February 2012 - Boost-users

MSVC static linking with Boost
by Andy Falanga (afalanga) 14 Feb '12

14 Feb '12

Hi, The team I work with is working on producing a Boost.Python library. Most of the Boost stuff we're using are header only, however, there is a couple of compiled library usages as well (e.g. regex). How can we make certain that the library we're building is statically linked with the stuff we're using from Boost? This way, we don't have to deploy any other DLLs but our own. I've gathered, from Google and another post here, that most of this magic happens at compile time with auto-linking. However, this isn't going all the way. I continually see Intellisense errors in my Visual Studio output window telling me that mixing static and dynamic Boost libraries is a bad idea (or something similar). So, for Visual Studio 2010, how do I ensure that the libraries are statically linked into our own product? Thanks, Andy

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BoostCon/C++Now! Talk: How I Code and Why
by Gottlob Frege 14 Feb '12

14 Feb '12

I talked about this last year, and this year I've submitted the proposal, so If you volunteered last year (and are still interested) and/or are interested in helping with a particular/peculiar talk at BoostCon/C++Now this year, then read on, and contact me offline: I'm planning on giving a talk, entitled "How I Code and Why". It is not meant to be presumptuous and tell you how *you* should code, but instead just explains how I code - day-to-day - and how I came to these patterns/conclusions. But who cares just about how *I* code, people want to hear how other members of the Boost community - people they've come to know and respect via the boost lists - code. So I'm hoping to have a few co-conspirators on stage with me, and have each explain a fundamental guiding principle that they follow in their every day code, how they came to adopt this principle and why they find it valuable. For example, I will tell the simple story ('epiphany') of why my favourite comment word is 'otherwise', and how this relates to advice you may have heard or read before. I like the flavour of [ simple, real world, specific ] ---> [ general principle ] The goal is to bring a more real world down to earth picture to the sometimes lofty fundamentals found in books and lectures. Instead of a book explaining how a guiding principle makes sense *in theory*, it would be great (I think) to hear how respected members of the community apply these principles in real life. So, if you want to participate, email me, and we will see what we can figure out. (And/or I might just have to track you down based on promises made last year!) Not sure how many people we need. I'm thinking 5-15 mins per 'principle', and I think you only need to present one (I think the weight of picking *just one* principle makes it all the more interesting). Anyhow, we can work out the details as we go along. Tony PS. this is not (yet?!) an accepted talk, but I have a bit of chicken/egg thing here: ie it would help to have a few people on board to show that the talk is viable, and thus be accepted.

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A plea for simpler tools
by Robert Ramey 14 Feb '12

14 Feb '12

Let me start by saying I love Boost and C++ as much or more than anyone here!!! But I'm really frustrated with the boost tools and believe they are a serious impediment to the progress of boost. Here is what I want to be able to do: a) create a directory structure outside of the boost tree which looks like: mylib build include src doc html docbook(maybe) boostbook(maybe) quickbook(maybe) test results ... b) a set of simple tools which 1) can build the library in the src directory 2) can translate quick/boost/doc book to html and place it in that directory 3) run each test in the test directory and add a record to the test/results/... log file which I will either just lookat or post process locally to my personal taste. c) what I don't need 1) tracking dependencies - I want to do this for on library I might be experimenting with. I can do this by hand. 2) I don't need to have my boost tree updated - in fact I want to know that I haven't changed it by just running a simple tool d) current tools: 1) presume that a library is part of the boost directory structure. So the documents show up somewhere in the boost tree. Note when I build the documents on my local boost release image I get pointers to the boost sandbox or on sourceforge.net or whatever. So for boostbook->html would like to be able to say boostbook2html -in <boostbookdir> -out <htmldirectory> or something simple like this. 2) the only way I've found to use the current tools is to create directories in my local boost release tree with my "experimental" library and run bjam. There are two problems with this i) I have to make a jamfile which might be more complicated that first meets the eye ii) I mucks up my boost release tree. iii) it I get something wrong, it fails deep within some bjam script which is extremely difficult to figure out. iv) For an example to iii) above, I had tweaked userconfig.v2 to include the name of my xsltproc program which was found through the path. Later I elimnated the directory of the xsltproc from my path. Later I found I couldn't build my library or run any tests. Turned out that bjam stopped when it failed to find the xsltproc program - even though it wasn't being used. I'm not critisizing bjam. I think it's impossible to make a program as ambituous as this totally perfect. But I question the need for such an elaborate tool for doing what seems to me should be something simple. Of course, I can do this myself - and likely will end up doing so. But: a) I've got other stuff to do b) I can't believe I'm the only one who needs this c) I think that boost tools are "too automatic" for my purposes. I understand the motivation for building all of boost. But for what I want to do it adds a huge layer of "conceptual overhead" that I have to wade through. Before I invest effort in this perhaps there's a way of using existing tools that I'm not aware that get's me closer to what I want and need. Comments welcome. Robert Ramey

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graph planar_face_traversal
by Andreas Fabri 14 Feb '12

14 Feb '12

Hello, I am wondering about the output of the example on the page http://www.boost.org/doc/libs/1_48_0/libs/graph/doc/planar_face_traversal.h… I would expect that the vertices on the border of the outer or unbounded face got reported in reverse order. The vertices of inner faces are reported in clockwise order which makes that for each edge shared by inner faces, we traverse it once from source to target, and once from target to source. This does not hold for edges on the outer face. Is this intentional, or just a documentation bug? Best regards, Andreas -- Andreas Fabri, PhD Chief Officer, GeometryFactory Editor, The CGAL Project phone: +33.492.954.912 skype: andreas.fabri

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Boost Date/Time
by asif saeed 13 Feb '12

13 Feb '12

Hi, I get a run-time error when I run the following code; std::string LocaleFormattedDateTime (::boost::posix_time::ptime pt) { std::string s; std::ostringstream ss; //::boost::posix_time::time_facet * tf = new ::boost::posix_time::time_facet; ::boost::posix_time::time_facet tf; //std::locale custom_locale (std::locale(""), tf); std::locale custom_locale (std::locale(""), &tf); // custom_locale takes ownership of the tf facet ss.imbue (custom_locale); //(*tf).format("%Y%m%d-%H%M%S-%f"); // date time tf.format("%Y%m%d-%H%M%S-%f"); // date time ss << pt; // don't explicitly delete tf - what's wrong with a stack variable? why this runtime error? What is the point of new() above and //what if I don't delete allocated memory here. return ss.str(); } void CurrentDateTimeWithMicroseconds(char s[], int sz = 100) { using namespace boost::posix_time; using namespace std; using boost::date_time::date_facet; ptime t = microsec_clock::local_time(); ostringstream ss; //time_facet *df = new time_facet(); time_facet df; //std::locale loc (std::locale(""), df); std::locale loc (std::locale(""), &df); ss << LocaleFormattedDateTime(t) ; memset(s,0,sz); strcpy(s,ss.str().c_str()); } Can you tell me the problem? I modified this code after copying this from some online source. Thanks in advance, Asif

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[date_time] greg_day_of_week as numeric type
by Claude 13 Feb '12

13 Feb '12

It is possible transform or use the greg_day_of_week (day_of_week() method) as a numeric type? Also seems to me that there is no day_of_month() method. Why? -- View this message in context: http://boost.2283326.n4.nabble.com/date-time-greg-day-of-week-as-numeric-ty… Sent from the Boost - Users mailing list archive at Nabble.com.

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Re: [Boost-users] Poor/erratic boost::interprocess named_semaphore performance
by Davidson, Josh 13 Feb '12

13 Feb '12

Ok, so I converted my example to native Windows semaphores, and it consistently completes in less than 250ms (up to 160x faster). Something is definitely going on. -----Original Message----- From: Davidson, Josh Sent: Sunday, February 12, 2012 9:01 PM To: boost-users(a)lists.boost.org Subject: Poor/erratic boost::interprocess named_semaphore performance I'm experiencing performance issues using named semaphores on Windows 7 x64. Currently, I'm on 1.49 beta 1, but the behavior was similar on 1.48 and 1.47. Below, I'm copying two sample programs. They simply synchronize with one another using a pair of semaphores. To run them, start the first program and then the second. They will synchronize with each other 100k times and then the second program will spit out the elapsed time. You can restart the second program to run again without bringing down the first program. On Windows, the elapsed time the first time around is anywhere from 20 - 40 seconds. If you leave the second program running, the following run will be only about 2-3 seconds. A third run it will be back up to 20-40 seconds, and it will keep bouncing back and forth like that. On Linux, the total elapsed time is consistently less than half a second. I'm guessing the Windows implementation isn't as efficient, but I wouldn't expect it to be 100 times slower than Linux. The other perplexing thing is how wildly different the results are on Windows from run to run. =====================Test1.cpp========================================== #include <boost/date_time/posix_time/posix_time.hpp> using namespace boost::posix_time; #include <boost/interprocess/sync/named_semaphore.hpp> using namespace boost::interprocess; #include <iostream> using namespace std; int main() { named_semaphore::remove("sem1"); named_semaphore::remove("sem2"); named_semaphore sem1(create_only_t(), "sem1", 0); named_semaphore sem2(create_only_t(), "sem2", 0); while(true) { sem1.wait(); sem2.post(); } return 0; } =====================Test2.cpp========================================== #include <boost/interprocess/sync/named_semaphore.hpp> using namespace boost::interprocess; #include <boost/date_time/posix_time/posix_time.hpp> using namespace boost::posix_time; #include <iostream> using namespace std; int main() { const size_t iterations = 100000; named_semaphore sem1(open_only_t(), "sem1"); named_semaphore sem2(open_only_t(), "sem2"); ptime start = boost::posix_time::microsec_clock::local_time(); for(size_t i = 0; i < iterations; ++i) { sem1.post(); sem2.wait(); } ptime end = boost::posix_time::microsec_clock::local_time(); time_duration delta = end - start; double seconds = double(delta.total_nanoseconds())/1000000000.0; cout << "Total elapsed time: " << seconds << endl;; cout << "Time per iteration: " << (seconds/double(iterations)) << endl; return 0; }

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iterating though an inifile section using boost.property_tree
by Sean Farrow 13 Feb '12

13 Feb '12

Hi Fokes: Ok, I've got a standard windows-stle ini file. I can check that a section exists, and then get that section, using it->second, where it is declared as: boost::property_tree::ptree::const_assoc_iterator it; I've then assigned the it->second variable to a new property_tree. What I now need to do is iterate though the tree I've just assigned and get all the section keys/values. I'm using the following code to add them all to a map: std::map<string, string> SectionProps; BOOST_FOREACH(boost::property_tree::ptree::value_type &v, SectionTree) { Key =v.first; Value =v.second; SectionProps.insert(std::make_pair(Key, Value)); } It seems that even though thwe values in the ini file will be strings, of the vorm Key1=valu1 as normal, I am still getting another ptree as my second argument of the pair. How do I obtain the value from this? There are never any sub sections. Any help appreciated. Cheers Sean.

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[tuple] Tuple arithmetic
by Bill Buklis 13 Feb '12

13 Feb '12

Is there any facility to perform arithmetic operations on a tuple? For example: struct data { double a, b; }; data d1 = {1.0, 2.0}; data d2 = {2.5, 5.5}; // These two lines are not valid, but simulate what I want. boost::tie(d1.a, d1.b) *= 10.0; // Multiply each element by 10.0 boost::tie(d1.a, d1.b) += boost::tie(d2.a, d2.b); // Add the elements from the second object After calculations, d1 should equal {12.5, 25.5}; Thanks, -- Bill

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[Format] No implicit conversion to string?
by John M. Dlugosz 13 Feb '12

13 Feb '12

It's shown prominently in the docs that a boost::format object can be sent to an ostream. cout << format("%2% %1%") % 36 % 77; But, there is no easy way to use it where a plain string is needed. E.g. throw runtime_error ( format("%2% %1%") % 36 % 77 ); One must use extra parens and a named function, either throw runtime_error ( (format("%2% %1%") % 36 % 77).str() ); or throw runtime_error ( str(format("%2% %1%") % 36 % 77) ); either of which detracts from the expression. Is there any good reason why an implicit conversion operator to the matching string class was omitted? I'd like to find out if there is some reason, before looking into submitting an update. —John

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