May 2006 - Boost-users - lists.preview.boost.org

Re: [Boost-users] [review] Boost.Fusion
by João Abecasis 16 May '06

16 May '06

Joel de Guzman wrote: > João Abecasis wrote: >> On the directory structure used for the headers, I like the modular >> approach but sometimes get the feeling that it's too fragmented. Having >> more top-level reflections of individual components would ease my >> concerns. Another aspect is that this structure diverges from what is >> used in MPL. Given the parallel between the two libraries I think an >> effort should be made to keep the structure similar. In fact, this is >> also part of the user interface. Still, in the end, I recognize that >> they're two independent libraries and must each follow its path. > > Understood. I'll give this a lot of thinking. At the very least, > we'll surely have a flat set of headers that forward to the > main headers. Where to place them is a matter to deliberate on. > Maybe <boost/fusion/hdr/xxx.hpp> ? or simply <boost/fusion/xxx.hpp> > and push the main tree downwards in another directory, say, "main"? Why do you need to have them in separate directories? Are there conflicting/overlaping headers when you mix the approaches (or are you just trying to keep everything nice and tidy ;-) ) ? >> Fusion is coded with the expectation that the library code will be >> optimized into very tight code, which seems to be a reasonable >> assumption with (any?) modern compilers. > > I hope g++ will catch up! See Dan's post regarding some Fusion > speed tests. g++ produces the fattest and slowest code :( > I wish I was using incorrect flags or I haven't found the > best compiler switches to use for g++. It will catch up :-) On a side note, it seems the tests were run with gcc 3.4. IIRC, gcc 4 and beyond introduced a couple of interesting optimizations so I wonder how far do those go towards narrowing the gap. > MS VC8.0 produces the tightest and fastest code, so far. > (No, I'm not a fan of MS. Those are just the facts.) Of course ;-) I like facts! From my limited experience, I've also seen MSVC produce the tightest code. Perhaps there should be a way to extract some benchmarks (e.g., code size, performance) from the Boost regression tests, or separate benchmark-tests for the different compilers could be integrated into the system. This could be interesting and useful information for library developers. >>> - What is your evaluation of the potential usefulness of the library? >> I believe Fusion has great potential as a library building block but >> also as a more application-oriented library. On the library building >> block side, I believe it has the potential to become a fundamental/core >> piece of Boost. For application developers, Fusion takes tuples to a new >> level, allowing one to make the most of information that is available at >> compile-time. I wanted to make an additional suggestion that might make Fusion's usefulness more visible, but it slipped my mind at the last minute. While I'm not that familiar with Boost.Serialization it seems to be a fairly popular library with developers of varying technical level. My suggestion is that Fusion Sequences be made serializable, using Boost.Serialization. This would go in a separate header (e.g., in fusion/sequence/io/serialization.hpp) and have the requirement that serialization be implemented for individual element types. If possible, the serialization would be generic, i.e., tied to the type sequence and not to the particular Fusion Sequence. With serialization in place, Fusion sequences could be used to manage a class's data and its serialization or they could be used as a proxy during serialization: archive & tie(a, b, c); Hmm... I see that the Quick Start mentions serialization as an example. Is there a reason for not offering the interface to Boost.Serialization in the library? Best regards, João

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[boost-users][serialization]Can I serialize wstring into text_oarchive?
by Wang Yun 16 May '06

16 May '06

Hi, all I do some tests and found it's ok to save/load wstring into/from text_oarchive, Am I very lucky? or it's safe to do this? When do I need to use text_woarchive? Thanks, Wang Yun

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Re: [Boost-users] newbie - boost::shared_ptr of type stringstream using << operator?
by EMalenfant＠interstarinc.com 15 May '06

15 May '06

From: Ed Johnson [mailto:ed@edwardotis.com] > > Thanks, I see where I was not using the correct constructor before. > However, even when I use the proper one, I get the same > results. I cannot get the '<<' operator to append to the > original string that I pass using the stringstream > constructor. It still begins at the first character and > begins overwriting the string. > > //constructor syntax > explicit stringstream ( openmode mode = in | out ); explicit > stringstream ( const string & str, openmode mode = in | out ); > > //updated code > boost::shared_ptr< std::stringstream > sharedStream(new > > std::stringstream("hello world", std::stringstream::out)); > > Is there something else I'm missing? > I think you have to use the "ate" or "app" openmode for that. HTH, Éric

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newbie - boost::shared_ptr of type stringstream using << operator?
by Ed Johnson 15 May '06

15 May '06

Hi, Is it possible to use shared_ptr to manage stringstreams, and still use the << operator on the stringstream? example: //I would like to print 'hello world!' in both cases #include <iostream> boost::shared_ptr< std::stringstream > sharedStream(new std::stringstream("hello world")); (*sharedStream) << "!"; std::cerr << (*sharedStream).str() << std::endl; std::stringstream tr; tr << "hello world"; tr << "!"; std::cerr << tr.str() << std::endl; output: !elloworld hello world! Many thanks, Ed Johnson

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ipp files
by Joe McCay 15 May '06

15 May '06

Simple question. What exactly are ipp files, and how are they used? jmccay

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Re: [Boost-users] [multi_index] thread safety
by Patel Priyank-PPATEL1 15 May '06

15 May '06

Thanks.. Let me try that out. Also, I will put check if mutex acquire method returns success or not during addition only than and than I will go ahead and add procedure in pool. Thanks Priyank ________________________________ From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Kobi Cohen-Arazi Sent: Friday, May 12, 2006 11:33 PM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [multi_index] thread safety Hi, comments below On 5/12/06, Patel Priyank-PPATEL1 <priyankpatel(a)motorola.com> wrote: Hi Joaquin, I have to use actually two or more threads on procedure pool. I start seeing same Problem when I have three/four threads working on same procedure pool. I tried to introduce mutex (ACE_Guard) but still having problems in execution in one/two minute of execution. Seems I am guarding every method that is used by container. Anything wrong with the Following code? int Procedure_Pool::add_by_id(Procedure * _procedure) { LD_TRACE("Procedure_Pool::add_by_id"); ACE_ASSERT(_procedure != 0); ACE_DEBUG((LM_DEBUG, "ADDING %d\n", _procedure->id())); if (find_by_id(_procedure->id()) == 0) { ACE_Guard<ACE_Mutex> guard(mutex_); { // procedure not found procedure_by_id_.insert(_procedure); } // debug info ACE_DEBUG((LM_DEBUG, "Added procedure : %d \n", _procedure->id())); // return success return 0; } else { // error ACE_ERROR((LD_ERROR "%N:%l Error in adding procedure : %d \n", _procedure->id())); // return failure return -1; } } int Procedure_Pool::remove_by_id(Procedure * _procedure) { LD_TRACE("Procedure_Pool::remove_by_id"); ACE_ASSERT(_procedure != 0); ACE_DEBUG((LM_DEBUG, "REMOVING: %d \n", _procedure->id())); if (find_by_id(_procedure->id()) != 0) { ACE_Guard<ACE_Mutex> guard(mutex_); { // procedure found procedure_by_id_.erase(_procedure->id()); } ACE_DEBUG((LM_DEBUG, "Removed procedure : %d \n", _procedure->id())); return 0; } else { ACE_ERROR((LD_ERROR "%N:%l Error in removing procedure : %d \n", _procedure->id())); return -1; } } Procedure * Procedure_Pool::find_by_id(int _id) { LD_TRACE("Procedure_Pool::find_by_id"); ACE_Guard<ACE_Mutex> guard(mutex_); { Procedure_By_Id::iterator it = procedure_by_id_.find(_id); if (it != procedure_by_id_.end()) { ACE_DEBUG((LM_DEBUG, "%N:%l Found procedure for id: %d \n", _id)); return *it; } } ACE_DEBUG((LM_DEBUG, "%N:%l Not able to found procedure for id: %d \n", _id)); // return null return 0; } Yes. There is a small theoretical problem with your code. A possible race condition. you tried to find_by_id, using mutex, than release that mutex and reacquire it for erase. That's a possible race condition. The "find" until the "erase" must be atomic. At least IMHO. Kobi.

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boost::iterator_adaptor
by Grisha Spivak 14 May '06

14 May '06

Hi, here is small code snippet to demonstrate my problrm: #include <stddef.h> #include <iostream> #include <boost/iterator/iterator_adaptor.hpp> template<typename T, size_t stride> class stride_iterator : public boost::iterator_adaptor<stride_iterator<T, stride>, T*> { public: stride_iterator() : stride_iterator::iterator_adaptor_( 0 ) { } explicit stride_iterator( T * p ) : stride_iterator::iterator_adaptor_( p ) { } private: friend class boost::iterator_core_access; void increment() { this->base_reference() = this->base() + stride; } void deccrement() { this->base_reference() = this->base() - stride; } void advance( ptrdiff_t d ) { this->base_reference() = this->base() + d*stride; } ptrdiff_t distance_to( stride_iterator const & i ) const { return ( i.base() - this->base() )/stride; } }; int main() { int arr[12] = {}; arr[3*2] = 33; arr[5*2] = 55; stride_iterator<int, 2> it( arr ); it[2] = -22; it[3] = it[5]; std::cout << arr[2*2] << ' ' << arr[3*2] << ' ' << arr[5*2] << '\n'; return 0; } It prints "-22 33 55" instead of "-22 55 55" (which I expected) - so "it[3] = it[5];" assignment didn't modifies array. Is it intended behaviour? Or maybe I'm doing something wrong?

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newbie - boost::shared_ptr of type stringstream using << operator?
by Ed Johnson 14 May '06

14 May '06

Hi, Is it possible to use shared_ptr to manage stringstreams, and still use the << operator on the stringstream? example: #include <iostream> boost::shared_ptr< std::stringstream > sharedStream(new std::stringstream("hello world")); std::cerr << (*sharedStream).str() << std::endl; (*sharedStream) << "!"; std::cerr << (*sharedStream).str() << std::endl; std::stringstream tr; tr << "hello everyone"; tr << "!"; std::cerr << tr.str() << std::endl; output: hello world !elloworld hello everyone! Thanks, Ed Johnson

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[review] Fusion review begins
by Ronald Garcia 14 May '06

14 May '06

The review of Joel de Guzman's Fusion library begins today, May 1, 2006, and continues through May 10, 2006. :Download: http://spirit.sourceforge.net/dl_more/fusion_v2.zip :Description: Fusion is a library of heterogenous containers and views and algorithms. A set of heterogenous containers (vector, list, set and map) is provided out of the box along with view classes that present various composable views over the data. The containers and views follow a common sequence concept with an underlying iterator concept that binds it all together, suitably making the algorithms fully generic over all sequence types. The architecture is somewhat modeled after MPL which in turn is modeled after STL. It is code-named "fusion" because the library is the "fusion" of compile time metaprogramming with runtime programming. Review questions ================ Please always explicitly state in your review, whether you think the library should be accepted into Boost. You might want to comment on the following questions: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Cheers, Ron

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Re: [Boost-users] [multi_index] thread safety
by Patel Priyank-PPATEL1 13 May '06

13 May '06

Hi Joaquin, I have to use actually two or more threads on procedure pool. I start seeing same Problem when I have three/four threads working on same procedure pool. I tried to introduce mutex (ACE_Guard) but still having problems in execution in one/two minute of execution. Seems I am guarding every method that is used by container. Anything wrong with the Following code? Thanks Priyank #ifndef PROCEDURE_POOL_H #define PROCEDURE_POOL_H /** * Identifier pool of procedure. This procedure will be un-sorted * hashed index provided by procedures unique id retuned by procedure. * It internally uses boost hashed index for indexing the procedures * in procedure pool. * * @author Priyank Patel * @since Mar 30, 2006 */ #include <ace/Mutex.h> #include <boost/multi_index_container.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/config.hpp> #include <boost/utility.hpp> #include <boost/shared_ptr.hpp> #include <boost/multi_index/key_extractors.hpp> #include "Procedure.h" using boost::multi_index_container; using namespace boost::multi_index; /** * Defines tag used for procedure id. */ struct procedure_id_tag { }; class Procedure_Pool: boost::noncopyable { private: /** * Type definition for multi index container. */ typedef multi_index_container< Procedure*, indexed_by< hashed_unique< tag<procedure_id_tag>, const_mem_fun<Procedure, int, &Procedure::id> > > > Procedure_Hashed_Pool; /** * Type definition for indexing based on procedure id tag. */ typedef Procedure_Hashed_Pool::index<procedure_id_tag>::type Procedure_By_Id; public: /** * Constructor. */ Procedure_Pool(): pool_(), procedure_by_id_(pool_.get<procedure_id_tag>()) { } /** * Adds specified procedure in this pool. * It will intenally used procedures id() method to index procedure. * @param _procedure Procedure to be added in this pool * @return Success (0) or Failure (-1) based on addition happened or not */ int add_by_id(Procedure * _procedure); /** * Removes procedure from this pool. * @param _procedure procedure that needs to be removed * @return Success (0) or Failure (1) based on removal happend or not */ int remove_by_id(Procedure * _procedure); /** * Retrieves procedure based on specified id. * @param _id Identifier * @return Procedure Pointer to procedure. Returns 0 if procedure not found */ Procedure * find_by_id(int _id); private: /** * Returns true if procedure is present otherwise returns false. * @param _procedure procedure that needs to found * @return true if found or false if not found */ //bool find_by_id(Procedure * _procedure); /** * boost multiindex object that is associated with this pool. */ Procedure_Hashed_Pool pool_; /** * Refernece of pool that is indexed by procedure id tag. */ Procedure_By_Id &procedure_by_id_; ACE_Mutex mutex_; }; #endif //===============================================================================/// #include "../include/Procedure_Pool.h" int Procedure_Pool::add_by_id(Procedure * _procedure) { LD_TRACE("Procedure_Pool::add_by_id"); ACE_ASSERT(_procedure != 0); ACE_DEBUG((LM_DEBUG, "ADDING %d\n", _procedure->id())); if (find_by_id(_procedure->id()) == 0) { ACE_Guard<ACE_Mutex> guard(mutex_); { // procedure not found procedure_by_id_.insert(_procedure); } // debug info ACE_DEBUG((LM_DEBUG, "Added procedure : %d \n", _procedure->id())); // return success return 0; } else { // error ACE_ERROR((LD_ERROR "%N:%l Error in adding procedure : %d \n", _procedure->id())); // return failure return -1; } } int Procedure_Pool::remove_by_id(Procedure * _procedure) { LD_TRACE("Procedure_Pool::remove_by_id"); ACE_ASSERT(_procedure != 0); ACE_DEBUG((LM_DEBUG, "REMOVING: %d \n", _procedure->id())); if (find_by_id(_procedure->id()) != 0) { ACE_Guard<ACE_Mutex> guard(mutex_); { // procedure found procedure_by_id_.erase(_procedure->id()); } ACE_DEBUG((LM_DEBUG, "Removed procedure : %d \n", _procedure->id())); return 0; } else { ACE_ERROR((LD_ERROR "%N:%l Error in removing procedure : %d \n", _procedure->id())); return -1; } } Procedure * Procedure_Pool::find_by_id(int _id) { LD_TRACE("Procedure_Pool::find_by_id"); ACE_Guard<ACE_Mutex> guard(mutex_); { Procedure_By_Id::iterator it = procedure_by_id_.find(_id); if (it != procedure_by_id_.end()) { ACE_DEBUG((LM_DEBUG, "%N:%l Found procedure for id: %d \n", _id)); return *it; } } ACE_DEBUG((LM_DEBUG, "%N:%l Not able to found procedure for id: %d \n", _id)); // return null return 0; } -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of JOAQUIN LOPEZ MU?Z Sent: Thursday, May 11, 2006 2:12 PM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [multi_index] thread safety ----- Mensaje original ----- De: george <george13p(a)yahoo.com> Fecha: Jueves, Mayo 11, 2006 7:27 pm Asunto: Re: [Boost-users] [multi_index] thread safety > hello Joaquin Hello George, > > > You have to lockguard every access to the container; note this also > > includes, for instance, container traversal with iterators, i.e. > > iterator displacement. Strictly speaking, iterator dereference > > should also be lockguarded, although I can say unofficially that > > unguarded dereference is OK. > > can you explain a litle more? > as I konw from STL, multiple readers is ok. Correct. > reading and inserting a new object does't invalidate iterators(for > pointer-based conteiners offcourse,list, map etc...) Correct. This also holds for multi_index_containers. > > a concurrent read and insert in multi_index are not (safely)possible? > I mean there might be an iterator invalidation? Concurrent reading and writing is not safe, but the issue has nothing to do with iterator invalidation. ...I think I've got a hunch about what you've got in mind. When I say that you've got to lockguard iterator displacement, what I mean is: consider a concurrent write operation and an iterator increment; this concurrency is not thread safe and undefined behavior results: a possible outcome is iterator invalidation, but you could also get an app crash, a corrupted data structure, an infinite loop or whatever. Tecnhically speaking, an invalid iterator is a perfectly legal state for an iterator to be in, which has nothing to do with undefined behavior resulting from violating thread safety guarantees. I'm not sure I made myself clear :) Insist on me if I didn't. > offcourse there is a chance for a 'dirty-read' but this for the domain > of the aplication if it is a problem and not for multi_index. I don't get what you mean here, would you care to elaborate? Joaquín M López Muñoz Telefónica, Investigación y Desarrollo _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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