- Boost - lists.boost.org

[context review] Quick Review
by Stewart, Robert 03 Jan '12

03 Jan '12

Here's my quick review of the proposed Boost.Context library. I'm not familiar with the kernel-level machinations involved to save and restore the execution state managed by the context class, so I cannot comment on such implementation details and whether they satisfy the acceptance criteria. Consequently, I didn't bother to look at the implementation. The examples are good, but the discussion or comments are somewhat lacking. For example, the Enumerator example is based upon an enumerator class type which is not commented and has very little introductory text. There's a link to C# documentation on the yield keyword, but no association of enumerator's yield_return() to C#'s "yield return" statement or yield_break() to "yield break". Those associations can be inferred easily enough, but are better stated explicitly. The enumerator example is further confused by indicating that a call to yield_return() in the power derivate returns a value to the while loop in main(). What's missing is that yield_return() calls context::suspend() on enumerator's context data member which returns control to enumerator<T>::get(), which is called by main()'s while loop. The entire enumerator example should be introduced by discussing the power class first, without implementation details: class power { public: power(int _base, int _exponent); bool get(int & _value); }; Then, the example can show main(), since the above interface is sufficient. That done, the example can turn the reader's attention to how to implement power by referring to the C# yield documentation example and then relating it to Boost.Context. That will lead to the enumerator class. (Making enumerator a class template complicates matters more than necessary, BTW.) Finally, you should show expected output. I'd like to see a performance comparison of using Boost.Context versus Chris Kohlhoff's coroutines. Can his coroutines be replaced with yours without loss of efficiency? Would it require a different stack allocator to match the performance of his coroutines? (Developing the example in that direction would be useful to illustrate writing a custom stack allocator.) I don't find anything related to the Movable Stack concept suggested in the acceptance criteria. The documentation of the StackAllocator is lacking, but I've suggested a rewrite below. With that rewrite, I think it satisfies the Stack concept required for acceptance. There are no performance figures for Windows. Shouldn't there be? I think I recall that the build system doesn't support the necessary information, by default, to permit building an ABI compatible version of the library. If that's not the case, then the "How to build and install" section needs more work. Either way, the Build acceptance criteria has not quite been met yet. The _suggested_ callback-based linking was not adopted in lieu of fc_link. There should be some rationale or a FAQ for that. I've called for still more work on the documentation, but as it stands, with the concept changes I've suggested, I'm satisfied that Oliver has met the documentation acceptance criteria. _____________________________________________ Documentation comments follow. _______________ Overview This section is useful and clear, except for the second sentence of the third paragraph. It doesn't connect to the library in question as it ought and is worded a little unclearly. I'd suggest the following instead: "By contrast, transferring control within a single thread, as _context_ does, requires only a few hundred CPU cycles since it involves no system calls." You might also add something like, "which makes them useful in more contexts, particularly when implementing higher level execution control systems", to that sentence. What's missing is a Motivation section or more information in the Overview to better explain why someone would want to use Boost.Context versus other options (whatever they may be). _______________ How to build and install There should be an introductory paragraph, something like the following: "Boost.Context must be built for the particular compiler(s) and CPU architecture(s) being targeted. Each combination requires specific build command arguments as documented below." The bullets at the top of the page are only needed until the library is accepted, so be sure to remove them upon acceptance. "On POSIX and Windows systems, GNU AS and MASM are respectively required for the assembler implementation of Boost.Context" is awkward. I suggest the following instead: "Boost.Context includes assembly code and, therefore, requires GNU AS for supported POSIX systems, and MASM for Windows systems." The Note is a little awkward and includes a spelling error. I suggest the following instead: "The architecture, instruction set, and address model are optional Boost.Build properties that must be given on the bjam command line, as shown in the table below." _______________ Executing a context 3rd para: s/a function or callable object/a _context-function_/ 5th para: this should be merged with para 4 and "and might be changed" should be inside the parentheses or I don't understand how it "might be changed". 6th para, 4th sent: Add the following to the end: ", after saving the new state of the original context" 6th para, last sent: Is there anything that ensures start() is called first and only once? Example: - The control transfer comments in fn() could be a little clearer: // transfer execution control back to main() ... // execution control transferred back from main() - The first "main() calls context ctx" would be better as "main() starts context ctx" - The comment, "// ctx.suspend() was called", in the while loop is only accurate until the for loop, in fn(), terminates, right? - Expected output is not shown _______________ Transfer of data Example: - Missing comments discussing the pointers on the receiving end. For example, in fn(), I'd expect the following: void * vp = ctx.suspend(&i); // vp is &x from main()'s call to ctx.resume(&x) int j = *static_cast<int *>(vp); // j == 10 because x == 10 in main() - Expected output is not shown _______________ Exceptions in context-function s/emits/emits/ Is forced_unwind a documented exception type? That is, can it be caught explicitly? If so, the reference to "forced_unwind" should be a link to its documentation and the following might be documented as legitimate: try { // code that might throw } catch (forced_unwind) { throw; } catch (...) { // possibly not rethrow pending exception } _______________ Terminating context Shouldn't this section name be something more like, "Handling execution context termination"? 2nd example: remove the "Done" line. The "never reached" comment can then be applied to "return EXIT_SUCCESS". _______________ Chaining contexts The first two sentences should be merged something like the following: "Boost.Context provides the ability to chain context instances by passing a reference to another context, other than _not-a-context,_ as the last constructor argument." You note that the application terminates or control is transferred back to the last invocation of context::resume(). Might not the transfer also be to context::start() (if suspend()/resume() are never called)? Important: I think you mean, "context::start() must not be called on a context that is a link in the chain begun by another context. That is, call context::start() only on the first context in a chain." _______________ Unwinding stack Name this section "Stack unwinding" 2nd para, 1st bullet: Should "not-a-context" be italicized? Speaking of italics, "context" is sometimes italicized and blue and other times plain. Example: Expected output is not shown Important: s/exception!/exceptions!/ _______________ context.html Variously through this page: s/an context/a context/ or s/an context/an instance/ s/unwinds the stack before destructing it/unwinds the stack first/ s/if precondition is not fulfilled/if a precondition is not satisfied/ s/nxt is linked/nxt becomes a subsequent link in a chain/ s/the execution control/execution control/ s/The execution control/Execution control/ s/Destroyes/Destroys/ Is the move assignment operator safe against self-move assignment? start(): s/with wich/with which/ s/When the function returns/Upon return/ (to avoid confusion about whether start() or fn() has returned) resume(): s/back resuming/back, resuming/ s/ (means suspend()/, which means that suspend() returns/ (note the formatting of "returns" should be normal, not code) "[[Returns:]" is malformed Effects could be rewritten, something like the following, to be clearer: "None, if *this was not suspended by a previous call to suspend(). Otherwise, execution control is transferred back to the caller of suspend(), thereby resuming *this. The argument, vp, will be returned by the previous call to suspend()." suspend(): I think Effects is incomplete. There are spelling errors. How about the following? "Transfers execution control to the caller of the most recent call to start() or resume(). The argument, vp, will be returned by start() or resume()." unwind_stack(): Effects: suggestion: "Destroys all objects allocated on the stack, owned by *this, in the reverse order of their allocation." Non-member function swap(): Effects: suggestion: "As if l.swap(r)." _______________ Stack allocation 1st para: - "stack allocator" should probably be italicized rather than rendered as code. - Concept names are usually rendered with camelcase. Thus, s/stack-allocator/StackAllocator/. 2nd para: This should be the start of a "StackAllocator Concept" section: "StackAllocator Concept "A stack allocator must satisfy the StackAllocator concept requirements shown in the following table, in which a is an object of a StackAllocator type, p is a void *, and s is a std::size_t: " " Expression | Return type | Notes " ----------------------------------------------- " a.allocate(s) | void * | Returns a pointer to s bytes allocated from the stack " ----------------------------------------------- " a.deallocate(p, s) | void | Deallocates s bytes of memory beginning at p, a pointer previously returned by alloc.allocate()" The current documentation of allocate() and deallocate() are no longer needed. Important: This should be rephrased in terms of the concept to something like the following: "The implementation of allocate() might include logic to protect against exceeding the context's available stack size rather than leaving it as undefined behavior." You might add a note that the result of calling deallocate() with a pointer not returned by allocate() results in undefined behavior. _______________ Helper functions 1st para: s/an easy/easy/ _______________ Low level API (boost_fcontext_t) You refer to "ucontext_t" with no link or description. The example code is out of place without first seeing the documentation of boost_fcontext_t and related functions. Following the -> navigation order, the example comes first. Commenting the example and providing an introduction explaining what it illustrates would work. There is no expected output shown for the example. Presumably, the low level API is the part to port to new platforms, yet you don't state that. _______________ Struct boost_fcontext_t and related functions There is no documentation for boost_fcontext_t, particularly as it appears to be just an alias for boost_fcontext. I thought for a moment that you intend to permit different platforms to redefine the typedef to refer to different structures, as needed, but you've documented boost_fcontext_stack's ss_base and ss_limit fields, which suggests that you intend those to be part of the low level, yet documented, API. The result is that I can't figure out the purpose of the typedef. The "fc_" prefix makes sense, since it is used in boost_fcontext. By contrast, the "ss_" prefix does not make sense. I could see "fcs_", for example. ss_limit: Is the stack defined by [ss_base, ss_limit) or [ss_base, ss_limit]? "Pointer to the bottom of the stack" is ambiguous. fc_stack: The description is a little off. How about, "Tracks the memory for the context's stack"? fc_link: The description could be improved: "The address of the next context link in a chain, if any." boost_fcontext_start(): Effects are a little confusing. My suggestion: "Stores the current context data (stack pointer, instruction pointer, and CPU registers) to *ofc and restores the context data from *nfc, which implies jumping to *nfc's execution context. This function must be called when first entering *nfc's execution context." boost_fcontext_start(): Need a "Returns:" "The result of calling boost_fcontext_jump()." boost_fcontext_jump(): This likewise needs some work: Effects: "Stores the current context data (stack pointer, instruction pointer, and CPU registers) to *ofc and restores the context data from *nfc, which implies jumping to *nfc's execution context. The pointer argument, vp, is passed to the current context to be returned by the most recent call to boost_fcontext_start() or boost_fcontext_jump() in the same thread." Returns: "The third pointer argument passed to the most recent call to boost_fcontext_jump(), if any." boost_fcontext_make(): Precondition: s/finished /finishes, / and s/inside/in/ boost_fcontext_make(): Effects: s/if the context is activated next time/when the context is activated next/ _______________ Continuation 1st para: s/from Java/from the Java/ 2nd para: s/for functors objects/for a functor/ 3rd para: You say the co-routines run "in parallel", but there is no parallelism, so you should be clear about what does occur. _______________ ASIO 2nd para: s/a echo/an echo/ 3rd para: I quickly got lost in this description because it assumes familiarity with code presented later. It also assumes familiarity with control flow in Asio which can be described rather than assumed. 3rd para: s/reentered a/reentered, a/ s/a asynch./an async/ 4th para: s/adavantage/advantage/ s/bind()-version/bind() version/ s/easier implemented/more easily implemented/ s/For instance if/For instance, if/ s/a message is partialy received/only part of a message is received/ s/parser or serviced)/parsed or serviced),/ _______________ Performance The bullets are too terse. Perhaps the following captures your intent: "Performance of Boost.Context was measured on the platforms shown in the following table. Performance measurements were taken using rdtsc, with overhead corrections, on x86 platforms. In each case, stack protection was active, cache warm-up was accounted for, and the one running thread was pinned to a single CPU. The code was compiled using the build options, 'variant=release cxxflags=-DBOOST_DISABLE_ASSERTS'. "The numbers in the table are the number of cycles per iteration, based upon an average computed over 1000 iterations." _______________ Rationale NoThrow guarantee: I think you meant the following: "Member functions of context do not throw exceptions but do require that certain preconditions are satisfied: context jumps can only be made by instances which are not a _not-a-context_ and which are not complete." Pimpl idiom, 1st para: s/ it was required to separate both features in separate classes via pimpl idiom/, the use of the Pimpl Idiom was necessary/ Pimpl idiom, 3rd para: I suggest the following: "The Pimpl Idiom allows type-erasing the _stack-allocator_ type." Unwinding: s/resource/resources/ and s/a exception/an exception/ Protecting the stack: There are many changes to make here, so I'll suggest this rewrite: "Because the stack's size is fixed -- there is no support for split stacks -- it is important to protect against exceeding the stack's bounds. Otherwise, in the best case, overrunning the stack's memory will result in a segmentation fault or access violation and, in the worst case, the application's memory will be overwritten. stack_allocator appends a guard page to the stack to help detect overruns. The guard page consumes no physical memory, but generates a segmentation fault or access violation on access to the virtual memory addresses within it." setjmp()/longjmp(): s/The C99/C99/ s/frame, e.g. jumping/frame. Therefore, jumping/ ucontext_t: I don't know why anything in this section is included after the first sentence. ucontext_t, para 1: s/makecontext():/makecontext() is:/ ucontext_t, para 2: s/alter/later/ I would omit the "The signature of func is" part. That's clear from the makecontext() function pointer argument. Windows fibers: s/befor/before/ _____ Rob Stewart robert.stewart(a)sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. 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[thread] feature request priority
by Vicente J. Botet Escriba 03 Jan '12

03 Jan '12

Hi, here they are a list of 26 feature requests for Boost.Thread. The features are classified as high, middle and low cost (form my point of view of course) I would like to know which features would you like to find on the next release. Please could you choose 3 features and if possible one for each category, the idea been to provide 1 high, 1 middle and 2 low features for the next release. High #2100 <https://svn.boost.org/trac/boost/ticket/2100> thread fails to compile with -fno-exceptions <https://svn.boost.org/trac/boost/ticket/2100> #6195 <https://svn.boost.org/trac/boost/ticket/6195> Provide the standard time related interface using Boost.Chrono <https://svn.boost.org/trac/boost/ticket/6195> #6217 <https://svn.boost.org/trac/boost/ticket/6217> Make uniform Boost.Thread and Boost.Interprocess synchronization interface <https://svn.boost.org/trac/boost/ticket/6217> #6230 <https://svn.boost.org/trac/boost/ticket/6230> Follows the exception reporting mechanism as defined in the c++11 <https://svn.boost.org/trac/boost/ticket/6230> #5150 <https://svn.boost.org/trac/boost/ticket/5150> boost::thread does not print or return the error value when creating a thread fails. <https://svn.boost.org/trac/boost/ticket/5150> #6194 <https://svn.boost.org/trac/boost/ticket/6194> Adapt to Boost.Move <https://svn.boost.org/trac/boost/ticket/6194> Middle #2741 <https://svn.boost.org/trac/boost/ticket/2741> proposal to manage portable and non portable thread attributes <https://svn.boost.org/trac/boost/ticket/2741> #2880 <https://svn.boost.org/trac/boost/ticket/2880> Request for Thread scheduler support for boost .. <https://svn.boost.org/trac/boost/ticket/2880> #3696 <https://svn.boost.org/trac/boost/ticket/3696> Boost Thread library lacks any way to set priority of threads <https://svn.boost.org/trac/boost/ticket/3696> #4710 <https://svn.boost.org/trac/boost/ticket/4710> Missing async() <https://svn.boost.org/trac/boost/ticket/4710> #4725 <https://svn.boost.org/trac/boost/ticket/4725> Synchronization and shared mutex's Get total_count <https://svn.boost.org/trac/boost/ticket/4725> #5173 <https://svn.boost.org/trac/boost/ticket/5173> boost::this_thread::get_id is very slow <https://svn.boost.org/trac/boost/ticket/5173> #5425 <https://svn.boost.org/trac/boost/ticket/5425> This patch will allow the user to obtain the users thread pointer from a thread group. <https://svn.boost.org/trac/boost/ticket/5425> #5956 <https://svn.boost.org/trac/boost/ticket/5956> Add optional stack_size argument to thread::start_thread() <https://svn.boost.org/trac/boost/ticket/5956> #6227 <https://svn.boost.org/trac/boost/ticket/6227> Use of variadic templates on Generic Locking Algorithms on compilers providing them <https://svn.boost.org/trac/boost/ticket/6227> #6228 <https://svn.boost.org/trac/boost/ticket/6228> Add promise and futures constructor with allocator following the standard c++11 <https://svn.boost.org/trac/boost/ticket/6228> #6229 <https://svn.boost.org/trac/boost/ticket/6229> Rename the unique_future to future following the c++11 <https://svn.boost.org/trac/boost/ticket/6229> Low #1789 <https://svn.boost.org/trac/boost/ticket/1789> thread_group not passing variables <https://svn.boost.org/trac/boost/ticket/1789> #1850 <https://svn.boost.org/trac/boost/ticket/1850> request for unlock_guard (and/or unique_unlock) to compliment lock_guard/unique_lock <https://svn.boost.org/trac/boost/ticket/1850> #2361 <https://svn.boost.org/trac/boost/ticket/2361> thread_specific_ptr: nature of the key, complexity and rationale <https://svn.boost.org/trac/boost/ticket/2361> #2637 <https://svn.boost.org/trac/boost/ticket/2637> shared mutex lock <https://svn.boost.org/trac/boost/ticket/2637> #3567 <https://svn.boost.org/trac/boost/ticket/3567> Request for shared_lock_guard <https://svn.boost.org/trac/boost/ticket/3567> #6224 <https://svn.boost.org/trac/boost/ticket/6224> Add the use of standard noexcept on compilers supporting them <https://svn.boost.org/trac/boost/ticket/6224> #6225 <https://svn.boost.org/trac/boost/ticket/6225> Add the use of standard =delete defaulted operations on compilers supporting them <https://svn.boost.org/trac/boost/ticket/6225> #6226 <https://svn.boost.org/trac/boost/ticket/6226> add explicit bool conversion from locks <https://svn.boost.org/trac/boost/ticket/6226> #6231 <https://svn.boost.org/trac/boost/ticket/6231> Add BasicLockable requirements in the documentation to follow c++11 <https://svn.boost.org/trac/boost/ticket/6231> Patches are welcome for any feature. Note that a feature that have all the needed patches, code, doc and tests could be included soon. Thanks in advance, Vicente

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[thread] Reducing the number of open tickets.
by Vicente J. Botet Escriba 03 Jan '12

03 Jan '12

Hi, I have committed the following tickets in trunk. Fixed Bugs: * [@http://svn.boost.org/trac/boost/ticket/2639 #2639] documentation should be extended(defer_lock, try_to_lock, ...). * [@http://svn.boost.org/trac/boost/ticket/3762 #3762] Thread can't be compiled with winscw (Codewarrior by Nokia). * [@http://svn.boost.org/trac/boost/ticket/3885 #3885] document about mix usage of boost.thread and native thread api. * [@http://svn.boost.org/trac/boost/ticket/3975 #3975] Incorrect precondition for promise::set_wait_callback(). * [@http://svn.boost.org/trac/boost/ticket/4480 #4480] OpenVMS patches for compiler issues workarounds. * [@http://svn.boost.org/trac/boost/ticket/4819 #4819] boost.thread's documentation misprints. * [@http://svn.boost.org/trac/boost/ticket/5423 #5423] thread issues with C++0x. * [@http://svn.boost.org/trac/boost/ticket/5739 #5739] set-but-not-used warnings with gcc-4.6 * [@http://svn.boost.org/trac/boost/ticket/6168 #6168] recursive_mutex is using wrong config symbol (possible typo). * [@http://svn.boost.org/trac/boost/ticket/6200 #6200] patch to have condition_variable and mutex error better handle EINTR. These are tickets with a simple solution or that had associated a complete patch or a clear solution. Anthony I would prefer that you do the merge so that you can check what goes on the release version. I have not closed the tickets. These tickets have just release 1.49 as Milestone. Please, close them when you merge to release. There were 113 tickets two days ago. There are now 114 tickets associated to Boost.Thread. I have closed some duplicates, but some news tickets have been created since. I would like to reduce by 10% the number of tickets every month. I encourage the Boost users that have created tickets for Boost to provide a clear an complete patch when possible so that we can reduce together the number of tickets associated to this Boost library and make it more portable/usable. Don't forget to provide tests that make evident the bug, or to add doc when you are proposing a anew feature. There are a lot of tickets associated to move semantics emulation. I have created a ticket to adapt Boost.Thread to Boost.Move hoping most of these bugs will be solved. As posted in another thread there is already a patch using Boost.Move that could be a good starting point. Of course the help offered by Ion will be too much appreciated. I have created another to adapt the interface to Boost.Chrono, but I will prefer to take care of this once the one for Boost.Move adaptation is committed, as the chance of collisions is big. On the mean time I will continue with some tickets specific to Windows platform. Best, Vicente

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[C++ Now! 2012] Reminder: Call for Submissions, deadline is January 10th, 2012
by Hartmut Kaiser 03 Jan '12

03 Jan '12

INAUGURAL C++ NOW! CONFERENCE 2012 Aspen CO, USA, May 14-18, 2012, www.cppnow.org CALL FOR SUBMISSIONS We invite you to submit session proposals to the Inaugural C++ Now! Conference: C++Now! 2012 (Aspen CO, USA, May 14 - 18, 2012). Based on the successful traditions of 5 years of BoostCon, which was the main face-to-face event for all things C++ and Boost (www.boost.org) C++Now! 2012 will present leading speakers from the whole C++ community. The conference name is changing to C++ Now! to reflect the current value of the language, the focus on its new state (from the new Standard), and the need to continually look to the future so the language remains useful to the C++ community. The focus of this conference will be the new C++11 language Standard and as usual Boost: what's new in C++, its Standard library, and in the Boost libraries, how to write and maintain them, how to evangelize or to deploy Boost within your organization. The new C++ Standard, but also the infrastructure and process of Boost, its vision and mission - no matter what you are interested in, it all comes together in the C++Now! sessions. Meet the colleagues, and feel the inspiration to support your work with C++ and Boost for the next year. The C++ Now! Conference is dedicated to discussion and education about C++, an open and free language and standard. Our Conference will focus on discussion and education about open source software usage and developments in the C++ developer and user community. To reflect the breadth of the C++ and Boost communities, the conference includes sessions aimed at three constituencies: C++ and Boost end-users, hard-core Boost library and tool developers, and researchers pushing the boundaries of computation. The program fosters interaction and engagement within and across those groups, with an emphasis on hands-on, participatory sessions. As a multi-paradigm language, C++ is a melting pot where the most compelling ideas from other programming communities are blended in powerful ways. Historically, some of the most popular sessions at C++Now! have highlighted these concepts, from DSLs to functional programming to transactional memory and more. Bring your C#, Python, Ruby or Haskell influences to bear in an environment that will broaden their exposure. IMPORTANT DATES New proposal submissions due: January 10th, 2012. Proposals decisions sent (tentative program): February 17th, 2012. Fully scheduled program available: February 25th, 2012. Session materials due: April 15th, 2012. BEST PRESENTATION AWARDS We know how much effort it takes to prepare talks for our conference. For this reason we will award the best presentations in the following categories: Best Presentation, Best Short Presentation, Best Tutorial, and Best Workshop. The awards will be given based on the audience's voting. 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Authors are invited (but are not required) to submit PDF versions of full papers of up to 10 pages in ACM conference proceedings format (see http://www.acm.org/sigs/publications/proceedings-templates) The full papers are not required unless you want them published in the proceedings. All accepted proposals will be made available in the Association for Computing Machinery (ACM) Digital Library (approval pending). Best papers, after further reviews, will be considered to be book chapters or journal articles in a renowned journal. The session materials go on the C++Now! website and will be available to attendees. For general information on the C++Now! 2012 paper submission or the scope of technical papers solicited, please refer to the conference website at www.cppnow.org. For any other questions about the submission process or paper format, please contact the Program Committee at cppnow2012(a)easychair.com. If you have any technical problems with EasyChair, please contact EasyChair for help. Note: Presenters must agree to grant a non-exclusive perpetual license to publish submitted materials, either electronically or in print, in any media related to C++ Now!. Hartmut Kaiser, email: hartmut.kaiser(a)gmail.com (Program Committee Chair) Dave Abrahams, email: dave(a)boostpro.com (Conference Chair) On behalf of the conference organizers

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How to get involved ?
by Vijeenrosh PW Vijeen 03 Jan '12

03 Jan '12

Good Morning , My name is Vijeenrosh P.W . Iam an Computer Science and Engineering student . I have knowledge in c,c++,python and linux , and an mind to extend my areas of knowledge. Recently while passing through the list of GSOC accepted organizations I met with boost libraries . it fits me since I have C++ && programming knowledge and is ready to work . I would like to know how to begin to contribute to the project . Where to begin . or is there any warm up excersices to get passed ? -- Vijeenrosh P.W CSE S3 blog : www.BlackJackVijeen.blogspot.com

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RFC: Multiprecision arithmetic library
by John Maddock 03 Jan '12

03 Jan '12

Folks, I'd like to get some feedback on a multiprecision arithmetic library I've been preparing for possible Boost inclusion. The code is in the sandbox under the "big_number" directory. Docs can be viewed online here: http://svn.boost.org/svn/boost/sandbox/big_number/libs/multiprecision/doc/h… The main features are: * A generic front-end that's capable of wrapping almost any type that's a "number". The front end is expression template enabled and handles all the expression optimization and code reduction. For example it's possible to evaluate a polynomial using Horner's rule without a single temporary variable being created. * A series of backends that need only provide a reduced interface and set of operations, implement the actual arithmetic, currently supported backends are: Integer Types ~~~~~~~~~ 1/ GMP (MPZ). 2/ libtommath. Rational Types ~~~~~~~~~~ 1/ GMP (MPQ). [ But note that the integer types can also be used as template aruments to Boost.Rational ] Floating Point Types ~~~~~~~~~~~~~~ 1/ GMP (MPF) 2/ MPFR 3/ cpp_float - an all C++ Boost-licensed backend based on Christopher Kormanyos' e_float code. [ Note these three types are fully compatible with Boost.Math Trunk - so you get full standard library plus special function support ] There's still a bunch to do, but I'd like to see what folks think, and where the main priorities should be before submission. Thanks in advance, John.

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[test] showtopper for release 1.49 - std::forward not found when compiling with clang 3.0 c++0x mode.
by Vicente J. Botet Escriba 03 Jan '12

03 Jan '12

Hi, I have created a show stopper ticket https://svn.boost.org/trac/boost/ticket/6345 as after updating the trunk, I'm unable to test any library using Boost.Test. Recent modification on Boost.Test make it unusable with clang 3.0 c++0x due to std::forward missing or not found. clang-darwin.compile.c++ ../../../bin.v2/libs/thread/test/test_thread.test/clang-darwin-3.0x/debug/threading-multi/test_thread.o In file included from test_thread.cpp:16: In file included from ../../../boost/test/unit_test.hpp:19: In file included from ../../../boost/test/test_tools.hpp:328: In file included from ../../../boost/test/tools/impl.hpp:25: ../../../boost/test/tools/assertion.hpp:278:21: error: no member named 'forward' in namespace 'std' : m_value( std::forward<T>(val) ) ~~~~~^ ../../../boost/test/tools/assertion.hpp:278:29: error: 'T' does not refer to a value : m_value( std::forward<T>(val) ) ^ The revision is https://svn.boost.org/trac/boost/changeset/75370 #ifndef BOOST_NO_RVALUE_REFERENCES explicit value_expr( T&& val ) : m_value( std::forward<T>(val) ) #else explicit value_expr( T const& val ) : m_value( val ) #endif #ifndef BOOST_NO_RVALUE_REFERENCES operator->*( T&& v ) const { return value_expr<T>( std::forward<T>( v ) ); } #else operator->*( T const& v ) const { return value_expr<T>( v ); } #endif This has as consequence that the authors developing mainly with this compiler and using Boost.Test to be unable to deliver new modifications. I have added #include <utility> without success. I guess that the standard library doesn't provides this function even if the compiler provides rvalue references. The code should test for a macro that states if std::forward is available. Please could someone help on this issue? Best, Vicente

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[Boost.Math] Re: [Monotone-debian] Bug#653764: FTBFS with Boost 1.48: lgamma_small.hpp:483:38: error: expected primary-expression before 'do'
by Steve M. Robbins 02 Jan '12

02 Jan '12

Hello, Boost Developers: I recently did rebuilds of all Debian packages that use Boost with Boost 1.48 and this is one of the casualties of the upgrade (from 1.46.1). On Sat, Dec 31, 2011 at 12:02:37PM +0100, Zack Weinberg wrote: > On Fri, Dec 30, 2011 at 9:53 PM, Steve M. Robbins <smr(a)debian.org> wrote: > > This package failed to build using the newest Boost version 1.48: > ... > > /usr/include/boost/math/special_functions/detail/lgamma_small.hpp: In function 'T boost::math::detail::lgamma_small_imp(T, T, T, const mpl_::int_<0>&, const Policy&, const L&)': > ... > > /usr/include/boost/math/special_functions/detail/lgamma_small.hpp:483:38: error: expected primary-expression before 'do' > > I'm not in a position to verify this for myself for another week, but > I have a horrible feeling I know what's wrong: Monotone defines > several one-character macros for its own use, and L() is one of them. > It looks like Boost is using L() for its own purposes and expecting it > not to be a macro. Zack, you are absolutely right. The lgamma_small header has a templated class method using "L" as one of the templates: template <class T, class Policy, class L> T lgamma_small_imp(T z, T zm1, T zm2, const mpl::int_<0>&, const Policy& pol, const L&) The compile error at line 483 is at a call to L(): result = log(gamma_imp(z, pol, L())); > I'd argue that Boost headers should take care to defend themselves > from the possibility of such macros, but fixing that in Boost might be > an enormous amount of work, and in any case, 1.48 is already out > there. Boost.Math developers: What is the right thing to do here? More descriptive class template parameters? Attached is a trivial file to reproduce the bug. Thanks, -Steve

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boost modularisation status?
by Robert Ramey 02 Jan '12

02 Jan '12

https://svn.boost.org/trac/boost/wiki/CMakeModularizationStatus hasn't been modified in 3 years. Also, when I peruse my local copy of the release tree, I don't see what I expect to see according to https://svn.boost.org/trac/boost/wiki/CMakeModularizeLibrary That is, I expect to seem include inside of the libraries at boost/libs/tr1/include - I don't see this. What is the current status of this? Robert Ramey

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[review] Boost.Context mini-review starts today, January 2nd
by Giovanni Piero Deretta 02 Jan '12

02 Jan '12

Hi all, we will start a new year of Boost reviews with a one week mini-review of the Boost.Context library of Oliver Kowalke. The review period starts today January 2nd and ends January 11. Please use [context review] as prefix of your post. Reviewers are strongly encouraged to send their reviews to the boost development mailing list as this is the I follow more assiduously. Please note that Boost.Context was already reviewed and conditionally accepted last May, so we are not voting for acceptance. Instead, this mini-review is to discuss whether the library meets the conditions on acceptance that were listed by Vicente Botet, the review manager at that time. You'll find the whole list at the end of this email. Since the end of the original review, Oliver has spent a large amount of time on a partial rewrite of the library and both me and Oliver decided to schedule this review only after we determined that all issues had been addressed or at least considered. In your review please state whether the acceptance conditions have been addressed satisfactorily. ---------------------------------------------------------------------------------- About the library: Boost.Context is a foundational library that provides a sort of cooperative multitasking on a single thread. By providing an abstraction of the current execution state in the current thread, including the stack (with local variables) and stack pointer, all registers and CPU flags, and the instruction pointer, a context instance represents a specific point in the application's execution path. This is useful for building higher-level abstractions, like coroutines and fibers. ---------------------------------------------------------------------------------- Useful Links: documentation: http://ok73.ok.funpic.de/boost/libs/context/doc/html/ library: git://github.com/olk/boost.context.git ---------------------------------------------------------------------------------- >From the original review result email: Point to be addressed before the mini review: Design 1. Separation of the context class in two interface: - A C-like interface that defines a POD struct that is memcpy-able and that can be implemented either using platform libraries, as ucontext, fibers or directly using assembler when a robust implementation is available. The context swap implementation don't need to save the signals as ucontext does. The following is just for illustrations purposes. struct boost_context; typedef void boost_context_fn_t(intptr_t); extern "C" void boost_context_make(boost_context* ctx, boost_context_fn_t * f, intptr_t p, ...); extern "C" void boost_context_swap(boost_context* from, boost_context const* to); extern "C" intptr_t boost_context_destroy( boost_context* fc); boost_context_make is a merge of get_context with make_context + some fields assignations. "A user will have lower expectations from such a low level API and at the same time will give more freedom for other people to implement on top of it higher abstractions as Boost.Corutines, Boost.Fibers ..." - A non-copiable but movable safe context class on top of the low level C-like interface, that will provide modern and efficient C++ interface, that is usable by a user in a safe way. The safe context class would just be one of the client of the C-like interface, other library authors could either use the underlying C-like API directly or the class context depending on wether they need the speed or safety. * The context class will not be templated any more, and the use of type erasure will ensure that. * The constructor will accept any C++ callable, function pointers, functors, ... * At this high level interface, the function provided by the user could throw exceptions, and the library must wrap the user function and needs to store the exception raised and provide an interface to retrieve them. 2. The stack implementation must ensure that the stack is unwound before it is destroyed. A stack should only be safely deallocated if either has been completely unwound or if it doesn't own any resources. A basic stack without protection seems mandatory. For debug purposes it has been required to provide some stack usage functions that allow to know the max size used for example. Implementation 3. The assembler implementation on Windows must be disallowed if the ABI bug reported by Holger is confirmed. As far as Windows provides a fiber implementation that is as efficient as the assembler one, the assembler implementation is not mandatory and the user of the provided Windows fiber is a preferable choice. 4. Most of the 'throw' statements in the context class should actually be asserts. 5. The provided stack should be used to store any context parameters as far as no major impediment is found during the implementation. This will avoid further allocations on the safe context class. Documentation 6. The documentation is very minimalist and should be expanded with a discussion on context switching and use cases. Take care of all the grammar/spelling improvements suggested by the reviewers (It will be great if Jeffrey could review the documentation before the mini-review). Some user land examples should be provided (why not the yield example). 7. The concept of (Movable) Stack must be clearly defined, as it is done in the standard, using expression requirements with semantic constraints. 8. The assembler implementation should be carefully documented, so others could maintain the code and add other implementations if needed. 9. Some performance measure should be added. Providing the number of cycles on each implemented platform would be nice. Build system 10. The default build on a platform must work (It must be ABI compatible with the underlying platform) and take care of the specific features. Of course, the build needs to support cross compiling, so the user should be able to override the default values. Others points that are not required but that can make the library more usable or efficient: 1. The assembler implementations could be simplified if the context itself was represented as a single pointer to the top of the stack. This would save some instructions to move the source address from the stack return address to the context struct and back. 2. Instead of supporting a 'fc_link' a-la ucontext, have the callback function return a new context (it is void now). 'fc_link' is useful only on some limited cases (usually when you have an external scheduler managing your contexts), while the having the callback return the 'next continuation' has more applications (note that fc_link can be implemented easily in term of the continuation returning variant, but the reverse is harder). This will be very useful, for example, to implement some kind of 'exit_to' functionality (unwind the stack and restore another context), a key piece for safe context destruction. 3. Give to boost_context_swap the ability to exchange a parameter with the other context: boost_context_parm_t boost_context_swap( boost_context * ofc, boost_context const* nfc, boost_context_parm_t parm) where boost_context_parm_t is either union boost_context_parm_t { void * ptr; int int_; }; or simply intptr_t; boost_context_swap saves the current context in ocf and restores the context ncf as usual; additionally, if ofc was 'captured' on a call to boost_context_swap, this call will return the value of parm on the original context. This extra parameter is equivalent to the second parameter of longjmp. If ofc was created with boost_context_swap, 'parm' will be an extra parameter to the function. Note that this can be potentially implemented with little or no overhead. 4. Add a variant of boost_context_swap that allows executing a function on the destination context (in this case 'parm' would be passed parameter to this function. This is mostly useful for injecting an exception on the destination context. This can be potentially implemented on top of the existing functionality, but would slow down every context switch; a possible efficient implementation would manipulate the destination stack to add a call to the function on top of it, so that the cost is paid only when required. 5. Add a current context function (thread local).

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