November 2013 - Boost-users - lists.preview.boost.org

[Multi-Index] performance difference between lower_bound() and upper_bound()
by Dominique Devienne 29 Nov '13

29 Nov '13

I have a multi-index BMI (Boost 1.44), with an ordered_non_unique index on a"name" string field, which is lexicographically ordered. I'm searching for the range of values of the form "$prefix $integer", i.e. "foo 1", "foo 99", etc... to obtain this "range", I initially used (pseudo-code): auto begin = by_name_index().lower_bound(prefix + " 0"); auto end = by_name_index().upper_bound(prefix + " 9"); and within the range I test the suffix for its number'ness and keep the largest number. But I was surprised to see it performed badly for large number of calls. I switched to using instead: auto begin = by_name_index().lower_bound(prefix + " 0"); auto end = by_name_index().lower_bound(prefix + " :"); And this performs much better (20x). The "corpus" of names of this particular test may be skewing the results, since entries are added to the BMI with monotonically increasing number suffixes, and all entries have the prefix I'm looking for, yet I'm very surprised of such a large performance difference between the lower/upper version, and the lower/lower version. Anyone has a clue what could be going on? Thanks, --DD PS: I'm assuming the two versions are equivalent. Let me know if I'm mistaken please. This is not yet thoroughly tested.

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Put the Library Name in the Subject Line (was: boost and c function pointers)
by Mateusz Loskot 29 Nov '13

29 Nov '13

On 29 November 2013 09:29, Matthijs Möhlmann <matthijs(a)cacholong.nl> wrote: > boost::function<int(void *, int, const char **, unsigned *)> callback = > boost::bind(&admin::callback_fun, this, _1, _2, _3, _4); Please, Put the Library Name in the Subject Line [1], it will save people's time. Name Boost refers to a *collection of libraries, hence Boost has nothing to do with C function pointers. [1] http://www.boost.org/community/policy.html#subject-line Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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boost and c function pointers
by Matthijs Möhlmann 29 Nov '13

29 Nov '13

Hello all, I'm not sure if this is possible at all, but let me explain: I have the following function signature: typedef int (*sasl_callback_ft)(void); That function in question gets called with unknown amount of parameters (usually 3 or 4) Now I want to assign a member function to it: class admin { public: int callback_fun(void *context, int id, const char **result, unsigned *len); } boost::function<int(void *, int, const char **, unsigned *)> callback = boost::bind(&admin::callback_fun, this, _1, _2, _3, _4); Obviously the compiler doesn't allow to assign callback to a sasl_callback_ft var sasl_callback_ft fun = callback; I get compiler errors like: matthijs@hammer:~/t2$ clang++ -o main -std=c++11 main.cpp main.cpp:22:19: error: no viable conversion from 'boost::function<int (void *, int, const char **, unsigned int *)>' to 'sasl_callback_ft' (aka 'int (*)()') sasl_callback_ft cbfun = cb; ^ ~~ /usr/include/boost/function/function_template.hpp:894:5: note: candidate function operator safe_bool () const ^ 1 error generated. Attached the testcase I made for this. Regards, Matthijs

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[mpl][fusion] How to transform vector_c into std::vector?
by Mostafa 29 Nov '13

29 Nov '13

How does one transform an mpl:vector_c into a regular std::vector? Sample input: typedef mpl::vector<int, int_<10>, int_<11>, int_<12> > some_vector_c; Thanks, Mostafa

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Where can I get ml64.exe
by niXman 28 Nov '13

28 Nov '13

Hi, I trying to build boost-1.55 using MinGW-W64 for x86_64 arch. boost.context library requires ml64.exe for building, but I can't find it. I have found ml.exe (it's for i686 arch) on MSDN site[1], but I can't find ml64.exe. The question is where can I get it? Thanks. [1] http://www.microsoft.com/en-us/download/details.aspx?id=12654 -- Regards, niXman ___________________________________________________ Dual-target(32 & 64-bit) MinGW-W64 compilers for 32 and 64-bit Windows: http://sourceforge.net/projects/mingw-w64/ ___________________________________________________ Another online IDE: http://liveworkspace.org/

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[Thread] Using thread accross libraries
by Sébastien Gallou 28 Nov '13

28 Nov '13

Hi all, first, thanks for this great library. I'm using Boost::thread and experiencing a problem when trying to interrupt thread executed in a dynamic library (DLL, under Windows). I reproduced it in a minimal example, that I join to this post (I don't know if attachment is authorized so I also put it on my GDrive<https://drive.google.com/file/d/0B3dXqBwTbfcAQ1E0MDRfU0hxNVE/edit?usp=shari…>, and copy the code at the end of this mail). In this code, I start a thread in the main, calling a function "doWork" of a plugin, dynamically loaded. The doWork just do some sleep and wait for boost::thread_interrupted exception. The problem is that the exception is never received when the main call interrupt on the thread. If the doWork code is in the main application, all works well. Trying to debug into Boost, I'm seeing that in the interruptible_wait function, the test "if(detail::get_current_thread_data() && detail::get_current_thread_data()->interruption_enabled)" doesn't give the same result if code is in DLL (test result is false) or in the main (true). What is the reason of this behaviour ? Thanks for your help, Sébastien Gallou Here is the code : *TestBoostThread.cpp :* IPlugin* Plugin; void doWork(){ try { Plugin->doWork(); } catch (boost::thread_interrupted&) { // End-of-thread exception was not catch by plugin, // it's a developer's error, we have to report it std::cout << "Plugin didn't catch boost::thread_interrupted."; }} int main(int argc, char* argv[]){ HMODULE libraryHandle = LoadLibrary(L"Dll.dll"); boost::function<IPlugin* ()> construct = (IPlugin* (*)(void))GetProcAddress(libraryHandle, "construct"); Plugin=construct(); boost::shared_ptr<boost::thread> thread = boost::shared_ptr<boost::thread>(new boost::thread(doWork)); Sleep(1500); thread->interrupt(); thread->join(); FreeLibrary(libraryHandle); return 0;} *Dll.cpp :* class MyPlugin : public IPlugin{ virtual ~MyPlugin(){} virtual void doWork() { try { while(1) { std::cout << "MyPlugin is running..."; // Give a chance to exit plugin thread boost::this_thread::sleep(boost::posix_time::milliseconds(1000)); }; } catch (boost::thread_interrupted&) { std::cout << "MyPlugin is stopped..."; } }}; extern "C" __declspec(dllexport) IPlugin* construct(){ return new MyPlugin;}

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Hash collision for pairs of int
by Saurabh T 27 Nov '13

27 Nov '13

Hi, I'm experiencing a lot of collisions using the hash_combine function in functional/hash/hash.hpp for integer-pairs-as-keys when there are few unique ints in each of the pair's positions (put together the keys themselves are unique of course). I've uploaded a simple enough test case here: http://www.speedyshare.com/Wcem6/hash.cc.gz. If there's a more preferred way to upload, let me know and I'll reupload. With 400K pairs, this returns only 86K unique indices and has a max of 18 collisions in size_t. Am I doing something really wrong here? Thank you. saurabh

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[Graph] filters and subgraphs?
by The Maschine 27 Nov '13

27 Nov '13

Hi all, What Im trying to do is the get a filtered or subgraph that holds the properties of the original graph (vertex and edge bundles). Ill use the 'subgraph' in other algorithms but from time to time I'd like to be able to trace the original vertex_descriptor and push data back to the original graph. (that might be able to happen via the original_vertex_d below but lets see..) Below is an attempt to use graph filters to do it but for reasons that can be found in topics by others, I think this is not going to work. (filtered graph are too simple.. etc) Is it possible to use the 'distance map', that I use to produce a filtered graph, for producing a subgraph that all info from the original (minus the filtered vertexes that we dont want of course) data are there and can be also further used in algorithms? Thanks ///////////////////////////// struct VertexProperties { boost::graph_traits<unGraph>::vertex_descriptor original_vertex_d; // might be needed for the question above double m_bc; // for betweenness ..... .... }; struct EdgeProperties { double m_weight1; double m_weight2; }; typedef double Weight; typedef boost::property<boost::edge_weight_t, double> EdgeWeightProperty; typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties> unGraph; typedef boost::graph_traits < unGraph >::vertex_descriptor Vertex; typedef boost::property_map < unGraph, boost::vertex_index_t >::type IndexMap; typedef boost::iterator_property_map < Vertex*, IndexMap, Vertex, Vertex& > PredecessorMap; typedef boost::iterator_property_map < Weight*, IndexMap, Weight, Weight& > DistanceMap; struct vertex_distance_filter { vertex_distance_filter() { } vertex_distance_filter(std::vector<Weight> distance_map, double radius) : m_dist_map(distance_map), m_radius(radius) { } bool operator()(const typename boost::graph_traits<unGraph>::vertex_descriptor& v) const { return m_radius > m_dist_map[v]; } double m_radius; std::vector<Weight> m_dist_map; }; ////// int i = 0; // simplified boost::graph_traits<unGraph>::vertex_descriptor s_vertex = boost::vertex(i, m_ugraph); // Filter std::vector<Vertex> predecessors(boost::num_vertices(m_ugraph)); std::vector<Weight> distances(boost::num_vertices(m_ugraph), std::numeric_limits<double>::max() ); IndexMap indexMap = boost::get(boost::vertex_index, m_ugraph); PredecessorMap predecessorMap(&predecessors[0], indexMap); DistanceMap distanceMap(&distances[0], indexMap); boost::dijkstra_shortest_paths(m_ugraph, s_vertex, boost::weight_map(boost::get(&EdgeProperties::m_weight1, m_ugraph)).predecessor_map(predecessorMap).distance_map(distanceMap)); vertex_distance_filter filter(distances, 400.0f); typedef boost::filtered_graph<unGraph, vertex_distance_filter> FilteredGraphType; FilteredGraphType filteredGraph(m_ugraph, filter); // Work on the filtered graph. Subgraph maybe??? std::vector< double > v_centrality_vec(boost::num_vertices(filteredGraph), 0.0); // different weight from above. here m_weight2 boost::brandes_betweenness_centrality(filteredGraph , boost::centrality_map(boost::make_iterator_property_map(v_centrality_vec.begin(),boost::get(boost::vertex_index, filteredGraph),double())).vertex_index_map(get(boost::vertex_index, m_ugraph)).weight_map(boost::get(&EdgeProperties::m_weight2, m_ugraph)) ); // here we start having problems... comments above boost::graph_traits<unGraph>::vertex_iterator vertex_iterator_begin, vertex_iterator_end; for ( boost::tie(vertex_iterator_begin, vertex_iterator_end) = vertices(filteredGraph); vertex_iterator_begin != vertex_iterator_end; ++vertex_iterator_begin) { // this is the original unfiltered graph!!!! m_ugraph[*vertex_iterator_begin].m_bc = v_centrality_vec[*vertex_iterator_begin]; }

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[log] switching from n loggers to 1
by Eric Prud'hommeaux 27 Nov '13

27 Nov '13

I'm updating an old library which sets up eight separate loggers with different channel labels: BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT(DefaultLog, SWObjectsLogger); BOOST_LOG_INLINE_GLOBAL_LOGGER_CTOR_ARGS(RewriteLog, SWObjectsLogger, (channel = "Rewrite")); ... BOOST_LOG_SEV(L::RewriteLog::get(), L::info) << "foo->bar\n"; I'd like to update to 1.54 (or 1.55) and before I `perl -i` the heck out of it, I'm wondering what are the tradeoffs around using a single logger: BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT(TheLogger, boost::log::sources::severity_channel_logger< severity_level >) ... BOOST_LOG_CHANNEL_SEV(L::TheLogger::get(), L:Rewrite, L::info) << "foo->bar"; I can guess that many loggers gives me more (future) versatility to log Rewrite stuff to a different stream and that these eight loggers come with some memory footprint. Is that about right? (Also, why does adding a template parameter for the channel BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT(TheLogger, boost::log::sources::severity_channel_logger< severity_level >) barf with macro errors? expressions_channel_severity_filter.cpp:306:127: error: macro "BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT" passed 3 arguments, but takes just 2 expressions_channel_severity_filter.cpp:306:1: error: ‘BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT’ does not name a type? ) -- -ericP office: +1.617.599.3509 mobile: +33.6.80.80.35.59 (eric(a)w3.org) Feel free to forward this message to any list for any purpose other than email address distribution. There are subtle nuances encoded in font variation and clever layout which can only be seen by printing this message on high-clay paper.

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[multiarray] How to make a generic one from an existing C multi-array.
by Mostafa 27 Nov '13

27 Nov '13

Given the following: template <typename T, std::size_t D1> void foo(T (&arr)[D1]) { typedef boost::multi_array_ref < typename boost::remove_all_extents<T>::type, boost::rank<T[D1]>::value > arr_type; // ? = ExtentList or extents_tuple. arr_type ma(arr, ?); } Are there any existing tools to create an ExtentList or extents_tuple obj from the type of arr? Thanks, Mostafa

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