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compiler error on using threads with boost
by Iskandar Prins 30 Mar '10

30 Mar '10

Hi, I get this compiler error : boost/thread/future.hpp", line 414: Error: Formal argument other of type boost::unique_lock<boost::mutex> in call to boost::unique_lock<boost::mutex>::operator=(boost::unique_lock<boost::mutex>) has an inaccessible copy constructor. Any idea why this is? I'm using the sun compiler to compile it with Regards, iskandar

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Accessing locale information
by Carla Strembicke 30 Mar '10

30 Mar '10

I need a call that allows me to specifiy the value locale information to retrieve. Does one exist in Boost. I have been swimming through the documentation but find that I am drowning. Background -> trying to replace windows GetLocaleInfo( ....) to become cross platform compliant. Thanks CONFIDENTIAL INFORMATION NOTICE: The information contained in this e-mail is privileged, confidential and intended solely for the use of the addressee named above. If the reader of this e-mail is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this e-mail is strictly prohibited. If you received this in error, please contact the sender and destroy all copies of this e-mail. Thank you.

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Boost Graph: add_edge causes compiler error
by Trevor Harmon 30 Mar '10

30 Mar '10

Hi, Could someone please help me understand why the simple program below won't compile? On the call to add_edge, I get: error: invalid conversion from ‘Foo*’ to ‘long unsigned int’ ...followed by two "initializing argument" errors. I've read all the docs I could find on add_edge, but I still don't understand why the code below won't work. Thanks for any help, Trevor #include "boost/graph/adjacency_list.hpp" using namespace boost; typedef struct FooType { } Foo; int main() { typedef adjacency_list<vecS, vecS, directedS, Foo*> Graph; Graph g; Foo foo1, foo2; add_vertex(&foo1, g); add_vertex(&foo2, g); add_edge(g[0], g[1], g); return 0; }

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Boost Graph: preventing duplicate vertices when constructing graph incrementally
by Trevor Harmon 29 Mar '10

29 Mar '10

Hi, The vast majority of Boost Graph's sample code has pre-defined source data. For example, from city_visitor.cpp: enum { SanJose, SanFran, LA, SanDiego, Fresno, LasVegas, Reno, Sacramento, SaltLake, Phoenix, N }; E edge_array[] = { E(Sacramento, Reno), E(Sacramento, SanFran), E(Reno, SaltLake), E(SanFran, SanJose), E(SanJose, Fresno), E(SanJose, LA), E(LA, LasVegas), E(LA, SanDiego), E(LasVegas, Phoenix) }; Unfortunately, static source data with enums as the vertices isn't very typical in real-world programs. It's much more common to construct the graph incrementally from a streaming data set, such as a file containing a list of edge pairs. But this presents a problem: As the list of edges is read in, a vertex may be encountered more than once, so add_vertex can't simply be called on every vertex found because that will result in redundant vertices. An obvious fix is to check whether a vertex exists before calling add_vertex. If it is found, it can be used for the edge; otherwise add_vertex can be called and the returned value used for the edge. The only question is, How do I check whether a vertex exists? I could iterate through all vertices in the graph, searching for one that equals the one I'm trying to add, but this approach doesn't scale well. It has a time complexity of O(V). A faster solution to this problem appears to be in the boost_web_graph.cpp sample. It deals with the same issue: It reads in graph data from a file called boost_web.dat, and this file contains the same vertex value in multiple places. Rather than call add_vertex multiple times (creating redundancies), the code puts every vertex it finds into a map. The map associates the vertex's unique value (a string in this case) with its corresponding vertex descriptor. Then, before calling add_vertex, the code checks the map for the unique value; if found, it uses the corresponding vertex descriptor; otherwise it calls add_vertex and adds the new ID/descriptor pair to the map. I assume that this is faster (compared to my naive approach of searching linearly through the vertices) because std::map's insert function is supposed to have logarithmic time complexity. It probably achieves this with a red-black tree, so as long as the keys are sortable, O(log(V)) complexity is guaranteed. Strings (used in the sample code) are certainly sortable, although in my program I'm using pointers as the vertex property. But I guess pointers are sortable too, since they're just numbers really. My initial tests show that this approach works properly with pointers as the values, though I've not done any performance testing, only correctness testing. Any feedback on this would be appreciated. Thanks, Trevor

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[GSoC]
by Andrew Sutton 29 Mar '10

29 Mar '10

Just a reminder, Google Summer of Code student applications can now be submitted here [1]. The deadline for submitting an application is Apr 9. Ideas for some student projects and other information about the program can be found here [2]. Andrew Sutton andrew.n.sutton(a)gmail.com [1] http://socghop.appspot.com/ [2] https://svn.boost.org/trac/boost/wiki/SoC2010

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boost/type_traits/has_new_operator.hpp and NVCC
by Denis Taniguchi 29 Mar '10

29 Mar '10

Hi all, I'm trying to compile boost::numeric::ublas with NVCC and I get the following errors: /usr/local/include/boost/type_traits/has_new_operator.hpp:28: error: `&' cannot appear in a constant-expression /usr/local/include/boost/type_traits/has_new_operator.hpp:28: error: template argument 2 is invalid This is related to #3919 and #3980 in a effort to make NVCC work with boost. Is there a known workaround so that I could tweak boost/config/compiler/nvcc.hpp? I'm using trunk under linux with the following piece of code: // Boost headers #include <boost/numeric/ublas/matrix.hpp> int main() { typedef boost::numeric::ublas::matrix<float> host_matrix_type; host_matrix_type host_mat; return 0; } Regards, Denis

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Re: [Boost-users] Boost serialisation: base ptr regression in 1.42
by Avi Bahra 29 Mar '10

29 Mar '10

The warning messages have gone when I used a const object. Thanks. However the "*unregistered class* " crash still remains if the if base/derived classes are placed in a static lib. (for 1.42 only). Robert Ramey wrote: >EXPORT has been made a little bit more elabort to >separate issues of code instantiation for class registration. These >changes were necessary to make EXPORT work properly with >DLLS. Look at the 1.42 documentation for an explanation. Not sure I understand this. In the 1.42 documentation under "Export Key" it says: "For programs which consist of only one module - that is programs which do not use DLLS, one can specify BOOST_CLASS_EXPORT(my_class) or BOOST_CLASS_EXPORT_GUID(my_class, "my_class_external_identifier") in either he* declaration header or definition*. These macros expand to invocation of the of both of the macros described above. *(GUID stands for Globally Unique IDentfier.)" * So I am not using DLL's, and have used BOOST_CLASS_EXPORT(Derived); in the implementation class. So the work around for unix's looks like: 1/ Place the BOOST_CLASS_EXPORT in the implementation and use explicit type registration 2/ Place the BOOST_CLASS_EXPORT in the header *_only_* In either case this is significant change, and should merit mention in the 1.42 release notes, and a change to the documentation Best regards, Ta, Avi

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newbie question - C++
by Figa Pelosa 29 Mar '10

29 Mar '10

hello, I'm using boost for the very first time and I'm having big problems in understanding how to proceed. I'm working in C++, and my aim would be creating a graph where each node is a 2D point and each edge is the distance between two points. I'd like to be able to say "vertex 0 and vertex 1 are 5mm apart". How to do that? This is what I got so far: typedef boost::adjacency_matrix<boost::undirectedS> Graph; class myClass { private: int numberOfNodes; Graph *g; char* name; public: myClass(int); addVertex(float,float,int); void addEdge(int[2],int); }; myClass::myClass(int number)fNodes){ g = new Graph(number_of_nodes); } myClass::addVertex(float x,float y) { add_edge(x,y,*g); } Now this seems to work, but how to incorporate coordinates? Thanks a lot for your help! Ale

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A question on the preciseness of the double used in MTL. Can anyone with kindness help me?
by fmingu 29 Mar '10

29 Mar '10

I am using MTL(Matrix Template Library) for Matrix computing in Dev-C++ 4.9.8.0 and updated the gcc version from 3.2 to 4.4.1 by installing tdm-mingw-1.908.0-4.4.1-2 and the boost version is 1.37.0. The system is Windows xp The sample code is : #include <boost/numeric/mtl/mtl.hpp> #include "boost/random/normal_distribution.hpp" #include <boost/random.hpp> #include <boost/random/uniform_real.hpp> int main(int argc, char* argv[]) { using namespace mtl; using namespace mtl::matrix; const unsigned n= 5; dense2D<double> A(n, n), B(n, n); morton_dense<double, doppled_64_row_mask> C(n, n), D(n, n); dense2D<double> F(n, n), E(n, n); hessian_setup(A, 3.0); hessian_setup(B, 1.0); hessian_setup(C, 2.0); hessian_setup(D, 11.0); B(1,1)=9.9999; .......................... std::cout << "The matrices are: B=\n" << B <<"\n"; std::cout << "The result is " <<1.0/3.0 <<"\n"; ……………………. But the result is shown that B(1,1) is 10, and 1.0/3.0 is 0.33. How can I get the highest precision of the type double and dense2D<double> for scientific computation? The same question occurred in random number generation in boost random library. Can anyone with kindness help me?

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compiler(iropt) error: get_leaf_hash_index: unknown constant type
by Iskandar Prins 29 Mar '10

29 Mar '10

Hi, When compiling certain boost features I get this error with the Sun Compiler (SunOS 5.10, x64) compiler(iropt) error: get_leaf_hash_index: unknown constant type I'm including the following: #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/stats.hpp> #include <boost/accumulators/statistics/mean.hpp> #include <boost/accumulators/statistics/kurtosis.hpp> #include <boost/accumulators/statistics/moment.hpp> #include <boost/accumulators/statistics/variance.hpp> #include <boost/accumulators/statistics/skewness.hpp> I'm using boost 1.42.0, any idea why this is? Regards, Iskandar

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