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boost::iostreams output filter doesn't work
by John Hendrix 11 Feb '11

11 Feb '11

Hi all, I desire to use boost::iostream input and output filters. I cannot make the "Filter Usage Examples" (para2.2.2) shown here () to work. the following, as far as I can tell, is exactly the same "Ordinary OutputFilter" example shown at (http://tinyurl.com/45bur3o) struct toupper_filter { typedef char char_type; typedef boost::iostreams::output_filter_tag category; template<typename Sink> bool put(Sink& snk, char c) { return boost::iostreams::put(snk, toupper((unsigned char) c)); } }; the following code is modeled on the code at para2.2.2, "Filter Usage Examples": int main(int argc, char *argv[]) { // read my_input.txt and save uppercase version of text into datastore.txt std::ifstream pt_input; pt_input.open("my_input.txt"); std::ostringstream oss; oss << pt_input.rdbuf(); // oss now contains the text stored in input text boost::iostreams::filtering_ostream out_stream; // the following line is expected to transform the input text to uppercase. // instead it causes no text to appear in the output file. If the following line of // code is commented-out then contents of "my_input.txt" is placed in "datastore.txt". out_stream.push(toupper_filter()); out_stream.push(boost::iostreams::file_sink("datastore.txt")); out_stream.write( oss.str().c_str(), oss.str().length()); out_stream.flush(); } I am obviously doing not adding the toupper_filter into the filter chain correctly. Can anyone point out what I am doing wrong? many thanks

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Re: [Boost-users] Generating Multinomial Random Numbers
by Stephan Kitchovitch 11 Feb '11

11 Feb '11

Thanks Steven, > The binomial_distribution implementation in the current release is very slow for large n. > I've written a replacement that should be reasonably fast. It will be released in 1.47. Do you know for roughly what range of n the binomial_distribution provided becomes very slow? It would be useful to know whether computing for, say, n approx. 10 or 100 would be efficient. I need to generate from a multinomial for a stochastic simulation. n is unlikely to be very large, however this generation (as well as some based on the gamma distribution) will need to be done at every time step and thousands of simulations would need to be executed. For this reason I would like to make this generation step as efficient as possible. Will it be a while before version 1.47 is released? Cheers, Stephan

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Re: [Boost-users] [Serialization] Registering containers ofuser-provided types
by Vivek 11 Feb '11

11 Feb '11

Robert Ramey wrote: > The rub here is your requirement that it be exported through a base class pointer. That's exactly right. The library stores user-defined types and returns them to user code, but doesn't know what those types are ahead of time, hence the need to serialize via base pointers. As it is, the BOOST_EXPORT_* macros require I know the types even before compile time (i.e. at the time of writing the library code)... I basically need a way of registering the type at a point between when I've written the code and when it is compiled (which I guess only comes up as an issue for those writing libraries). That would be the way to do it. However, someone proposed a solution > to this problem and uploaded it as a track item. I found it intriguing, > But I decided not to implement it to keep the library from getting > any more complicated than it already is. You might want to > paste this proposed enhancement into your own code. Do you have a ticket number or link for this?

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Boost::Asio on ARMV5TE
by Peter Meyer 11 Feb '11

11 Feb '11

Hi, i've wrote a litte proxy using boost::asio (boost 1.45). Program runs well on Intel (Linux kernel 2.6.35.10 and gcc 4.5.1). Same code cross compiled for ARMV5TE (Linux 2.6.24.4 and GCC 4.1.2 or GCC 3.4.3) crashes always at the same point. Stacktrace looks like this Program terminated with signal 11, Segmentation fault. #0 0x400e3e20 in ?? () (gdb) backtrace #0 0x400e3e20 in ?? () #1 0x0001cfb0 in boost::asio::detail::posix_mutex::lock (this=0x7d) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/posix_mutex.hpp:52 #2 0x0001cfe6 in scoped_lock (this=0xbe8a98d0, m=@0x7d) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/scoped_lock.hpp:36 #3 0x00069bf4 in boost::asio::detail::epoll_reactor::run (this=0x191538, block=true, ops=@0xbe8a994c) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/impl/epoll_reactor.ipp:275 #4 0x0006a06c in boost::asio::detail::task_io_service::do_one (this=0x1914e0, lock=@0xbe8a99d4, this_idle_thread=0xbe8a9990) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/impl/task_io_service.ipp:264 #5 0x0006a33c in boost::asio::detail::task_io_service::run (this=0x1914e0, ec=@0xbe8a9a0c) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/impl/task_io_service.ipp:130 #6 0x0006a426 in boost::asio::io_service::run (this=0xbe8a9bc4) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/impl/io_service.ipp:57 #7 0x00073504 in proxy::Server::run (this=0xbe8a9bb4) at server.cpp:71 #8 0x0004e2a4 in main (argc=3, argv=0xbe8a9da4) at proxy.cpp:111 It looks like the internal epoll_events data structure (descriptior_state) is corrupted. Any advice is welcome. With best regards Peter ------------------------------------------------------------------------------------

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Generating Multinomial Random Numbers
by Stephan Kitchovitch 10 Feb '11

10 Feb '11

Hello, I was looking through the Math/Statistical Distributions and Random boost libraries to see if they provide an efficient way to generate random numbers from the multinomial distribution. I have read that one way of achieving this is to generate from binomial distributions sequentially, although I am uncertain as to how efficient this approach would be. Are there any alternative efficient approaches I could use? Does boost provide any other libraries that may help with this? If anyone could recommend another reliable random number generator that does generate from a multinomial dist it would be great! Thanks in advance. Regards, Stephan

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[boost.any] Inline allocation of small objects in any.
by Adarsh Soodan 10 Feb '11

10 Feb '11

Hi, The frequent heap usage of boost::any was problematic to me for small object sizes. So I made a small tweak in boost::any which provides inline allocation of objects smaller than a certain template defined size. It practically eliminated the performance overhead of heap allocation and deallocation in my project while providing all benefits of boost::any. You can see the changed file at http://gitorious.org/athi/athi/blobs/master/core/any.hpp It is not cleaned up, but I thought it worthwhile to have any comments from somebody who solved the same problem. Thanks, Adarsh

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[Serialization] Registering containers of user-provided types
by Vivek 10 Feb '11

10 Feb '11

I am writing a library that will handle storing and serializing user-defined types. The user-defined types are required to be themselves serializable. However the library uses templates to create containers of user types. These containers are then serialized through a base class pointer. I don't know how to export the container types to boost::serialization through the templates. The only way I can do it is to force the user of the library to BOOST_CLASS_EXPORT_GUID() every container type. I've tried unpacking the macro by looking at boost/serialization/export.hpp, but it is slightly complex... Is there a way to export a class as part of the template instantiation? Or another way to write the library to easily serialize containers of user-defined types? Thanks -v Example code: #include <iostream> #include <vector> #include <boost/foreach.hpp> #include <boost/serialization/access.hpp> #include <boost/serialization/vector.hpp> #include <boost/serialization/base_object.hpp> #include <boost/serialization/export.hpp> #include <boost/archive/text_oarchive.hpp> ////////////////////////////////////////////////////////////////////////////// // Example code that would reside in the library ////////////////////////////////////////////////////////////////////////////// struct type_container_base { private: virtual void make_abstract() const {} friend class ::boost::serialization::access; template <typename ARCHIVE> void serialize(ARCHIVE &, const unsigned int) {} }; BOOST_SERIALIZATION_ASSUME_ABSTRACT(type_container_base) template <typename USER_TYPE> struct type_container : type_container_base { void add(const USER_TYPE& d) { _vector.push_back(d); } private: std::vector<USER_TYPE> _vector; friend class ::boost::serialization::access; template <typename ARCHIVE> void serialize(ARCHIVE & ar, const unsigned int) { ar & ::boost::serialization::base_object<type_container_base>(*this); ar & _vector; } }; ////////////////////////////////////////////////////////////////////////////// // Example user code that would use the library ////////////////////////////////////////////////////////////////////////////// struct user_type { user_type(int i) : _val(i) {} private: int _val; friend class ::boost::serialization::access; template <typename ARCHIVE> void serialize(ARCHIVE & ar, const unsigned int) { ar & _val; } }; // *** Is there a better way than forcing the user to do this for every // *** user_type they want to use with the library? BOOST_CLASS_EXPORT_GUID(type_container<user_type>, "type_container<user_type>") int main() { std::vector<type_container_base*> containers; type_container<user_type>* tc = new type_container<user_type>(); tc->add(user_type(7)); tc->add(user_type(42)); tc->add(user_type(1776)); containers.push_back(tc); { boost::archive::text_oarchive ar(std::cout); const std::size_t size = containers.size(); ar << size; BOOST_FOREACH(type_container_base* p, containers) ar << p; } return 0; }

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TTI library updated in the sandbox to version 1.2
by Edward Diener 10 Feb '11

10 Feb '11

I have updated the TTI library in the sandbox 'tti' directory to version 1.2. The TTI library, which is an abbreviation for the 'Type Traits Introspection' library, allows a programmer to introspect at compile time the inner elements of a C++ type. The introspection process depends on specifying the name of the inner element by different macros for different types of elements, and then using a generated metafunction to determine whether that element exists within the enclosing type. The inner elements which can be introspected are type, class template, member data, member function, static member data, and static member function. The main feature of the update is a set of macros generating metafunction classes for passing the metafunctions of the library as metadata. The documentation has also been updated and the code implementation has been made easier to follow. The TTI library is based on the type_traits_ext portion of the Concept Traits Library, with improvements and additions, and also reproduces functionality ( without changing existing code ), for the purposes of completeness, from Boost.MPL regarding introspection of types and templates. The purpose of the library is to provide a consistent set of interfaces for doing compile-time introspection of a type, which other template metaprogrammers can use in their code. If you are at all interested in compile-time introspection of types, please take a look at the functionality of this library. There is a readme.txt in the top-level sandbox tti directory, for anyone browsing the sandbox for interesting libraries, which basically replicates what is written here. There is a build.txt file in the doc subdirectory for building the documentation and running the tests. The documentation is also included as part of the sandbox files for those who can not build the docs. The library has been tested and works with gcc 3.4.2, 3.4.5, 4.3.0, 4.4.0, 4.5.0-1, 4.5.2-1 and VC++ 8.0, 9.0, 10.0. It may also work with other compilers. Questions, comments, suggestions, and bug reports are all welcome.

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[DateTime] convert to timeval
by John Rocha 09 Feb '11

09 Feb '11

Is there a method from the boost date time library to convert a ptime to a timeval? I see a method for converting to a struct tm, but not the other common basic time types. Thanks in advance, -=John

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graph
by Soso F 09 Feb '11

09 Feb '11

Hello, I'm using BGL to build a graph which represents a network. I'm wondering if I can read a file to be the input " vertices , edges and weight" without using graphviz. Thx

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