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Re: [boost] [operators] moving forward use return by reference for compilers with proper support?
by Niall Douglas 04 May '13

04 May '13

> Operators returning rvalue references are NOT safe. The C++98/03/11/14+ rules > apply to this scenario: > > X temporary(); > const X& r = temporary(); // ok, lives as long as r does > X&& r2 = temporary(); // ok, lives as long as r2 does > > They do NOT apply to this scenario: > > X&& func(X&& x) { return std::move(x); } > const X& r3 = func(temporary()); // DANGLING REFERENCE > X&& r4 = func(temporary()); // DANGLING REFERENCE > > The Standardization Committee made this mistake when applying rvalue > references to string's operator+(), which was fixed before C++11 was released. I completely agree. 99.9% of the time the only reason to *ever* return rvalue refs from an operator() is when you're passing through a parameter. Otherwise, return by value and leave the compiler's optimizer do its job. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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GSoC 2013 Bernoulli Numbers
by David Joy 03 May '13

03 May '13

Hi, I'm an Open University student completing my Open degree this summer (CompSci / Pure- & Applied Maths / Classical History) and am very interested in the Bernoulli numbers project for the Google Summer of Code. As well as the OU I've done quite a bit of mathematics elsewhere (Durham and KCL). Enclosed is my (naive) response to your challenge to implement the Akiyama–Tanigawa algorithm. I use the Boost framework for rational numbers, so as not to lose precision (though haven't yet adapted the solution for arbitrary precision numbers). [It would be more aesthetically pleasing if I could write the main algorithm in a STL-style so that it iterates of the vector, rather than explicitly using an index.] I have yet to get to grips with Boost.Test, but the enclosed shell script can generate a list of results, which matches the table found on the Bernoulli Number Page <http://www.bernoulli.org/> out to B_20. All code criticism gratefully accepted, David Bernoulli.cpp <http://boost.2283326.n4.nabble.com/file/n4646219/Bernoulli.cpp> Bernoulli_test.sh <http://boost.2283326.n4.nabble.com/file/n4646219/Bernoulli_test.sh> -- View this message in context: http://boost.2283326.n4.nabble.com/GSoC-2013-Bernoulli-Numbers-tp4646219.ht… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Re: [boost] GSoC Boost.Multiprecision project
by Jyotesh Choudhari 03 May '13

03 May '13

Hello, > Hi Jyotesh. >> Thank you for your valuable feedback. I have written >> project proposal for the first time in my life. So, I did >> not know what details to include. I have made some >> changes to my proposal as per your suggestions. > The proposal is a lot better. Now you need to submit > it to Google's melange site. > Please note that the proposal must be submitted > to Googles melange site. Some candidates have > been sending the proposals directly to us, and > this is incomplete. I have uploaded my proposal on http://www.google-melange.com/gsoc/proposal/review/google/gsoc2013/jyoteshr… >> I was studying the code for cpp_bin_float and I >> have some doubts in my mind. >> 1. What are eval_ops_signed_type, eval_ops_unsigned_type and >> eval_ops_float_type? > Eval-ops are the global binary arithmetic operatory, > and the eval_ops-types are those types that will be > supported for global binary math with the radix-2 > back-end. >> 2. What is the use of following lines? >> typedef mpl::list<eval_ops_signed_ type>? signed_types; >> typedef mpl::list<eval_ops_unsigned_type> unsigned_types; >> typedef mpl::list<eval_ops_float_type>? ? float_types; > It's Boost's way of creating a list of built-in types. > Again, these are the types that will be supported for > global binary math. >> These are not used in the class elsewhere. Similar lines >> are present in cpp_dec_float.hpp also and not used >> elsewhere in the class. > They are used by the multiprecision::number front-end > to actually implement global binary math ops. >> 3. In the function from_float_type, I think the variable >> number_of_digits should be initialized to zero before >> using it in while loop. > cpp_bin_float is in a rudimentary state right now. > It is not even close to working. That's the point of > the GSoC project. So stuff might not be quite right > yet. Thank you solving my doubts. I will see the code multiprecision::number also to see how above types are used. >> Lastly, I have seen on mailing list, that some of the >> students are submitting code samples. > It's too late for code. Get your best shot at a good > proposal onto melange. If you would like to submit > code sample, you can do it after your proposal is up. > Good luck. > Sincerely, Chris. Thanks and regards, Jyotesh Choudhari

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Voronoi benchmark update
by Sebastien Loriot 03 May '13

03 May '13

Hello, I'm involved in the CGAL Project, and saw the Voronoi benchmark. It would be nice if you could change the CGAL code slightly, as it is not as bad as it currently seems. Attached is the diff to the trunk of boost. Concerning the Voronoi diagram of points, a CGAL user, would use the Delaunay_triangulation_2 class. Concerning the Voronoi diagram of segments (that do not intersect) one would make a better choice for number types and traits classes. Also one better first inserts the endpoints and then the segments (I agree, this should definitely go into a member function). Admittedly our examples could be better. Cheers, Sebastien

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[gsoc-2013] Physics Library Abstraction Layer
by Preston Hamlin 03 May '13

03 May '13

On Sun, Apr 21, 2013 at 9:37 PM, Michael Marcin <mike.marcin(a)gmail.com>wrote: > On 4/19/2013 8:59 PM, Preston Hamlin wrote: > >> >> I have completed a draft proposal and would appreciate some feedback: >> >> https://www.dropbox.com/s/**7xhha0a3ahk5p6r/preston_** >> hamlin_gsoc_proposal_draft.pdf<https://www.dropbox.com/s/7xhha0a3ahk5p6r/preston_hamlin_gsoc_proposal_draf…> >> >> >> > Seems like a fine proposal. > > Do take note of boost coding guidelines. > > -- > Use the naming conventions of the C++ Standard Library (See Naming > conventions rationale): > > * Names (except as noted below) should be all lowercase, with words > separated by underscores. > * Acronyms should be treated as ordinary names (e.g. xml_parser instead of > XML_parser). > * Template parameter names begin with an uppercase letter. > * Macro (gasp!) names all uppercase and begin with BOOST_. > -- > > http://www.boost.org/**development/requirements.html#**Guidelines<http://www.boost.org/development/requirements.html#Guidelines> > > Prefer object interfaces to pointers. > > For example instead of: > bxPhysics* physics(___); > > prefer: > boost::physics::physics physics_(____); > > Although on second thought naming might need some more thought here. > > What exactly is it that PxCreatePhysics creates? Is it a physics context > like an OpenGL context? Is it more like a physics service like a > boost::asio::io_service? Is it a physics simulation? Is it physics object > factory? > > I'm not sure but I think it's almost certainly not just a physics. > > > In any event it looks good to me. > > My apologies for the belated response. With ACM duties and finals week I have had no more than a few minutes to sit down. I typically try to follow the Google style guide for coursework and the like, so changing naming conventions is but a minor change. The PxPhysics object is used to create and maintain a "realm" of physics. It keeps track of collision methodologies and is essentially the backbone of how edges and vertices interact with one-another. It is build on top of a PxFoundation object which provides the "foundation" of the program, including callback management and some behind-the-scenes memory allocation. The PxScene object manages the elements of a particular "scene" or "world" including pointers to the various objects and gravity. I am not sure how (other than routing messages between objects) boost::asio::io_ would provide much of anything in terms of physics. It is similar to a context like a Device Context or OpenGL Rendering Context but is not used directly and instead used in the creation of more modular objects which are linked to it upon creation. There are no built-in emitters (something that could be provided in this project) and the documentation states that the non-fluid particle system uses rigid bodies that interact with the world but not eachother, which makes sense. I was unsure how prefixes should/would be used in a project like this, which is why I used the "bx" prefix. One thing to note is that PhysX uses a 3-vector class to hold vector data. It is pretty basic but also moderately fleshed out in the source. Would compatibility with the uBLAS matrices (as vectors are to be consolidated) be desirable? The PhysX design uses pointers for just about everything, so that could mean some interesting design considerations. I will be spending the Summer assisting one of my professors with his research project (half-time) and will update my proposal accordingly. Also, if I have some free time this weekend, I can crank out some *rough* proof of concept code if it is desired. Many thanks, -Preston

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[GSOC 2013]Boost.Math Proposal
by Nikhar Agrawal 03 May '13

03 May '13

Hi everyone, I have been in touch with mentors for the project "Boost.Math Bernoulli Numbers and Applications to Special Functions" for the past three weeks. And after regular interactions and assignments and suggestions from them, I have finally posted my proposal. I was a little late because in submitting the proposal because of my end semester examinations. But that now they are over, I have all the free time to completely concentrate on the project. Here's the link to the proposal. http://www.google-melange.com/gsoc/proposal/review/google/gsoc2013/nikhar/1 I'd be really grateful if you guys could review it and suggest improvements. Thanks a lot. :) Nikhar P.S.:- If anyone wants I could also forward the conversations I've had with the mentors until now and I could upload the assignments I've done if anyone's interested.

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[gsoc-2013] proposal for approximate string matching
by Yu Jiang 03 May '13

03 May '13

Hi, I'm a student from Tsinghua University in china and interested in the idea about "approximate string matching". Below is my proposal for this. Could you please view it and give me any kinds of suggestions on it? Thanks! (1) Personal Details * Name: Yu Jiang * College/University: Tsinghua University, China * Course/Major: Computer Science and Technology * Degree Program: M.Sc. * Email: sunlightt07(a)gmail.com * Homepage: do not have one * Availability: - How much time do you plan to spend on your GSoC? Since I have a long summer holiday, I can spend 30 hours a week. - What are you intended start and end dates? I will follow the calendar of GSoC. I have plenty of time from June to September. - What other factors affect your availability (exams, courses, moving, work, etc.)? I have some courses this term which will end before June. 15th. However, these courses don't have heavy workload, I still have enough time to work on GSoC. (2) Background Information * Please summarize your educational background (degrees earned, courses taken, etc.). I majored in Computer Science and got my bachelor degree in Tsinghua University from 2008 to 2012. I learned some basic courses such as algorithm, data structure, algebra and logic. I also learned many advanced courses such as database, operating system, network, formal language, compiler, computer architecture. Currently I'm working for my master degree. My research interest is database. * Please summarize your programming background (OSS projects, internships, jobs, etc.). This is the first time I plan to take part in an OSS projects. I have worked as an intern in Hulu, an online video website, for one year, mainly focus on frontend webpages. I have used C++ to finish many course projects, such as a simple ftp server and client, completing a tiny os and so on. Recently I am learning the new features in C++11 and get to know much more about the C++ language. * Please tell us a little about your programming interests. I really love to optimize on the implantation of an algorithm by making full use of the compiler and the architecture(e.g. cache, SIMD). Besides, I like to write webpages using different kinds of excellent frameworks. * Please tell us why you are interested in contributing to the Boost C++ libraries. Boost is the most famous C++ libraries. It is powerful and can be used in many different kinds of programs. It's my honor to add some new features into it. * What is your interest in the project you are proposing? It's related to my research interest. Nowadays data are produced rapidly. To clean or integrate them so that we can get a better view, "Approximate string matching" is rather a powerful tool. I'd like to see such functions in boost library. * Have you done any previous work in this area before or on similar projects? Yes. My lab has focused on researching on such algorithms for 3-5 years. The "best" algorithm for general string similarity search and join is called "passjoin", which is invented by our lab. I have implemented it and done a lot of optimizations. Early this year we attended a string similarity search & join competition[1] and achieved champion. The code is mainly written by me. [1] http://www2.informatik.hu-berlin.de/~wandelt/searchjoincompetition2013/Resu… * What are your plans beyond this Summer of Code time frame for your proposed work? I will make efforts to make it accepted by the boost library. If it can be released someday, I will maintain it. * Please rate, from 0 to 5(0 being no experience, 5 being expert), your knowledge of the following languages, technologies, or tools: -C++: 3 -C++ Standard Library: 3.5 -Boost C++ Libraries: 2 -Subversion: 3 * What software development environments are you most familiar with? Eclipse. I use it in both windows and linux. * What software documentation tool are you most familiar with? Doxygen. (3) Project Proposal Approximate string matching is a "hotspot" in recent years. It's widely used in big data processing such as search engine, DNA matching. It also can be used in simple tasks like spell checking. However, there isn't a high performance and well-designed library in such area. I wish to see such algorithms in boost so that many people can benefit from this! My proposal contains two parts: A. To implement basic similarity metrics. Edit distance and Jaccard may be the most popular ones. Well, I'll implement more similarity metrics, such as Hamming distance, dice and cosine. B. To implement the fastest algorithm for string similarity search and join. Similarity metrics will be edit distance only since it is most commonly used. Similarity search is to find out all the strings in a given set S, which are "similar" to a query string. Similarity join is to find out all the string pairs<r,s>, where r is in set R and s is in set S and r is similar to s. They are the most useful operators in large data processing. However, the brute-force method for such problem is too slow. And it's not easy to write a correct and high performance algorithm without reading the details in many research papers and debugging them for a long time. To avoid reinventing the wheel, I strongly propose to implement it in boost library. Here is a prototype for the interface: Part A. basic similarity metrics (use edit distance as an example) (1) int edit_distance(const Range1T&, const Range2T&); // return edit distance. (2) int edit_distance(const Range1T&, const Range2T&, int threshold); // return edit distance if it is no larger than threshold, else return -1 or threshold + 1. (3) int edit_distance(const Range1T&, const Range2T&, equal_func); // use uqual_func to determine whether two elements are equal or not. (4) int edit_distance(const Range1T&, const Range2T&, insert_cost_func, delete_cost_func, substitute_cost_func); // use three cost functions to calculate the cost for one insert/delete/substitute operation. (5) some functions to return the sequence of operations? Version (1) may be the most common case. Version (2) can use the given threshold to do optimization for the speed (O(m*n) -> O(threshold * min(m, n))). It's useful since sometimes we only care about the exact edit distance if it is small. Version (3) and (4) extend the flexibility of this utility algorithm. I'm not sure whether to support (5) or not. Part B. string similarity search and join algorithms, focus on edit distance class searcher { void insert(IDType id, const string &word); // insert a word to the index, id is used as an identifier of this word. void erase(IDType id); // erase a word from the index, id should be the same one used in insertion process. vector<Result> search(const string &query, int threshold); // performing similarity search, which will return all the strings which are similar to the query string. Result may be a pair of the id and real edit distance. }; class joiner { vector<PairResult> join(const string_and_id_container &R, const string_and_id_container &S, int threshold); // performing similarity join. Usually we are doing on-line join, which means we cannot pre-build the index. So we only need this one function. It will return all the <r,s> pair where r is in R and s is in S and r is similar to s. PairResult may be a tuple of r's id, s's id and real edit distance. }; (4) Proposed Milestones and Schedule Now – June 15 To be more familiar with the Boost library. Discuss the details and interfaces with my mentor and on the develop mail list. June 15 – July 15 Develop a beta version of the approximate matching library. Most functions will be done at this time. July 15 – August 1 Review my code and improve its performance and quality. Discuss with my mentor for mid-term evaluation and future works. August 1 – September Write documentation, test code for my library. Make it "boost" like.

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[GSoC 2013] Proposal Boost.Math Bernoulli Numbers and Applications to Special Functions
by Łukasz Marecik 03 May '13

03 May '13

Hi, I would like to introduce my proposal to project "Boost.Math Bernoulli Numbers and Applications to Special Functions". It is available at https://google-melange.appspot.com/gsoc/proposal/review/google/gsoc2013/luk… Please note that HTML version is not the best one: the formatting is not very nice, there is also lack of equations and source codes (there are provided in external files). So please take a look at PDF-version of my proposal (follow the link at Google Melange site). Kind regards, Lukasz Marecik

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GSoC: Data structures and algorithms for integer ranges.
by Jeremy Murphy 03 May '13

03 May '13

Hello Boost community, I realized almost too late (two days ago) that GSoC 2013 is happening, and that Boost is in. Obviously I have missed the boat on "engaging with the community" early, but I still plan to submit a proposal. The one thing I would love to get some brief feedback on in these last hours is scope: how much should I expect to get done in 12 weeks? Unsurprisingly, it is one of the hardest questions for an inexperienced worker in any field to answer. The core of my proposal is to implement i) a van Emde Boas tree and ii) three counting sort algorithms: "counting", radix and bucket. Is that enough? Too much? Any advice would be helpful, thanks. Cheers. Jeremy

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Google summer of code 2013
by Jawad Elomari 03 May '13

03 May '13

Hi everyone, I want to join the Google summer of code this year, for the PaGMO/PyGMO<http://www.google-melange.com/gsoc/org/google/gsoc2013/pagmo> library. I'm interested in the Racing projects, but I'm not sure which Boost library is most suitable for it. Any ideas? Regards,

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