- Boost - lists.boost.org

shared_ptr/shared_count and the cost of use counter allocation
by Hendrik Schober 10 Sep '08

10 Sep '08

Hi, I have taken the task to replace a proprietary smart pointer (a fork of an earlier 'shared_ptr' variant) used in a library used for rendering of 3D scenes by the boost's current 'shared_ptr'. The reason is that I have found a couple of syntactic problems with the proprietary smart pointer that 'shared_ptr' doesn't have. While I succeeded syntactically, in certain performance tests the proprietary smart pointer performs about 20 times better than 'shared_ptr'. It seems that this is caused by the allocation of the use counter. For the proprietary smart pointer this allocation can be tweaked by passing allocators as template arguments, while 'shared_ptr' seems not to allow this. I have yet to find out what that performance difference means for real projects, but according to those familiar with the library the reason the allocators where introduced is that there's code that very extensively creates and destroys smart pointers which suffered badly from allocation costs. Is there a way for me to tweak 'shared_ptr's performance other than by again forking into a proprietary smart pointer and introducing allocators for that one? or is there any interest in the boost community for doing this? Thanks, Schobi

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[thread_pool] Dependencies between tasks
by vicente.botet 10 Sep '08

10 Sep '08

Hi, the tread_pool pattern is very useful to improve parallelism. But sometimes we need to constraint this parallelism, for example when several task are related to the same 'instance' it could be safer to sequence them. Is there a mechanism that allows to do thinks like that on the thread_pool library? Best, Vicente

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boost graph: How to add existing subgraphs to the root graph and how to use boost::write_graphviz with subgraphs?
by Lisa Wilhelm 10 Sep '08

10 Sep '08

Hi, I am a newbie in using boost libraries and template programming, and I try to get familiar with the graph library at the moment. My first problem is, that I want to create subgrahps in "sub-functions" and create the whole graph out of these subgraphs in the calling function. I tried to create the subgraph in the calling function and pass it to the sub-function, but then, the new vertices were added to the root-graph and not to the subgraph. I solved this in the calling-function with adding all the new vertices and their edges again to the subgraph. Is there a better way to do that? My second problem is just as mentioned in the subject line. How to use boost::write_graphviz to print out subgraphs? It works for "normal" graphs but not for subgraphs. I hope this is the right place to ask these questions. Thanks for your answers. Lisa __________________________________________________ Do You Yahoo!? Sie sind Spam leid? Yahoo! Mail verfügt über einen herausragenden Schutz gegen Massenmails. http://mail.yahoo.com __________________________________________________ Do You Yahoo!? Sie sind Spam leid? Yahoo! Mail verfügt über einen herausragenden Schutz gegen Massenmails. http://mail.yahoo.com

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Any interest in a Simple Thread Pool Library?
by Koushik Biswas 10 Sep '08

10 Sep '08

Hi, I am a new subscriber to boost mailing list, though I am a long time boost user. Recently, I needed a simple thread pool for my application, but did not find anything on Boost. I went ahead and developed my own. I believe that with some modifications to make it more generic, it will be a valuable addition to Boost. Following the guidelines specified in "Boost Library Submission Process" page, I am trying to gauge the interest. Synopsis: 1. Will be header only. User will derive from class "ThreadPoolJob" and override its DoJob() method with any action he wants the thread pool to perform. 2. User will instantiate an object of the Pool (can mention initial size), and simply call SubmitJob() with the pointer of an instance of his derived Thread Pool Job class - and the job will be get done. 3. In my current version, a job submission simply accepts the pointer to a new job class, hence the user has to wait until the job is done and then needs to clean up the memory. In the final library, I will take ownership of the memory while accepting a submitted job by using smart pointers. 4. Features: Dynamic shrinking/ expansion of the pool, ability to assign priorities to jobs, schedule future job execution, etc. are ion the roadmap - though I do not need any of these for my own application, the design is generic enough to add these features. Can somebody guide me to the next steps if approved? I could not log in to the boost vault with my mailing list user name and password. Do I need to create a new set? Thanks & Regards, Koushik Biswas Principal Technical Yahoo, Yahoo! Inc.

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boost::throw_exception / exception library update
by Emil Dotchevski 09 Sep '08

09 Sep '08

This is a repost of my original message, with a better subject line as suggested by Felipe, to perhaps attract more readers for this important discussion. Here is a link to the original thread: http://www.nabble.com/-exception--library-update-tt19377623.html Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode On Mon, Sep 8, 2008 at 10:59 AM, Emil Dotchevski <emil(a)revergestudios.com> wrote: > I've finished a major refactoring of the Exception library: > > 1) Thanks to Peter Dimov's boost/detail/sp_typeinfo.hpp, it now works > with or without RTTI support. > > 2) I would like to thank Dave and Robert for complaining about the > added weight to boost/throw_exception.hpp. I managed to reduce that > cost to less than 400 lines total, all contained in > boost/exception/exception.hpp which now does not #include anything > (not even standard headers.) If there are more concerns about this > issue, let's discuss them now. > > The latest documentation can be viewed at > http://svn.boost.org/svn/boost/trunk/libs/exception/doc/boost-exception.html.

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[multi_index_container] Compiling the examples
by Robert Jones 09 Sep '08

09 Sep '08

Trying to multi_index_container I'm getting these compile errors. Apart from #include <string> and using namespace boost this lifted verbatim from the example documentation. #include <string> struct employee { int id; std::string name; employee(int id,const std::string& name):id(id),name(name){} bool operator<(const employee& e)const{return id<e.id;} }; #include <boost/multi_index_container.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/identity.hpp> #include <boost/multi_index/member.hpp> using namespace boost; // define a multiply indexed set with indices by id and name typedef multi_index_container< employee, indexed_by< // sort by employee::operator< ordered_unique<identity<employee> >, // sort by less<string> on name ordered_non_unique<member<employee,std::string,&employee::name> > > > employee_set; My error is multi.cpp:23: error: `indexed_by' was not declared in this scope multi.cpp:25: error: `ordered_unique' was not declared in this scope multi.cpp:25: error: `identity' was not declared in this scope multi.cpp:25: error: template argument 2 is invalid multi.cpp:25: error: expected unqualified-id before '>' token multi.cpp:25: error: expected `,' or `;' before '>' token I'm using Boost 1.36 and gcc 3.4.4 (maybe this too old?). Can anyone tell me what I'm doing wrong? Thanks, Rob. -- ACCU - Professionalism in programming - http://www.accu.org

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[multi_index_container] push_back?
by Robert Jones 09 Sep '08

09 Sep '08

Still having a little teething trouble with multi_index_container. This code, #include <string> #include <boost/multi_index_container.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/identity.hpp> #include <boost/multi_index/member.hpp> using namespace boost; using namespace boost :: multi_index; struct Employee { int id; std :: string name; }; bool operator < ( Employee const & l, Employee const & r ) { return l.id < r.id; } int main( ) { typedef multi_index_container< Employee, indexed_by< ordered_unique<identity<Employee> >, ordered_non_unique<member<Employee, std :: string, & Employee :: name> > > > EmployeeSet; Employee employees[ ] = { { 1, "Adam" }, { 2, "Craig" }, { 3, "Brian" }, { 4, "Dave" }, }; // EmployeeSet eSet( employees, employees + sizeof( employees ) / sizeof( Employee ) ); EmployeeSet eSet; std :: copy( employees, employees + sizeof( employees ) / sizeof( Employee ), std :: back_inserter( eSet ) ); return 0; } Gives me an error stating there is no push_back method on the container. /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h:364: error: 'class boost::multi_index::multi_index_con tainer<Employee, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::identity<Employee >, mpl_::na, mpl_::na>, boost::multi_index::ordered_non_unique<boost::multi_index::member<Employee, std::string, &Employ ee::name>, mpl_::na, mpl_::na>, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na , mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<Employee> >' has no member named 'push_back' is there something I'm missing out? Thanks, Rob.

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[smart_ptr] release()
by Phil Bouchard 09 Sep '08

09 Sep '08

As it turns out I think a release() member function should be added to the smart pointer. Its purpose is to give away ownership of the object. See the following pseudo-code: template <typename T> class smart_ptr { ... smart_ptr(element_type *); value_type * get(); element_type * release() { element_type * __p = pointer_ref(); pointer_ref() = 0; if (-- counter_ref()) return 0; else return __p; } }; It follows the same idea of its predecessor auto_ptr<> but will return a null pointer if the object is still shared thus not ready to be deleted. This way the allocator will be much easier to support either by calling this function before deallocate(), inside it or by using a specialized wrapper class to handle it: template <typename T> class allocator { ... typedef smart_ptr<T> pointer; void deallocate(pointer & __p) { delete p.release(); } }; -Phil

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[thread_safe_signals] changing the namespace used
by Stjepan Rajko 09 Sep '08

09 Sep '08

Hello, In trying to use thread_safe_signals with Dataflow.Signals, I did the following before including the headers to cause thread_safe_signals to use the boost::signals namespace instead of boost::signalslib (I needed this because Dataflow.Signals adds to the boost::signals namespace): #define signalslib signals #define signals signals The first line was to change the namespace used, and the second to prevent thread_safe_signals from aliasing boost::signals to itself. This worked for gcc on OS X, but I just found out that msvc 2005 express chokes on it (in some preprocessing file iteration loop). Is there a better solution for this? Thanks, Stjepan

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[dataflow][review] loading Dataflow.Signals components from shared libraries
by Stjepan Rajko 09 Sep '08

09 Sep '08

In the Dataflow library / Dataflow.Signals layer review discussions, a few people have mentioned the potential usefulness of loading components at runtime (e.g., from a shared library). I put together a small example of how this could be done for Dataflow.Signals components using the (prototype) Dataflow.Blueprint layer and the Extension library: http://svn.boost.org/svn/boost/sandbox/SOC/2007/signals/libs/dataflow/examp… The component_add.cpp file contains the implementation of a component (that adds two numbers and outputs the result), and the code required to access it through an Extension factory_map. The extension_example.cpp file loads the shared library created from component_add.cpp, instantiates the provided component, and uses it to complete a network. The Blueprint layer is still under development (and has somewhat ugly syntax), but I hope this example can still demonstrate some future possibilities of the Dataflow library with regards to loading components at run-time. It has been tested to work with MSVC 2005. Regards, Stjepan

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