function > >std::string foo(std::string s) >{ > //e.g., append something to s > //... > > //compiler can perform rvo (compiler would likely not > //perform nrvo if just used 'return s;') > > return move(s); >} > > >//use-case: moving a value to a function/ctor, when the value is not >//required by the calling code after the function/ctor call > >std::string s("hello"); >void bar(std::string s){...} > >bar(s); //copy >bar(move(s)); //move >//s has now been moved out of > > >//use-case: moving a value into place >void MyClass::MyClass(std::string s) >{ > //move value from s into default constructed member s_ > move(s, s_); >} > >Note that the combination of both moving a value to a function/ctor and >then moving it into place, e.g., > >std::string lv; >//... > >MyClass mc(move(lv)); > > >effectively results in a zero-copy invocation, with just a small number of >fixed size swap, default ctor and shallow dtor calls, so this is pretty >efficient. >//use-case: moving a temporary into an lvalue >std:: string lv; >move(foo(), lv); > > >> - Jeff >Tom Tom

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Re: [boost] [non-instrusive move] interest in new library?
by Thomas Jordan 11 Jan '13

11 Jan '13

Joseph Gauterin wrote: > Out of curiosity, how are you detecting if a member function swap exists? >> it detects at compile-time if the type of the >> argument(s) has a member swap function //Type trait to determine whether a type has a swap() member function //Uses SFINAE and the "sizeof trick" from the book "C++ Template Metaprogramming" //by Abrahams and Gurtovoy template<typename T> struct has_swap { typedef char yes; typedef char (&no)[2]; //SFINAE eliminates this when the type is invalid template <typename U, U> struct Check; //this overload will be selected if the Check type is valid template <typename U> static yes Tester(Check<void(U::*)(U&), &U::swap>*); //overload resolution prefers anything at all over ... template <typename U> static no Tester(...); static bool const value = sizeof(Tester<T>(0)) == sizeof(yes); }; > > In general, there's no way of knowing if a member swap function is > more efficient than a single assignment. It isn't even for all the > examples you gave - boost::array<T,N>::swap performs N boost::swaps, > which, if T doesn't provide an efficient swap, results in N calls to > std::swap, and 3*N assignments. In general I'm wary of using swap in a > generic context unless the intent is to swap (i.e. not as a potential > optimization of assignment). Thanks, point taken. I've responded to the exact same point in Jeffrey Lee Hellrung Jr.'s comment on my original post, and also made some alternative suggestions. Would certainly appreciate any further feedback you have there.

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Boost.Exception and constexpr
by Marshall Clow 10 Jan '13

10 Jan '13

I was playing around with Boost.Array tonight, seeing if I could make the signatures more closely match std::array. Specifically, I wanted to add 'constexpr' to "operator [] (size_t) const" and "at (size_t) const"as proposed in http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3470.html But I ran into a problem. Here are the implementations: const_reference operator[](size_type i) const { BOOST_ASSERT_MSG( i < N, "out of range" ); return elems[i]; } const_reference at(size_type i) const { rangecheck(i); return elems[i]; } static void rangecheck (size_type i) { if (i >= size()) { std::out_of_range e("array<>: index out of range"); boost::throw_exception(e); } } BOOST_ASSERT does not fit into the constexpr world at all, and neither does rangecheck. I could rewrite rangecheck so it could be constexpr, but only (I believe) by throwing the exception directly, rather than using boost::throw_exception. static void rangecheck (size_type i) { if (i >= size()) throw std::out_of_range e("array<>: index out of range"); } or even just: BOOST_CONSTEXPR const_reference at(size_type i) const { return i >= size () ? throw std::out_of_range e("array<>: index out of range") : elems[i]; } Has anyone put any effort into making Boost.Exception (and BOOST_ASSERT) work with constexpr? -- Marshall Marshall Clow Idio Software <mailto:mclow.lists@gmail.com> A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait). -- Yu Suzuki

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Re: [boost] [mailman] trouble with list subscription
by Eric Niebler 10 Jan '13

10 Jan '13

Thanks for your timely response, DongInn. No worries, **it happens. Eric On 1/10/2013 11:47 AM, DongInn Kim wrote: > OK, guys. It seems to be back to normal. > > I am sorry for all the inconveniences and troubles with the mailman websites. > > Regards, > > -- > - DongInn > > On Jan 10, 2013, at 2:34 PM, Marshall Clow wrote: > >> >> On Jan 10, 2013, at 11:19 AM, DongInn Kim <dikim(a)cs.indiana.edu> wrote: >> >>> I am sorry for this. I am working on it. I will be back with you guys soon. >> >> Thank you! >> -- Marshall >> >>> On Jan 10, 2013, at 2:18 PM, Marshall Clow wrote: >>> >>>> I'm seeing this too >>>> -- Marshall >>>> >>>> >>>> Begin forwarded message: >>>> >>>>> From: Eric Niebler <eric(a)boostpro.com> >>>>> Subject: [boost] [mailman] trouble with list subscription >>>>> Date: January 10, 2013 10:46:39 AM PST >>>>> To: Boost mailing list <boost(a)lists.boost.org>, DongInn Kim <dikim(a)osl.iu.edu> >>>>> Reply-To: boost(a)lists.boost.org >>>>> >>>>> Many of the subscription links on >>>>> <http://www.boost.org/community/groups.html> are currently taking me to >>>>> a mailman error page. See for instance >>>>> <http://lists.boost.org/mailman/listinfo.cgi/boost>. I'm guessing this >>>>> has to do with the recent upgrade of the mailman software that DongInn >>>>> did. Does something need to change on the Indiana side, or are our links >>>>> out of date?

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[mailman] trouble with list subscription
by Eric Niebler 10 Jan '13

10 Jan '13

Many of the subscription links on <http://www.boost.org/community/groups.html> are currently taking me to a mailman error page. See for instance <http://lists.boost.org/mailman/listinfo.cgi/boost>. I'm guessing this has to do with the recent upgrade of the mailman software that DongInn did. Does something need to change on the Indiana side, or are our links out of date? -- Eric Niebler BoostPro Computing http://www.boostpro.com

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