September 2011 - Boost-users - lists.preview.boost.org

multi-array and pdes
by petros 07 Nov '11

07 Nov '11

Hi, These can very well be very naive questions, since I am relatively new to this - apologies..: I am trying to write a pde solver for a 3D problem. Multi-array seems like a very natural choice for a data structure to store the functtion values. The method I am trying to use is operrator splitting. This amounts to solving a tridiagonal system for each dimension in sequence. Suppose then that I have a MA( M, N, L ): It is highly desirable to maintain this xyz (let's call it) "logical" system of reference since incorporation of boundary conditions and stencil calculations would be conceptually straightforward -otherwise very complicated. The idea being that, I would then have the tridiagonal opertator ( and rhs) in the "rotated" system and all other calculations in the "logical" one. Therefore, I need some fascility to rotate my MA, from the xyz to yzx etc (cyclically). Is there functionality ( as a view to the data ) that would allow me to do this off-the-shelve? Also, a couple of other points: -If I wanted to use views to subgrids, in parallelized calculations, are there memory allocations that happen under the hood for which I should worry (for performance)? -Is a one dimensional MA usable? -Are there adapters between 2D MAs and uBlas matrices? Thank you very much for your help in advance! P-

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Boost asio deadline_timer, bug?
by Allan Nielsen 13 Oct '11

13 Oct '11

Hi Is this a bug, or am I doing something wrong? #include <iostream> #include <boost/asio.hpp> #include <boost/bind.hpp> using namespace std; using namespace boost::asio; struct A { A(io_service & service) : timer1(service), timer2(service) { timer1.expires_from_now( boost::posix_time::seconds(5) ); timer1.async_wait(boost::bind(&A::handler, this, _1)); timer2.expires_from_now( boost::posix_time::seconds(2) ); timer2.async_wait(boost::bind(&A::interrupt, this, _1)); } void handler(const boost::system::error_code &ec) { cout << "Forbidden handler" << endl; assert(0); } void handler_interrupted(const boost::system::error_code &ec) { cout << "Hello world" << endl; } void interrupt(const boost::system::error_code &ec) { cout << "Interrupted" << endl; int res = timer1.cancel(); assert(res > 0); timer1.expires_from_now( boost::posix_time::milliseconds(0) ); timer1.async_wait(boost::bind(&A::handler_interrupted, this, _1)); } int count, max, timeout1, timeout2; deadline_timer timer1; deadline_timer timer2; }; int main() { io_service service; A a(service); service.run(); return 0; }

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testing command-line interface using Boost.Test
by Olaf Meeuwissen 11 Oct '11

11 Oct '11

Dear all, I've been using Boost.Test with Test First and TTD approaches to library development and am one happy hacker. All tests are integrated with our continuous integration setup so we get test reports with every build. Now I'm starting on a few command-line utilities and would like to use Boost.Test to do the same. I have something simple going now with a test fixture to help with redirecting standard input, output and error and running commands in a way that the test runner does not hang when a command-line invocation returns a failure status. The gist of my tests would be as follows when testing the GNU coreutils `true` and `false` utilities BOOST_AUTO_TEST_CASE (test_false) { BOOST_CHECK_EQUAL (EXIT_FAILURE, my_system ("false")); } BOOST_AUTO_TEST_CASE (test_true) { BOOST_CHECK_EQUAL (EXIT_SUCCESS, my_system ("true")); } where my_system() basically does explicitly what system() would do for you. See [1] for an implementation of my_system(). When using system() instead of my_system(), the test runner fails the first test incorrectly(!) and hangs. It starts but never finishes the second test. Using my_system() the first tests still incorrectly fails but now at least the second tests completes and succeeds as expected. The first test produces unknown location(0): fatal error in "test_false": child has exited; pid: 19788; uid: 1000; exit value: 1 and I assume it never gets to the comparison that BOOST_CHECK_EQUAL() is supposed to do. Any suggestions on how to get this to work? Maybe even alternative approaches to testing command-line interfaces? [1] http://www.gnu.org/software/libc/manual/html_node/Process-Creation-Example.… Thanks in advance, -- Olaf Meeuwissen, LPIC-2 FLOSS Engineer -- AVASYS CORPORATION FSF Associate Member #1962 Help support software freedom http://www.fsf.org/jf?referrer=1962

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Problems installing boost 1.47.0
by Allan Nielsen 10 Oct '11

10 Oct '11

Hi I'm trying to install boost 1.47 in a single threaded edition but it does not seems to work. Here is what I tried: ./bootstrap.sh --without-icu --without-libraries=graph_parallel,mpi,python ./b2 threading=single --layout=system --prefix=/usr/local Here is the error I got on the second command: Building the Boost C++ Libraries. Performing configuration checks - has_icu builds : yes - ../config//has_gcc_visibility builds : yes - ../config//has_long_double_support builds : yes /storage/src/boost_1_47_0/tools/build/v2/build/virtual-target.jam:1079: in virtual-target.register-actual-name from module virtual-target error: Duplicate name of actual target: <pstage/lib>libboost_system.so.1.47.0 error: previous virtual target { common%common.copy-libboost_system.so.1.47.0.SHARED_LIB { gcc%gcc.link.dll-libboost_system.so.1.47.0.SHARED_LIB { gcc%gcc.compile.c++-error_code.o.OBJ { error_code.cpp.CPP } } } } error: created from ./stage-proper error: another virtual target { common%common.copy-libboost_system.so.1.47.0.SHARED_LIB { gcc%gcc.link.dll-libboost_system.so.1.47.0.SHARED_LIB { gcc%gcc.compile.c++-error_code.o.OBJ { error_code.cpp.CPP } } } } error: created from ./stage-proper error: added properties: <threading>single <warnings>on error: removed properties: <threading>multi <warnings>all /storage/src/boost_1_47_0/tools/build/v2/build/virtual-target.jam:490: in actualize-no-scanner from module object(file-target)@2784 /storage/src/boost_1_47_0/tools/build/v2/build/virtual-target.jam:135: in object(file-target)(a)2784.actualize from module object(file-target)@2784 /storage/src/boost_1_47_0/tools/build/v2/build-system.jam:749: in load from module build-system /storage/src/boost_1_47_0/tools/build/v2/kernel/modules.jam:283: in import from module modules /storage/src/boost_1_47_0/tools/build/v2/kernel/bootstrap.jam:142: in boost-build from module /storage/src/boost_1_47_0/boost-build.jam:17: in module scope from module Is there anything I can do to fix this locally ?? Best regards Allan W. Nielsen

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a tuple from a pair?
by Krzysztof Żelechowski 07 Oct '11

07 Oct '11

How come a tuple, being a generalisation of a pair, cannot be constructed from one? I mean something along the lines make_tuple (pair const &p) { return make_tuple (p.first, p_second); } Would be good to have.

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[property_tree] Writing comments in JSON format
by Ruediger Berlich 07 Oct '11

07 Oct '11

Hi there, by trying it out with a modified debug_settings example, I can see that property_tree accepts Javascript ("//") comments inside of the JSON files it parses. I want to find out whether it makes sense to use JSON as an alternative to boost.program_options for configuration files. The idea would be to use a JavaScript-based GUI to modify or create the configuration files in a comfortable way and to use the same files as input for my C++-based programs. As my configuration files are auto-generated by my objects and not everybody loves GUIs, I need to be able to add comments to a property_tree object, so that they are emitted during a "write_json" call. The easiest way to add comments to the config files would be to just add a "comment" data member. This would indeed be very useful for the JavaScript usecase, as comments can be integrated into the GUI / Browser, and would still give guidance to those wanting to modify the JSON files with a standard editor. However, this does not help me to write things like a header, or to add information targeted only at those who modify the files by hand. For these I still need to be able to generate "//"-style comments. From the documentation I could not find out whether this can be done in a standard and portable way. Any pointer would be very welcome! Thanks and Best Regard, Ruediger

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[boost-users] [serialization] working example of (intrusive) serialization of class with no default constructor? and handling of nested classes with no default constructor
by alfC 07 Oct '11

07 Oct '11

Hi, this question has been asked thousand of times and I still can not see a detailed answer. How can I deserialize a class with no default constructor. The usual response is to point to this documentation http://www.boost.org/doc/libs/1_35_0/libs/serialization/doc/serialization.h… . I read the documentation many time and I can not figure out what does it mean and how it can be used. Does any body has a working small example where this is effectively used? Ideally, I am looking for something like the following, I am willing to accept other options, like making a2 a pointer, etc. int main(){ { A a( ... ); // proper construction syntax std::ofstream ofs("A.xml"); boost::archive::xml_oarchive oa(ofs); a & BOOST_SERIALIZATION_NVP(a); } { std::ifstream ifs("A.xml"); boost::archive::xml_iarchive ia(ifs); A a2(ia); // construct from iarchive or some other intermediate class { a2 & BOOST_SERIALIZATION_NVP(a2); //data can still be loaded in existing object (as usual) } } return 0; } Even if I want to implement my own reading of the xml_iarchive inside the constructor of A, it looks like I need to access the nested elements of the class before accessing to the level of the class (I am thinking in xml terms here). This is where I am stuck, the syntax above forces me to define A::A(boost::archive::xml_iarchive& ia){ ... } If all members are default constructible I can do: A::A(boost::archive::xml_iarchive& ia){ ia & BOOST_SERIALIZATION_NVP(*this); } (yes, the solution in intrusive but the at least I avoid default constructor at all cost) but if one of the member is not default constructible (and I can modify that class) I should be able to do something like, A::A(boost::archive::xml_iarchive& ia) : member1( ...ia?... ){ // ia & BOOST_SERIALIZATION_NVP(member2); // not possible because the archive is still waiting for class of type A to be read } which has two problems, 1) I need to access the elements of the archive (e.g. member2 before A is really handled by boost.serialization) 2.a) for member1 it regresses the problem to the member1 type, which is fine because all this objects will at some point be composed only from build-in "default constructible" types 2.b) if I have no way to modify member1 and it is not default constructible then I can't continue but that is also fine because that means that member1 was not serializable anyway. The real problem is 1). because if I have access to all the classes I will reach a point in which I have to read a built-in class from the iarchive, but I have have access to those nested elements directly, at least not with the documented interface. Thanks, Alfredo

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A forward iterator need not be default-constructible
by Krzysztof Żelechowski 04 Oct '11

04 Oct '11

== Problem == The following code fails to compile: #include <vector> #include <boost/iterator/transform_iterator.hpp> #include <boost/range/algorithm.hpp> #include <boost/range/adaptor/transformed.hpp> static inline void trigger (::std:: vector < int > const &p_v) { /* i: p_v [i] + 0 >= 0 */ ::boost:: lower_bound (p_v | ::boost:: adaptors:: transformed (::std:: bind1st (::std:: plus < int > (), 0)), 0); } Details: See [[#Evidence]]. == Workaround == The following definition causes the code to compile successfully, as of GNU C++ 4.6: #define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0 Disadvantages and risks: * The macro BOOST_RANGE_ENABLE_CONCEPT_ASSERT is undocumented. * It disables concept checking altogether, which may be a good thing or a bad thing, depending on your needs. The official motivation for concept checking is that it makes error messages more readable; in this particular case, I am not convinced. == Background == TL;DR: If all you can say is that such an iterator does not meet the requirements imposed by the standard, I am not interested. If you are willing not to treat the standard as the ultimate and unquestionable oracle, you may read on :-) The standard C++ library defined iterators to serve and additional task to serve as abstract pointers that may be singular, i.e. not corresponding to any object and distinct from any other iterator. To this end, the standard requires that interators may be constructed out of thin air, and that such an iterator is singular. This requirement is only useful iterators that do not correspond to containers like the standard input stream iterator which you can use to find something in it, and even then the end iterator, which is singular, is created explicitly by the calling code and not by library code. Requiring conformance to this particular requirement in Boost is counterproductive, as it causes perfectly valid and obvious code to fail to compile for no reason at all except for respecting the letter of the standard. == Conclusions == 1. The macro BOOST_RANGE_ENABLE_CONCEPT_ASSERT should be documented, as it is necessary to keep the concepts BS at bay. 2. The concept mechanism used by Boost should not require singular iterators to exist; the standard is obnoxious and misguided here and promotes sloppy coding. == Note == I believe that it is possible to design algorithms so that they do not construct singular iterators anywhere; moreover, I believe that doing so would be beneficial to the library implementation, as evidenced in GNU libstdc++ Bug #45488. (My similar report against Plauger’s library was declined by Microsoft, which means I have to use a replacement algorithm fixed by myself.) == Evidence == g++ -g doit.cpp -o doit In file included from doit.cpp:4:0: /usr/include/boost/iterator/transform_iterator.hpp: In constructor ‘boost::transform_iterator<UnaryFunction, Iterator, Reference, Value>::transform_iterator() [with UnaryFunc = std::binder1st<std::plus<int> >, Iterator = __gnu_cxx::__normal_iterator<const int*, std::vector<int> >, Reference = boost::use_default, Value = boost::use_default]’: /usr/include/boost/concept_check.hpp:130:10: instantiated from ‘boost::DefaultConstructible<TT>::~DefaultConstructible() [with TT = boost::transform_iterator<std::binder1st<std::plus<int> >, __gnu_cxx::__normal_iterator<const int*, std::vector<int> >, boost::use_default, boost::use_default>]’ /usr/include/boost/range/concepts.hpp:148:16: instantiated from ‘static void boost::concepts::requirement<boost::concepts::failed************ Model::************>::failed() [with Model = boost::range_detail::ForwardIteratorConcept< boost::transform_iterator<std::binder1st<std::plus<int> >, __gnu_cxx::__normal_iterator<const int*, std::vector<int> >, boost::use_default, boost::use_default> >]’ /usr/include/boost/range/concepts.hpp:264:1: instantiated from ‘boost::ForwardRangeConcept<const boost::range_detail::transform_range<std::binder1st<std::plus<int> >, const std::vector<int> > >’ /usr/include/boost/concept/detail/has_constraints.hpp:42:5: instantiated from ‘const bool boost::concepts::not_satisfied<boost::ForwardRangeConcept<const boost::range_detail::transform_range<std::binder1st<std::plus<int> >, const std::vector<int> > > >::value’ /usr/include/boost/concept/detail/has_constraints.hpp:45:31: instantiated from ‘boost::concepts::not_satisfied<boost::ForwardRangeConcept<const boost::range_detail::transform_range<std::binder1st<std::plus<int> >, const std::vector<int> > > >’ /usr/include/boost/mpl/if.hpp:67:11: instantiated from ‘boost::mpl::if_ <boost::concepts::not_satisfied<boost::ForwardRangeConcept<const boost::range_detail::transform_range<std::binder1st<std::plus<int> >, const std::vector<int> > > >, boost::concepts::constraint<boost::ForwardRangeConcept<const boost::range_detail::transform_range<std::binder1st<std::plus<int> >, const std::vector<int> > > >, boost::concepts::requirement<boost::concepts::failed************ boost::ForwardRangeConcept<const boost::range_detail::transform_range<std::binder1st<std::plus<int> >, const std::vector<int> > >::************> >’ /usr/include/boost/concept/detail/general.hpp:50:8: instantiated from ‘boost::concepts::requirement_<void (*)(boost::ForwardRangeConcept<const boost::range_detail::transform_range<std::binder1st<std::plus<int> >, const std::vector<int> > >)>’ /usr/include/boost/range/algorithm/lower_bound.hpp:45:1: instantiated from ‘typename boost::range_iterator<const ForwardRange>::type boost::range::lower_bound(const ForwardRange&, Value) [with ForwardRange = boost::range_detail::transform_range<std::binder1st<std::plus<int> >, const std::vector<int> >, Value = int, typename boost::range_iterator<const ForwardRange>::type = boost::transform_iterator<std::binder1st<std::plus<int> >, __gnu_cxx::__normal_iterator<const int*, std::vector<int> >, boost::use_default, boost::use_default>]’ doit.cpp:8:114: instantiated from here /usr/include/boost/iterator/transform_iterator.hpp:99:26: error: no matching function for call to ‘std::binder1st<std::plus<int> >::binder1st()’ /usr/include/boost/iterator/transform_iterator.hpp:99:26: note: candidates are: /usr/include/c++/4.6/backward/binders.h:109:7: note: std::binder1st<_Operation>::binder1st(const _Operation&, const typename _Operation::first_argument_type&) [with _Operation = std::plus<int>, typename _Operation::first_argument_type = int] /usr/include/c++/4.6/backward/binders.h:109:7: note: candidate expects 2 arguments, 0 provided /usr/include/c++/4.6/backward/binders.h:100:11: note: std::binder1st<std::plus<int> >::binder1st(const std::binder1st<std::plus<int> >&) /usr/include/c++/4.6/backward/binders.h:100:11: note: candidate expects 1 argument, 0 provided Kompilacja nie powiodła się make: *** [doit] Błąd 1

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[boost-newbie] g++ Version 3 (MinGW) and compiling boost
by Robert Hartmann 01 Oct '11

01 Oct '11

Hi there, does anyone could say me how can I compile Boost.Filesystem with MinGW: Is something wrong with my b2-call see below, or is my project-config.jam buggy? ========================= import option ; using gcc ; using python : 2.7 # version : E:/Programme/Python27 # cmd-or-prefix : E:/Programme/Python27/include # includes : E:/Programme/Python27/libs # libraries ; using mpi : : <find-static-library>mpi <library-path>"E:/Programme/MPICH2/lib" <include>"E:/Programme/MPICH2/include" : "\"E:\\Programme\\MPICH2\\bin\\mpiexec\"" ; option.set keep-going : false ; ========================== g++ (GCC) 3.4.2 (mingw-special) Copyright (C) 2004 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. gcc (GCC) 3.4.2 (mingw-special) Copyright (C) 2004 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. I got as error message for Boost.Filesystem: ./boost/filesystem/v3/config.hpp:49:5: #error Configuration not supported: Boost.Filesystem V3 and later requires std::wstring support That means Boost.Filesystem V2 should work? Can I compile it without other boost things? I run set BUILDPATH=G:/Downloads/Libraries/boost_1_47_0/ownbuild set INSTALLPATH=G:/Downloads/Libraries/boost_1_47_0/distrib b2 --prefix=%INSTALLPATH%/libs/boost-1.47.0/distrib ^ --toolset=gcc ^ --build-dir=%BUILDPATH% ^ --layout=versioned ^ --variant=debug,release ^ --runtime-link=static ^ --link=shared,static ^ --threading=multi ^ --without-mpi ^ --without-python stage >build.log 2>&1 And in build.log I found many errors after waiting some Minutes: ...failed updating 26 targets... ...skipped 30 targets... ...updated 842 targets... If I doesn't use the options --without-mpi --without-python than about 30 seconds later I got this output in build.log: ====================== G:/Downloads/Libraries/boost_1_47_0/tools/build/v2/build\virtual-target.jam:1079: in virtual-target.register-actual-name from module virtual-target error: Duplicate name of actual target: <pstage\lib>mpi.pyd error: previous virtual target { common%common.copy-mpi.pyd.PYTHON_EXTENSION { gcc%gcc.link.dll-mpi.pyd.PYTHON_EXTENSION { gcc%gcc.compile.c++-python\collectives.o.OBJ { python/collectives.cpp.CPP } } { [...] error: created from ./stage-proper error: added properties: <debug-symbols>off <define>NDEBUG <inlining>full <library>object(file-target)@4418 <library>object(file-target)@4420 <library>object(file-target)@4488 <library>object(file-target)@4490 <library>object(file-target)@4602 <library>object(file-target)@4604 <library>object(file-target)@4617 <library>object(file-target)@4619 <library>object(searched-lib-target)@4507 <optimization>speed <runtime-debugging>off <variant>release <xdll-path>/G:/Downloads/Libraries/boost_1_47_0/ownbuild/boost/bin.v2/libs/mpi/build/gcc-mingw-3.4.2/release/threading-multi <xdll-path>/G:/Downloads/Libraries/boost_1_47_0/ownbuild/boost/bin.v2/libs/python/build/gcc-mingw-3.4.2/release/threading-multi <xdll-path>/G:/Downloads/Libraries/boost_1_47_0/ownbuild/boost/bin.v2/libs/serialization/build/gcc-mingw-3.4.2/release/threading-multi error: removed properties: <debug-symbols>on <inlining>off <library>object(file-target)@2472 <library>object(file-target)@2474 <library>object(file-target)@2542 <library>object(file-target)@2544 <library>object(file-target)@2656 <library>object(file-target)@2658 <library>object(file-target)@2671 <library>object(file-target)@2673 <library>object(searched-lib-target)@2561 <optimization>off <runtime-debugging>on <variant>debug <xdll-path>/G:/Downloads/Libraries/boost_1_47_0/ownbuild/boost/bin.v2/libs/mpi/build/gcc-mingw-3.4.2/debug/threading-multi <xdll-path>/G:/Downloads/Libraries/boost_1_47_0/ownbuild/boost/bin.v2/libs/python/build/gcc-mingw-3.4.2/debug/threading-multi <xdll-path>/G:/Downloads/Libraries/boost_1_47_0/ownbuild/boost/bin.v2/libs/serialization/build/gcc-mingw-3.4.2/debug/threading-multi G:/Downloads/Libraries/boost_1_47_0/tools/build/v2/build\virtual-target.jam:490: in actualize-no-scanner from module object(file-target)@5073 G:/Downloads/Libraries/boost_1_47_0/tools/build/v2/build\virtual-target.jam:135: in object(file-target)(a)5073.actualize from module object(file-target)@5073 G:/Downloads/Libraries/boost_1_47_0/tools/build/v2\build-system.jam:749: in load from module build-system G:\Downloads\Libraries\boost_1_47_0\tools\build\v2/kernel\modules.jam:283: in import from module modules G:\Downloads\Libraries\boost_1_47_0\tools\build\v2\kernel\bootstrap.jam:142: in boost-build from module G:\Downloads\Libraries\boost_1_47_0\boost-build.jam:17: in module scope from module ============================== Please, can any one help me? Best regards, Robert

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question regarding Depth First Search algorithm
by Pablo Fleurquin 01 Oct '11

01 Oct '11

Hi, My name is Pablo Fleurquin.I am a student of M.Sc in Physics at the UIB (Palma de Mallorca, Spain) and I'm also working in the IFISC institute (Institute for Interdisciplinary Science and Complex Systems). I have a question regarding the Depth First Search algorithm. Ihave beenlooking at the Boost library page but I'm a newbie with this stuff. *Having a directed graph G (that could be a connected graph or not), I want my program to find the cycles within the graph and remove all the edges that are part of them. It doesn't matter which cycle is erased first as long as the result is the graph G without edge that formely were part of a cycle (in other words, the remaining edges are those that doesn´t form cycles) [attached is example1]* Intuitively, I am sure that using the depth_first_search() function and recalling it recursively for each "new" graph G "with less" cycles will finally arrive to graph G with no cycles. The problem is that I have the idea, but my knowledge of c++ is not so vast to implement this code. I would be gratefully, if you could show me a code for this implementation or a function that does that. Thank you. Pablo Fleurquin P.S: Example 2 is a situation that might happen. If the code can be implemented to eliminate these 2 cycles that share a link it would be greate, if not it will work fine as well.

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