June 2016 - Boost-users - lists.preview.boost.org

boost unit test framework exports std::basic_ostringstream
by Sascha Kremers 30 Jun '16

30 Jun '16

The boost unit test framework exports std::basic_ostringstream to the dll. This causes linker errors on visual studio 2012 (LNK 2005), if the tested code contains std::basic_ostringstream. You can confirm the symbol std::basic_ostringstream is in boost_unit_test_framework-vc110-mt-1_61.dll by using dependency walker. I have the same problem with my self-built dlls as well as the ones downloaded from https://sourceforge.net/projects/boost/files/boost-binaries/. Is this a problem with boost or did I configure the build wrong? Thank you. I posted the issue on Stack Overflow a week ago [1]. Please excuse, if this still counts as cross posting. Regards Sascha [1] http://stackoverflow.com/questions/37922117/stdbasic-ostringstream-exported…

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Re: [Boost-users] Multiprecison: converting a complex class to a number<> backend
by John Maddock 30 Jun '16

30 Jun '16

On 29/06/2016 22:17, Christopher Kormanyos wrote: > > In my opinion, trying to adapt a complex number class to the backend > requirements of number might not be the best way to go. > > I would recommend writing an extended complex template class > that is intended to be instantiated for both user-defined types as well as > float, double and long double. > > The real and imag parts are template parameter types. They could be > of type mpfr_float because the template parameter type is > determined at compile-time when the class is instantiated. > > In the winter, I wrote an extended complex class and tested it extensively > with multiprecision and fixed point. There was also another candidate > implementation of extended complex a few years ago from another > developer, but it never got to review. > > I have not yet made my extended complex code available. > > I am not subscribed to the user's list. If the post gets to the > developer's > list, there is a good chance I will see it. I'm curious as to what you see as the stumbling block to providing a complex number backend to class number<> ? The main advantages are that the expression-template code and all operator overloads are "just there" already, what do you see as the drawbacks? Best, John.

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Multiprecison: converting a complex class to a number<> backend
by Daniel Brake 29 Jun '16

29 Jun '16

Hi Boost, I have implemented my own complex class wrapping around Boost.Multiprecision number<>, particularly mpfr_float. Now, I'd like to take the class I've written, and extend/convert it into a backend suitable for use in number<>. While I've read the documentation describing the requirements for a backend <http://www.boost.org/doc/libs/1_61_0/libs/multiprecision/doc/html/boost_mul…>, and think I understand what I need to do, I have found 0 examples in the wild. My current setup has a pair of files mpfr_complex.hpp, mpfr_complex.cpp describing something like (just what you'd expect, really) --------- class complex{ mpfr_float real_, imag_; public: // the *= family of operators, getters, setters, // some factory functions, etc }; //the free operators defined down here, along with pow, exp, etc. -------------- I think what I'd like to write is a new complex_backend.hpp file which implements the required functions for the complex wrapper around mpfr_float. In this file, I believe I implement the family of functions such as eval_multiply(b, a) in terms of the operators for my complex class. Is this right? In a related vein, with et_on for mpfr_float, I've started adding templated overloads for the complex operators and math function accepting expressions of reals, and I think this is going to get out of hand, so using number<> would conceivably save me a ton of time writing my own functions. It will also save me a ton of errors for hand-writing the expression templates for complexes, which appear to be ready to go from Boost.Multiprecision once I get a backend implemented. Again, my goal is expression templates for complexes with real and imaginary fields consisting of mpfr_floats, leveraging the number<> template, with et_on, and my own backend. Do you have any advice? Any references to any other custom backends? Daniel Brake University of Notre Dame Applied and Computational Mathematics and Statistics

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Boost interprocess mutex with shared memory
by Ashok Palaniswamy 28 Jun '16

28 Jun '16

Hi all, I want to implement boost interprocess mutex with shared memory. This mutex will protect the SMBUS access between multiple processes. In the entire source code, this mutex will be used across different the files. Please let me know if you have any sample programs available. Thanks, P.Ashok L&T Technology Services Ltd www.LntTechservices.com<http://www.lnttechservices.com/> This Email may contain confidential or privileged information for the intended recipient (s). If you are not the intended recipient, please do not use or disseminate the information, notify the sender and delete it from your system.

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boost::serialize 1.61 ticket #12141 not quite fixed for Visual Studio 15?
by Colin Humphries 27 Jun '16

27 Jun '16

After converting to boost 1.61 and Visual Studio 15 we now see a problem closely related to one reported in ticket #12141. Our XML archives now end with the following 2 lines: </boost_serialization> </boost_serialization> Could someone suggest a quick fix please? I think the problem must be in archive/impl/xml_woarchive_impl.ipp but I can't seem to grasp how the archive destructor emits the last line. Regards, Colin Humphries

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Backend of multi_index container
by Anaswara Nair 27 Jun '16

27 Jun '16

Hi, I was going through the documentation of boost::multi_index container. I would like to know what is in its back end. Something like B-Tree,B+tree,etc.? Actually I want to create a database(in the sense it contains millions of records), but need not be reusable at a later period of time. i.e, I am looking only for run-time persistent data. Once data is inserted to this, it will not be modified. And there will be a unique id for each record. I would also like to know whether multi_index is the best suited one for the implementation of my so called database.. Thankyou

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Re: [Boost-users] Backend of multi_index container
by anaswara 26 Jun '16

26 Jun '16

I have 7 fields in each record,two strings and five 64 bit integers. Of these,one of the integers is unique. I need to store all such records into the DB. In multi-index, I have a structure and this structure is being indexed by that integer value. If I have to similarly create a structure and store it as the value in LMDB, then what is its difference from multimap? I can do the same in multimap also. Then how does LMDB become a database. Sent from Samsung Mobile -------- Original message -------- From: degski <degski(a)gmail.com> Date: 24/06/2016 7:43 PM (GMT+05:30) To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Backend of multi_index container On 24 June 2016 at 15:51, Anaswara Nair <anaswara.nn(a)gmail.com> wrote: I have gone through LMDB. However AFAIK LMDB stores the data as a key-value pair. Yes, it's a key-value store. Though duplicate keys are allowed, I couldn't find any relation between these entries. I couldn't understand its use as a database as well. It's like std::(multi)map, maybe the wikipedia entry helps. Can you provide some help so that I can go deeper into this. In your original question, you refer to having one unique ID and some related data per record. Maybe you could expand a bit on what you would like to achieve. degski

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[Boost.PropertyTree] Application hangs (Boost 1.61)
by Andrew C 25 Jun '16

25 Jun '16

Hi! It seems to be a bug that this application hangs inside "erase" method: #include <boost/property_tree/ptree.hpp> int main() { boost::property_tree::ptree pt; pt.erase(pt.begin()); // enters infinite loop... } Compiled with Cygwin/GCC-5.4.0. Is it really a bug or my misuse? Thanks!

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CPack, CMake and Boost's shared libraries
by r＠primef.actor 25 Jun '16

25 Jun '16

What is the canonical cross-platform way to package boost shared libraries with CPack (and/or CMake)? On Windows, DLLs can be copied to the executable's folder and it will "just work". On OS X, one can use install_name_tool to set up a so-called rpath pointing to a relative location where the libraries reside, relative to the executable. On Ubuntu, one can similarly use ldd for setting up the correct pointers to where the libraries will reside relative to the executable. The question is then: is there some documentation on how to ship boost libraries along with your executable, in a cross-platform and canonical way, with CPack? Here's a question on stack overflow [1] that addresses the same problem, however the proposed solution of using set(CMAKE_EXE_LINKER_FLAGS "-Wl,-rpath='$ORIGIN'") in CMake does not seem cross-platform to me (MSVC won't recognize the command). Regards, Raoul [1]: http://stackoverflow.com/questions/26142948/packaging-c-program-using-boost…

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[Interprocess] Sharing FFMPEG Datatypes
by Loren Garavaglia 25 Jun '16

25 Jun '16

Hi All, I'm trying to figure out if it's possible using Boost to share FFMPEG data between 2 processes. What I'm trying to do is have one process read from a video stream and place the received packets in a buffer. The other process then reads from the buffer, decodes the packet, and does some analysis on the image. Unfortunately, due to some constraints I cannot take a multi-threaded approach to this problem. My data that I would like to share is as follows: struct FFMPEGData { AVFormatContext *pFormatCtx; AVCodecContext *pCodecCtx; AVCodec *pCodec; AVFrame *pFrame, dst; AVPacket *packet; AVPacket* pack = new AVPacket[packetNum]; struct SwsContext *convert_ctx; }; With "pack" being my buffer with a set size. I tried following the boost example here <http://www.boost.org/doc/libs/1_57_0/doc/html/interprocess/allocators_conta…> but it seems to be for a simpler form of complex data. All of the FFMPEG datatypes are structs themselves, so I wasn't sure what to do. My question is, is it even possible to share these kinds of datatypes between processes using Boost Interprocess and if so do I need to create allocators and containers for all of the data fields within these FFMPEG datatypes? Thanks, Loren

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