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

[Proto] Bug in TArray Example
by Hossein Haeri 30 Dec '10

30 Dec '10

Dear all,wel;iqserhqweuo;h

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[intrusive] linear hashing
by Ephraim Sinowitz 30 Dec '10

30 Dec '10

Hi, Can anyone explain the performance characteristics of linear hashing. I read the Wikipedia article and I'm still not sure. The article mentions growing the hash table incrementally by 1, but the instrusive unordered_set doesn't grow/rehash unless you tell it to? When does it make sense to use the linear hashing option? Why is it not on by default? Is it because it slows down the address lookup into the table. Is the ideal bucket size still 1 per expected element. Thanks -ephi

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[MPL] Permutations of a List of Types
by Edward Terchunian 30 Dec '10

30 Dec '10

I am trying to create a list containing the permutations of a given type list. The below code seems to function, though without the intended result, when I use a specified list instead of generating a new list by removing from the actual input. This is demonstrated by the difference between permutation_helper and broken_helper below. Am I using remove incorrectly, or am I running into a different problem? #include <boost/mpl/list.hpp> #include <boost/mpl/transform.hpp> #include <boost/mpl/fold.hpp> #include <boost/mpl/push_front.hpp> #include <boost/mpl/joint_view.hpp> #include <boost/mpl/remove.hpp> #include <boost/mpl/assert.hpp> #include <boost/mpl/equal.hpp> namespace mpl = boost::mpl; struct test_type1 {}; struct test_type2 {}; struct test_type3 {}; template< typename T > struct permutations; template <typename value> struct permutations<mpl::list1< value > >: mpl::list1<mpl::list1< value > > {}; template< typename value, typename T> struct permutation_helper: mpl::transform< typename permutations< mpl::list1<test_type3> >::type, mpl::push_front< mpl::_1, value> > { }; template< typename value, typename T> struct broken_helper: mpl::transform< typename permutations< mpl::remove<T, value> >::type, mpl::push_front< mpl::_1, value> > { }; template< typename T > struct permutations: mpl::fold< T, mpl::list0<>, mpl::joint_view< mpl::_1, broken_helper<mpl::_2, T > > > { }; typedef mpl::list2<test_type1, test_type2> typelist; typedef permutations<typelist>::type perms; int main() { BOOST_MPL_ASSERT(( mpl::equal< perms, typelist > )); return 0; } I used the assert to determine what is being returned from the function, typelist is not the expected result. This is the message the assert returns for broken_helper: testcase.cpp: In function ‘int main()’: testcase.cpp:45: error: no matching function for call to ‘assertion_failed(mpl_::failed************ boost::mpl::equal<boost::mpl::joint_view<boost::mpl::joint_view<boost::mpl::list0<mpl_::na>, boost::mpl::l_end>, boost::mpl::l_end>, boost::mpl::list2<test_type1, test_type2>, boost::is_same<mpl_::arg<-0x00000000000000001>, mpl_::arg<-0x00000000000000001> > >::************)’ The output using permutation_helper is an actual list: testcase.cpp: In function ‘int main()’: testcase.cpp:45: error: no matching function for call to ‘assertion_failed(mpl_::failed************ boost::mpl::equal<boost::mpl::list2<test_type1, test_type2>, boost::mpl::joint_view<boost::mpl::joint_view<boost::mpl::list0<mpl_::na>, boost::mpl::l_item<mpl_::long_<1l>, boost::mpl::l_item<mpl_::long_<2l>, test_type1, boost::mpl::list1<test_type3> >, boost::mpl::l_end> >, boost::mpl::l_item<mpl_::long_<1l>, boost::mpl::l_item<mpl_::long_<2l>, test_type2, boost::mpl::list1<test_type3> >, boost::mpl::l_end> >, boost::is_same<mpl_::arg<-0x00000000000000001>, mpl_::arg<-0x00000000000000001> > >::************)’

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pthread_exit() from boost::thread segfaults ?
by Viatcheslav.Sysoltsev＠h-d-gmbh.de 30 Dec '10

30 Dec '10

Hi people, does anybody have an idea why the following simple programm segfaults: #include <boost/thread.hpp> void tf() { pthread_exit(NULL); } int main() { boost::thread t(tf); t.join(); return 0; } > g++ test2.cpp -lboost_thread && gdb a.out GNU gdb (GDB) 7.2 Copyright (C) 2010 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-unknown-linux-gnu". For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>... Reading symbols from /home/vsysolts/test/boost_thread/a.out...done. (gdb) r Starting program: /home/vsysolts/test/boost_thread/a.out [Thread debugging using libthread_db enabled] [New Thread 0x7ffff6cd5950 (LWP 21145)] Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x7ffff6cd5950 (LWP 21145)] 0x00007ffff798a565 in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib64/libstdc++.so.6 (gdb) bt #0 0x00007ffff798a565 in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib64/libstdc++.so.6 #1 0x00007ffff7988a46 in ?? () from /usr/lib64/libstdc++.so.6 #2 0x00007ffff7988a73 in std::terminate() () from /usr/lib64/libstdc++.so.6 #3 0x00007ffff7bd898a in thread_proxy () from /usr/lib64/libboost_thread.so.1.36.0 #4 0x00007ffff6cdd070 in start_thread () from /lib64/libpthread.so.0 #5 0x00007ffff71ce11d in clone () from /lib64/libc.so.6 #6 0x0000000000000000 in ?? () (gdb) I am using opensuse 11.1, x86_64 architecture, gcc 4.3.2, boost 1.36 -- Slava

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Re: [Boost-users] Create Module with boost
by derleader __ 30 Dec '10

30 Dec '10

>> Hi, >> Can you tell me how I can create a modules with boost? > > >You've already asked that on this thread: >http://thread.gmane.org/gmane.comp.lib.boost.user/64732 > >but haven't clarified your question. >_______________________________________________ >Boost-users mailing list >Boost-users(a)lists.boost.org >http://lists.boost.org/mailman/listinfo.cgi/boost-users > Sorry, I deleted the last message by mistake. > I'm new to Boost and I'm new C++ developer. I'm looking for examples how > to write application divided into modules using Boost. Is there already done > example? I need to see how to write C++ module. What do you mean by saying "module"? Compile-time unit or a binary module that you'll load in run-time? I'm not sure what are the differences between compile-time unit and binary module. I suppose that the best for me will be to use binary module which will be loaded in run-time. Is there example of such modules? I think that the best way for communication between the modules will be to user mapping share memory. What can you advice me? Regards Peter

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[message_queue.hpp]is it possible to use a boost message queue without data getting interleaved from multiple processes
by rohini chandra pallapothu 30 Dec '10

30 Dec '10

Hi, I have used boost message queues to setup IPC between a command client and a server on Linux. The client is a command which sends the command options and the server fetches the data and sends it to the client. The client prints the output received from server on the console. The data sent from the command is small but the data sent by the server to the command is huge(~11Mb). Server need to send the data to multiple command clients simultaneously as it is common to execute commands with different options at the same time from different terminals. The commands take quite some time to complete as the data sent from the server is huge. So more than one command running simultaneously is common. I do not see data missing when only one command is executed at a time. But when I execute two commands simultaneously, it seems that the data addressed to the two commands gets interleaved. I need to make sure that data addressed to multiple command clients is not interleaved. Only data addressed to that client should be received by a client. Since the same boost message queue with the same name is used for all the command clients, how can this problem be addressed. I read that Windows Named pipes handle this problem inherently . Could this be a problem with my implementation or is this a limitation of the boost message queues? Please let me know if you need more details Regards, Rohini Chandra

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It seems a bug in boost::property_tree when I use custom allocator.
by SONGFY 29 Dec '10

29 Dec '10

I use custom stl allocator to replace std::basic_string like this: typedef std::basic_string<char, std::char_traits<char>, MySTLAllocator<char> > MyString; I want basic_ptree can use my allocator to do parse work, so I write code like this: typedef boost::property_tree::basic_ptree<MyString, MyString> PropertyTree; PropertyTree propertyTree; boost::property_tree::read_ini(std::ifstream(configFile.c_str()), propertyTree); And I met error at ini_parser.hpp, line 109~111: Str key = property_tree::detail::trim( line.substr(1, end - 1), stream.getloc()); if (local.find(key) != local.not_found()) the Str is a typedef at the begin of this function: typedef std::basic_string<Ch> Str; So my custom string can not assign to the key, so it seems can not use custom allocator at all. There have the same problem in xml_parser.

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Create Module with boost
by derleader __ 29 Dec '10

29 Dec '10

Hi, Can you tell me how I can create a modules with boost? Regards Peter

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Create Module with boost
by derleader __ 29 Dec '10

29 Dec '10

Ok, thank you. Is there another way than binary modules loaded at run-time? What are the options for creating modular applications with boost? Regards Peter First, at the moment there is no standard way to do this. Second, there is a library that is meant to do this and will be proposed to boost once complete enough. It's boost::extension : http://boost-extension.redshoelace.com/docs/boost/extension/index.html Now, (correct me if I'm wrong), the author said some months/years ago that he cant continue developpement because of language limitations that C++0x will certainly fix (I'm not sure what but I guess it's about ABI?). Anyway, it seems to be working and used by some people, but not as complete as the author would like too. (and the documentation could be improved I think). There are other libraries providing the same functionallity, like Poco's Shared Libraries ( http://pocoproject.org/slides/120-SharedLibraries.pdf ). Boost::extension and Poco Shared Libraries are cross-platform. Other than that and calling platform-specific API functions, there is no boost library that allows binary modules loaded at run-time. But I guess that's already helping. On Wed, Dec 29, 2010 at 18:20, derleader __ derleader(a)abv.bg > wrote: >> Hi, >> Can you tell me how I can create a modules with boost? > > >You've already asked that on this thread: > http://thread.gmane.org/gmane.comp.lib.boost.user/64732 > >but haven't clarified your question. >_______________________________________________ >Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > Sorry, I deleted the last message by mistake. > I'm new to Boost and I'm new C++ developer. I'm looking for examples how > to write application divided into modules using Boost. Is there already done > example? I need to see how to write C++ module. What do you mean by saying "module"? Compile-time unit or a binary module that you'll load in run-time? I'm not sure what are the differences between compile-time unit and binary module. I suppose that the best for me will be to use binary module which will be loaded in run-time. Is there example of such modules? I think that the best way for communication between the modules will be to user mapping share memory. What can you advice me? Regards Peter _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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[GIL] Inspecting any_image
by Szymon Gatner 29 Dec '10

29 Dec '10

Is it possible to find out which of allowed image formats any_image actually has? For example, if image is loaded with code provided in dynamic_image.cpp: typedef boost::mpl::vector<gray8_image_t, rgb8_image_t, gray16_image_t, rgb16_image_t> my_images_t; any_image<my_images_t> dynamic_img; jpeg_read_image("test.jpg",dynamic_img); how to figure out which colorspace / layout loaded image have? -- Szymon Gatner

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