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[GIL] any_image difference
by Olivier Tournaire 08 Nov '10

08 Nov '10

Hi all, What is the best way to compute the difference between 2 any_image? Of course, the input any_image may not be of the same type... So, if pixels are unsigned int for the 1st one and double for the 2nd one, the result must be stored as double. I (accidently) found pixel_minus_t in pixel_numeric_operations.hpp but cannot figure how to use it. Hope you could help. Regards, Olivier

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signals2::slot_type & g++ anti-aliasing warning
by Ákos Maróy 08 Nov '10

08 Nov '10

Hi, I bumped into an issue, where g++ would give me an anti-aliasing warning for very basic / straightforward signals2 code. consider the following sample code: #include <iostream> #include <boost/bind.hpp> #include <boost/signals2.hpp> typedef boost::signals2::signal<void (void)> sig_t; void ff(void) { std::cout << "ff" << std::endl; } int main(void) { sig_t::slot_type ss = boost::bind(&ff); return 0; } when compiled with the -Wall and -O2 flags, I get the following compiler warning: ... sample.cxx:13: instantiated from here /home/maroy/src/mxp/usr/include/boost/function/function_base.hpp:321: warning: dereferencing type-punned pointer will break strict-aliasing rules /home/maroy/src/mxp/usr/include/boost/function/function_base.hpp:325: warning: dereferencing type-punned pointer will break strict-aliasing rules (I can provide the full compiler output if needed) this is with boost 1.44 on a linux x86_64, g++ version 4.4.3 omitting either the -O2 or the -Wall flags will make the warning go away. what am I doing wrong? Akos

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[polygon] Valgrind errors when normalizing any angle polygons
by Josh Pieper 08 Nov '10

08 Nov '10

Hello, We have been using the 1.44.0 release of polygon for some internal projects and have come across a number of oddities. The first one I've got is a valgrind error when normalizing polygons with numerically large coordinate values. Using the gmp_override.hpp header does resolve these problems, but my understanding is that it is the intent for the library to merely be numerically imprecise, rather than crash, for coordinates which are too large. Our simplified test case is below, and was compiled on an AMD64 Ubuntu 10.4 system. The first call to Normalize has no problems, but the second call causes valgrind to report both uninitialized memory usage and invalid reads. (I can produce the valgrind log on demand, but it is somewhat large for inclusion in an email). While we have deployed 1.44.0 internally, I tested against the most recent svn version and the problem still exists. Is this merely a mis-use of the API? Regards, Josh Pieper ------------------------ #include <stdint.h> #include "boost_polygon/r66294/polygon/polygon.hpp" typedef boost::polygon::point_data<int32_t> BoostPoint; typedef boost::polygon::polygon_data<int32_t> BoostPolygon; typedef boost::polygon::polygon_set_data<int32_t> BoostPolygonSet; typedef boost::polygon::polygon_with_holes_data<int32_t> BoostPolygonWithHoles; typedef std::vector<BoostPolygonWithHoles> BoostPolygonWithHolesVector; template <typename Array> void Normalize(const Array& data, int32_t scale) { std::vector<BoostPoint> points; for (size_t i = 0; i < sizeof(data) / sizeof(*data); i += 2) { points.push_back(BoostPoint(data[i] / scale, data[i + 1] / scale)); } using namespace boost::polygon::operators; BoostPolygonSet poly_set; poly_set |= BoostPolygon(points.begin(), points.end()); BoostPolygonWithHolesVector normal; poly_set.get(normal); } int main() { int32_t data[] = { 0, 0, -1000000, -1000000, 19000000, -1000000, 18292893, 707106, 8292893, -9292893, 8170784, -9440890, 8078584, -9610754, 8000000, -10000000, 8078584, -10389245, 8170784, -10559109, 8292893, -10707106, 18292893, -20707106, 19000000, -19000000, -1000000, -19000000, 0, -20000000, 0, 0, }; Normalize(data, 10); // Fine. Normalize(data, 1); // Crashes. }

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multi_array and variants
by Alle Meije Wink 08 Nov '10

08 Nov '10

Dear all, This still seems to be a problem that every once in a while someone tries to solve and then stops. It's my turn again... I'm trying to make a wrapper template class for 1,2,...8-dimensional images whose values can be char,short,...double to store brain image statistics. I had a go at this before and followed the suggestions described here http://lists.boost.org/boost-users/2009/08/50732.php What I now have is a class bisArray: ... template<typename T> class bisArray: public bisObject { typedef boost::variant < boost::multi_array_ref<T, 1>, boost::multi_array_ref<T, 2>, boost::multi_array_ref<T, 3>, boost::multi_array_ref<T, 4>, boost::multi_array_ref<T, 5>, boost::multi_array_ref<T, 6>, boost::multi_array_ref<T, 7>, boost::multi_array_ref<T, 8>, boost::multi_array_ref<T, 9> > bisArray_t; bisArray_t _bisArray; ... and a class bisImage, which has a bisArray as well as a pointer to the data as read from file (1-dimensional structure): ... template<typename T> class bisImage: public bisObject { public: /** Constructor using existing array data Reformats array as bisImage */ bisImage ( T* _data, size_t _dimensions, std::vector<size_t> _sizes ): data(_data), dimensions(_dimensions) { this.storage=bisArray<T>( _data, _dimensions, _sizes); this.dummy = T(); } ... When I try to initialise an image read from file using ... bisImage<unsigned char> newimage=bisImage<unsigned char> ((unsigned char *)testimage->data, ndim, dims); ... I get, as the first of many errors, this message bisimage.hpp|33|error: no matching function for call to ‘canabis::bisArray<unsigned char>::bisArray()’| That seems to suggest that I call an empty (default) constructor, which I don't do *anywhere* Has anyone ever tried to do something similar? Or do you have any thought about what I am doing wrong here? Is it multi_array complaining or variants? Many thanks Alle Meije

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boost MPI issue on windows
by Nick Collier 08 Nov '10

08 Nov '10

Hi, I've got an MPI application that uses the boost mpi libraries. It runs fine on OSX and Linux when compiled using both debug and more optimized compiler flags. Unfortunately, on windows, the application only runs when compiled using Visual Studio 2008 debug configuration. When I run the executable compiled in the release configuration it crashes, but not in the same place every time in my code. It does only occur though when I make communicator::send and communicator::recv calls, sending and receiving vectors of ints. In those cases, I get exceptions like: {routine_=0x00d37d38 "MPI_Send" result_code_=805931010 message="MPI_Send: Invalid count, error stack: MPI_Send(176): MPI_Send(buf=0x001BF950, count=-1833296, MPI_PACKED, dest=1, tag=2001, MPI_COMM_WORLD) failed MPI_Send(101): Negative count, value is -1833296" } Sometimes its for a send and sometimes for a receive, but the exception is always for a "negative count" which looks suspiciously like an uninitialized integer. I figured I'm doing something wrong either in how I've compiled the boost libraries or in my own code (although its odd that it works in both linux and osx). Any suggestions obviously appreciated. This is for boost-1.39. We are prevented from using anything newer because the machine we ultimately deploy on has boost-1.39 installed. On windows, I'm using microsoft's mpi implementation (based on MPICH2) under windows 7. The boost mpi libraries are compiled in both static debug and release mt versions. thanks very much, Nick

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[BGL] Unable to sort list of edge_descriptors
by Mike Douglass 08 Nov '10

08 Nov '10

I'm trying to sort a list of edge_descriptors, but I get the compiler error described below. typedef adjacency_list < vecS, vecS, bidirectionalS >::edge_descriptor edgeDescriptor; // defined globally template < typename Graph, typename edgeDescriptor > struct SortByName : public binary_function<edgeDescriptor, edgeDescriptor, bool> { bool operator()(const Graph & g, const edgeDescriptor& a, const edgeDescriptor& b) { return g[a].eName < g[b].eName; } }; template < typename Graph > void Sort_Test(Graph & g) { typedef std::list<edgeDescriptor> edge_list; typename graph_traits<Graph>::edge_iterator edge_iter, edges_end; edge_list A; for (tie(edge_iter, edges_end) = edges(g); edge_iter != edges_end; ++edge_iter) A.push_back(*edge_iter); for (edge_list::iterator i = A.begin(); i != A.end(); ++i) cout << " *i = " << " " << g[*i].eName << "\n"; // If the following line is commented out the program compiles and runs OK. A.sort(SortByName< typename Graph, typename edgeDescriptor >()); //With the above line uncommented the compiler says: /* ./Includes/Utilities.cpp: In function ‘void Sort_Test(Graph&)’: ./Includes/Utilities.cpp:539: error: wrong number of template arguments (1, should be 2) ./Includes/Utilities.cpp:513: error: provided for ‘template<class Graph, class edgeDescriptor> struct SortByName’ make: *** [plc] Error 1 */ } But clearly there are two template arguments - < typename Graph, typename edgeDescriptor > Thanks

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Asio and bind. Queuing a bind call.
by Nick.Adamson＠generaldynamics.uk.com 08 Nov '10

08 Nov '10

Hi All. I'm putting together a class which provides a single point of contact to a resource. I'm planning on using the asio IO service in conjunction with a ASIO strand to control flow of method calls to my resource. I've got this working and ASIO has made this so easy. One of the things I've got to do is to be able to pause and queue function calls to the resource if the resource can't service the request. I figured the best way of doing this was putting the result of boost::bind in to some sort of queue when the resource is unavailable and then when it becomes available processing the items in the queue. Is this the best way to do it or does the strand or IO service have a way of doing it? As the result of boost::bind is a template I don't know of an stl or boost container which will store these objects. As there are a number of functions that can be called on my resource with differing arguments I don't think I can use a boost::function as I don't know the arguments to my generic post call. Here's some sudo code which may help to explain it. class CResourceManager { public: // post. // this function takes in a bound function and addes it to the queue of functions to call. // it reserves the sequence of calls by using the io strand. // this means that any function called by this post call is guaranteed to be called in sequence and will be the only function called at that time. template <typename CompletionHandler> void Post(CompletionHandler handler) { if (m_bStrandEnabled) { m_strand.post( handler ); } else { // strand is not enabled. ?????? m_queuedCalls.push( handler ); ????? } } void EnableStrand() { iterate through queue posting functions on to the strand. ?????? code would depend on container used. m_bStrandEnabled = true; } boost::asio::io_service &m_ioService; boost::asio::io_service::strand m_strand; private: bool m_bStrandEnabled; // as a boost bind function is templated we have to work out a way of putting an unknown template in to the queue. queuedfuncitoncontainer m_queuedCalls; } at the moment I don't know what type the "queuedfuncitoncontainer" should be. Because the result of boost::bind is dependent on the function being bound it doesn't seem like I can use stl::queue. Anyone have any ideas how I can do this? I've done a bit of googling and didn't really get any ware. I did look at the boost code to see how strand does it and it seems like its using raw pointers, I didn't really want to go down that road if I can help it. Thanks. Nick. Nick Adamson Software Engineer Advanced Projects and Technology General Dynamics United Kingdom Limited Bryn Brithdir, Oakdale Business Park, Blackwood, South Wales, NP12 4AA Telephone: +44 (0)1495 23 6467 Email: Nick.Adamson(a)generaldynamics.uk.com Website: www.generaldynamics.uk.com <http://www.generaldynamics.uk.com/> To help reduce waste paper, please only print this email if you really need to.

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Re: [Boost-users] Does anybody interested in active object
by Marat Abrarov 08 Nov '10

08 Nov '10

To Dean Michael Berris: Thank you for your patience and detailed answers. > Nope, sorry, s11n_example::connection is not an active object. What it actually is, is an execution > context -- or sometimes people call it a continuation, a generator, or a state machine. Because you're > using the execution context relevant with a particular connection, it doesn't imply that the > operations are performed on a different thread. Ok. May be I'm wrong trying to name it "active object". "Continuation", "state machine", "execution context" - this is very close to what I had in mind. Therefore, I conclude that we understand each other (despite some language barriers with my hand). I thought all of "Continuation/state machine/execution context" was related to the pattern of "active object", hmm... > If you have unlimited number of cores and no limits on the number of threads you can spawn for each > active object you create, then yes. I think the main feature of "Continuation/state machine/execution context" is not saving threads, but organizing flexible and comfortable way of communication between state machines (yes - it is tasks and queues, but wrapped in async method call with callback). That is what I try to implement by means of Boost.Asio. It was chosen "historically" (started from network programming), but for the now times I see it is the best choice :) > Otherwise, you can stick with continuations, asynchronous completion handlers, and just plain data > parallelism. At the "samples" I develop (thanks to Boost.Asio examples - the are the first) the main goals were: 1) share execution context (thread pool) between different "state machines". 2) (make possible to) divide execution contexts of different "state machines" and application layers when it is needed (session and session_manager - not layers but are close to them). 3) develop a simple way of implementing async method call (for the "state machines") with required callback. (with required usage of "custom memory allocation" which can make usage of async methods as cheap as possible) Regards, Marat Abrarov. > Message: 3 > Date: Mon, 8 Nov 2010 10:29:02 +0800 > From: Dean Michael Berris <mikhailberis(a)gmail.com> > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] Does anybody interested in active object > Message-ID: > <AANLkTimW0ozMYQ_GfstJw4mV111=2JTc0JSh+0YzLdYF(a)mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > On Mon, Nov 8, 2010 at 7:11 AM, Marat Abrarov <abrarov(a)mail.ru> wrote: > > To Dean Michael Berris: > >> You'd be better of doing data parallelism with Boost.MPI > > > > No. Because I'm speaking about thread-based parallelism (with shared > > memory access). > > Processed-based parallelism and IPC supplement but don't replace > > thread-based parallelism in general. > > > > Well, which is why I said 'data parallelism'. This implies a whole different kind of programming, > which doesn't typically include threads and synchronization. ;) > > > > >> and/or Boost.Asio's io_service > >> run on multiple threads, and having independent tasks multiplexed > >> across a number of processors (either through processes or threads) > > > > Tie this tasks with the data they share and You will have an active object. > > Nope, sorry, that's not an active object. An Active Object requires that you have a at least one > thread of execution dedicated to the active object, and that you have a synchronous interface to that > object. > > > If the tasks don't have shared data - they don't need an active object. > > Active Objects really have nothing to do with shared data. It's a design pattern that prescribes a way > of isolating the synchronization and serialization of operations applied to an object that is assumed > to be shared across multiple threads of execution. The way the active object does it is by lining up > the operations to be performed asynchronously and perform those in a different thread of execution. > > You can implement an active object without involving shared data -- for example you want to model a > processor, or a math kernel, which does all its work on a single thread because maybe you have a > library underneath that is not thread-safe. In situations like these it makes sense to have an active > object implementation. > > > I think - active object is built on task-based parallelism but it does > > not mean that "active object" should replace "task-based parallelism" > > everywhere. > > > > I think you have it wrong. The active object pattern is a design pattern that doesn't know about task- > based parallelism. Task-based parallelism is a different pattern and different paradigm altogether. > The active object pattern by itself is just a design pattern, nothing more. > > > > >> But what you're describing is not the active object pattern. ;) > > > > http://en.wikipedia.org/wiki/Active_object > > http://en.wikipedia.org/wiki/Active_object_(Symbian_OS) > > What about ma::echo::server::session class - is it an active object? > > > > I haven't looked at your examples, because I was only commenting on the issue regarding massive > parallelism. Maybe when I have enough time I'll look through your examples. ;) > > > > > http://www.boost.org/doc/libs/1_44_0/doc/html/boost_asio/example/chat/ > > chat_c > > lient.cpp > > Is chat_client an active object? If "yes" then why? > > chat_client::write have no completion callback - and this is not > > enough sometimes (I can say "always", if You don't implementing > > "fire-and-forget" logic which is rather seldom). > > > > No, this is not an active object. An active object has its own lifetime thread. In this situation the > lifetime thread is shared between Boost.Asio's IO subsystem and all the ASIO related handlers. > > Also, you don't need a completion callback for a class to model the Active Object pattern. You can > create methods that return 'void' and just execute the actions asynchronously in its own lifetime > thread. > > > > > http://www.boost.org/doc/libs/1_44_0/doc/html/boost_asio/example/seria > > lizati > > on/connection.hpp > > s11n_example::connection is an active object and have completion callback... > > but it's much simpler then ma::echo::server::session_manager - I try > > to suggest "samples" that can help to build such a kind of complex > > active objects. > > > > Nope, sorry, s11n_example::connection is not an active object. What it actually is, is an execution > context -- or sometimes people call it a continuation, a generator, or a state machine. Because you're > using the execution context relevant with a particular connection, it doesn't imply that the > operations are performed on a different thread. > > All this is doing is encapsulating callbacks and the protocol implementation into an object. It > exposes a means of asynchronously scheduling operations, but it doesn't hide these details from the > interface. The goal of the active object pattern is to hide the asynchronous nature of the > implementation from the user of the object. > > > > > http://www.drdobbs.com/go-parallel/blog/archives/2009/09/parallelism_s > > ho.htm > > l > >> We are surrounded by parallelism even more so that serial activities. > >> Social and biological systems are immersed in parallelism and these > >> systems have worked out the kinks over millions of years. > >> In biological systems, independent units perform simple computations > >> or activities independently and in parallel. > > and > >> IMPLICATIONS FOR COMPLEX REALTIME SYSTEMS: > >> Complex real-time systems would be a sea of state machine objects > >> interacting with each other. There will be low level state machines > >> which would work together to implement high level state machine behavior. > > > > Here's the place for active object pattern. > > > > If you have unlimited number of cores and no limits on the number of threads you can spawn for each > active object you create, then yes. > Otherwise, you can stick with continuations, asynchronous completion handlers, and just plain data > parallelism. > > The place for an active object is where you have to expose a synchronous interface to a resource which > underneath performs the actions asynchronously. This is like the half-sync half-async pattern which, > once you understand, is what the active object implementation provides. > > -- > Dean Michael Berris > deanberris.com

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Re: [Boost-users] [mpl] Iterator Concept Checking? SOLVED + Recommendation.
by Stirling Westrup 08 Nov '10

08 Nov '10

On Sun, Oct 31, 2010 at 6:16 PM, Stirling Westrup <swestrup(a)gmail.com> wrote: > On Sat, Oct 30, 2010 at 8:57 PM, David Abrahams <dave(a)boostpro.com> wrote: >> >> At Sat, 30 Oct 2010 17:55:35 -0400, >> Stirling Westrup wrote: >>> >>> I am writing some algorithms to operate on MPL sequences, and I would >>> like to use some form of concept checking to ensure that the types >>> passed in that are supposed to be iterators are, in fact, iterators. >>> I have solved the problem I was working on, but as I'm not completely happy with my solution, I thought I'd post it here and make a recommendation for a small change to MPL that would have simplified my work. I discovered while reading about the iterator_category metafunction that the iterator tags had ascending values. ( http://www.boost.org/doc/libs/1_44_0/libs/mpl/doc/refmanual/iterator-catego… ). This is only documented there, and not in the description of the individual iterator categories. In fact, the individual iterator categories are completely misleading as they state that there is a member named 'category' that is convertible to the type of the tag. Since a random iterator is a refinement of a forward iterator and therefor has at least the same set of requirements, it would imply that: BOOST_MPL_ASSERT (( is_convertible<RandomIterator::category,forward_iterator_tag>)) should succeed, and it does NOT. It would seem that one should use iterator_category to determine if something is an iterator or not, but its only actually defined when its type is an iterator, so that doesn't really work. I ended up writing my own version that was defined for all types, like this: struct non_iterator_tag : mpl::int_<INT_MIN> { typedef non_iterator_tag type; }; BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_category,category,false) template<bool b, typename T> struct category_impl { typedef non_iterator_tag type; static const type::value_type value = type::value; }; template<typename T> struct category_impl<true,T> { typedef typename mpl::iterator_category<T>::type type; static const int value = type::value; }; // just like mpl::iterator_category<T> but can be passed any // type, and returns mplx::not_iterator_tag on bad types. Note // that this value will compare less-than any valid iterator // tag. template<typename T> struct category : category_impl<has_category<T>::value,T> {}; template<typename Iterator> struct is_forward_iterator { typedef typename mpl::greater_equal < typename category<Iterator>::type , mpl::forward_iterator_tag >::type type; }; template<typename Iterator> struct is_bidirectional_iterator { typedef typename mpl::greater_equal < typename category<Iterator>::type , mpl::bidirectional_iterator_tag >::type type; }; template<typename Iterator> struct is_random_access_iterator { typedef typename mpl::greater_equal < typename category<Iterator>::type , mpl::random_access_iterator_tag >::type type; }; The above works, but it relies upon me testing to see if there is an embedded category member, which I suspect is going to get deprecated by iterator_category<> just like all the other members were. It would be far preferable for me if there was an actual non_iterator_tag and iterator_category<> were already defined for all types, so it could both be used in a convenient manner, and so that there was an obvious way to write a specialization in the case that, for instance, one needed the type 'int' to be an iterator. In the very least, please update the documentation to mention the actual relationships between the tags in the discussion about the iterators, and to remove the incorrect 'convertible' description. -- Stirling Westrup Programmer, Entrepreneur. https://www.linkedin.com/e/fpf/77228 http://www.linkedin.com/in/swestrup http://technaut.livejournal.com

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What's so cool about Boost.MPI?
by David Abrahams 08 Nov '10

08 Nov '10

Just wanted to call some attention to this article I wrote about Boost.MPI: http://daveabrahams.com/2010/09/03/whats-so-cool-about-boost-mpi/ I think it might be useful to link that from the Boost.MPI docs, too. -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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