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Matrix-Matrix reference
by Wilken, Marc 18 Dec '02

18 Dec '02

Hello, does ublas support a matrix method like blitz++ .reference() method? (This method allows different matrices to share the same matrix datas.) Marc Wilken This e-mail contains confidential information for the exclusive attention of the intended addressee. Any access of third parties to this e-mail is unauthorised. Any use of this e-mail by unintended recipients such as copying, distribution, disclosure etc. is prohibited and may be unlawful. When addressed to our clients the content of this e-mail is subject to the General Terms and Conditions of GL's Group of Companies applicable at the date of this e-mail. GL's Group of Companies does not warrant and/or guarantee that this message at the moment of receipt is authentic, correct and its communication free of errors, interruption etc.

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Problem with "this" and shared_ptr
by Michael Brinkmann 18 Dec '02

18 Dec '02

Hello, given the following code which uses shared_ptrs, I'm getting a double-free onto an object of type A: ------------------------------------------------------ #include <boost/shared_ptr.hpp> #include <list> #include <iostream> class A { public: A(void){} void makeSomething(void); void makeSomethingOther(void) { std::cout << "A" << std::endl; } }; typedef boost::shared_ptr<A> APtr; class B { public: B(const APtr& a) : mA(a) {} void makeSomething(void) { std::cout << "B" << std::endl; mA->makeSomethingOther(); } private: APtr mA; }; void A::makeSomething(void) { B b(this); // here I want to hand over the "A" shared pointer to "B", but I have only my "this" at hand. std::cout << "A" << std::endl; b.makeSomething(); } int main(void) { APtr a(new A); a->makeSomething(); } ------------------------------------------------------ (please don't ask me about why I'm doing it in that way, the code is stripped down from a much bigger program) I understand that the problem results from the accesss to "this" in the commented line. Is there an elegant way to get the shared_ptr pointing to "this" from "this", which would be the solution to the fault? Or do I have to store a shared_ptr member variable referencing "this" in the class A which is set by a A::method from outside of A to reference it? (not very beautiful) Sorry if this is a FAQ, but I didn't find a solution on news.gmane.org kind regards Michael

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Re: [Boost-Users] Re: Thread library: get thread id
by dick.bridges＠tais.com 18 Dec '02

18 Dec '02

<alternative exemplar> When I implemented the Leader-Follower thread pattern described by Schmidt, et al in Pattern-Oriented Software Architecture, I couldn't figure out a way around comparing the thread id to the current leader in the promote_new_leader function. Probably lack of imagination and/or experience on my part, but having the thread id sure made it easier. </alternative exemplar> "William E. Kempf" To: <Boost-Users(a)yahoogroups.com> <wekempf(a)cox.net cc: > Subject: Re: [Boost-Users] Re: Thread library: get thread id 12/16/2002 01:20 PM Please respond to Boost-Users olivier_debels said: > --- In Boost-Users(a)yahoogroups.com, "William E. Kempf" <wekempf@c...> > wrote: >> >> olivier_debels said: >> > >> > I'm using boost_1_29_0 and need to get the id of the current > thread. >> >> Why? >> > I have several threads which pop messages from the queue. I want to > keep track of what each thread pops (depending on some rules) without > adding an extra parameter (threadId) in the pop-function. I don't follow this. > By this way threads just call the pop-function (they don't know > anything about the internal cooking of the queue). They get a > message, which fulfills the rules (one of the rules is f.e. that no > two threads can handle the same message at the same time). How does a thread id figure into this? What little of this description I understand gives no need for a thread id. William E. Kempf Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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switching to BGL
by Daniel Varga 18 Dec '02

18 Dec '02

Hi, I'm planning to throw away my own little undirected graph implementation in favor of Boost Graphs. My implementation is based on an STL map< Node,set<Node> > adjecency map. I see that it's very easy to get the same functionality using the BGL adjecency_list. But what I really like about my implementation is that I have const set<Node>& Graph::lookupNeighbours(const Node&) const; This means that in no time I can get a _container_ of the neighbours, and not just a pair of iterators. Of course teoretically they are equivalent. But I want to rewrite as little code as possible, so I would like to wrap my old graph interface around the Boost Graph. (Not hiding its own, better interface, of course. :) ) Should I write a wrapper container class simulating const set<Node>? Or does adjecency_list expose the very same const set<Node>& for me?

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Threads question
by Martin Johnson 18 Dec '02

18 Dec '02

Hi, This has probably been asked before. I cant find doco giving detail. So excuse me if this is old topic. I am involved with GPL project that uses boost::threads. I have a problem understanding implementation and what threadmon.dll is for. I see that the code is attempting to manage tss stuff. How is the tss stuff managed when lib is a static link under win32? Is it correct that if I wish to static link that I need this other threadmon.dll as well. Has it been suggested that structured exceptions can perform the same function on win32 with a finally() handler from within thread_proxy? This is a gurantee of invocation. The cleanup attempt could though win32 doco states cleanup is guranteed, though couldnt a lib global could easily handle main thread cleanup? Regards Martin Johnson

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Thread library: get thread id
by olivier_debels <olivier_debels＠yahoo.com> 17 Dec '02

17 Dec '02

I'm using boost_1_29_0 and need to get the id of the current thread. Is there a way to get the id of the current thread using boost? I don't see how I can access the current thread (Is there some sort of current function?). If I could access the current thread, I could write a getId() function (in a class subclassed from boost::thread). Only problem there is the return type. It seems the id is an int in windows environment, a pthread_t in POSIX and a MPTaskID in MACOS. Those last two seems to be pointers to struct. I guess it is possible to cast all of them to long (using reinterpret casting), but maybe I am overlooking something then. thanks, Olivier.

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Issues on getting the reference of the held value of boost::any
by Seishi Onishi <looper2k＠yahoo.com> 17 Dec '02

17 Dec '02

I'm using a collection of boost::any for the variable container class which has this map member. std::map<std::string, boost::any> m_collection; As you imagine, the container class can keep anything even the container class itself recursively. You know, an boost::any may hold copy expensive object. So I need a method to get the reference of the value held in boost::any not to make the expensive copy. But I found that the current any_cast implementation was not well support the reference. Issue 1: The following code causes compiler error on VC6&7. boost::any dany = double(1.2); double& rd = boost::any_cast<double>(dany); Issue 2: The following code works but one copy constructer called. class Foo foo; boost::any fany( foo ); class Foo& rfoo = boost::any_cast<class Foo>(fany); Actually, I found the way to sneak out of the issues. double& rd = *boost::any_cast<double>(&dany); class Foo& rfoo = *boost::any_cast<class Foo>(&fany); But the problem is these codes won't throw bad_any_cast. And I also wonder this *any_cast usage may not be the way the developer supposed. So I expect that the current any_cast code will be changed to well support the reference access. It can be, template<typename ValueType> const ValueType& any_cast(const any & operand) { const ValueType * result = any_cast<ValueType>(&operand); if(!result) throw bad_any_cast(); return *result; } template<typename ValueType> ValueType& any_cast(any & operand) { ValueType * result = any_cast<ValueType>(&operand); if(!result) throw bad_any_cast(); return *result; } -Seishi

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[Boost-Users][BGL] Permutation of a graph
by Paolo Fosser 17 Dec '02

17 Dec '02

Hi all, I'm using BGL in some graph matching algorithms. Now I have to shuffle a bit one of the graphs I'm comparing. I think it all ends up in considering the nodes in a different order when cycling on them. (BTW am I right?). So my question: is there an elegant way to do this in BGL? The only solution that comes into my mind is to build up a map from the range of vertex descriptors to a permutation of them. TIA, Paolo -- Do you want to live forever? Alex Chiu has invented a device which will give you physical immortality. Click here! http://www.alexchiu.com/affiliates/clickthru.cgi?id=pfosser

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testing if shared_ptr has been assigned
by TEA Hartmann, Steven 16 Dec '02

16 Dec '02

I need some help in testing for the condition of whether a shared_ptr has been assigned. In the following example, the "if( b != NULL ) does not work. How would I do this test? typedef boost::shared_ptr<int> IPtr; int i( 0 ); IPtr a( i ); IPtr b; if( some condition ) b = a; if( b != NULL ) { // How should this really be coded? } Best Regards, Steve [Non-text portions of this message have been removed]

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Borland: Cannot generate template specialization
by Felix E. Klee 16 Dec '02

16 Dec '02

Hi, I'm trying to compile C++ code that uses the boost/numeric/ublas matrix library with the Kylix C++ Compiler (BC++ 5.7 for LINUX). However, I get several error messages, among them: Error E2299 boost_1_29_0/boost/numeric/ublas/matrix.hpp 522: Cannot generate template specialization from 'container_reference<C>' in function matrix<complex<double>,row_major,unbounded_array<complex<double> > >::iterator1::iterator1(matrix<complex<double>,row_major,unbounded_array<complex<double> > > &,complex<double> * const &) Any ideas how to work around this problem? Felix

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