May 2010 - Boost-users - lists.preview.boost.org

[ASIO] Resolve hostname to IPv4 or IPv6
by Alexander Lamaison 31 May '10

31 May '10

I'm trying to add IPv6 support to my program without breaking IPv4. What is the canonical way, if any, to do this win ASIO on Windows. My previous code to take the hostname of a server and resolve it to and IP looked like this: tcp::resolver resolver(m_io); tcp::endpoint endpoint; typedef tcp::resolver::query Lookup; Lookup query( endpoint.protocol(), host, lexical_cast<string>(port), Lookup::all_matching | Lookup::numeric_service); tcp::resolver::iterator endpoint_iterator = resolver.resolve(query); tcp::resolver::iterator end; error_code error = host_not_found; while (error && endpoint_iterator != end) { m_socket.close(); m_socket.connect(*endpoint_iterator++, error); } if (error) BOOST_THROW_EXCEPTION(system_error(error)); I originally though that all_matching would mean this code would resolve an IPv6 address if necessary but it doesn't. So I made the following changes: tcp::resolver resolver(m_io); typedef tcp::resolver::query Lookup; Lookup query( tcp::v6(), host_name, lexical_cast<string>(port), Lookup::all_matching | Lookup::v4_mapped | Lookup::numeric_service); This works on my test IPv6 setup but is it good enough? There are all sorts of things I don't understand like mapping and tunnelling so I'm looking for a best practice for IP-agnostic name resolution. Many thanks. Alex Lamaison -- SFTP for Windows Explorer (http://www.swish-sftp.org)

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[Interprocess] Problem with reserve for vector of weak_ptr
by Gaetan Gaumer 31 May '10

31 May '10

Hello, I'm currently trying to store shared_ptr to data in a vector in fixed_managed_shared_memory. The problem is that my program is crashing during a weak_ptr assignment. Since the problem is difficult to explain, I designed a little example which crash every time for me : #include <iostream> #include <algorithm> #include <boost/interprocess/managed_shared_memory.hpp> #include <boost/interprocess/smart_ptr/shared_ptr.hpp> #include <boost/interprocess/smart_ptr/weak_ptr.hpp> #include <boost/interprocess/containers/vector.hpp> #include <boost/interprocess/allocators/allocator.hpp> using namespace boost::interprocess; struct Foo { Foo( int _x ) : x(_x) {} ~Foo() { std::cout << "Destructing a Foo with x=" << x << "\n"; } int x; /* ... */ }; typedef managed_shared_ptr<Foo, fixed_managed_shared_memory>::type FooSharedPtrType; typedef managed_weak_ptr <Foo, fixed_managed_shared_memory>::type FooWeakPtrType; typedef allocator<FooWeakPtrType, fixed_managed_shared_memory::segment_manager> FooWeakPtrAllocatorType; typedef vector<FooWeakPtrType , FooWeakPtrAllocatorType> FooWeakPtrVectorType; struct FooPtrOps { void operator()( const FooWeakPtrType & a ) { std::cout << a.lock()->x << "\n"; } }; int main() { //Remove existing segment shared_memory_object::remove("MySharedMemory"); //Create a new segment with given name and size fixed_managed_shared_memory segment(create_only, "MySharedMemory", 65536); //Initialize shared memory STL-compatible allocator const FooWeakPtrAllocatorType alloc_inst (segment.get_segment_manager()); //Construct a vector named "MyVector" in shared memory with argument alloc_inst FooWeakPtrVectorType *foo_vector = segment.construct<FooWeakPtrVectorType>("MyVector")(alloc_inst); FooSharedPtrType foo_ptr = make_managed_shared_ptr(segment.construct<Foo>(anonymous_instance)(2), segment); foo_vector->reserve(1); (*foo_vector)[0] = foo_ptr; foo_vector->reserve(2); (*foo_vector)[1] = foo_ptr; foo_vector->reserve(3); (*foo_vector)[2] = foo_ptr; std::cout << "foo_vector:\n"; std::for_each( foo_vector->begin(), foo_vector->end(), FooPtrOps() ); } The crash occurs during the last assignment. Investigating using gdb it seems that just before the assignment the value of (*foo_vector)[2] is : {m_pn = {m_px = 0x0, m_pi = 0x4000000000000fe2}} Obviously the m_pi address is wrong which cause the crash. I think it should be 0x0 like m_px. So, did I do something wrong or did I find a bug ? Thanks for your help. Gaëtan.

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[statistics] chi-square test with boost
by Christine SINOQUET 31 May '10

31 May '10

Hello, I have to implement chi square tests. As I already use the boost library boost_1_38 for other purposes, I would like to use it for this purpose too. However I can find no documentation relative to this or the information I find is not correct. Can somebody indicate me how I can to use accumulators/statistics ? Is the boost_1_38 appropriate ? Which file should I include and which function should I use ? I just need to specify the columns in a matrix I wish to test for independence, the data itself and a threshold alpha. I would like the test statistic in return, as well as the p-value. If my question is not the object of this diffusion list, please tell me. Thank you in advance. Regards.

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Re: [Boost-users] spirit and property_tree headers conflict
by Artem Kozlov 30 May '10

30 May '10

> > On Thu, 27 May 2010 11:11:31 -0700 (PDT), Artem Kozlov<akz328(a)yahoo.com> > wrote: >> Hello, >> >> When attempting to compile a program which includes the following > headers >> (at once): >> >> #include<boost/property_tree/json_parser.hpp> >> #include<boost/spirit/include/qi.hpp> > > I suspect this is because the JSON parser is implemented in > Spirit.Classic. I eventually want to switch to Qi, but until then, I have > no idea what to do. I thought Classic and Qi can coexist, but maybe I'm > doing something wrong. > It should co-exist. What are the problems, exactly? Well, here is the bunch of errors that I see during compilation: /usr/include/boost/spirit/home/classic/attribute/closure_fwd.hpp:33: error: expected type-specifier /usr/include/boost/spirit/home/classic/attribute/closure_fwd.hpp:33: error: expected '>' /usr/include/boost/spirit/home/classic/attribute/closure.hpp:68: error: 'tuple_element' in namespace 'boost::phoenix' does not name a type /usr/include/boost/spirit/home/classic/attribute/closure.hpp:68: error: expected unqualified-id before '<' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp:88: error: invalid use of '::' /usr/include/boost/spirit/home/classic/attribute/closure.hpp:88: error: expected ';' before '<' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp: In constructor 'boost::spirit::classic::closure_context<ClosureT>::closure_context(const ClosureT&)': /usr/include/boost/spirit/home/classic/attribute/closure.hpp:75: error: class 'boost::spirit::classic::closure_context<ClosureT>' does not have any field named 'frame' /usr/include/boost/spirit/home/classic/attribute/closure.hpp: In member function 'ResultT& boost::spirit::classic::closure_context<ClosureT>::post_parse(ResultT&, const ParserT&, const ScannerT&)': /usr/include/boost/spirit/home/classic/attribute/closure.hpp:84: error: 'frame' was not declared in this scope /usr/include/boost/spirit/home/classic/attribute/closure.hpp:84: error: 'tuple_index' is not a member of 'boost::phoenix' /usr/include/boost/spirit/home/classic/attribute/closure.hpp:84: error: expected primary-expression before ')' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp: At global scope: /usr/include/boost/spirit/home/classic/attribute/closure.hpp:128: error: invalid use of '::' /usr/include/boost/spirit/home/classic/attribute/closure.hpp:128: error: expected ';' before '<' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp: In constructor 'boost::spirit::classic::init_closure_context<ClosureT>::init_closure_context(const ClosureT&)': /usr/include/boost/spirit/home/classic/attribute/closure.hpp:115: error: class 'boost::spirit::classic::init_closure_context<ClosureT>' does not have any field named 'frame' /usr/include/boost/spirit/home/classic/attribute/closure.hpp:115: error: 'convert_actors' is not a member of 'boost::phoenix' /usr/include/boost/spirit/home/classic/attribute/closure.hpp:115: error: expected primary-expression before '>' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp: In member function 'ResultT& boost::spirit::classic::init_closure_context<ClosureT>::post_parse(ResultT&, const ParserT&, const ScannerT&)': /usr/include/boost/spirit/home/classic/attribute/closure.hpp:124: error: 'frame' was not declared in this scope /usr/include/boost/spirit/home/classic/attribute/closure.hpp:124: error: 'tuple_index' is not a member of 'boost::phoenix' /usr/include/boost/spirit/home/classic/attribute/closure.hpp:124: error: expected primary-expression before ')' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp: At global scope: /usr/include/boost/spirit/home/classic/attribute/closure.hpp:144: error: 'tuple_element' in namespace 'boost::phoenix' does not name a type /usr/include/boost/spirit/home/classic/attribute/closure.hpp:144: error: expected unqualified-id before '<' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp:149: error: 'attr_t' was not declared in this scope /usr/include/boost/spirit/home/classic/attribute/closure.hpp:149: error: template argument 2 is invalid /usr/include/boost/spirit/home/classic/attribute/closure.hpp:212: error: redeclared with 13 template parameter(s) /usr/include/boost/spirit/home/classic/attribute/closure_fwd.hpp:62: note: previous declaration 'template<class DerivedT, class T0> struct boost::spirit::classic::closure' used 2 template parameter(s) /usr/include/boost/spirit/home/classic/attribute/closure.hpp:213: error: expected template-name before '<' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp:1009: error: 'actor_result' in namespace 'boost::phoenix' does not name a type /usr/include/boost/spirit/home/classic/attribute/closure.hpp:1009: error: expected unqualified-id before '<' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp:1017: error: 'actor_result' in namespace 'boost::phoenix' does not name a type /usr/include/boost/spirit/home/classic/attribute/closure.hpp:1017: error: expected unqualified-id before '<' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp:1032: error: 'actor_result' in namespace 'boost::phoenix' does not name a type /usr/include/boost/spirit/home/classic/attribute/closure.hpp:1032: error: expected unqualified-id before '<' token /usr/include/boost/spirit/home/classic/attribute/closure.hpp:1040: error: 'actor_result' in namespace 'boost::phoenix' does not name a type /usr/include/boost/spirit/home/classic/attribute/closure.hpp:1040: error: expected unqualified-id before '<' token Regards, Artem

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[gil] Compilation errors with MSVC10
by Christian Henning 30 May '10

30 May '10

Hi there, there seems to be some problems with the new MSVC10 compiler and bit_aligned images in gil. The following was compiling fine before I started using MSVC10. Here is some sample code: #include <vector> #include <algorithm> #include <boost/gil/gil_all.hpp> using namespace std; using namespace boost; using namespace boost::gil; int main(int argc, char* argv[]) { typedef bit_aligned_image1_type< 1, gray_layout_t >::type image_t; typedef image_t::view_t view_t; typedef view_t::reference pixel_t; typedef vector< unsigned char > buffer_t; typedef bit_aligned_pixel_iterator< pixel_t > it_t; vector< unsigned char > buf; it_t begin = it_t( &buf.front(), 0 ); it_t end = it_t( &buf.front(), 0 ); image_t img; image_t::view_t v = view( img ); std::copy( begin , end , v.row_begin( 0 ) ); return 0; } The error message is: c:\program files (x86)\microsoft visual studio 10.0\vc\include\xutility(2216): error C2665: 'std::_Copy_impl' : none of the 2 overloads could convert all the argument types Anyone, any idea? I'll keep investigating. Regards, Christian

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boost.MPI for a scheduler design
by Jack Bryan 30 May '10

30 May '10

Hi, I want to design an application program (C++) that can distribute computing tasks on a cluster with MPI installed. I would like to use boost.MPI to do the data communication and Rhapsodia.Schedulerto do the task scheduling. For example, I need to solve a big problem, which can be divided into multiple small tasks. These small tasks can be done independently on different nodes. So, when they are done, they return their results to one node, which combine their results into a solution for the big problem. Right now, the big problem has been programmed with C++. It is a sequential algorithm. I need to design a task/job scheduler that can do the above scheduling on cluster system so that the small tasks can be run in parallel. In this way, we can improve the performance of the sequential algorithm. Does my idea make sense ? Any help is appreciated. thanks Jack May 29 2010 _________________________________________________________________ Hotmail is redefining busy with tools for the New Busy. Get more from your inbox. http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:…

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base_from_member problem
by Olaf Peter 29 May '10

29 May '10

Hello, in the example attached I've got the compiler error base_from.cpp: In constructor ‘header_fixture::header_fixture()’: base_from.cpp:48: error: type ‘client::detail::header_grammar<boost::spirit::karma::detail::output_iterator<const char*, mpl_::int_<15>, boost::fusion::unused_type> >’ is not a direct base of ‘header_fixture’ /home/olaf/Projects/programming/cpp/boost/trunk/boost/utility/base_from_member.hpp:69: error: ‘client::detail::string_grammar<boost::spirit::karma::detail::output_iterator<const char*, mpl_::int_<15>, boost::fusion::unused_type> > boost::base_from_member<client::detail::string_grammar<boost::spirit::karma::detail::output_iterator<const char*, mpl_::int_<15>, boost::fusion::unused_type> >, 0>::member’ is protected where the 2nd error is due to the 1st one. Why does it not work? without karma::grammar it compiles. How to fix it? Thanks, Olaf

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Cannot compile boost mpi example
by Hernan Grecco 29 May '10

29 May '10

I have downloaded boost 1.43 and run many of the examples without a problem. However, I am not able to compile any of the parallel graph examples. I traced the problem to using boost MPI. For example when I compile the first example in: http://www.boost.org/doc/libs/1_43_0/doc/html/mpi/tutorial.html I get: /tmp/ccwOi38z.o(.text+0x132): In function `main': : undefined reference to `boost::mpi::environment::environment(int&, char**&, bool)' /tmp/ccwOi38z.o(.text+0x13b): In function `main': : undefined reference to `boost::mpi::communicator::communicator()' /tmp/ccwOi38z.o(.text+0x144): In function `main': : undefined reference to `boost::mpi::communicator::size() const' /tmp/ccwOi38z.o(.text+0x150): In function `main': : undefined reference to `boost::mpi::communicator::rank() const' /tmp/ccwOi38z.o(.text+0x1b1): In function `main': : undefined reference to `boost::mpi::environment::~environment()' /tmp/ccwOi38z.o(.text+0x1e2): In function `main': : undefined reference to `boost::mpi::environment::~environment()' MPI works fine as I have tested with the example in: http://www.boost.org/doc/libs/1_43_0/doc/html/mpi/getting_started.html#mpi.… I am running linux 64 bits, gcc 3.4. Thanks in advance, Hernan

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[phoenix][lambda] lambda to phoenix translation: get arguments from expression
by alfC 29 May '10

29 May '10

Hi I have a phoenix expression of type actor< composite< divides_eval, vector< LambdaExp, composite< minus_eval, vector< argument<0>, value<double> > > > > > f_expr with boost.lambda I could extract the different components (Lambda and the actual value stored by value<double>) from f_expr as: get<0>(f_expr.args) //for lambda and get<1>(get<1>(f_expr.args).args) //for lambda what is the equivalent for Boost.phoenix?, it seems that the phoenix actor doesn't have the member "args". something like at_c<1>(at_c<1>(f_expr)) seems to be in the right direction but it returns something of type value<double> from which I don't know how to extract the value in the same way at_c<1>(f_expr) returns the denominator, but it is not an actor, so it is not a lambda expression. the corresponding lambda type was: lambda_functor<lambda_functor_base< arithmetic_action<divide_action>, tuple< lambda_functor<// LambdaExp >,// lambda_functor<lambda_functor_base< arithmetic_action<minus_action>, tuple< lambda_functor< placeholder<1> >, double const // <-- attention adds const to avoid unreadable errors > > > > > > f_expr Thank you, Alfredo

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[lambda] helping lambda to deduce return type and then avoid 'ret<T>'
by alfC 29 May '10

29 May '10

Hi, the lambda manual says: "The return type deduction system may not be able to deduce the return types of some user defined operators or bind expressions with class objects. A special lambda expression type is provided for stating the return type explicitly and overriding the deduction system. To state that the return type of the lambda functor defined by the lambda expression e is T, you can write:" and indeed for even very simple arithmetic user-defined classes (for example boost.units quantities) the lambda expression is poluted with many many ret<T> statements, for example _1*_1/(_1+x)/(_1-x) becomes ret<anothertype>(ret<usertype>(_1*_1)/ ret<othertype>(ret<usertype>(_1+x)/ret<usertype>(_1-x))); the question is, is there a way to help lambda library to help deducing the return type to avoid the repeated use of ret<T>. Thank you, Alfredo

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