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[spirit][qi] Fastest way to parse file
by Antony Polukhin 24 Feb '12

24 Feb '12

Hi, Boost.Spirit documentation advices to use multi_pass iterators for parsing files (or reading data to a STL container and then passing the begin and end of the container to Spirit.Qi). Much better solution would be to use a memory mapped file: boost::interprocess::file_mapping fm(filename.c_str(), boost::interprocess::read_only); boost::interprocess::mapped_region region(fm, boost::interprocess::read_only, 0, 0); const char* begin = reinterpret_cast<const char*>(region.get_address()); const char* const end = b + region.get_size(); Comparing to multi_pass iterator, mmap approach increased parsing speed more than 5 times, reduced memory usage and CPU load. Mmap approach is also a little bit faster than reading data to STL container and mmap sometimes requires less memory (depending on OS). I think, that such solution should be at least mentioned in Spirit documentation. May be mmap shall be wrapped in some class for tighter integration with Spirit and simpler usage: int main() { namespace spirit = boost::spirit; using spirit::ascii::space; using spirit::ascii::char_; using spirit::qi::double_; using spirit::qi::eol; spirit::file_parser first("multi_pass.txt"); // class that does mmap`ing std::vector<double> v; bool result = spirit::qi::phrase_parse(first , spirit::make_default_multi_pass(base_iterator_type()) , double_ >> *(',' >> double_) // recognize list of doubles , space | '#' >> *(char_ - eol) >> eol // comment skipper , v); // data read from file if (!result) { std::cout << "Failed parsing input file!" << std::endl; return -2; } std::cout << "Successfully parsed input file!" << std::endl; return 0; } Best regards, Antony Polukhin

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Updated boost::base_from_member for C++2011
by Daryle Walker 22 Feb '12

22 Feb '12

This is in changeset 76982. I tried it on my system, with Apple-supplied GCC 4.0.1 and GCC-direct 4.6 (from MacPorts) on a Mac/PowerPC system. It just does the slam-dunk implementation of this concept that C++2011 allows (and therefore showing its power). The new code should be isolated to only systems that can handle it. Now the code is over the wall, and it's time to see who crashes & burns (hopefully no one) in the tests.... Daryle W.

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Unsubscribe not working
by Ben Robinson 22 Feb '12

22 Feb '12

I have changed to a new email address for Boost and need to unsubscribe this one. The unsubscribe option here: http://lists.boost.org/mailman/options.cgi/boost-users is not working for me. Thanks in advance for your help. Ben Robinson

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Boost BloomFilter Status
by Joel 22 Feb '12

22 Feb '12

Alej, How is progress going on your BloomFilter library? Back in August you were looking at being ready for proposal by EOY 2011. http://comments.gmane.org/gmane.comp.lib.boost.devel/222842 By any chance, have you looked at the NPS Bloom filter package? linked to from: http://afflib.org/ I'm very interested in your library and in your response to Phil's request for the ability to mmap in existing filters. Thanks! Joel

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Re: [boost] TR2 is dead; multiple TR's coming instead
by Brian Wood 21 Feb '12

21 Feb '12

Beman Dawes : > The C++ committee met last week. There was lot's of discussion and > plans to markedly increase the size of the standard library. Boost has > an important part to play; Bjarne Stroustrup hoped for "doubling the > output of Boost." Sounds like Pharoah, but I'm sure he meant to be encouraging. > > Here are some of the process changes: > > * Library proposals will be taken on as "work Items". A decision as to > whether a work item ends up in a technical report, in the standard > itself, or even becomes a stand-alone international standard, will be > deferred until technical work is complete (I.E. full standardese > complete, polished, and ready to ship). > > * Domain specific "Study Groups" will replace the LWG's current > sub-groups. Study groups have official ISO standing, so can get more > work done between meetings than the old sub-groups, which were > unofficial. > > * Technical reports will likely be smaller than in the past, and may > be domain specific. How will they be named? I'm fine with multiple TRs, but calling the next one TR2 seems reasonable to me. > > These changes are intended to allow work on different libraries to > proceed in parallel. Medium to large libraries managed by study groups > will most likely end up as a TRs and will ship when ready rather than > being held waiting for a larger TR to become ready. > > The study groups set up so far: > > * SG1: Concurrency and Parallelism (chair: Hans Boehm). This is the > old Concurrency sub-group. > > * SG2: Modules (chair: Doug Gregor). A new sub-group of the > committee's evolution working group (EWG). I'm hoping there will be support for partial classes here. I don't think Vandevoorde's proposal takes this into account. Is there another modules proposal? > > * SG3: File System (chair: Beman Dawes). A LWG sub-group to handle the > Boost.Filesystem work item approved at the meeting. > > * SG4: Networking (chair: Kyle Kloepper). A LWG sub-group to handle > the Boost.Asio work item approved at the meeting. > It looks like cryptography is slipping through the cracks. If there are signs of life in the crypto lib you're using please let me know. > There should be a "Call for Library Proposals" in the committee's > post-meeting mailing in roughly 10 days. While C++ needs more libraries, I'd like to see it get rid of/improve some existing libraries. Herb mentioned valarray being little used. I think that's right. -- Brian Wood Ebenezer Enterprises http://webEbenezer.net "Prepare your work without, and make it fit for yourself in the field; and afterward build your house." Proverbs 24:27

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[1.49.0] Release candidates available
by Beman Dawes 21 Feb '12

21 Feb '12

Release candidate files for 1.49.0 are available at http://boost.cowic.de/rc/ As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. This helps ensure the candidates build OK before we push them out to SourceForge. Thanks, --Beman --PS: I tested the 7z version, and it built without errors on Win7/VC++ Express 2010 sp1

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Review Calendar Update
by Ben Robinson 21 Feb '12

21 Feb '12

Hello, The GitHub repository for my submission of Singularity on the review calendar has moved. The new location is: https://github.com/cppmaven/Singularity Can this could be updated on the review calendar? Thank you kindly, Ben Robinson

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Is there an equivalent to "bjam install-docs"?
by Steve M. Robbins 21 Feb '12

21 Feb '12

Hi, Is there a convenient way to install or copy the entire set of documents reachable from index.html? Since the docs are available on the web site [1], I suspect there might be, but I haven't found one. Thanks, -Steve P.S. I'm wondering about this because I need to copy the docs for the Debian package "libboost-doc". At the moment, I use a very inconvenient method that involves putting boost on a web server and using wget. [1] http://www.boost.org/doc/libs/1_48_0/

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Update on maximum adjacency search implementation
by Fernando Vilas 21 Feb '12

21 Feb '12

Hi, I think I have finally fixed the maximum adjacency search... Since the last post: - All parameters other than the graph are available as named parameters - Visitor is now pass-by-value - Documentation written Still potential to-do: - Update documentation with graphical walkthrough on a small graph - Python interface? - Find a way to make the priority queue work without unwrap_ref() - Do not depend on one_bit_color_map internals in min_cut_mas_visitor - Other suggestions from Boost community -- Thanks, Fernando Vilas fvilas(a)iname.com

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Discrete speedometer
by Justinas V. Daugmaudis 19 Feb '12

19 Feb '12

Currently Boost has date_time library and it especially has time_duration. However, what I find lacking is some means to track the number of discrete events that happen during some specified time_duration window. Something modelled after boost::progress. For example, consider that we are interested in how many files have been copied per five minutes, or how many packets have been received per ten minutes, etc. Obviously, the bigger the time window, the more stable the speedometer. I would like to do something like this: discrete_speedometer ds(posix_time::minutes(5)); // Tracks the events using the 5 minute window for( ... ) // Some inner loop { ds += number_of_events; } >From time to time I can do this: double events_per_second = speed_per_duration<double>(ds, posix_time::seconds(1)); or even more succinctly double events_per_second = speed_per_second(ds); I have implemented such a feature, and the code is here: http://people.binf.ku.dk/~jvd/discrete_speedometer.hpp Is there any interest in such a utility class? Regards, Justinas

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