April 2013 - Boost - lists.preview.boost.org

Re: [boost] [operators] The future of Boost.Operators
by Andrew Ho 25 Apr '13

25 Apr '13

> Maybe we're talking past each other. I have 3 overload set variants in > mind: > > (A) > T operator?(T, T); > > (B) > T operator?(T const &, T const &); > ... > T operator?(T&&, T&&); > > (C) > T operator?(T const &, T const &); > ... > T&& operator?(T&&, T&&); > > AFAICT, neither (A) nor (B) have any safety issues. Oh, but now I see the > problem with (C): T&&'s are implicitly convertible to T&'s...that's what I > was missing before. Sorry for being dense. > > So if you do > > T& a = b + c; > This succeeds in VS2012 with all (no compile or runtime problems, oddly VS2012 extends the lifetime of ref returned by C to be valid), and fails with all in gcc 4.7.2 (compiler error) :P > invalid initialization of non-const reference of type 'T&' from type 'T&&' Yep, this is what happens in gcc for me. > > I swear I just tried a T& y = static_cast<T&&>(x) on gcc and finding it > compiled fine. This gave a compiler error for me. > Now you can ask the same question with T const& instead... Compile succeeds, with only two operands the called overload returns a T, not T&& so there's no problems. If you had: const T& r = a + b + c; (A) and (B) are perfectly safe, but (C) will have runtime issues. Same goes for: T&& a = b + c; T&& r = a + b + c; First line doesn't have any problems with (A), (B), or (C) because of which overload is used. The second line (A) and (B) have no problems but (C) will have runtime issues. Of course, (C) will have a few extra temporaries created (which may or may not be optimized away). The question originally posed is do we: 1. Ignore this problem with (C) to get better performance and just document the problem? 2. Implement (B) to take advantage of move semantics with no internal problems, albeit with a few temporaries being created (if they aren't optimized away by the compiler)? 3. Implement a user-accessible macro switch to let the user decide globally As Jeff said, (3) is ugly especially when linking different codes together, but does provide the most options to the user. (2) isn't necessarily the most efficient but is completely safe. It may also end up being just as efficient as (1) if compilers support the optimization to remove unnecessary temporaries. Daniel's argument is that the problems which occur with (C) are typically a result of user error, and (C) in general guarantees the least amount of temporaries being used. Are there any cases where the problems described above with (C) would be a result of intended behavior with no acceptable work-around? Hopefully we're on the same page now.

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Google Summer of Code Proposal Feedback
by Niall Douglas 25 Apr '13

25 Apr '13

> aware of GSOC until recently. I had strongly considered writing a proposal > for Boos.ASIO, but I fear my lack of experience with Linux, POSIX, and > concurrency in general might prove to be too great of an obstacle. If the > subject matter can be learned relatively quickly, I would love to discuss > what such a project would require with the mentor, Niall Douglas, or a > community member who has is familiar with the project. I'm hardly "the" mentor in Boost.ASIO. I'm probably just the only one to have registered as a potential mentor so far. It's still early days. A lot more potential mentors will register in time, then depending on project scoring and people's availability and of course Google's preferences, we'll see what turns out. > My original proposal probably isn't unique, and much to my chagrin as I > read the hints for successful proposals it seems a popular topic. I am of > course suggesting a project dealing with Trees. Rather than suggest > building a generic tree, I am suggesting the start of a tree library, or > the addition of several types of trees to existing libraries, as I am not > sure which is more appropriate. An awful lot of students expose their ignorance of what Boost, or indeed the C++ standard library, provides during GSoC. It really doesn't help them to be scored well which is why Boost strongly recommends that students discuss their ideas here first before submission. 95% of the time their idea is already implemented. For example, there are multiple tree implementations in the C++ STL and Boost. Look into Boost.Intrusive for example. > Because trees are such a fundamental data type in computer science, I have > found it difficult to understand why there are no explicit tree classes in > the c++ standard. They generally don't have "tree" in their name ;) > tested in an afternoon, while implementing a Red Black Tree would take > considerably longer, yet the C++ standard has linked lists and not Red > Black Trees. Red-black trees are called std::map<>, std::set<> et al. in C++ since 1998. Of course std::map<> et al. doesn't *have* to be implemented as red-black, but most implementations do since the SGI STL defined std::map<> using stl_tree<>. > The library I am proposing should eventually be able to satisfy almost > anyone requiring the use of a tree. It should have many different types of > trees, Binary trees, AVL Trees, Red Black Trees, Treeps, B-Trees, > Skip-Lists, etc. It should support common methods of traversal, inorder, > preorder, postorder, and user defined traversal methods. Eventually, the > library should support an n-ary trees and their operations. Trees in the > library should also be performant, fail gracefully, be well documented, > unit and integration tested, as exception safe as possible, and, someday, Look into Boost.Intrusive. They're the most appropriate category for what you propose. Niall

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Discussion Policy
by Rob Stewart 25 Apr '13

25 Apr '13

If you're relatively new to this list, you may not have taken the time to read Boost's discussion policies[1]. Even if you've been on the list for a while, reviewing the policies may be educational. Thanks for your efforts to make discussions easier and more consistent for all. ___ Rob (Sent from my portable computation engine) [1] http://www.boost.org/community/policy.html

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Re: [boost] Going forward with Boost.SIMD
by Niall Douglas 25 Apr '13

25 Apr '13

> A GPU is an accelerator for large regular computations, and requiring sending > memory and receiving it back. It's also programmed with a very constrained > programming model that cannot express efficiently all kinds of operations. > > A CPU, on the other hand, is a very flexible processor and all memory is already > there. You can make it do a lot of complex computations, irregular, sparse or > iterative, can do dynamic scheduling and work stealing, and have fine-grained > control on all components and how they work together. :) You're actually wrong on that, and it's one of the first big surprises anyone who sits on ISO committees experiences: the change in scope of definitions. When you're coming at things from the level of international engineering standards, a computer's CPU is not defined as anything approximating what any of us use on a regular basis. It includes large NUMA clusters, it includes Cray supercomputers all of which don't do SIMD anything like how a PC does. It *also* includes tiny embedded 8-bit CPUs, the kind you find in watches, inlined in wiring, that sort of thing. Some of those tiny CPUs, believe it or not, do SIMD and have done SIMD for donkey's years, but it's in a very primitive way. Some of those CPUs, for example, work in SIMD 3 x 8 bit = 24-bit or even 3 x 9 bit = 27-bit not 32-bit integers, that sort of thing. Yet international engineering standards must *always* target the conservative majority, and PCs or even CPUs designed more recently than the 1990s are always in a minority in that frame of reference. Don't get me wrong: you could standardize desktop class SIMD on its own. But generally you need to hear noise complaining about the costs of lack of standardization, and I'm not aware of much regarding SIMD on CPUs (it's different on GPUs where hedge funds and oil/gas frackers regularly battle lack of interop). > However, SIMD has been here for 25 years and is still in the roadmap of future > processors. Across all this time it has mostly stayed the same. > > On the other hand GPU computing is relatively new and is evolving a lot. > It's also quite trendy and buzzword-y, and is in reality not as fast and versatile as > marketing makes it out to be. > A lot of people seem to be intent on standardizing GPU technology rather than > SIMD technology; that's quite a shame. Thing is, had Intel decided Larrabee was worth pushing to the mass market - and it was a close thing - PC based SIMD would look completely different now and we wouldn't be using SSE/NEON/AVX which is really an explicit prefetch opcode set for directly programming the ALUs and bypassing the out of order logic, not true SIMD (these are Intel's own words, not mine). As it is, convergence will simply take longer. Some of those new ARM dense cluster servers look awfully like Larrabee actually, 1000+ NUMA ARM Cortex A9's in a single rack, and their density appears to be growing exponentially for now. Given all this change going on, I'd still wait and see. Niall

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Google Summer of Code Proposal Feedback
by Paul Kirth 25 Apr '13

25 Apr '13

Hello Boost community, I am a student interested in the Google Summer of Code (GSOC), and have a few proposals in mind. If I have posted this in the wrong place, my apologies, but applicants are encouraged to post to the mailing list, and after some research this seemed like the best list to post to. I have an original proposal for Boost, and strong interest in the Boost.ASIO idea. I've decided to seek some feedback from the community on their feelings about my idea, in the hopes that I can better define them, and increase my chances of success in being selected for the GSOC. I realize it is a bit late to begin discussing proposals, but I wasn't really aware of GSOC until recently. I had strongly considered writing a proposal for Boos.ASIO, but I fear my lack of experience with Linux, POSIX, and concurrency in general might prove to be too great of an obstacle. If the subject matter can be learned relatively quickly, I would love to discuss what such a project would require with the mentor, Niall Douglas, or a community member who has is familiar with the project. *About Me* First, let me begin with a bit about myself. My name is Paul Kirth, and I am currently pursuing a masters in Computer Science. This statement may be a bit misleading, however, as I received my BS in Civil Engineering from UCLA in 2005, and have only recently decided to pursue a course of study in Computer Science. I have for the last two years taken CS classes to prepare for Masters level courses, but am still a bit of a novice in CS. I would say that I am at about a 3rd year level in CS, proficient in C++ and python, and competent in Java, with a limited amount of assembly, and very little work in concurrency. I have not spent much time doing engineering work in the last few years, as my focus has been on my education, but I was fairly good at solving linear systems, and had a good amount of experience with design and collaboration. As an undergraduate I made the mistake of not pursuing summer internships or jobs, and as a result I found that many of my peers had a much easier time with our courses as a result of their work experience. After all, 20-30 hours a week solving engineering problems will generally make you more proficient at solving them than someone who doesn't. I do not wish to make the same mistake with my new career path, and desperately want to gain experience in professional software design, and in working on a collaborative project. I am keenly aware of my lack of experience, and really wish to use this opportunity to push myself, and gain as much expertise as possible during the few months of the summer. *Original Proposal* My original proposal probably isn't unique, and much to my chagrin as I read the hints for successful proposals it seems a popular topic. I am of course suggesting a project dealing with Trees. Rather than suggest building a generic tree, I am suggesting the start of a tree library, or the addition of several types of trees to existing libraries, as I am not sure which is more appropriate. Because trees are such a fundamental data type in computer science, I have found it difficult to understand why there are no explicit tree classes in the c++ standard. I have read the arguments that there is no standard use for a tree, and as such it cannot be made to satisfy enough users. I have read more arguments stating that std::sets and std::map use tree structures underneath their interface. Furthermore I have read in several places that it is common to use Boost.graph to make trees. Trees have myriad uses, and a library implementation should consider this heavily when designing the data structure, but trees are common enough to warrant a standard implementation in the same way as lists, queues, and stacks. I will concede that trees can be considered, and in fact are, graphs, and that many graph algorithms are very powerful tools. But trees don't always need those algorithms, and graphs don't always maintain the tree in the way we wish. Using an std::set or std::map is not the same thing as using a tree, regardless of how they are implemented. Conservatively, a linked list can be fully implemented and tested in an afternoon, while implementing a Red Black Tree would take considerably longer, yet the C++ standard has linked lists and not Red Black Trees. This seems a bit counter intuitive. We have a relativity simple data structure in the standard, and a more complex one is not. I'm sure that linked lists are more common than red black trees, but by how much? If self balancing binary trees are considered a fundamental data structure by every computer science curriculum, why aren't comprehensive, reliable implementations of them part of the standard, or widely available in 3rd party libraries like Boost? The library I am proposing should eventually be able to satisfy almost anyone requiring the use of a tree. It should have many different types of trees, Binary trees, AVL Trees, Red Black Trees, Treeps, B-Trees, Skip-Lists, etc. It should support common methods of traversal, inorder, preorder, postorder, and user defined traversal methods. Eventually, the library should support an n-ary trees and their operations. Trees in the library should also be performant, fail gracefully, be well documented, unit and integration tested, as exception safe as possible, and, someday, concurrency safe/compatible. I'm unsure of the Boost stance on inheritance is, but my initial feeling is that users should be able to use tree classes as base classes if they desire. Proposing a large library as a summer project is ridiculous, hence I am proposing a start to this library, containing a few tree classes that can be implemented, tested, and documented within a few months, and a set of standards for new entries in the library. I don't expect the whole library to immediately be accepted into Boost, but the project will aim to meet those standards, with a long term goal of eventually being included into Boost. My research has found several projects that implement single tree classes, or groups of tree classes, but no tree library. A good c++ example is the rbrees project at https://code.google.com/p/rbtrees/ , or python has a few implementations of trees, such as bintrees 0.3.0, https://pypi.python.org/pypi/bintrees/0.3.0, which is a binary tree library, containing BinaryTree, AVLTree, and RBTree classes. I feel that bintrees 0.3.0 is a good project to mimic in the early stages, as binary trees are fairly easy to implement, test, and maintain with AVL and RB Trees. I am comfortable with binary, AVL and Red Black Trees, and feel very confident in my ability to implement them. I would like to do more, and push myself this summer, but I am not sure how much work unit and integration testing are, how long they take, and how much extra time is required for classes/libraries to be refined to Boost standards. I am sure that this time is non trivial, but as a student I'm very unsure about how much time things take, or how much time they should take. In general I would like to work on a project that would expose me to more new ideas, but I really think the world deserves access to a C++ tree library that can have some guarantees for performance, and is part of a larger, well documented, highly respected library. I understand that this project is virtually guaranteed to take more that one summer's worth of effort, and I am comfortable with staying involved in the project beyond the length of GSOC, or having the work done absorbed into another library/project. Whether or not this project is accepted into GSOC, if there is support for this effort in the community I would love to help as I am able. Obviously if I am working this summer my commitment will not be able to be as substantial, but I do feel strongly about the need for standard, performant, reliable tree classes in c++. Thank you for reading my lengthy first post to the mailing list. I hope to have more discussions with this community in the future, and I am eager to hear your thoughts about how this proposal could be improved. -- Paul Kirth (310) 709-2516

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proposal for date_time implementation
by Shamsher Siddiqui 25 Apr '13

25 Apr '13

hi mentors plz review my project and give me suggestion to improve to my proposal Name :Shamsher Ahmed College/University:University Insititute of Engineering &Technology,Chandigarh,India Course/Major:Computer Science & Engineering Degree Program:Bachelor of Engineering Email:mail.shamshersiddiqui@gmail.com Homepage:Not yet Availability: How much time do you plan to spend on your GSoC? I can work full time to complete this project. What are your intended start and end dates? I will start the project according to GSOC 2013 schedule but i will try to finish the project 2 weeks before so that I can have the necessary time for debugging and for unforeseen situation it occurs. What other factors affect your availability (exams, courses, moving, work, etc.) ? My semester exam will get start from 18 may and it will end on 28 may .So I will have complete time to dedicate. I don’t have any course or work during this summer . Background Information: • Please summarize your educational background (degrees earned, courses ,taken, etc.) I passed out 10+2 from Indian School Certificate in 2010 and I am currently pursing bachelor of engineering from university institute of Engineering & Technology, Chandigarh Till now I mainly focused in learning programming language (C,C++,Java). I have mastered over Java and c++ but scratchy in C.I have also taken course on Algebra, Calculus, Data Structure & Algorithm ,database etc etc. • Please summarize your programming background (OSS projects, internships,jobs, etc.) This will be my first OSS project at such large level. I have developed many things in c++ & Java. During my last summer I have done my internship in slr infotech ,a small software firm . • Please tell us a little about your programming interests : I am programming from 8th grade .In 10 and +2 board exam I obtained 96 and 97 respectively in my computer science subject. I love to code for hours .And most important thing about open-source I like about is sharing, helping and hacking code . • Please tell us why you are interested in contributing to the Boost C++ Libraries? Boost c++ Libraries are one most powerful libraries of c++ used by many well known organizations .It is cross platform library which has high efficiency And it goes together with standard template library in c++. I will get support from boost community and it is documented very well which makes it very easy to understand and if any bugs comes than it is easily recognized and eliminated , lastly while working with bright minds I will be able to learn from them and impart my experience , knowledge to other developers • What is your interest in the project you are proposing? Libraries were mystery for me when I started learning my first programming language c but after some time I was able to perform the same task without using library but there was increase in time and length of code for doing the same program.I want to develop this project because it will increase the reusability of code and in Boost community best minds works together to give the one of the best libraries of c++. Date library will be always used in every development project whether big or small and When I read this project https://svn.boost.org/svn/boost/sandbox/chr ono_date/libs/date/doc/date.html .This is small library but will be most efficient and will be able to perform all task and save time ,reusability of code is very high. • Have you done any previous work in this area before or on similar projects? No ,I haven’t done any project regarding libraries but I am using libraries in my other project. But me and my friend are developing a tagging software which creates a folder on the basis of album,artist,track number etc. We have implemented internal structure but GUI part is left which my friend is working on. and developed small games in c++ as my project assignment. • What are your plans beyond this Summer of Code time frame for your proposed work? After Summer of code ,I will remain involve with the boost c++ community and I would like to add more feature to current project.Secondly I will work with the boost community in building in their library because I love coding for long hour. I enjoy this work. • Please rate, from 0 to 5 (0 being no experience, 5 being expert), your knowledge of the following languages, technologies, or tools:  C++: 4  C++ Standard Library: 3  Boost C++ Libraries: 2  Subversion :2 • What software development environments are you most familiar with (Visual Studio, Eclipse, KDevelop, etc.) I generally use Qt creater or Visual studio depending on the operating system I am using . • What software documentation tool are you most familiar with (Doxygen, DocBook, Quickbook, etc.)? I am familiar with Doxygen Project Proposal Goals & Implemenatations 1) Construction of Date: • Date can be represented in two ways field representation or as an serial representation . In field based representation(YMD) date value is constructed from individual year,month,and day value in three integral value. In serial reprensentation(SERIAL) data values are stroed in intergral number of days from an implementation defiend epoch date, there is third hybrid version to represent the date which implemantd the both representation and it is named HH_YMD_SERIAL_X where x represents the size of types in byte. • Providing support for entering the date in form YDM(year,day,month) which is lacking currently in chrono:date library • No invalid dates can be entered considering range cheaking ,non existent date if entered bad_date exception is thrown . • Constructing constant object for day,week_day. Eg. last/may/2000 represents 31 may 2000 • Construction of meta data for date 1) Leap year flag 2) Nth day of month 3) Nth weekday month 2) Arithematic Operation On date Date airthematic can be done on three units i.e day,month,year.In chrono date ::calendar(Gregorian calendar) length of month and year is not fixed : • day arithematic 1) Adding number of days to date until range doesn’t exceed 2) Implementing last day arithmetic to avoid the bad date excepti Eg. aug/last/2011 +months(1)= sep/30/2011 aug/31/2000 +months(1)=sep/31/2000 //invalid date bad date excep thrown • month arithmetic Month arithmetic is quite complex compared to day arithmetic since number of are not fixed . 1) (month day <=28 || month day =last day ) always add month 2) month day =29 cheak for leap year and than add month 3) Month day>=30 add but don’t add if resulting month is feb 4) Using constant objects for month arithmetic. • year arithematic 1) Always add year to date considering the condition of leap year 2) Reversal of date back to original date 3) Usage of last day during year arithematic During any of the airthematic operation result should not be an invalid date if it occurs than bad_date exception is thrown. 3) InterConversion field representation & serial representation Some operation are quite fast on field but airthematic operation are much faster on serial campared field representation .So it is necessary to provide the inter-coversion so that it can be easily converted from one representation to another. 1) Constructing bi-directional conversion of serial and field by making use of static cache to optimize conversion 4) Building function for week days & date formatting 1) weekday of a date used. 2) nextweek day of date used. 3) previous weekday of date used. 4) finding number of weeks in month 5) formatting of date according of all types 5)Interoperability with other calendar Current chrono::calendar is Gregorian calendar which exist everywhere in date & time library of every programming language.(c,c++,java) and ISO 8601 and POSIX. This section provides conversion of chrono calendar to client calendar. 1) Conversion of chrono ::calendar to Julian Calendar 2) Conversion of chrono :: calendar to Hebrew calendar 3) Conversion of chrono :: calendar to hindu calendar 4) Conversion of chrono :: calendar to Chinese calendar 5) Conversion of chrono :: calendar to Buddhist calendar 6) Conversion of chrono :: calendar to Islamic calendar Hindu ,Chinese ,Buddhist ,Hebrew(Jewish ) calendars are lunisolar calendar with a very little difference. Julian, Gregorian are very much similar except the method of finding the leap year. Islamic calendar is lunar calendar(totally dependent on moon ) which is quite unpredicatable. Hence accurate conversion is rare. TimeLine Until 17 June :Community bonding , understanding boost c++ libraries ,discussing with mentor about the details of proposal . 17 June to 27 June: Construction of date 28 June to 12 july : testing &debugging of construction of date and implementing date arithemetic 13 july to 29 july (Mid term evaluation) : implementation of interconversion of serial and field representation and testing ,debugging and making more efficient the previous code develop. 30 july to 15 August :Implementation of date formatting and developing function on weekday. 16 August to 30 August: testing ,debugging and aadding more feature to weekday and implementation of interconversion of calendar. 31 August to 23 Sept:testing ,debugging ,making efficient the whole code .

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Fwd: [asio]Extension for audio device service
by adrien courdavault 24 Apr '13

24 Apr '13

Hello. I make this new thread to be clearer. There is currently no way to manage audio endpoints cconnection easily. It looks like some people might find this usefull (as I do), and I've been suggested on the boost dev list to try to detail this, as an extension to Boost.ASIO. For this reason I create this thread. I'm trying to make a very basic first draft of the concepts and see if this may be a good idea. I attached here the first things I've written. This is very short and general. I would like to know: * do you think I'm going in the right direction by seing this as Boost.ASIO extension. * do you have suggestions * would someone like to participate ? Thank you

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[gsoc-2013]Boost.multiprecision project
by Sagar Massand 24 Apr '13

24 Apr '13

Hi, I wanted to submit a proposal for the boost.multiprecision project. Please find attached the files:1)Proposal for the project 2)Naive code for karatsuba multiplcation in C. It would be very kind of you if you could give me suggestions, point out flaws etc. in this. Regards, Sagar Massand

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Going forward with Boost.SIMD
by Mathias Gaunard 24 Apr '13

24 Apr '13

Hi, This week I presented a proposal to the C++ standards committee to provide a standard library component for SIMD computation based on the library in development Boost.SIMD (not yet a Boost library). I was hoping to get feedback on the interface and establish an API that would satisfy hardware and compiler vendors. Unfortunately the concurrency/parallelism group has decided that they do not want C++ to provide types representing SIMD registers. I'm afraid I don't quite understand the rationale for such a refusal; proposing more high-level constructs similar to valarray (or to our own library NT2) was suggested, but that's obviously a more complex and limited API, not a basic building block to program portably a specific processor unit. Development of Boost.SIMD will still proceed, aiming for integration in Boost, but standardization appears to be definitely out of the question. Any feedback of the API presented in the proposal is welcome. <http://open-std.org/JTC1/SC22/WG21/docs/papers/2013/n3571.pdf>

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[Runtime parameters reference]Regarding Call Stack Trace
by Hemanth Choudary M V (RBEI/ETA1) 24 Apr '13

24 Apr '13

Hello, We are running a boost unit test using command line (cmd). The command is: C:\> /c "D:\MyExecutable.exe" --run_test=testcase1,testcase2,testcase3, --report_format=xml --report_level=detailed --log_format=xml --log_level=all >test_log.xml 2>test_report.xml The output format is in XML. I would like to have the call stack for the failed test cases. Is it possible to write the call stack trace in test_report.xml or test_log.xml ? Is there any macro or Boost API can help me achieve this? Mit freundlichen Grüßen / Best Regards, Hemanth Choudary MV RBEI/ETA1

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