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

boost::timer elapsed time
by Federico Golfrè Andreasi 31 Mar '10

31 Mar '10

Hi, I've read the post from Roman, and I'm not sure that I've understand. Under linux the timer.elapsed() function will not return the total time needed to do all the operations but only the CPU time, this excludes network communication in parallel programs, time spent for I/O operations ? For example if I need to measure the time needed to read an input file I should not use the timer library? What else? Thank you, Federico

3 2

[Boost.UTF] Strange (failed) result on comparing floats
by Olaf Peter 31 Mar '10

31 Mar '10

Hi, I'm checking some data of consistence using boost's unit test framework (1.42): BOOST_CHECK_CLOSE( *v[1].y.max, -43.0e-3, std::numeric_limits<double>::epsilon() ); which fails with: difference{1.6137e-14%} between *v[1].y.max{-0.043000000000000003} and -43.0e-3{-0.042999999999999997} exceeds 2.2204460492503131e-16% where v is a std::vector,y a struct and max a boost::optional<double>. The data where parsed by boost.spirit. This is the only failed test case from 16 parsed doubles. What's gone wrong here? Do I miss something? Thanks, Olaf

4 4

Android ndk-r3 and Boost
by Carlos 31 Mar '10

31 Mar '10

Hi!! I have been successful in compiling my app with android ndk-r2 and boost libraries. However, I have some problems in compiling my app with it with the new version of android ndk. I have done the same steps but with no results until now. I do the following steps: *1º* Building my toolchain using your instruction; *2º* Compile boost using the prebuild binary for step 1: sudo bjam install --prefix=/usr/local/boost_1_42_0 toolset=gcc-arm *3º* try to compile my program. bjam toolset=gcc-arm link=static runtime-link=static include="/home/carlos/Projectos/android-ndk-r3/build/platforms/android-3/arch-arm/usr/include" include="/usr/local/boost_1_42_0/include" library="/usr/local/boost_1_42_0/lib/libboost_system.a" library="/usr/local/boost_1_42_0/lib/libboost_thread.a" library="/usr/local/boost_1_42_0/lib/libboost_program_options.a" library="/home/carlos/Projectos/android-ndk-r3/build/platforms/android-3/arch-arm/usr/lib/libc.a" The following lines is an example of error I have: */usr/local/boost_1_42_0/include/boost/config/requires_threads.hpp:29:4: error: #error "Threading support unavaliable: it has been explicitly disabled with BOOST_DISABLE_THREADS" /usr/local/boost_1_42_0/include/boost/thread/detail/platform.hpp:67:9: error: #error "Sorry, no boost threads are available for this platform." /usr/local/boost_1_42_0/include/boost/thread/mutex.hpp:18:2: error: #error "Boost threads unavailable on this platform" /usr/local/boost_1_42_0/include/boost/asio/detail/socket_types.hpp:165: error: 'INET_ADDRSTRLEN' was not declared in this scope* I really appreciate if you could give me some help or any advice that could lead me in the right way.

1 0

[unordered] Are unordered containers thread safe?
by Ralf Goertz 31 Mar '10

31 Mar '10

Hi, are unordered containers thread safe, e.g. can I do something like typedef boost::unordered_multimap<int, int> Map; Map m; std::vector<int> v; bool needs_to_be_erased(int val); //heavy function telling me whether val is //needed in the map; //fill m //fill v uniquely with all keys in m; int i; #pragma omp parallel for // parallelize the loop for (i=0;i<v.size();++i) { std::pair<Map::iterator,Map::iterator> r=m.equal_range(v[i]); for (Map::iterator mi=r.first;mi!=r.second;) { Map::iterator to_be_erased=m.end(); if (needs_to_be_erased(mi->second)) { to_be_erased=mi; } ++mi; if (to_be_erased!=m.end()) { m.erase(to_be_erased); to_be_erased=m.end(); } } } The reason I ask is that every once in a while the program crashes because of an assertion failure: BOOST_ASSERT(b2 == buckets_end() || !b2->empty()); (line 1018) in boost/unordered/detail/hash_table_impl.hpp function void recompute_begin_bucket(bucket_ptr b1, bucket_ptr b2). It seems as if erasing from m can cause problems even though it is guaranteed that one and the same element is never tried to be erased by different threads (they never "see" the same elements). Interestingly, the assertion failure occurs in a function for which the comment says: "This is called when a range has been erased" but I never erase ranges. Furthermore, using "schedule(dynamic)" in the omp pragma above almost always leads to one or more threads not finishing.

2 1

edges
by Figa Pelosa 31 Mar '10

31 Mar '10

hello. My graph is an: typedef adjacency_list < mapS, vecS, undirectedS, my_vertexProperty, property < edge_weight_t, float > > Graph; I have 100 edges, and I also have an array with 100 weights. How do I assign weight[i] to edge[i], and how do I create a weightmap to use in dijkstra_shortest_paths()? Thanks a lot AC

2 1

boost header files
by mh00219＠surrey.ac.uk 31 Mar '10

31 Mar '10

Hello , I am very new to boost libraries and infact to C++. I have very basic questions. I know that when we have a header file (.hpp) then there must also be a (.cpp) that is the implementation of the header file. But when i see the boost header files in \boost directory I dont find any .cpp files. Where are they? And what if I am using boost header files in my program then in the makefile I need to compile these header files with the corresponding .cpp files. So what path should I use for them? Waiting for your kind reply...Please reply. regards Hammad

2 1

Re: [Boost-users] A question on the preciseness of the double used in MTL. Can anyone with kindness help me?
by fmingu 31 Mar '10

31 Mar '10

I really do not know how to solve it and need help to get through my work. Can anyone with kindness help me? ---------- 转发邮件信息 ---------- 发件人："fmingu <fmingu(a)163.com>" 发送日期：2010-03-29 09:02:29 收件人：boost-users(a)lists.boost.org 主题： Re:Re: [Boost-users] A question on the preciseness of the double used in MTL. Can anyone with kindness help me? 在2010-03-29 08:28:13，"Steven Watanabe" <watanabesj(a)gmail.com> 写道： >AMDG > >fmingu wrote: >> 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. >> > >Use std::setprecision to print more digits. > >In Christ, >Steven Watanabe > I rewrote the program following your advice but std::cout << "The matrices are: B=\n" << std::setprecision(5)<<B<<"\n"; do not show any changes while the code: std::cout << "The result is " << std::setprecision(10)<<1.0/3.0 <<"\n"; worked well. How can I do now? Thanks a lot.

1 0

Boost Graph: iterating over internal vertex property
by Trevor Harmon 31 Mar '10

31 Mar '10

Hi, My graph is defined like this: typedef adjacency_list<vecS, vecS, directedS, Foo*> Graph; The vertex indices can be iterated over like this: typedef property_map<Graph, vertex_index_t>::type IndexMap; IndexMap index = get(vertex_index, g); typedef graph_traits<Graph>::vertex_iterator vertex_iter; std::pair<vertex_iter, vertex_iter> vp; for (vp = vertices(g); vp.first != vp.second; ++vp.first) { std::cout << index[*vp.first] << " "; } (This is straight out of the "Quick Tour" document.) But what if I want to iterate over the Foo pointers in my graph? I suppose one way is this: for (int i = 0; i < num_vertices(g); i++) { Foo *foo = g[i]; } But I assume this wouldn't scale if I were to use listS instead vecS. Also, I'd want to use a proper vertex_iterator anyway, so I can grab all the properties I want in one loop. But how can I access my Foo pointer from the vertex_iterator? I've looked though the docs and sample code but I just can't figure it out. Thanks for any tips, Trevor

2 1

[boost-build] dynamic linking and qt under Mac OS X (10.6)
by Tim Odenthal 30 Mar '10

30 Mar '10

Hi! I'm having problems installing software which is compiling perfectly under windows and (k)ubuntu on a (intel) mac. Having using darwin ; in the user-config.jam and having <link>static as a requirement in the jamroot, everything but the parts relying on qt compile, link and work. BUT: - dynamic linking fails (leaving out the <link>static requirement) - linking to the qt libraries fails ( as on ubuntu, I have " import qt ; \ using qt4 : /usr/local/Trolltech/Qt-4.6.2 ;" in my user-config.jam, obviously with the correct path): the linker complaining about "ld: library not found for -lQtOpenGL_debug" (or the same without _debug for release mode) - there are files for *.a, *.la, *.framework, what is the linker looking for? If I try to use "using gcc ;" not even static linking works, the linker complaining about "ld: unknown option: --start-group". I installed qt from source in the most naive way (without any special options to configure). Can anybody give me some hints what might be wrong - which options I should try or where else I went astray? Thanks a lot in advance Tim P.S.: boost tarball was extracted to /usr/local/boost_1_42_0, I built the libraries we use (system, filesystem, serialization, date_time).

1 0

How to retrieve the bundled property map of a compressed_sparse_row_graph
by 吴焱 30 Mar '10

30 Mar '10

I need to get the bundled property map with a key_type of the vertex_descriptor and a value_type of the bundled vertex property type from a compressed_sparse_row_graph by get(vertex_bundle, g), but it failed. It works when the graph is an adjacency_list. 1 #include <iostream> 2 #include <string> 3 #include <boost/graph/graph_traits.hpp> 4 #ifndef CSR 5 #include <boost/graph/adjacency_list.hpp> 6 #else 7 #include <boost/graph/compressed_sparse_row_graph.hpp> 8 #endif 9 using namespace boost; 10 using namespace std; 11 struct City { 12 string name; 13 int population; 14 int zipcode; 15 explicit City(string const &n = "", int pop = 0, int zip = 0) : name(n), population(pop), zipcode(zip){} 16 }; 17 struct Highway { 18 string name; 19 double miles; 20 int speed_limit; 21 explicit Highway(string const &n = "", double m = 0, int s = 0) : name(n), miles(m), speed_limit(s){} 22 }; 23 #ifndef CSR 24 typedef adjacency_list<listS, vecS, bidirectionalS, City, Highway> Graph; 25 #else 26 typedef compressed_sparse_row_graph<directedS, City, Highway> Graph; 27 #endif 28 int main(int argc, char* argv[]) 29 { 30 City ct[3] = { City("Beijing", 20, 100000), City("Tianjin", 10, 200000), City("Shanghai", 18, 300000) }; 31 Highway hway[2] = { Highway("JJWay", 200, 100), Highway("JHWay", 1300, 120) }; 32 graph_traits<Graph>::vertex_iterator vi, vi_end; 33 #ifndef CSR 34 Graph map; 35 Graph::vertex_descriptor v[3]; 36 v[0] = add_vertex(ct[0], map); 37 v[1] = add_vertex(ct[1], map); 38 v[2] = add_vertex(ct[2], map); 39 add_edge(v[0], v[1], hway[0], map); 40 add_edge(v[0], v[2], hway[1], map); 41 #else 42 typedef pair<size_t, size_t> Edge; 43 Edge edges[2] = { Edge(0, 1), Edge(0,2) }; 44 Graph map(edges_are_unsorted, edges, edges + 2, hway, 3); 45 int i = 0; 46 for (tie(vi, vi_end) = vertices(map); vi != vi_end; ++vi) 47 map[*vi] = ct[i++]; 48 #endif 49 property_map<Graph, vertex_bundle_t>::type index = get(vertex_bundle, map); 50 for (tie(vi, vi_end) = vertices(map); vi != vi_end; ++vi) 51 cout<<index[*vi].name<<" \t"<<index[*vi].population<<" \t"<<index[*vi].zipcode<<endl; 52 property_map<Graph, std::string City::*>::type Names = get(&City::name, map); 53 for (tie(vi, vi_end) = vertices(map); vi != vi_end; ++vi) 54 cout<<Names[*vi]<<endl; 55 } g++ test.cpp is OK but g++ -DCSR test.cpp errors at line 49.

2 1