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

Release milestone.
by Vicente J. Botet Escriba 08 Apr '13

08 Apr '13

Hi, I would like to merge some fixes in Boost.Thread, but I suspect that the release branche should be blocked as for https://svn.boost.org/trac/boost/wiki/ReleaseSchedule. On which stage (milestone) is the release process? Best, Vicente

2 2

[gil] numeric extension, arithmetic operators
by Harg Tholan 08 Apr '13

08 Apr '13

Hey, Do we plan to overload arithmetic operators for Pixel as wrappers of the numeric extension? or should users derive a class from Pixel adding such functionality? ATM, for diving two pixels (rgb_8 for example), I have to call the division this way: pix_r = pixel_divide_t<rgb_8_pixel_t, rgb_8_pixel_t, rgb_8_pixel_t>().operator()(pix2, pix1); The thing is that I have a template class that makes use of operator/ at some point on one of the template parameters, and I would like to be able to use it with 'Pixel' type. Thank you!

3 7

Re: [boost] future<>::then() Error returning future<void> (on trunk)
by Vicente J. Botet Escriba 07 Apr '13

07 Apr '13

Le 22/01/13 22:56, Vicente Botet a écrit : > Fernando Pelliccioni wrote >> Hi Vicente, hi all, >> >> I noticed that in the trunk there is a implementation of >> future<>::then(). >> Thank you very much for your efforts to implement it! > Hi Fernando, > > I have started with a restricted implementation. While trying to cover with > the whole requirements I didn't reach to get correct implementation. This is > way this new feature is not delivered yet. For the time been I don't think > the current implementation is ready for production code. > > >> The following example, compiles OK >> >> boost::future >> <int> >> f1 = boost::async([]() { return 123; }); >> f1.then([](boost::future >> <int> >> const& f) { >> return std::string(""); >> }); >> >> >> But this one fails to compile: >> boost::future >> <int> >> f1 = boost::async([]() { return 123; }); >> f1.then([](boost::future >> <int> >> const& f) { >> }); >> >> Here future<>::then() have to returns future >> <void> >> like ... >> >> boost::async([]() { }); >> >> Am I right? > Yes, it should. I have no access to my development environment for this > week. Could you post the compiler error? > > >> On the other hand, have you taken into account the following paper? >> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3451.pdf > I read it and the mail exchanges related to this paper. > Currently I didn't reached to make it working at all when the future > destructor blocks, but I'm not sure this is the hidden problem as I have > also other issues when the future destructor doesn't blocks. > > I'm really sorry that the current state is not really usable :( > Hi Fernando, I have reworked the future::then function, and even if it is not yet complete (e.g. deferred is not implemented for c++98 compilers) it start to be usable for c++11 compilers, even if BOOST_THREAD_DONT_PROVIDE_FUTURE_INVALID_AFTER_GET is not defined. BTW, joining on the async future destructor works also. Please could you give it a try and let me know whatever you can find that doesn't works as you expect, Best, Vicente

2 3

C++11 and compilers not supported by vendors any more
by Antony Polukhin 06 Apr '13

06 Apr '13

Hi, I've got an almost ready patch for Boost.Any, that adds rvalues support to it via Boost.Move. But the trouble is following: Current version of patch may (and would) break compilation on ancient compilers, like MSVC6, BCC 5.5 and g++ 2.95. It can be tuned, to work even on those platforms, but: * I have no access to those antiquities, so it is impossible to run tests * It will take huge amount of time, to make it work What is the current policy in such situations (may ancient compilers support be dropped)? -- Best regards, Antony Polukhin

4 3

Re: [boost] Review managers wanted for augmented data structures
by James Hirschorn 06 Apr '13

06 Apr '13

Vadim Stadnik wrote > Hi all, > > > At present, neither Boost library nor STL provides containers using > augmented data structures. I suggest that the Boost community consider > solving the challenging problem – how to extend STL by integrating > advanced > data structures. > > ... > > Augmented trees are non-standard due to different performance guarantees. > At the same these data structures are beneficial for complex algorithms, > since they offer a wider set of more efficient operations compared to > standard containers. The typical performance improvement for one operation > is O(log N) against O(N). For less efficient operations these trees > normally provide running time O(log N) against O(1), which is good enough > for many applications. This is very similar to a project I have been working on, with the intention of submitting to boost. The new data structure I have implemented is called a skip list. They can be used in place of balanced trees, and according to the inventor, insertion and deletion are significantly faster than for balanced trees (I have not tested this yet). See, e.g. William Pugh. 1990. Skip lists: a probabilistic alternative to balanced trees. Commun. ACM 33, 6 (June 1990), 668-676. DOI=10.1145/78973.78977 http://doi.acm.org/10.1145/78973.78977 The difference in performance guarantees are much more subtle than you describe above. For example, skip lists have expected O(log n) insert, delete and search, versus O(log n). In practice, the expected O(log n) time is just as good as true O(log n), unless a performance bound is required with certainty, because the probability of the skip list having height much larger than log n is extremely low. I also implemented what I called augmented skip lists, which allow for expected O(log n) rank lookup (i.e. random access). I wasn't aware of the counter tree library, or else I would probably have just used it instead of implementing skip lists. I used skip lists to provide "drop in" STL replacements. Now I have skip_list::set and skip_list::multiset, and I could similarly make skip_list::map and skip_list::multimap. There is also augmented_skip_list::set and augmented_skip_list::multiset. For now the augmented versions have an additional member function nth_element providing E[O(log n)] random access. Hopefully, this will be helpful towards the goals you have described. > There are two libraries in the Boost review schedule: > > http://www.boost.org/community/review_schedule.html > > "STL Extensions" and "Countertree". None of them has as yet a review > manager. The order of the reviews may not be significant. It is more > important that at least one library pass the review. This would help > integrating other advanced data structures. > > > Are there Boost experts who could volunteer to take responsibility of > review manager for any of these two libraries? Data structures are very interesting to me, and I am in between jobs, so I have time to review one of these. If I take the time to review, I hope someone will be willing to review my skip list library, if I complete it and submit it to boost. -- View this message in context: http://boost.2283326.n4.nabble.com/Review-managers-wanted-for-augmented-dat… Sent from the Boost - Dev mailing list archive at Nabble.com.

3 4

[any] C++11 support
by Antony Polukhin 06 Apr '13

06 Apr '13

Hi, There is a patch for Boost.Any, that adds rvalue references support (via Boost.Move) and noexcepts (see ticket #6999 any.patch). It also includes a set of tests, and they pass well. Previous maintainers of the library are away for a long time, so if there will be no objections till the end of next weekend, I'll apply the patch. -- Best regards, Antony Polukhin

1 0

Scope Tracer or General Scope Function with parameter or variable values
by Anlin Zhang 06 Apr '13

06 Apr '13

Hi, I'm wondering if a "Scope Tracer" or a "General Scope Function" can be easily implemented with existing boost libraries now. One example use case is to log variable or parameter values or any program state when entering or leaving a scope, but it can do more than just logging, it can, for example, lock/unlock mutex, or prepare/teardown test cases, etc. For logging requirement, to give you an idea, the expected log message looks like this: >04/10/09 05:29:12:210257 entering func foo with parameter a=10, b=1.5, d.x=10, d.y=[string], global d=2, filename:test.cpp>04/10/09 05:29:12:210257 entering while() a=10, b=1.5, d.x=10>04/10/09 05:29:12:210257 leaving while() a=9, b=1.5, d.x=9>04/10/09 05:29:12:210257 entering while() a=9, b=1.5, d.x=9>04/10/09 05:29:12:210257 leaving while() a=8, b=1.5, d.x=8>...>04/10/09 05:29:12:210257 entering while() a=2, b=1.5, d.x=2>04/10/09 05:29:12:210257 leaving while() a=1, b=1.5, d.x=1>04/10/09 05:29:12:210257 entering while() a=1, b=1.5, d.x=1>04/10/09 05:29:12:210257 leaving while() a=0, b=1.5, d.x=0>04/10/09 05:29:12:210257 leaving function foo with parameter a=0, b=1.5, d.x=0, d.y=[string], global d=2, filename:test.cpp It does not have to be logging, it can do any general processing when entering/leaving a scope. I implemented a small library to do so in 2008 mainly for tracing, it worked fine for me and I never revisited it again until recently. Wondering if boost has libraries to support such a requirment. My implementation has a template class logger_class which can manage the log-level at runtime and send the log message to standard-output or other places. Application code use a macro to invoke the library, the macro can be disabled at compile time, or weakened to only log scope without variables. Example of the macro definition: #ifdef ENABLE_ONLY_SCOPE_TRACER #define SCOPE_TRACER(logger_class, logger, args, level, scope) \ scope_tracer<logger_class> tracer_obj(logger, __FUNCTION__, __FILE__, __LINE__); \ if (logger.get_level() >= level){ \ tracer_obj.init(level, scope).noMore(); \ } #else #ifdef DISABLE_SCOPE_VAR_TRACER #define SCOPE_TRACER(logger_class, logger, args, level, scope) #else #define SCOPE_TRACER(logger_class, logger, args, level, scope) \ scope_tracer<loggerClass> tracer_obj(logger, __FUNCTION__, __FILE__, __LINE__); \ if (logger.get_level() >= level){ \ tracer_obj.init(level, scope) << args; \ tracer_obj.noMore(); \ } #endif#endif Application code example: int globalVar; void MyClass::func1( A a, B&b, C* c, int d, std::string & s){ SCOPE_TRACER(MyLogger, test_logger, a<<b<<c<<d<<s<<globalVar, LOG_LEVEL_TRACE, "func1"); ... int localVar; while(x){ SCOPE_TRACER(MyLogger, test_logger, x<<a<<b<<c<<d<<s<<globalVar<<localVar, LOG_LEVEL_TRACE, "while(x)"); ... } ... } As you see, "<<" operator is being used. But it does not have to be only "<<" operator. Basically any C++ operator can be supported between the logger class and logged type. And the logger_class is not limited to just do tracing, it can virtuall do anything. I can attach the code if needed. The code was compiled with GCC on linux and VisualStudio on Windows. If the above functionality can be easily achieved using existing boot library, please advise how. Otherwise is it worth to request such a feature in boost? Thanks,Anlin

2 1

Regression tests crashing
by Tom Kent 03 Apr '13

03 Apr '13

Sometime yesterday most of the regression tests that I run (not the incremental ones?) started crashing and not sending any results. The screen output is the general error: "No such file or directory: '/home/tomkent/teeks99-02/a/results/boost/bin.v2/libs/any/test/any_test.test'" Looking at the tail of the results/bjam.log file shows this: error: at /home/tomkent/teeks99-02/a/tools_bb/kernel/modules.jam:107 error: Unable to find file or target named error: 'has_float128.cpp' error: referred to from project at error: '../libs/multiprecision/config' That was on Ubuntu 12.04, running the gcc-4.6 tests, but the others (including windows) have the same error. I don't believe anything else changed on the machines that were running the regression tests. You can still see the previous results on the regression results page. Tom Kent

1 0

[utility]result_of - erroneous result type from a C++11 lambda
by Vicente J. Botet Escriba 03 Apr '13

03 Apr '13

Hi, I've started to use C++11 lambda functions with Boost.Thread. The following works with clang-3.2 boost::future<int> f1 = boost::async( []() -> int {return 123;} ); But it fails with gcc-4.6.2, 4.7.2 and 4.8.0 ../example/lambda_future.cpp:25:91: erreur: conversion from ‘boost::future<void>’ to non-scalar type ‘boost::future<int>’ requested boost::future<int> f1 = boost::async( []() -> int {return 123;} ); The current implementation of boost::async uses boost::result_of to get the result type of the callable parameter. Is this a know bug on boost::result_of or gcc compiler? Best, Vicente

9 15

generate algorithm
by Fabian Bösch 02 Apr '13

02 Apr '13

Dear Boost community I am developing a library which extends the STL generate algorithm. It's aim is to improve performance for highly optimized (e.g. vectorized) generation mechanisms while it retains the same interface. This is especially useful when dealing with random number generation as there are several libraries (e.g. Intel MKL or AMD ACML) which provide means to generate a block of random values at once. However, the current STL generate algorithm is not able to cope with such "range generation". Is there any interest in a such a library for Boost? Cheers, Fabian Bösch

4 5