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Re: [boost] [GIL] integration between boost libraries (gil / multiarray)
by fabien.castan＠free.fr 23 Jun '10

23 Jun '10

>> For now view concepts from gil and multi_array are not compatible I >> would say. Hopefully in the future we can agree on 2D and 3D >> container and container view concepts that should be implemented by >> all libs who need such functionality. In the same we way boost needs >> a common point2D structure. ;-) > >I'm not sure why it should be true that we need a common point2D. But >then, maybe I'm missing something. It's not a good thing that some computation functions become dependant to gil only for a point class. To compute a geometric transformation, I cannot directly get a gil point, multiply it by a scalar and return it, because this operator is not define in gil... Or more generally I cannot directly compute a product with an uBlas matrix. Maybe some cast operators and constructors from/to bounded_vector can be suffiscient to have interoperability. >> For example, inside an algorithm I need to maintain a data structure for each pixel. So I would like to create an array of MyCustomStruct. I can use gil to do that but I need to have a notion of colorspace and operators between >> pixels, which have no sense in this particular case. But subsampled_view, cache_locator, etc. have a sense. > >In theory you're right. But both libraries were developed by different >people at different times without having the need to have compatible >concepts. Yes I understand, I discuss possible improvements. I think there is a need to have compatible concepts. >> I have only one criticism: the integration with other boost libraries and firstly with multiarray. >> Because manipulating an image consists of manipulating an array of pixels. Many gil's operations are not present in multiarray: >> flip_view, subsampled_view, subimage_view, n_channel_view, x_iterator, y_iterator, xy_locator, cache_locator, plannar or interleaved arrays, virtual views, static_for_each, ... > >Multi_array is for N-dimensional arrays. GIL only makes sense for 2D >right now. A simple solution can be to implement those gil ideas, which can be applied to N-dimensional, in multi-array to propose the same fonctionnalities ?

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Book "The Boost C++ Libraries" now in English
by Boris Schaeling 23 Jun '10

23 Jun '10

Andreas and I are pleased to announce that the book "The Boost C++ Libraries" is now available in English: <http://en.highscore.de/cpp/boost/> At this point I have to thank Andreas who started translating the 16 chapters of my book nearly a year ago and managed to finish this tremendous amount of work after all that time. Without him there wouldn't be a single sentence of my book available in English. Thank you, Andreas! :-) While you can simply click on <http://en.highscore.de/cpp/boost/> and have a look, here are some explanations in case someone is interested: * The book is licensed under a Creative Commons License and can be copied, distributed and transmitted for non-commercial use. As the part "for non-commercial use" might raise some concerns: You are definitely allowed to use the book at work (print it, hand it out to colleagues, publish it on intranet web servers etc.). We also welcome trainers who want to use the book in classes about the Boost C++ libraries (even if you are paid as a trainer). There is no need to ask us for permission either. What we don't want to see though is e.g. a commercial IT magazine simply filling pages by printing the book. * The book currently consists of 16 chapters. While there are some chapters which present only one library, others introduce a couple of libraries. I decided not to write one chapter per library because some libraries are so small that it's all explained within a few paragraphs. If you want to lookup libraries though you find direct links in the overview at <http://en.highscore.de/cpp/boost/introduction.html#introduction_overview>. * There is a link "Found an error? Fix it in your browser!" below the table of contents in every chapter (your browser must support Javascript to display the link). If you click on the link the webpage becomes editable. This makes it rather easy to fix typos or other mistakes. Changes are saved on the server and will be reviewed (to protect against spam). * If you click on "Found an error? Fix it in your browser!" there is another option called "Mark keywords". If you select this option you can mark words (by clicking on them). The idea is to create an index by marking those words which you think should be included in an index. As it's quite a lot of work to create a good index we welcome proposals of what to include. * For those who know German there is still the original version of the book at <http://www.highscore.de/cpp/boost/>. The content is the very same (even same sample codes). We will also keep the books in sync (it's not that the German version won't be updated anymore). * You can download the HTML version of the book from <http://en.highscore.de/cpp/boost/The%20Boost%20C++%20Libraries.zip>. The ZIP file contains all the web pages and other resources you need to read the book offline. For those who'd like to get a PDF or ePub version of the book there are links to download them. You'll notice that the download of those versions is not for free. The money is used to pay server costs and to finance new chapters. We hope you agree that the prices are reasonable. * If you purchase the ePub version of the book I am very interested in your feedback. As the eBook market is still rather small it's difficult to get the feedback you need to understand what to improve. Given that there have been many discussions lately about what's wrong with Boost, we hope that this book will give the Boost libraries and C++ another, well, boost. :-) Boris

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[chrono] Valgrind complains
by Roland Bock 23 Jun '10

23 Jun '10

Hi Vicente, Valgrind complains about Conditional jump or move depends on uninitialised value(s) several times for the following line: { boost::chrono::stopclock<> stopclock(std::cerr); } Regards, Roland

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Removal request
by Gennaro Prota 22 Jun '10

22 Jun '10

Hi, I've left Boost long ago but I still appear as a maintainer of dynamic_bitset. Could anyone remove me from both Trac and maintainers.txt? Thanks. -- Gennaro Prota | name.surname yahoo.com Do you need expertise in C++? I'm available. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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[GIL] kth_channel_view
by fabien.castan＠free.fr 22 Jun '10

22 Jun '10

Hi, I have some difficulties using kth_channel_view. I'm trying to modify the "convolution.cpp" example, like that: #include <boost/gil/gil_all.hpp> ... kernel_1d<float> kernel2(gaussian_1,9,4); convolve_rows<rgb32f_pixel_t>(kth_channel_view<0>(const_view(img)),kernel2,kth_channel_view<0>(view(img))); jpeg_write_view("out-convolution2.jpg", view(img)); ... This doesn't compile. Regards, Fabien

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[trac] Milestone 1.43 still open.
by Daniel James 22 Jun '10

22 Jun '10

Hi, Please can someone mark 1.43 as completed in trac? thanks, Daniel

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[gsoc][review/comments] Request community input on project interface
by Brian Bartman 22 Jun '10

22 Jun '10

Hello, I'm currently working on my GSoC project and I wanted some feedback from the community about the interface of a data structure I'm working on called a "bitfield_tuple". The bitfield_tuple makes it easy and simple to create and use specific bitfields. Currently, this works only over integral types, although there are plans to extend this in later versions of the data structure. bitfield_tuples correctly work with different types of endianness as well as provide the mechanisms to allow users to explicitly define the size of the structure's storage space. The bitfield_tuple is a tuple like sequence of elements but, instead of providing direct access to an instance of a type, a proxy to the element stored within the bitfield_tuple is returned. This is similar to std::vector<bool>'s reference type. Example bitfield_tuple declaration, struct red; struct green; struct blue; typedef bitfield_tuple< storage<unsigned int>, member<int,red,5>, member<int,green,6>, member<ing,blue,5> > bft_example; The internal storage type which all of the bitfields are stored in is specified by the storage template. The members are used to specify the different bitfields which are to be stored within that storage type. The member template is specified the exact same way a normal c++ bitfield would be specified inside of a struct or class. int red:5; member<int,red,5> A member template is specified in the order of: type, name, width of bitfield. The order the member templates are given in is the order in which they are stored within the bitfield_tuple. However, the storage template does not take up an index within the bitfield_tuple. So the template member<int,red,5> will be stored at index 0. Each member template requires a name be specified; this is for ease of access, later described in the get function. Each name must be unique within a single bitfield_tuple. The width of the bitfield is handled internally. The starting point for each bitfield is the bit after the previous bitfield, or 0 if it's the first bitfield. bitfield_tuple interface summary: Default constructor, copy constructor, and a constructor which allows for the construction over an initial value which is of the same as the storage type. bitfield_tuple(); bitfield_tuple (bitfield_tuple const&); bitfield_tuple (storage_type); Assignment operators for assignment from the storage type, similar to the constructor above, and copy assignment. bitfield_tuple const& operator=(storage_type); bitfield_tuple const& operator=(bitfield_tuple const&); The get function operates similar to the boost.tuple with slight modification. Specifically, the get function will return a reference type. There are two ways to use the get function. The first way is by using a unsigned integral constant as an index: bft_example temp; temp.get<0>(); // returns a proxy reference to the bitfield represented by member<int,red,5> The second way to use it is to call get using the name provided to the member parameter: temp.get<red>(); // does the same thing as get<0>(); I provide both const and non const versions of both functions. The bitfield_tuple is also a boost.fusion sequence. It models an associative array type by using the following category: struct bft_category : boost::fusion::random_access_ traversal_tag, boost::fusion::associative_tag { }; The btifield_tuple's fusion extension was created through the fusion sequence extension provided by boost.fusion. bitfield_tuple supports the following fusion functions and all of the intrinsic functions which are supported from the implementation of these functions. begin end is_sequence is_view category_of at size at_key tag_of The btifield_tuple_iterator supports the following fusion functions: deref value_of next prior distance key_of value_at_data deref_data advance If you would like to look at the code for bitfield_tuple, it is located here: http://svn.boost.org/svn/boost/sandbox/SOC/2010/bit_masks/boost/integer/bit… -- thanks, Brian Bartman

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Re: [boost] [msm] Message queue and copy constructed events
by Christophe Henry 22 Jun '10

22 Jun '10

Hi Richard, >Lets separate 2 thinks. > >1: no heap operation this is a nice to have feature we can live with >it. According my understanding the only place where heap is used is in >the std:queue ? Am I correct ? If yes than if the user has a >possibility to provide its own queue implementation than he/she can >make sure about avoiding heap usage. In the queue AND in the boost::function objects contained in the queue. So merely changing the container will not be sufficient to eliminate all heap usage (read further on). >2: event copying. You saying copy is happening when bind is used to >anonymize events to be able to store them in a queue. >According my understanding of event driven systems we can say that as >log an RTC step is not finished -> means that the most outer >process_event does not retuned the event which was used in the call of >the process_event should be valid. This means that events will be >valid even with queuing for queues which are used during pseudo entry >and exit because the processing of those events are always finished >before the more outer process_event is returned. >The only place where this is not true ->when the event should be >available longer than the RTC step is when the event is deferred. >So I think it would be enough for non deferred queues to internally >before the bind store the event in a ref/cref and bind that and put >to the queue -> no copy. This is incorrect. You can have the same behaviour with the event queue. Consider test/SimpleWithFunctors.cpp: You have a transition: Row < Empty , cd_detected , Stopped , store_cd_info , ... > And in the action, we generate another event: struct store_cd_info { template <class EVT,class FSM,class SourceState,class TargetState> void operator()(EVT const&,FSM& fsm ,SourceState& ,TargetState& ) { fsm.process_event(play()); // temporary play will be queued, then the function returns // ooops, temporary is gone } /// end of action, transition now ends and will start examining the queue and will find inside a reference to a destroyed event }; Now, if msm was using ref/cref, we would be processing a destroyed event, which would not end well ;-) Unfortunately, it is not possible for process_event to know if the event object is a temporary, therefore the copy. The only way to change this would be to have the user tell msm about it and take responsibility for ensuring event validity. We could: - have an extra parameter to process_event (run-time cost for all users) - allow some compile-time flag (compile-time cost for all users) None is very appealing to me as I doubt many will require this, especially as I fail to see why you could not pimpl the event data, thus making the event cheap to copy. But everybody would have to pay for it somehow. And the heap issue would still be unsolved. This would likely also end at the very bottom of my feature list. I think a possible solution would be the fact that I intend to offer customization of the queue container, which is a much more popular feature. Instead of calling push on it with the boost::function object, I could call push(event), so that you can provide a container not of function objects but of anything (like of a pointers to some base event type or void* if you prefer to cast a little, which I prefer not knowing of ;-) ). This allows complete removal of any heap usage AND could also be used to get rid of event copying (in this case though, you are taking responsibility of having thought of the event objects' lifetime). The downside is that providing a new container will require slightly more work. >For deferred queues there is 2 ways to go. >First is to copy the event during bind or have a user implement a >queue which interacts whit the underlaying zero copy scheduler. and >only again store a ref/cref in a bind. maybe it is enough to have 2 >callback to the user when an event is deferred and when it is recalled >and not needed any more. Fore the deferred queue, I can provide the same mechanism, so that you have have different containers for both if you wish. Using boost.parameter will make these extra template arguments more bearable. Regards, Christophe

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[GIL] integration between boost libraries (gil / multiarray)
by fabien.castan＠free.fr 22 Jun '10

22 Jun '10

Hi, I'm a big fan of gil. It's one of the best library I know. It has really improved my work, which consists of writing image processing algorithms. Thanks to the authors. I have only one criticism: the integration with other boost libraries and firstly with multiarray. Because manipulating an image consists of manipulating an array of pixels. Many gil's operations are not present in multiarray: flip_view, subsampled_view, subimage_view, n_channel_view, x_iterator, y_iterator, xy_locator, cache_locator, plannar or interleaved arrays, virtual views, static_for_each, ... For example, inside an algorithm I need to maintain a data structure for each pixel. So I would like to create an array of MyCustomStruct. I can use gil to do that but I need to have a notion of colorspace and operators between pixels, which have no sense in this particular case. But subsampled_view, cache_locator, etc. have a sense. Another less important thing, I find unfortunate that a structure like "point" is inside gil. Many operators are not defined. Some parts of my code are becoming dependant to gil just for a "point" class, or I need to work with one structure and make a conversion... Is there really nothing in boost for such thing ? Maybe just a typedef on a bounded_vector<2> could be sufficient ? Best regards, Fabien

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[polygon] 1.44 release?
by Simonson, Lucanus J 22 Jun '10

22 Jun '10

I notice that Monday is the deadline for closing the 1.44 release to new libraries. Boost.Polygon is checked into the trunk and more or less passing tests on all the platforms I expect tests to pass. Is there any possibility of making it into the 1.44 release? Thanks, Luke

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