March 2010 - Boost-users - lists.preview.boost.org

[posix_time] time_duration operator/() overload
by Norbert Wenzel 04 Apr '10

04 Apr '10

Hello, I use boost::posix_time a lot in my code and I really do appreciate the library. But there's one thing I was recently missing when comparing time_durations to each other. double time_duration::operator/(time_duration); From my point of view this is a perfectly valid operation (as opposed to operator*(time_duration)) that returns the proportion of the two durations. I need that operation to compute statistics like "n% of the time I did x" or similar. What I'm currently doing is computing the proportions via time_duration::total_*() which works fine, but leads to some coding effort, since I'll have to cast one result to a real number to avoid integer division and some checks to prevent /0. I assume I'm not the first to compare time_durations so I was wondering if there was a reason operator/() is not overloaded for time_duration? Or if there is generally a better way to compare two durations? thanks, Norbert

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Using type_trait-like functionality to detect incomplete types
by Michael Cox 04 Apr '10

04 Apr '10

I'm using googlemock to do some unit-testing via mock objects and I'm getting compiler errors on some of my mock methods. Because googlemock has some sophisticated meta-template programming techniques to allow it to print out the arguments passed to a mock method, I'm getting compiler errors on some of the methods that have incomplete types used as arguments. Is there anyway via boost::/tr1:: type_traits that I can detect this situation and have the gmock PrintTo template function just print "incomplete". I was hoping to find a nice "is_complete<T>" template function that would do the trick, but haven't found such a thing. Is it even possible to detect it without causing a compiler error? Michael

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[Proto?][Phoenix?] : Advice on creating lazy data structures
by Manjunath Kudlur 03 Apr '10

03 Apr '10

With Phoenix or lambda-like DSELs implemented with Proto, it is easy to implement stuff when the expected actual parameters to the lambda expressions are primitive types. When I want to pass arbitrary types to the lambda expression and manipulate it in the lambda expression, things become complex. For example, consider the following function : struct point { float x; float y; }; float sum(point p) { return p.x+p.y; } If I want to have a lazy version of this function, I cannot simply do (arg1.x + arg1.y)(p). I have to implement functions that return Proto or Phoenix expressions and use it in the language. In the above case, it would look something like (point_get_x_(arg1) + point_get_y_(arg2))(p). So for every type I want to support in the DSEL, I have to implement lazy versions of functions to get and set the type members, or call some methods. In other words, the language has to be aware of all the data types that can be used with it. I am looking for some advice on a standard or a generic way for creating such lazy data structures. Has something like this been done before? I will be grateful for any pointers and suggestions. Thanks, Manjunath

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[Graph] Problem trying to delete vertices from a graph using named vertices, please help!
by Camillo Anania 02 Apr '10

02 Apr '10

Hi guys, I have a graph so defined: typedef boost::adjacency_list<boost::listS, boost::listS, boost::bidirectionalS, Osm::VertexProperties, EdgeProperties> Graph; Graph osmGraph; I'm trying to delete some vertices from osmGraph using the usual remove_vertex(Vertex, Graph) but I get the following error from Visual Studio 2008 when compiling: boost_1_40_0\boost/graph/named_graph.hpp(349) : error C2664: 'boost::multi_index::detail::hashed_index_iterator<Node,BucketArray> boost::multi_index::detail::hashed_index<KeyFromValue,Hash,Pred,SuperMeta,TagList,Category>::erase(boost::multi_index::detail::hashed_index_iterator<Node,BucketArray>)' : cannot convert parameter 1 from 'void *' to 'boost::multi_index::detail::hashed_index_iterator<Node,BucketArray>' the code I use is: { vector<int> component(num_vertices(osmGraph)); int num = strong_components(osmGraph, make_iterator_property_map(&component[0], get(&Osm::VertexProperties::id, osmGraph)), vertex_index_map(get(&Osm::VertexProperties::id, osmGraph))); int main_comp = component[depotID]; for (int i = 0; i != component.size(); i++){ if (component[i] == main_comp) continue; if (is_incident_to_required_edge(osmGraph, i)){ cerr << "Required components on input topology are not strongly connected. Check the input .osm file" << endl; return 1; } else { clear_vertex(osm_get_vertex(i, osmGraph), osmGraph); Osm::Vertex osm_v = osm_get_vertex(i, osmGraph); cout << "id=" << osmGraph[osm_v].id << endl; remove_vertex(osm_v, osmGraph); } } } why it doesnt work? why the same code with the graph defined in the following way works? typedef adjacency_list < listS, listS, bidirectionalS, property < vertex_name_t, std::string, //vertex property property < vertex_unique_id_t, int, property < vertex_color_t, boost::default_color_type> ............. >, //edge property property < edge_index_t, int, property < edge_num_bins_t, int, property < edge_unique_id_t, int, property < edge_name_t, std::string> ..............> > Graph; PLEASE help. Camillo Ciao

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Cross compiling boost 1.33.1
by srinath duraisamy 01 Apr '10

01 Apr '10

Hi all, I have to cross compile the boost 1.33.1 for my development board. I downloaded boost_1_33_1 from the sourceforge download page and I followed the steps provided as per this link ( http://www.boost.org/doc/tools/build/doc/html/bbv2/tasks/crosscompile.html ) 1. specify your cross compiler in user-config.jam using gcc : arm : arm-none-linux-gnueabi-g++ ; 2. bjam toolset=gcc-arm It needs bjam, so I download and installed the bjam from boost download page. when I run bjam toolset=gcc-arm, I am getting the following error: don't know how to make toolset=gcc-arm ...found 1 target... ...can't find 1 target... It will be very helpful, if someone guide me with the steps to cross compile boost1.33.1 version. Thanks in advance.

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[serialization] baffled by very long archive load time
by Martin Weinberg 01 Apr '10

01 Apr '10

I have been developing and maintaining a large computatation statistics package (http://www.astro.umass.edu/BIE) It is an MPI application that uses boost::sersialization to implement persistence. After recently adding a new class, I notice that the archive load times have gone from seconds to over an hour!! The binary archive size is 30MB. Regression tests suggest that the resumed state is correct albeit the very long load time. The package is implemented in multiple shared libraries and classes are exported as suggested in the documentation. I have noticed that I need to compile with "-Ox -fno-inline-small-functions" when x=2,3. I'm not sure if this is significant. The system is Debian/GNU Linux, 2.2Ghz 0pteron 64bit. The behavior is the same with Boost 1.37, 1.38 and 1.42. The new class has many nested STL container instances e.g. vector< vector<float> > . . . but very few archived pointers. I've not been able to isolate the cause in test cases (e.g. making very large instances of STL nested containers; these are deserialized in under a second). Any thoughts on things to track down? Thanks! -- Martin Weinberg Phone: (413) 545-3821 Dept. of Astronomy FAX: (413) 545-4223 530 Graduate Research Tower weinberg(a)astro.umass.edu University of Massachusetts Amherst, MA 01003-4525

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[Iostreams] How to check whether file has ben opened?
by Daniel Eiband 01 Apr '10

01 Apr '10

Hi, I'm using Boost 1.42.0 and I have the same problem like vandamme described in this post at the end: http://groups.google.com/group/boost-list/browse_thread/thread/c290c987bf1f… The following code will assert if the file "test" does not exist: std::string filename("test"); boost::iostreams::stream<boost::iostreams::file_source> file; file.open(filename.c_str()); if (file.is_open()) { // assert fires if file "test" does not exist assert(boost::filesystem::exists(filename)); } The indirect_streambuf doesn't check the device and just returns true if open has been called (independent of whether open has been successful). If I use the std::ifstream supplied with MSVC 9.0 is_open() returns false if the file does not exits. Checked by replacing file declaration with: std::ifstream file; Is this a bug? If not how can I test whether opening the stream succeeds? Thanks, Daniel

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boost::thread destructor and detach()
by Eric J. Holtman 01 Apr '10

01 Apr '10

It looks like the new C++ standard threading library is going to call terminate() on a thread if it's being destructed, and has not been detached or joined. Is boost::thread going to change to emulate that behavior? (Currently, it calls detach(), not terminate()). I hadn't been calling detach () in my programs when I was spinning off a thread that I didn't care about joining later. Should I be doing that, just so my code works with either library?

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boost path???
by mh00219＠surrey.ac.uk 31 Mar '10

31 Mar '10

Hello everybody, Can you please tell me should I give the path of boost libraries in my windows PATH variable after installation.? thank you

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[serialization][Fwd: Re: Saving and reloading a container to/from disk]
by Jeff Flinn 31 Mar '10

31 Mar '10

I've forwarded this from comp.lang.c++. The OP has tried the demo.cpp example (I think), and is getting results different from those the demo says are expected. This is related to versioning... but I'm confused as to what should be the result. Jeff -------- Original Message -------- Subject: Re: Saving and reloading a container to/from disk Date: Wed, 31 Mar 2010 13:59:16 +0200 From: jacob navia <jacob(a)jacob.remcomp.fr> Reply-To: jacob(a)jspamsink.org Organization: lccwin Newsgroups: comp.lang.c++ References: <4bb2e6b3$0$15818$ba4acef3(a)reader.news.orange.fr> <81gc4oFua5U6(a)mid.individual.net> Ian Collins a écrit : > On 03/31/10 07:07 PM, jacob navia wrote: >> Hi >> >> What would be the best way to save and reload later a container >> to/from disk in C++? > > It depends, there isn't really a best way. Do you want portability? > > http://www.boost.org/doc/libs/1_42_0/libs/serialization/doc/index.html > > Is a good place to start. > Thanks. I downloaded the boost libraries, and compiled them in my machine. Unziped the source code is 269MB. Compilation took 14 minutes. Machine Mac-pro OS X with 8 CPUs and 12GB RAM. Then, I compiled the example of the serialization. The class being saved/restored looks like this: original schedule 6:24 bob 0x0x100200440 34?135'52.56" 134?22'78.3" 24th Street and 10th Avenue 0x0x1002004d0 35?137'23.456" 133?35'54.12" State street and Cathedral Vista Lane 0x0x100200530 35?136'15.456" 133?32'15.3" White House when restored, the restored stuff looks like this: 6:24 0x0x100200e30 34?135'52.56" 134?22'78.3" 24th Street and 10th Avenue 0x0x100200f40 35?137'23.456" 133?35'54.12" State street and Cathedral Vista Lane 0x0x1002012c0 35?136'15.456" 133?32'15.3" White House As you can see the name "bob" is missing. The same bug appears with all other saved/restored class instances. I am not fluent in C++ to figure out this, sorry. But maybe this is a bug in the example, I can't determine what is the reason. jacob

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