May 2009 - Boost-users - lists.preview.boost.org

symmetric_matrix operation
by Archie14 26 May '09

26 May '09

I am very new to the whole Ublas library. I have two symmetric matrices and I need to divide each element of the first matrix to the element in the second matrix. I am now doing smth like this: int _matrixsize; symmetric_matrix<double> mfirst(_matrixsize); symmetric_matrix<double> msecond(_matrixsize); symmetric_matrix<double> ratio (_matrixsize); for (int ifirst = 0; ifirst < _matrixsize; ifirst++) for (int isecond = 0; isecond < _matrixsize; isecond++) ratio(ifirst, isecond) = mfirst(ifirst, isecond) / msecond (ifirst, isecond); My questions are: 1. Can I use iterators (begin1, begin2) and if yes, then how? Examples in the doc use above method of iterating through elements, without using iterators. 2. I did not find built-in operators in the symmetric_matrix to do this division, but may be I overlooked smth or did not understand the docs? 3. If matrix "msecond" contains zeros - what is the "boost-way" to deal with this?

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Re: [Boost-users] [Serialization] Guard against attempting to deserialize the wrong type
by Dan Eaton 26 May '09

26 May '09

Robert, Could you please clarify what you mean by that? Do you mean the first and last tags of the archive are checked? I can't reproduce that behaviour either. int foo = 1; unsigned int bar =1; // create stream & output xml archive oarchive << BOOST_SERIALIZATION_NVP(foo); // create input xml archive from stream iarchive >> BOOST_SERIALIZATION_NVP(bar); This deserializes happily. Thanks, Danny From: Dan Eaton Sent: Monday, May 25, 2009 1:30 PM To: 'boost-users(a)lists.boost.org' Subject: [Serialization] Guard against attempting to deserialize the wrong type Hello, I'm just wondering if NVP/XML archives check the name during deserialization? I just had a problem whereby I tried deserializing an object to one type, but the archive actually contained a different (larger ) object type. The first serialized element of the object just so happened to be an unsigned int, and I was trying to deserialize an enum, so the output actually seemed sensible, and didn't cause any problems until I later deserialized the full object from the same archive, which caused a segmentation fault in the boost::serialize source (trying to get ETI from a null pointer). I was using a polymorphic text archive, and as I mentioned above, am wondering if I switched to an XML archive if this sort of user-error would be detected. Thanks, Dan Eaton Software Developer Acceleware Corp. (TSX-V:AXE) www.acceleware.com<http://www.acceleware.com/> Phone: +1.403.249.9099 Ext.295 Fax: +1.403.249.9881 Email: daniel.eaton(a)acceleware.com<mailto:daniel.eaton@acceleware.com> Get superpowered! Acceleware gets your products to market faster, better and stronger! This e-mail may contain information that is privileged and confidential and subject to legal restrictions and penalties regarding its unauthorized disclosure or use. You are prohibited from copying, distributing or otherwise using this information if you are not the intended recipient. If you have received this e-mail in error, please notify us immediately by return e-mail and delete this e-mail and its attachments from your system. Thank you. (c) 2008 Acceleware, Inc. All Rights Reserved

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Question about enable_if / disable_if
by Zachary Turner 26 May '09

26 May '09

Suppose I have a template function template<typename T> void f(const std::string&, T); which I want there to be a couple of different variants of. Version 1 - Enabled if and only if boost::is_same<T, bool> Version 2 - Enabled if and only if boost::is_same<T, foo> (foo is a class) Version 3 - Enabled if and only if boost::is_enum<T> Version 4 - Otherwise Is there an easy way to express this? It seems I run into a bunch of overload ambiguity problems. I'm sure I can get around this by adding to every version the negation of all the other conditions, but this seems unnecessarily complicated.

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Second call: The Boost Bug Sprint is coming!!
by Marshall Clow 26 May '09

26 May '09

The boost bug sprint is coming! It starts _this_ Friday, May 28th, and runs through Sunday June 7th. The goal is to address a large number of open bugs/patches/feature requests in the Trac system at <http://svn.boost.org/trac/report/1>. There are currently 791 open tickets; we'd like to knock that number down _a lot_. What can you do? 1) You can fix bugs. * If you are a library maintainer, you can commit your fixes. ;-) * If you are not a library maintainer, you can fix a problem on your local machine (and test it!!), and then attach your fix as a patch to the Trac ticket for the library maintainer to commit. If you do this, please provide a test case that exercises the problem; i.e, one that fails w/o your patch, and succeeds afterwards. 2) You can characterize bugs. * You can attempt to replicate the bug on your system(s), and attach information that you discover to the Trac ticket. This will make it easier for other people to solve the problem, even if you cannot. * You can write test cases demonstrating the problem, and attach them to the Trac ticket. * You can determine if the bug still exists; sometimes they get fixed, and the ticket never gets closed. In this case, try to identify a checkin that addresses the bug; it's always suspicious when bugs go away "by accident." 3) You can test patches. * Some of the tickets in the Trac system contain patches - some are quite old. You can install these patches on your system, and determine if they (a) build, and (b) work. * You can write test cases for the patches, and attach them to the ticket. 4) You can help implement new features. * There are a whole set of "feature requests" in the Trac system. If you have an idea about one of these, you can add comments to the Trac system. You can attempt to implement these new features, and attach the patch to the ticket. (Don't forget the test cases!!). Every day during the bug sprint, I'll post the # of tickets modified/closed/opened on the previous day, as well as the total number of open tickets. --------- Sign-up sheet -------- The following people have committed to participate in the bug sprint. Please add you name here, along with what you can do. 1) Marshall Clow (coordination, Mac OS X characterization) 2) Beman Dawes (filesystem, system, timer) 3) Doug Gregor (function, graph, logic, mpi, numeric, property_map, signals) 4) "joel falcou" <joel.falcou(a)u-psud.fr> ( linux gcc testing/VC 2008 testing, patching) 5) Michael Caisse <boost(a)objectmodelingdesigns.com> (bug fixing) 6) Jeremiah Willcock <jewillco(a)osl.iu.edu> (will test and commit graph patches) 7) David Abrahams (iterator, python) 8) Sohail Somani (patches for g++ 4.2.4) -- -- Marshall Marshall Clow Idio Software <mailto:marshall@idio.com> It is by caffeine alone I set my mind in motion. It is by the beans of Java that thoughts acquire speed, the hands acquire shaking, the shaking becomes a warning. It is by caffeine alone I set my mind in motion.

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Units library and wstring
by Macumber, Daniel 26 May '09

26 May '09

Hello, my group has been simultaneously incorporating the boost units library into our code as well as converting all internal strings from std::string to std::wstring. I am having difficulty merging the changes, it seems that the boost units library has hard coded std::string as the return type for the methods which print units, powers, etc. Is there an easy way to template use of the units library on wchar_t instead of char? Are there any other suggestions on how to use the units library in a program which uses wstring for everything else? Thanks a lot, Dan

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[BGL] dijkstra_shortest_paths on dynamically growing and shrinking graphs
by Ingo Maindorfer 26 May '09

26 May '09

Hello, consider the follwoing Graph: struct EP { double weight; }; typedef boost::adjacency_list< boost::listS, boost::vecS, boost::directedS, boost::no_property, EP > Graph; The call of dijkstra_shortest_paths is clear to me on that graph: boost::dijkstra_shortest_paths( m_graph, a_start_idx, weight_map( m_weight_map ).distance_map( &distance_vector[0]).predecessor_map( &parent_vector[0] ) ); where parent_vector and distance_vector are plain std::vector of the according size. Over time, I have to remove the "oldest" edges and vertices with lower index via remove_vertex() and remove_edge() from the graph and add some "newer" edges and vertices to the graph. My problem is, that the dijkstra_shortest_paths method dosen't work when I provide a plain std::vector to the distance_map() and predecessor_map() parameter of the dijkstra_shortest_paths call because of the mapping from the vertex descriptor to position in the vector. Can anybody tell me how to provide the "right" type of parameter for distance_map() and predecessor_map() ? Maybe something like boost::property_map< Graph, double EP::*>::type m_weight_map = boost::get( &EP::weight, graph ); that I'm already have done for the weight_map parameter but I'm looking for something that can handle the mapping stuff of vertex descriptors correctly. Performance is not a subject because of a few hundred vertices and edges. I'm on Boost 1.39. Kindly, Ingo

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Re: [Boost-users] wide-char version of boost::mapped_file?
by Tan, Tom (Shanghai) 26 May '09

26 May '09

By borrowing code from boost::filesystem V3, I re-implemented the to_string function like this: std::string to_string(const wstring& ws) { const size_t BUFFER_SIZE = (ws.size() << 1) + 1; shared_array<char> p_mcb(new char[BUFFER_SIZE]); int count = ::WideCharToMultiByte( AreFileApisANSI() ? CP_THREAD_ACP : CP_OEMCP, WC_NO_BEST_FIT_CHARS, ws.c_str(), ws.size(), p_mcb.get(), BUFFER_SIZE, 0, 0 ); return (-1 == count) ? std::string() : std::string(p_mcb.get(), count ); } This seems to have solved the conversion problem. Is it possible to add an overloaded constructor based on this code to take std::wstring or just take a boost::path when V3 comes out.? It would ease the usage a lot in my opinion. -----Original Message----- From: Tan, Tom (Shanghai) Sent: 2009-05-26 11:55 To: 'boost-users(a)lists.boost.org' Subject: wide-char version of boost::mapped_file? I am trying to use boost::mapped_file in the iostream library. While I like the interface. The fact that it only supports the ANSI version of windows API, thus dictating an ANSI version of file path, really drives me crazy. In my code I use std::wstring everywhere. Because boost::mapped_file asked for a std::string to construct like this: explicit mapped_file( const std::string& path, std::ios_base::openmode mode = std::ios_base | std::ios_base, size_type length = max_length, boost::intmax_t offset = 0 ); I wrote a small routine to convert it like this: std::string to_string(const wstring& ws) { const size_t BUFFER_SIZE = (ws.size() << 1) + 1; shared_array<char> p_mcb(new char[BUFFER_SIZE]); setlocale( LC_ALL, ".2052"); size_t count = wcstombs(p_mcb.get(), ws.c_str(), BUFFER_SIZE ); return (-1 == count) ? std::string() : std::string(p_mcb.get()); } It does not really work well when I have Enlish and Chinese characters mixed together in the path, while it does for pure Chinese paths. So I traced down to the source code to find out why a std::string instead of basic_string<Char> is needed, anyway, it's just a path, and has nothing to do with mapping it does. There seems to be no clue except for the ANSI version of Win32 APIs, which actually have wide-char versions. Did I missing any design requirement that force it to be like what it is today? Another issue is, it throws exception from inside the constructor when it tries to map a zero-length file. IMHO, it's not good to throw for a legal file, be its length zero, and not good to throw from the constructor either.

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wide-char version of boost::mapped_file?
by Tan, Tom (Shanghai) 26 May '09

26 May '09

I am trying to use boost::mapped_file in the iostream library. While I like the interface. The fact that it only supports the ANSI version of windows API, thus dictating an ANSI version of file path, really drives me crazy. In my code I use std::wstring everywhere. Because boost::mapped_file asked for a std::string to construct like this: explicit mapped_file( const std::string& path, std::ios_base::openmode mode = std::ios_base | std::ios_base, size_type length = max_length, boost::intmax_t offset = 0 ); I wrote a small routine to convert it like this: std::string to_string(const wstring& ws) { const size_t BUFFER_SIZE = (ws.size() << 1) + 1; shared_array<char> p_mcb(new char[BUFFER_SIZE]); setlocale( LC_ALL, ".2052"); size_t count = wcstombs(p_mcb.get(), ws.c_str(), BUFFER_SIZE ); return (-1 == count) ? std::string() : std::string(p_mcb.get()); } It does not really work well when I have Enlish and Chinese characters mixed together in the path, while it does for pure Chinese paths. So I traced down to the source code to find out why a std::string instead of basic_string<Char> is needed, anyway, it's just a path, and has nothing to do with mapping it does. There seems to be no clue except for the ANSI version of Win32 APIs, which actually have wide-char versions. Did I missing any design requirement that force it to be like what it is today? Another issue is, it throws exception from inside the constructor when it tries to map a zero-length file. IMHO, it's not good to throw for a legal file, be its length zero, and not good to throw from the constructor either.

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Re: [Boost-users] [Serialization] Guard against attempting to deserialize the wrong type
by Dan Eaton 25 May '09

25 May '09

Actually, it doesn't seem to be doing any check... looking at the contents of the XML emitted, the name is definitely different than the one I'm requesting. oarchive << BOOST_SERIALIZATION_NVP(foo); iarchive >> BOOST_SERIALIZATION_NVP(bar); This works fine where foo & bar are the same type (using xml_iarchive / oarchive) Am I doing something wrong? From: Dan Eaton Sent: Monday, May 25, 2009 1:30 PM To: 'boost-users(a)lists.boost.org' Subject: [Serialization] Guard against attempting to deserialize the wrong type Hello, I'm just wondering if NVP/XML archives check the name during deserialization? I just had a problem whereby I tried deserializing an object to one type, but the archive actually contained a different (larger ) object type. The first serialized element of the object just so happened to be an unsigned int, and I was trying to deserialize an enum, so the output actually seemed sensible, and didn't cause any problems until I later deserialized the full object from the same archive, which caused a segmentation fault in the boost::serialize source (trying to get ETI from a null pointer). I was using a polymorphic text archive, and as I mentioned above, am wondering if I switched to an XML archive if this sort of user-error would be detected. Thanks, Dan Eaton Software Developer Acceleware Corp. (TSX-V:AXE) www.acceleware.com<http://www.acceleware.com/> Phone: +1.403.249.9099 Ext.295 Fax: +1.403.249.9881 Email: daniel.eaton(a)acceleware.com<mailto:daniel.eaton@acceleware.com> Get superpowered! Acceleware gets your products to market faster, better and stronger! This e-mail may contain information that is privileged and confidential and subject to legal restrictions and penalties regarding its unauthorized disclosure or use. You are prohibited from copying, distributing or otherwise using this information if you are not the intended recipient. If you have received this e-mail in error, please notify us immediately by return e-mail and delete this e-mail and its attachments from your system. Thank you. (c) 2008 Acceleware, Inc. All Rights Reserved

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[Serialization] Guard against attempting to deserialize the wrong type
by Dan Eaton 25 May '09

25 May '09

Hello, I'm just wondering if NVP/XML archives check the name during deserialization? I just had a problem whereby I tried deserializing an object to one type, but the archive actually contained a different (larger ) object type. The first serialized element of the object just so happened to be an unsigned int, and I was trying to deserialize an enum, so the output actually seemed sensible, and didn't cause any problems until I later deserialized the full object from the same archive, which caused a segmentation fault in the boost::serialize source (trying to get ETI from a null pointer). I was using a polymorphic text archive, and as I mentioned above, am wondering if I switched to an XML archive if this sort of user-error would be detected. Thanks, Dan Eaton Software Developer Acceleware Corp. (TSX-V:AXE) www.acceleware.com<http://www.acceleware.com/> Phone: +1.403.249.9099 Ext.295 Fax: +1.403.249.9881 Email: daniel.eaton(a)acceleware.com<mailto:daniel.eaton@acceleware.com> Get superpowered! Acceleware gets your products to market faster, better and stronger! This e-mail may contain information that is privileged and confidential and subject to legal restrictions and penalties regarding its unauthorized disclosure or use. You are prohibited from copying, distributing or otherwise using this information if you are not the intended recipient. If you have received this e-mail in error, please notify us immediately by return e-mail and delete this e-mail and its attachments from your system. Thank you. (c) 2008 Acceleware, Inc. All Rights Reserved

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