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

How to manage the internal memory allocation in boost libraries?
by Tang Jiang Jun 11 Sep '10

11 Sep '10

Hello, I am seeking a way to manage the internal memory allocation in boost libraries, and it seems that most of boost libraries do not support allocator parameter, so they can not be handled like STL library. But for my project, our memory management need to control all the memory allocation even it happens in the third-party libraries. Could somebody give me some suggestions to accomplish that? Regards, Tang Jiang Jun

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[Unordered] Penultimate Iterator
by Hossein Haeri 11 Sep '10

11 Sep '10

Dear all, What is the quickest way to get hold of the penultimate iterator in an unordered_map? I'm aware of this one -- which is O(n), where n == container_.size(): container_type::const_iterator i = container_.begin(); advance(i, container_.size() - 1); Is there no O(1) solutions? TIA, --Hossein

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[Boost.Test] Understanding the correct use of BOOST_CHECK_CLOSE and BOOST_CHECK_CLOSE_FRACTION
by Torri, Stephen CIV NSWCDD, W15 10 Sep '10

10 Sep '10

I am trying to understand how to be use BOOST_CHECK_CLOSE and BOOST_CHECK_CLOSE_FRACTION for my problem. My problem is being able to check that two floating point values agree within 12 decimal digits. That is the difference between the two values is smaller than 1e-12. I see from the documentation that BOOST_CHECK_CLOSE requires a percent of agreement while BOOST_CHECK_CLOSE_FRACTION requires a fraction value. So when I used BOOST_CHECK_CLOSE_FRACTION to compare two value I got output that I didn't know how to read: /test_sgp4_orbit_data.cpp(52): error in "default_calculate_semi_major_test": difference{1e-12} between result{1.1219271770198256} and 1.1219271773271688{1.1219271773271688} exceeds 9.9999999999999998e-13 I used BOOST_CHECK_CLOSE_FRACTION as: BOOST_CHECK_CLOSE_FRACTION ( result, 1.1219271773271688, 1e-12 ); What I am intending is if 'result' and the value differ by more than 1e-12 then I have an error. If the difference is smaller than 1e-12 I wish to have the comparison succeed. From the output I don't know why the exceeds value is not written as '1e-12' since that is what I used. Where am I going wrong in my use of BOOST_CHECK_CLOSE_FRACTION? Stephen Stephen Torri, PhD NAVAL SURFACE WARFARE CENTER DAHLGREN 17214 Ave B Suite 121 Dahlgren, Va. 22448 540-653-1082 I am not a contracting officer. I cannot modify or initiate contracts, nor do I have the authority to financially commit the government in any way.

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[python] python 3 with boost 1.44, without using bjam
by Geoff Hilton 10 Sep '10

10 Sep '10

I'm working on a DLL that I would like to expose to Python as a module, but as I came into Python only when Python 3 was available, that's what I know and therefore would like to use. A while ago I took a stab at learning bjam, but for now I've reverted to regular msvc projects, I was able to compile boost.python initially with bjam when I updated to Boost 1.44, the result generated the following files of relevance: libboost_python3-vc90-mt-1_44.lib libboost_python3-vc90-mt.lib libboost_python3-vc90-mt-sgd-1_44.lib libboost_python3-vc90-mt-sgd.lib which is great.. but when I try to compile my project it looks for libboost_python-vc90-mt-1_44.lib or libboost_python-vc90-mt-gd-1_44.lib as appropriate. How can I make msvc compile it successfully? I know bjam is a compiler driver, so I imagine there's a way... (FYI, here are the compilation commands I use from a batch file when compiling a new boost release. I used to use the recommended commands but they stopped working when boost changed the naming conventions to use version-independent naming, probably because I hadn't modified project settings in some way, but a lot of projects would get effected, so after some fiddling this is what I came up with). start bjam --toolset=msvc variant=debug link=static threading=multi runtime-link=static stage start bjam --toolset=msvc variant=release link=static threading=multi runtime-link=shared stage Many thanks, Geoff Unrelatedly, a comment I think might be interesting (if only speculative): from what I recall, I think boost was partially influenced to switch to version-independent naming because (among other reasons) Microsoft was using the version-independence way of thinking via the .Net model with the GAC, but I found an article at one point (which I can no longer find) saying that they realized after much experience with .Net that it's actually still quite possible to get version/DLL conflicts as a result of the version-independence naming (I believe it had to do with GUID generation or some such thing, but don't quote me on that), and quite a lot harder to debug. As a result they would be rethinking .Net and/or changing to a model where version-dependence plays a more prominent role at some point in the future. I wish I could point out the article, but at any rate I know I remember thinking it was funny (if possibly unfortunate) that boost was switching to this new naming convention, a move partially influenced by Microsoft's current methodology in some capacity, after Microsoft had discovered this issue and would eventually be (as I understand it) reverting to what essentially equates to the traditional pre-.Net DLL where versioning can be a more important issue.

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Boost.accumulators : weighted_median
by Maximilian Matthe 10 Sep '10

10 Sep '10

Hi! I want to calculate the median color (along some other data) of the pixels of an image from its histogram: std::vector<int> m_Hist; // m_Hist[i] contains number of pixels with color i. using namespace boost::accumulators; accumulator_set<double, features<tag::weighted_mean, tag::weighted_median(with_p_square_quantile), tag::weighted_variance(lazy), tag::weighted_skewness >, double> acc; for(int i = 0; i < 256; i++) acc(i, weight = m_Hist[i]); float mm = weighted_mean(acc); float stdD = sqrtf(weighted_variance(acc)); float med = weighted_median(acc); float sk = weighted_skewness(acc); mean und stdD work correctly, but the median is too large. It gives me about 200, but the real value should be around 75 (I checked that manually). The skewness is around 11000 (which also seems quite large to me). So, what am I doing wrong with accumulators?

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[boost-users][serialization]Linking time problems with a class hierarchy
by Laszlo Orban 10 Sep '10

10 Sep '10

Currently we are having a class hierarchy consisting of 50+ class definitions (all descendants of one class) along with some assistant structures; the typical you would expect from a 'real' application, and this base is growing each day. We are serializing and deserializing objects from these classes in a kind of client-server application. Everything works fine (testing on both linux and windows platform using gcc 4.4.1), however we are experiencing a rather weird issue. It started quite some time ago, but only starting to get really annoying nowadays: the compile and linking time of the projects that uses these classes are starting to get ridiculous and we could trace this back to serialization. As usual for polymorphic archives, we are using the BOOST_CLASS_EXPORT_GUID macro for creating the necessary singletons for the class definitions. To narrow down the problem we have tried the following checks: 1.) If we comment out all the BOOST_CLASS_EXPORT_GUID macros, the problem is gone, linking and compiling time is reduced to some seconds, the length of the executable and the object files are 'normal', but of course the serialization doesn't work. If I put the macros back, the compiling of the source file that contains them skyrockets to 2-3 minutes, also the linking time to around the same time on a Core2Duo 2 GHz machine, and the length of the object file (and thus the executable) goes from several hundred Kbs to 15+ Mb-s. (A bit varied values on the same code depending if it is linux or windows, but the same behaviour nonetheless.) 2.) We have tried to mess around with the number of macros running, and it seems the increase of the compile time is linear, linking time is more like exponential. 3.) We have tried to 'clean' the class structure and reduced the members in the classes to only some basic booleans and integers (even purged the std::string-s), in most classes completely eliminating all members just let the 'skeleton' there, and still: no significant change in compile and linking time. 4.) We have tried to do all this is in a 'clean' project with only a "void main() {}" method and the class hierarchy, to ensure that not somehow the usage of it causes the problem: negative, the problem still exists. Now it is not a great problem that the compile is so slow, as that causes a problem only when the class hierarchy is changed. Also the executable size is only a bit irritating, but not a serious problem. However the linking time is something we need to solve asap, as it is hindering our development a lot, especially as this class hierarchy is used in several applications (naturally, we wouldn't need serialization otherwise), thus the linking problem affects all of them. (And this will be worse later, as the class hierarchy is growing each day.) Any ideas about how to go on from here? Is there any way I can change the BOOST_CLASS_EXPORT_GUID macro to a more simple? effective? one? Or maybe all this is normal and we have to live with it? (This is a strongly reduced snippet on how we are using the polymorphic serialization with boost_1_42, but as I mentioned, it is working nicely: class Mess { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & messageId; } protected: int messageId; public: (...) }; class CMess : public Mess { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & boost::serialization::base_object<Mess>(*this); ar & cma; } protected: int cma; (...) }; (...) BOOST_CLASS_EXPORT_GUID(CMess, "CMess") Thanks for reading it!

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[serialization] simple binary archive problem
by Paul Graphov 10 Sep '10

10 Sep '10

Hello Boost users! I've upgraded to boost-1.44 and got a problem with binary serialization archives. This code sample http://pastebin.com/Uv465sGt worked well with 1.43 but doesn't work with 1.44 This is a program that creates a struct, serializes it, deserealizes back and compares, archive file name should be supplied as command line parameter. After switching from binary_*archive to text_*archive it works well. With binary_*archive it fails with terminate called after throwing an instance of 'std::bad_alloc' Stack trace is quite huge. p.s. [druid@druid-desktop tmp]$ uname -a Linux druid-desktop 2.6.32-24-generic #42-Ubuntu SMP Fri Aug 20 14:21:58 UTC 2010 x86_64 GNU/Linux [druid@druid-desktop tmp]$ gcc --version gcc (Ubuntu/Linaro 4.4.4-13ubuntu2) 4.4.5 20100902 (prerelease)

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Help with shared_ptr and template
by Mario Chacon 10 Sep '10

10 Sep '10

Hello: I have this problem and I do not how to fix it, I know I cannot write template typedefs, its a limitiation of the C++ syntax, right? or I'm wrong? I saw that the best way is to wrap your typedefs in a struct, which can be templated, but I'm still stack with problems. The best way to explain it's with an example: #include <cstdlib> #include <iostream> #include <boost/shared_ptr.hpp> template< typename tvalue > class CValue { public: CValue( tvalue value ) : value_(value) {}; private: tvalue value_; }; template< typename tvalue > struct Type{ typedef boost::shared_ptr< CValue< tvalue > > pValue; }; int main(int argc, char *argv[]) { Type<bool>::pValue a; return EXIT_SUCCESS; } How can I create a shared_ptr for the template class "CVALUE"?? Please I do not know what else I can prove... :( Thank you.. Mario.. Salu2...

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Warnings when I include posix_time.hpp
by André Santee 10 Sep '10

10 Sep '10

I'm getting the following warning just by including the <boost/date_time/posix_time/posix_time.hpp> header file in my msvc express 2008 project: c:\program files (x86)\microsoft visual studio 9.0\vc\include\iosfwd(607) : warning C4996: 'std::char_traits<char>::copy': Function call with parameters that may be unsafe - this call relies on the caller to check that the passed values are correct. To disable this warning, use -D_SCL_SECURE_NO_WARNINGS. See documentation on how to use Visual C++ 'Checked Iterators' I know that the reason why it's giving me the warning is self explanatory but boost headers aren't supposed to give us warnings. In fact, the warning is not even in the boost header file, but it seems to be included/caused by it. I just want to know if I'm doing something wrong or this is the MSVC header that is messed up. Thanks, André.

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Date Time header only
by Mohamed Bana 10 Sep '10

10 Sep '10

Hi Folks, What parts of the Date Time library is header only? Our applications run on several platforms and it's quite troublesome to get date time to compile on all of them. In my attempt, I was to get it to work on all our platforms except Solaris. I'm aware that I need to use stlport on Solaris, but we can't because we need to interface with another library which doesn't use stlport. To summarise, the whole situation is rather messy and I'm looking for a header only library. If there isn't any, are there any other date and time libraries aside from boost that doesn't require a very strict C++ compliant compiler? If you need more info, just ping me.

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