March 2009 - Boost-users - lists.preview.boost.org

[Graph] Using a bit-based ajacency matrix.
by Thorsten Ottosen 01 Mar '09

01 Mar '09

Dear All, Does anybody have experience with the above. That is, to represent the graph as a bit-based ajacency matrix, and then use that together with Boost.Graph? I'm thinking that Boost.Graph will not exploit this representation optimally. Am I correct? Thanks in advance -Thorsten

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newbie thread synchronization question
by Cory Riddell 01 Mar '09

01 Mar '09

I'm a total newbie with the Thread library, so please forgive me if this is a dumb question. Say I make a class called Shared that looks something like this: class Shared { private: boost::mutex monitor; int qty; public: Shared() : qty(0) { } void lock() { monitor.lock(); } void unlock() { monitor.unlock(); } int getQty() { return qty; } void setQty(int q) { qty = q; } }; If I use it in from multiple threads with code that looks like: // s is an instance of Shared s.lock(); int q = s.getQty(); ++q; s.setQty(q); s.unlock(); will it work reliably on a multi-core machine? When the mutex unlock() happens, does that flush the CPU cache and write the value of s.qty to main memory? Does the mutex lock() operation clear the CPU cache and force a reload of s from the main memory? I'm trying to understand how synchronization works among multiple cpus. I've only worked on multithreaded code in Java and there the memory model is well defined. AFAIK, that isn't the case in C++. Cory

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asio tcp socket receive timeout value
by Lennyk 01 Mar '09

01 Mar '09

Hi, I'm using boost 1.35 on Linux. I would like to change the timeout value of the tcp socket receive call. I know that the default value is 30 seconds. Thanks, Lenny.

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unresolved external issue and who do I pass a boost patch to?
by Sean Farrow 01 Mar '09

01 Mar '09

Hi: can Anybody help I'm using the boost::filesystem library, and am including <boost/filesystem/path.hpp> and am getting: 1>O2ServerImpl.obj : error LNK2019: unresolved external symbol "class boost::system::error_category const & __stdcall boost::system::get_system_category(void)" (?get_system_category@system@boost@@YGABVerror_category@12@XZ) referenced in function "void __cdecl boost::system::`dynamic initializer for 'system_category''(void)" (??__Esystem_category@system@boost@@YAXXZ) 1>O2ServerImpl.obj : error LNK2019: unresolved external symbol "class boost::system::error_category const & __stdcall boost::system::get_generic_category(void)" (?get_generic_category@system@boost@@YGABVerror_category@12@XZ) referenced in function "void __cdecl boost::system::`dynamic initializer for 'generic_category''(void)" (??__Egeneric_category@system@boost@@YAXXZ) I am linking with: libboost_filesystem-vc80-mt-gd-1_39.lib libboost_system-vc80-mt-sgd-1_39.lib Anyone with any ideas? Also I've modified a boost header file, who do I pass this too for update to the svn trunk? Cheers Sean.

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Lambda issue.
by Surya Kiran Gullapalli 01 Mar '09

01 Mar '09

Hello all,I've a class with boost::variant as its member ; class A { public: A() { } boost::variant<int, string, double, date>& getValue (const string& key) { ... } private: map<string, boost::variant<int, string, double, date> >m_member ; } I've list of A's like this list<A> myList. when trying to find a particular element with integer value (1 say) which is stored in m_member, I'm doing this.. find_if (myList.begin(), myList.end(), (boost::lambda::bind(&A::getValue, boost::lambda::_1, "SomeKey") == 1)); This is giving lot of errors. I've tried casting the result of bind to Variant, and then converting the variant to int using boost::get<int>().. but no help. Any ideas how to do this ? Surya

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Some question about cross-compiling boost
by 邹磊 01 Mar '09

01 Mar '09

Hi, Volodya. Thanks for your reply. I have tried the method in the document ( http://www.boost.org/boost-build2/doc/html/bbv2/tasks/crosscompile.html ), there were still some problems. Some libraries has been built successfully, but many not (such as libboost_serialization, libboost_wave and so on). I got the information as following: >>...failed gcc.compile.c++ bin.v2/libs/math/build/gcc-3.8.0/release/link-static/threading-multi/sph_neumannf.o... >>.......... >>...skipped <p/usr/local/lib/>libboost_serialization-gcc38-mt.a for lack of<p/usr/local/lib>libboost_serialization-gcc38-mt-1_38.a... I didn't know why these libraries built failed. I wonder whether the problem is due to my gcc kernel of cross-compiler . Maybe it's version is too low to build that libraries? How to solve the problem? Thank you! Zou ___________________________________________________________ 好玩贺卡等你发，邮箱贺卡全新上线！ http://card.mail.cn.yahoo.com/

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Having a tough time installing and setting up Boost and associated libraries
by ajay gopalakrishnan 01 Mar '09

01 Mar '09

Hi all, I am a newbie when it comes to using boost. My primary motivation behind using boost is that I want to use the Text processing, Numerical computing facilities together in one common language. Boost Regex, Spriti and The BLas Libraries would serve my purpose. However, I am having a tough time installing and running it. I am not able to find any good documentation for using this. My requirement is this: 1. I want to be able to install Boost locally in my Unix account. I don't have root privileges. 2. There is a wrapper called Boost Numerics Package written and hosted at http://mathema.tician.de/software/boost-bindings. I want to be able to use this also. This allows me to use ATLAS, BLAS in Boost. I would also like to know, how tough is it to interface C++ code with Python using Boost.Python. I am not an expert in Python. What is the procedure to do this? Your help will be highly appreciated. Thanks, Ajay G.

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shared_ptr memory leak
by gast128 01 Mar '09

01 Mar '09

Dear all, we managed to create a shared_ptr memory leak, without making a cycle. Granted it is highly controversial case. One has to make call in the destructor of the owned object which loops back to the point of assignment. Is this something for the documentation, or may this indeed be flagged as a 'nut' case. Code below is a simplified example, the production case was with some kind of change manager which notification bounced back to the point of assignment. One has to split out header and cpp to get it compilable. void TestSharedPtrLeak() { //make the leak KTestBoostHlpSpLeakParent leak; leak.Reset(false); } //ktestboosthlpspleakparent.h struct KTestBoostHlpSpLeakParent { KTestBoostHlpSpLeakParent(); void Reset(bool b); boost::shared_ptr<KTestBoostHlpSpLeak> m_ptr; }; //ktestboosthlpspleakparent.cpp KTestBoostHlpSpLeakParent::KTestBoostHlpSpLeakParent() { Reset(true); } void KTestBoostHlpSpLeakParent::Reset(bool b) { boost::shared_ptr<KTestBoostHlpSpLeak> ptr(new KTestBoostHlpSpLeak(this, b)); m_ptr = ptr; //m_ptr.swap(ptr); //would solve it btw } //ktestboosthlpspleak.h struct KTestBoostHlpSpLeak { KTestBoostHlpSpLeak(KTestBoostHlpSpLeakParent* p, bool b); ~KTestBoostHlpSpLeak(); public: KTestBoostHlpSpLeakParent* m_p; bool m_b; }; //ktestboosthlpspleak.cpp KTestBoostHlpSpLeak::KTestBoostHlpSpLeak(KTestBoostHlpSpLeakParent* p, bool b) : m_p(p) , m_b(b) { } KTestBoostHlpSpLeak::~KTestBoostHlpSpLeak() { if (m_b) { //recursive call m_p->Reset(false); } }

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error when using boost with visual c++
by Sean Farrow 01 Mar '09

01 Mar '09

Hi; When using boost with visual c++ 2005, I'm getting the following two error: c:\program files\microsoft visual studio 8\vc\include\intrin.h(198) : error C2373: '_InterlockedExchange' : redefinition; different type modifiers c:\program files\boost\boost\detail\interlocked.hpp(60) : see declaration of '_InterlockedExchange' Has anyone got any ideas what is causing this? I'm including the following files in the file that is indicating the error: #include <vector> #include <boost/algorithm/string.hpp> #include <boost/array.hpp> #include <boost/filesystem/path.hpp> #include <boost/foreach.hpp> #include <windows.h> #include <psapi.h> #include <ole2.h> #include <exdisp.h> #include <mshtml.h> #include "O2ServerImpl.h" #include "Globals.h" //Crypto++ remove as necessary. #include <default.h> #include <filters.h> #include <hex.h> #include <md5.h> #include <ripemd.h> #include <rng.h> #include <gzip.h> #include <randpool.h> #include <ida.h> #include <base64.h> #include <factory.h> #include <whrlpool.h> #include <tiger.h> any help appreciated. Sean.

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