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[BGL] parallel BGL does not scale
by Quaglino Alessio 14 Dec '15

14 Dec '15

Good Morning, I am trying to use the parallel BGL to compute the weakly connected components of a graph. I have managed to obtain the correct results with the code pasted below, however I am getting the following times: - Sequential BGL 0.01 seconds - Parallel BGL on 1 core 0.04 seconds - Parallel BGL on 2 cores 0.64 seconds That doesn’t look right to me. What am I doing wrong? using namespace boost; using boost::graph::distributed::mpi_process_group; typedef adjacency_list<vecS, distributedS<mpi_process_group, vecS>, undirectedS> Graph; typedef iterator_property_map<std::vector<int>::iterator, property_map<Graph, vertex_index_t>::type> LocalMap; int getConnectedComponents(std::vector< std::pair<int,int> > &arcs, const std::vector<int> &isActive) { // Allocate structures Graph G(nV+1); std::vector<int> localComponent(nV+1); std::vector<int> globalComponent(nV+1); // Only rank 0 has got the arc data structure if( rank == 0 ) { // Add dummy edges to each vertex (required to avoid BGL crash for a single node with no edges) for( int i=0; i<nV; i++ ) add_edge(vertex(i,G),vertex(i,G),G); // Add edges to the graph for(std::vector<std::pair<int,int> >::iterator it = arcs.begin(); it != arcs.end(); ++it) if( isActive[arcCnt++]==0 ) add_edge(vertex(it->first,G),vertex(it->second,G),G); } synchronize(G); // Compute number of connected components LocalMap components(localComponent.begin(),get(vertex_index, G)); int num = connected_components_ps(G, components); // Let rank 0 collect the global component vector if( rank == 0 ) { components.set_max_ghost_cells(0); for( PetscInt i = 0; i < nV+1; i++ ) globalComponent[i] = get(components, vertex(i, G)); } synchronize(components); } Regards, ------------------------------------------------- Alessio Quaglino Postdoctoral Researcher University of Lugano

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by daniele.barzotti＠eurocomtel.com 14 Dec '15

14 Dec '15

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Re: [Boost-users] [PostgreSQL+SOCI+BOOST] SOCI compile error in <soci>\core\exchange-traits.h with PG and SOCI on Windows
by Lawry, Brian 14 Dec '15

14 Dec '15

>> Hi. >> This isn't strictly a Boost question but I?ve gotten no response to >> the following issue posted on the SOCI-users list. [See http://sourceforge.net/p/soci/mailman/message/34675052/ for original message.] >> Thanks. >It's not exactly true. >You've already been answered in SOCI mailing list http://sourceforge.net/p/soci/mailman/message/34675052/ >Could you check proposed solution? >Best Regards, >Sergei Nikulov Hi Segei. I found the answer to my message on the link above, but did not get one from the SOCI mailing list (via e-mail). The workaround from https://github.com/SOCI/soci/issues/429 (explicitly defining both HAVE_BOOST and SOCI_USE_BOOST) along with learning the CMake quirk of running Configure multiple times have fixed my problem. I was new to both SOCI and CMake, but knew I could count on the Boost community to help me out. Thanks for pointing me in the right direction. Brian

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Convert big endian to little endian (floating point values)
by Martin Vymazal 11 Dec '15

11 Dec '15

Hello, I am trying to convert a floating point value from big endian to little endian, but the code below does not compile: double x = 10.0; const double x_big_endian = boost::endian::native_to_big(x); boost::endian::native_to_big_inplace(x); and the compiler (gcc 5.2) only offers overloads for integer types. This is with boost 1.59. Are floating point values currently supported (the website of boost::endian says so)? Am I doing something wrong? Thank you. Martin

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[dynamic_bitset] arbitrarily wide bitset
by Michael Powell 11 Dec '15

11 Dec '15

Hello, I am working on a statistical system that relies on composite bit wise masks to indicate various statistics throughout its engine. Bit wise "vocabulary" is known at compile time and may be of arbitrary length, although consistent across vocabulary categories. I am curious how wide dynamic_bitset may be? Potentially, std::bitset<N> is sufficiently up to the task? Should also be serializable; i.e. composite masks may be formed. Should also be capable of serving as a map key; i.e. a lookup of statistical values. Reading a couple of blogs, on SO, for instance, it seems like this should be doable. Reference: http://en.cppreference.com/w/cpp/utility/bitset http://www.cplusplus.com/reference/bitset/bitset/ http://www.boost.org/doc/libs/1_59_0/libs/dynamic_bitset/dynamic_bitset.html http://stackoverflow.com/questions/14433626/variable-size-bitset http://stackoverflow.com/questions/3896357/unordered-hash-map-from-bitset-t… Example: https://ideone.com/fork/WnmfyW Thank you. Regards, Michael

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<BGL>Filter vertices/edges by vertex/edge attributes?
by Amit Prakash Ambasta 11 Dec '15

11 Dec '15

Hi, In a boost graph, how can I filter vertices or edges by some attribute of Vertex/Edge Property? I tried taking a look at FilteredGraph, but the operator function would also need to be able to call boost::get(boost::vertex_bundle, graph_instance)[vertex] while only vertex is passed to the operator.

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Integrate Boost Server in DLL
by Jithendrakumar K 11 Dec '15

11 Dec '15

Hi, Can we use Boost ASIO async TCP Server example and integrate it into DLL, any example would be better. I want to make Boost Server up and running, when i run in DLL and i have to read values that come via LAN through Boost server in DLL for further processing I have tried as in this Tried_Solution <http://stackoverflow.com/questions/33448734/how-to-integrate-boost-asio-ser…> . Please suggest if there's a way to achieve it. -- Regards, Jithendrakumar K, 8019514041.

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[BGL] k-shortest path
by Ireneusz Szcześniak 11 Dec '15

11 Dec '15

Hi, I need to find k-shortest paths, but there is no such algorithm in BGL. I can get edge-disjoint k-shortest paths with a max-flow algorithm, but I don't need the k-shortest path to be edge-disjoint -- that's too strict for me. I would appreciate it if someone could share an implementation of the Yen or Eppstein algorithms using BGL. I found some implementations on the Internet, but they don't use BGL. Thanks & best, Irek

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[boost][qvm] Formal review for QVM
by Adam Wulkiewicz 10 Dec '15

10 Dec '15

Dear Boost community, The formal review of Emil Dotchevski's QVM library begins on 7th Dec and ends on 16th Dec. Boost QVM defines a set of generic functions and operator overloads for working with quaternions, vectors and matrices of static size with the emphasis on 2, 3 and 4-dimensional operations needed in graphics, video games and simulation applications. While it provides its own quaternion, matrix and vector types, it is designed to work primarily with user-defined types through user specializations of the q_traits, v_traits and m_traits templates. QVM's source code is available on Github: https://github.com/zajo/boost-qvm Full documentation is also viewable on Github: http://zajo.github.io/boost-qvm/ We encourage your participation in this review. At a minimum, kindly state: - Whether you believe the library should be accepted into Boost * Conditions for acceptance - Your name - Your knowledge of the problem domain. You are strongly encouraged to also provide additional information: - What is your evaluation of the library's: * Design * Implementation * Documentation * Tests * Usefulness - Did you attempt to use the library? If so: * Which compiler(s) * What was the experience? Any problems? - How much effort did you put into your evaluation of the review? More information about the review process can be found here: http://www.boost.org/community/reviews.html We await your feedback! Best regards, Adam Wulkiewicz

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[PostgreSQL+SOCI+BOOST] SOCI compile error in core\exchange-traits.h with PG and SOCI on Windows
by Lawry, Brian 10 Dec '15

10 Dec '15

Hi. This isn’t strictly a Boost question but I’ve gotten no response to the following issue posted on the SOCI-users list. I’m posting here in the hope that someone has experience building SOCI for PostgreSQL with Boost type support on Windows. Configuration: Using SOCI 3.2.3, Boost 1.59.0, PostgreSQL 9.4 (same with 9.5b2), and Microsoft Visual Studio 2010 on Win 7 Pro 64-bit (everything but OS is 32-bit). Target is 32-bit SOCI DLL with PostgreSQL support and Boost integration (at least tuple). Ran 'soci_postgresql_test.exe' and all tests under 'SOCI PostgreSQL Tests' passed except: test 6 skipped (dynamic backend) NOTICE: table "soci_test" does not exist, skipping NOTICE: table "soci_json_test" does not exist, skipping NOTICE: table "soci_test" does not exist, skipping I can build an application that doesn't use boost::tuple without error. However, if I do use boost∷tuple, I get: c:\develop\soci-3.2.3\core\exchange-traits.h(40): error C2065: 'x_type' : undeclared identifier // ----example----------------------------------------------------- #include "stdafx.h" /* stdafx.h includes: #define _ITERATOR_DEBUG_LEVEL 0 #include "targetver.h" #include <stdio.h> #include <tchar.h> */ #include <string> #include <iostream> #include <boost/tuple/tuple.hpp> #include <boost-tuple.h> #include <soci.h> #include <soci-postgresql.h> #pragma comment(lib, "libsoci_core_3_2.lib") #pragma comment(lib, "libsoci_postgresql_3_2.lib") #pragma comment(lib, "libpq.lib") int _tmain(int argc, _TCHAR* argv[]) { soci::session sql(soci::postgresql, "host=localhost user=postgres password=XXXXX dbname=postgres port=5432"); sql << "CREATE TABLE IF NOT EXISTS t (i INTEGER, s TEXT)"; sql << "TRUNCATE TABLE t"; sql << "INSERT INTO t (i, s) VALUES (0, 'frist')"; int i; std::string s; sql << "SELECT i, s FROM t WHERE i = 0", soci::into(i), soci::into(s); std::cout << i << "\t" << s << std::endl; boost::tuple<int, std::string> r; // following line causes error C2065: 'x_type' : undeclared identifier in core\exchange-traits.h sql << "SELECT i, s FROM t WHERE i = 0", soci::into(r); std::cout << r.get<0>() << "\t" << r.get<1>() << std::endl; return(0); } //--------------------------------------------------------------------- Thanks. [cid:image003.jpg@01D13328.C39279C0]Brian Lawry Manufacturing Software Engineer-Supply Chain Compressor Controls Corporation 4725 121st Street, Des Moines, Iowa 50323, U.S.A. blawry(a)cccglobal.com<mailto:blawry@cccglobal.com> / www.cccglobal.com<http://www.cccglobal.com> / LinkedIn<http://www.linkedin.com/company/compressor-controls-corporation>

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