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threads within threads
by pmedrow 23 Jun '03

23 Jun '03

Hi I am attempting to create a boost thread within an existing boost thread, i.e. a function called by the operator() function of an existing, running thread is attempting to make more threads. The new threads function objects are of the same type, but different from the parent function object type. This compiles and runs, but takes time equivalent to the threads running sequencially on a single thread. CPU usage indicates that both threads are running in parallel. Very strange... I am building with gcc v3.2.3 on red-hat linux build 2.4.20. Any ideas gratefully received!

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boost::filesystem build in MS Visual Studio .NET 2003
by Stuart C. Schaffner 23 Jun '03

23 Jun '03

Sorry if this is a repost. I am having trouble with my mail system. I tried to build the boost libraries per the instructions on "Building Boost Libraries" at www.boost.org, but most of the builds failed. I did set up the two variables for msvc. However, I noticed that vcvars32.bat is not in the directory that the build script specifies. I can fix this, but I suspect that other things are also in different places in .NET 2003. Any suggestions? Stu Schaffner The MITRE Corp.

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Passing shared_ptr to function that creates obj that shared_ptr points to
by Drew 23 Jun '03

23 Jun '03

[Moderator's note: The only apparent connection this message has to Boost is in the subject line. I am approving it on the assumption that the missing declarations for ParentPtr and DerivedPtr are typedefs using boost::shared_ptr.] Hello everyone... I am attempting to do the following: class Parent { public: int m_value; }; class Derived : public Parent { }; void Fn(ParentPtr& pObj) { pObj = ParentPtr(new Parent()); pObj->m_value = 10; } int main() { ParentPtr pParent; DerivedPtr pDerived; Fn(pDerived); return 0; } If I pass the parent pointer, it compiles and works fine. If I pass the derived pointer I get: error C2664: 'Fn' : cannot convert parameter 1 from 'DerivedPtr' to 'ParentPtr &' Does anyone know how to solve my problem? TIA, Drew

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[BGL] negative_edge thrown inside dijsktra for boost' file dependency example.
by Dan Dimerman 23 Jun '03

23 Jun '03

Hello, The problem I'm having is that I get an exception thrown when I run the example related to File precedency on parallel compilation, using dijkstra algorithm. I mean, there's no code of mine at all, so that reduces the probabilities of it being me to a 75%... ;) thanks...

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Signals library safety
by Eugene Talagrand  22 Jun '03

22 Jun '03

Hello to all, I'm looking into using the Boost.Signals. The library claims not to be thread safe. What does this mean exactly? When using Boost.Threads, can I make concurrent calls to connect as long as I wrap each call in a Mutex? If this is possible, do tackable objects also still work (if two trackable objects get destroyed in two different threads there might be a problem from what I understand) On an different note, I am trying to use Boost.Signals for network event handling. I'd like to set it up so that it uses something similar to he JavaScript event model, where every slot returns a boolean value. If that value is false, the remaining slots are not called. Would anyone have any recommendations on how to do this? Should I wrap each slot in a function that takes the return value and sets a global flag, then every subsequent slot checks the flag? It looks like combiners would not be appropriate, as it appears they are used after each slot is called (unless the InputIterator' opeator* actually calls the slot??) Thanks for any help -Eugene

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FW: [Spirit-general] RE: [Boost-Users] boost::spirit and asts
by HartmutKaiser＠t-online.de 22 Jun '03

22 Jun '03

-----Original Message----- From: Giovanni Bajo [mailto:giovannibajo@libero.it] Sent: Sunday, June 22, 2003 1:39 AM To: Hartmut Kaiser Subject: Fw: [Spirit-general] RE: [Boost-Users] boost::spirit and asts You may want to forward this to boost-users, the mail bounced because I'm not subscribed to it. Giovanni Bajo Giovanni Bajo <giovannibajo(a)libero.it> wrote: > Hartmut Kaiser <hartmutkaiser(a)t-online.de> wrote: > > >>> [AST] >>> a problem -- I can't seem to figure out how to put right-to-left >>> associative operators into the tree properly. I had this as a guess, >>> but I'm really not sure: r = value | value >> root_node_d[ch_p('=')] >>> >> r; > >> Meanwhile I'll >> forward this message to the Spirit mailing list, maybe somebody >> remebers it. Giovanni? > > > The proposed code should work as expected wrt tree generation, but you need > to left-factor it to make it actually work: > > r = value >> !(root_node_d[ch_p('=')] >> r); > > Giovanni Bajo > > > > ------------------------------------------------------- > This SF.Net email is sponsored by: INetU > Attention Web Developers & Consultants: Become An INetU Hosting > Partner. Refer Dedicated Servers. We Manage Them. You Get 10% Monthly > Commission! INetU Dedicated Managed Hosting > http://www.inetu.net/partner/index.php > _______________________________________________ > Spirit-general mailing list > Spirit-general(a)lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/spirit-general

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enable_if part of boost ?
by Anders Moe 22 Jun '03

22 Jun '03

Hi all. After reading about enable_if in CUJ I decided to see if this was present in boost, which it is, sort of, in function_base.hpp. However, it seems to exist in function::, and my impression is that its not really an official boost component. Is this correct ? Regards, Anders.

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boost::thread and .NET
by Bruno Martínez 22 Jun '03

22 Jun '03

Hello, I was wondering what outcome to expect from mixing .NET managed c++ and boost::thread. According to ms's docs a c++ application compiles for .net unchanged, but what kind of api can it expect? What may happen if I try to execute .net code in a thread created by boost::thread? Thanks in advance, Bruno Martinez ------------------------------------------------------ Internet en Uruguay es http://www.internet.com.uy

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boost::spirit and asts
by Dan Nuffer 21 Jun '03

21 Jun '03

Hi, I'm trying to write a grammar for a scripting language, and to do this I'm building an AST of each expression. I have this working fine, for the most part, but I've run into a problem -- I can't seem to figure out how to put right-to-left associative operators into the tree properly. I had this as a guess, but I'm really not sure: r = value | value >> root_node_d[ch_p('=')] >> r; _____________________________________________________________ <a href="http://www.gamedev.net">GameDev.net Email Service</a> - "Plenty of 1's and 0's" _____________________________________________________________ Select your own custom email address for FREE! Get you(a)yourchoice.com, No Ads, 6MB, IMAP, POP, SMTP & more! http://www.everyone.net/selectmail?campaign=tag

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Using Ublas for eigenvalue problems.
by Amit Bhatia 20 Jun '03

20 Jun '03

Hello everyone, I am working on trying to use ublas for finding the eigenvalues and eigenvectors of a positive definite matrix. I am not too sure whether this can be done in ublas. I have seen that there are calls for solving system of equations as well as doing rank updates, but still am not sure whether this could be done "safely" (eigenvalues getting close to zero) and efficiently ? I have read at a couple of places the advice' of using prewritten routines for this rather than trying to write one's own for this non trivial problem. I am a newbie! Any advice/suggestion/past experience with the same will be most welcome. regards, amit.

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