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Re: [Boost-users] [Boost.CircularBuffer] begin()/end() arithmetic not working out quite right
by Jan Gaspar 11 Jun '09

11 Jun '09

Hi David, you just cannot rely on this. I don't think standard says anything about begin() moving forward after push_back(). Correct me if I'm wrong. The way how it is implemented is that if the circular_buffer is empty begin() returns the same iterator as end(). There is also a note about iterator invalidation for push_back(): "Does not invalidate any iterators with the exception of iterators pointing to the overwritten element." It means iterator 'a' in your first example will point to the same element as it was before calling push_back() - which is end(). This explains the behaviour you are describing. Regards, Jan ----- Original Message ---- From: David Baird <dhbaird(a)gmail.com> To: Jan Gaspar <jano_gaspar(a)yahoo.com>; boost-users(a)lists.boost.org Sent: Thursday, 11 June, 2009 1:01:54 Subject: [Boost.CircularBuffer] begin()/end() arithmetic not working out quite right Hi, Firstly, thanks for the work on a circular buffer. This is very useful since many of my applications require it. I am having a problem though... I am using Boost 1.38.0. When I call push_back(), the iterator math makes it appear that begin() moves backwards and end() remains constant. (Based on other STL libraries, I expect that begin() will remain constant and end() will keep advancing as I call push_back()). In other words, this assertion fails (but I expect it to succeed): circular_buffer<int> buf(8); circular_buffer<int>::iterator a; circular_buffer<int>::iterator b; a = buf.begin(); buf.push_back(1); b = buf.begin(); assert(a == b); // Fails!! Also, this code fails too (but I expect it to succeed): circular_buffer<int> buf(8); circular_buffer<int>::iterator a; circular_buffer<int>::iterator b; a = buf.end(); buf.push_back(1); b = buf.end(); assert(a != b); // Also fails! Below is a full example that you can compile and try out: #include <boost/circular_buffer.hpp> #include <stdio.h> int main () { typedef boost::circular_buffer<int> buf_type; // Instead of "end" moving ahead, "begin" is moving backwards when // // using "push_back". { buf_type buf1(1024); buf_type::iterator a; buf_type::iterator b; a = buf1.end(); buf1.push_back(1); buf1.push_back(2); b = buf1.end(); printf ("%d\n", a == b); // >>> // got: 1 // expected: 0 printf ("%d, %d\n", a-buf1.begin(), b-buf1.begin()); // >>> // got: 2, 2 // expected: 0, 2 } { buf_type buf2(1024); buf_type::iterator c; buf_type::iterator d; c = buf2.begin(); buf2.push_back(1); buf2.push_back(2); d = buf2.begin(); printf ("%d\n", c == d); // >>> // got: 0 // expected: 1 // (i.e. "begin()" is not still pointing to first item!! // This is incorrect, isn't it?) printf ("%d, %d\n", buf2.end()-c, buf2.end()-d); // >>> // got: 0, 2 // expected: 2, 2 } return 0; } Thanks, David

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[MPI] Derived class not properly registered, even if it is.
by Mathieu Larose 11 Jun '09

11 Jun '09

Hi, I'm using MPI and I've come to an strange assertion fail from the library and I was wondering if it was "normal". Here is the code. I've got three files: header.hpp main.cpp other.cpp - - - - - - - - header.cpp - - - - - - - - #ifndef HEADER_HPP #define HEADER_HPP #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> // Abstract class A { friend class boost::serialization::access; template <class Archive> void serialize(Archive & ar, const unsigned int version) {} public: virtual void foo() = 0; }; class B : public A { friend class boost::serialization::access; template <class Archive> void serialize(Archive & ar, const unsigned int version) { ar & boost::serialization::base_object<A>(*this); } public: void foo() {} }; #endif - - - - - - - - main.cpp - - - - - - - - #include <iostream> #include <boost/mpi.hpp> #include "header.hpp" // #include <boost/serialization/export.hpp> // BOOST_CLASS_EXPORT(B); int main(int argc, char * argv[]) { boost::mpi::environment env(argc, argv); boost::mpi::communicator world; if (world.rank() == 0) { A * a = new B; world.send(1,0,a); std::cout << "sent" << std::endl; } } - - - - - - - - other.cpp - - - - - - - - #include "header.hpp" #include <boost/serialization/export.hpp> BOOST_CLASS_EXPORT(B); If I run this code I've got this assertion fail: a.out: ./boost/archive/impl/archive_pointer_oserializer.ipp:64: static const boost::archive::detail::basic_pointer_oserializer* boost::archive::detail::archive_pointer_oserializer<Archive>::find(const boost::serialization::extended_type_info&) [with Archive = boost::mpi::packed_oarchive]: Assertion `it != boost::serialization::singleton< oserializer_map<Archive> >::get_const_instance().end()' failed. I realized that if I uncomment these lines in main.cpp: #include <boost/serialization/export.hpp> BOOST_CLASS_EXPORT(B); My code runs correctly. It seems that BOOST_CLASS_EXPORT needs to be in the same .cpp file (i.e main.cpp) where MPI is used. When using serialization only, BOOST_CLASS_EXPORT could be in any .cpp files. Is this normal? Also, if A is no more an abstract class, BOOST_CLASS_EXPORT(B); could be called from other.cpp and the code runs correctly. I'm using version 1.39.0. Thank you, Mathieu Larose

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[conversion] Using Lexical_cast to convert string to float
by Ryan McConnehey 11 Jun '09

11 Jun '09

In writing some unit tests to convert strings to floats I've come across a puzzling situation. I was trying to test that a std::bad_cast was thrown if a number was too large to fit into a float. The error wasn't thrown but the float was given 1.#INF000. The work around I used was to cast to a double and then do a numeric_cast on the result. This provided an exception for values larger than could fit in a float. Lexical_cast on a double though works as I would have expected. If a value is too large to fit into a double then a std::bad_cast is called. float test = boost::lexical_cast<float>("3.4e050"); //test will have the value of 1.#INF000 float test = boost::numeric_cast<float>( boost::lexical_cast<double>("3.4e50"); //std::bad_cast is thrown double test = boost::lexical_cast<double>("3.4e350"); //std::bad_cast is thrown Is the lexical_cast for float behaving correctly? Ryan P.S. This code is using boost 1.38.0

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[Boost.CircularBuffer] begin()/end() arithmetic not working out quite right
by David Baird 10 Jun '09

10 Jun '09

Hi, Firstly, thanks for the work on a circular buffer. This is very useful since many of my applications require it. I am having a problem though... I am using Boost 1.38.0. When I call push_back(), the iterator math makes it appear that begin() moves backwards and end() remains constant. (Based on other STL libraries, I expect that begin() will remain constant and end() will keep advancing as I call push_back()). In other words, this assertion fails (but I expect it to succeed): circular_buffer<int> buf(8); circular_buffer<int>::iterator a; circular_buffer<int>::iterator b; a = buf.begin(); buf.push_back(1); b = buf.begin(); assert(a == b); // Fails!! Also, this code fails too (but I expect it to succeed): circular_buffer<int> buf(8); circular_buffer<int>::iterator a; circular_buffer<int>::iterator b; a = buf.end(); buf.push_back(1); b = buf.end(); assert(a != b); // Also fails! Below is a full example that you can compile and try out: #include <boost/circular_buffer.hpp> #include <stdio.h> int main () { typedef boost::circular_buffer<int> buf_type; // Instead of "end" moving ahead, "begin" is moving backwards when // // using "push_back". { buf_type buf1(1024); buf_type::iterator a; buf_type::iterator b; a = buf1.end(); buf1.push_back(1); buf1.push_back(2); b = buf1.end(); printf ("%d\n", a == b); // >>> // got: 1 // expected: 0 printf ("%d, %d\n", a-buf1.begin(), b-buf1.begin()); // >>> // got: 2, 2 // expected: 0, 2 } { buf_type buf2(1024); buf_type::iterator c; buf_type::iterator d; c = buf2.begin(); buf2.push_back(1); buf2.push_back(2); d = buf2.begin(); printf ("%d\n", c == d); // >>> // got: 0 // expected: 1 // (i.e. "begin()" is not still pointing to first item!! // This is incorrect, isn't it?) printf ("%d, %d\n", buf2.end()-c, buf2.end()-d); // >>> // got: 0, 2 // expected: 2, 2 } return 0; } Thanks, David

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boost::multi_array SWIG binding
by NJ Duncan 10 Jun '09

10 Jun '09

Hi all, I'm fairly new to C++ and learning as I go, but there is very little info out there on my particular problem. I am trying to turn a model I've written in C++ into a python module using SWIG. The main problems I'm having are initializing Boost multiarray containers then getting data into and out of them. Here is some sample code: #include <iostream> #include <vector> #include <algorithm> #include "boost/multi_array.hpp" typedef boost::multi_array<double,2> array_typef; typedef boost::multi_array<int,2> array_typei; class G2G_hydro_model { public: array_typei A; array_typef S; G2G_hydro_model(int A_ncols,int A_nrows,int S_ncols,int S_nrows):, A(boost::extents[A_ncols][A_nrows]), S(boost::extents[S_ncols][S_nrows]) {}; ~G2G_hydro_model(void) {}; void read_floating(int x, int y, array_typef& data, double& element); void write_floating(int x, int y, array_typef& data, double& element); void write_integer(int x, int y, array_typei& data, int& element); void functions_to_do_stuff(array_typef&,array_typei&) }; void G2G_hydro_model::read_floating(int x, int y, array_typef data, double element) {element = data[x][y];} void G2G_hydro_model::write_floating(int x, int y, double element, array_typef data) {data[x][y] = element;} void G2G_hydro_model::write_integer(int x, int y, int element, array_typei data) {data[x][y] = element;} Code is pushed through SWIG to create bindings, then compiled as a linked library. Compiles ok with no warnings and Python accepts the module. But when I try to use with Python code like this: import sys import numpy as np import G2G h = G2G4.G2G_hydro_model(A.cols,A.nrows,S.cols,S.rows) element = 9 for x in range(0,A.cols) for y in range(0,A.rows) h.write_integer(x, y, element, h.A) Unfortunately I get the following error message: python: /usr/include/boost/multi_array/multi_array_ref.hpp:481: boost::multi_array_ref<T, NumDims>& boost::multi_array_ref<T, NumDims>::operator=(const ConstMultiArray&) [with ConstMultiArray = boost::multi_array<double, 2ul, std::allocator<double> >, T = double, long unsigned int NumDims = 2ul]: Assertion `std::equal(other.shape(), other.shape()+this->num_dimensions(), this->shape())' failed. I think I have assigned the array extents incorrectly, but I'm not sure of the proper way to do this as part of a C++ class. Any ideas, I'm starting to pull my hair out, I hope there is a simple answer. Many Thanks Niall -- __________________________________________________________________ Niall Duncan, Postgraduate Student Institute for Energy Systems, School of Engineering and Electronics The University of Edinburgh www.see.ed.ac.uk -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

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[Intrusive] safe_link assertion with list
by Pearl Rothman 10 Jun '09

10 Jun '09

I am using Fedora 9, gcc 4.3.0, and boost 1.38.0. I get the following error when calling the destroyMessage function. boost/intrusive/detail/utilities.hpp:421: void boost::intrusive::detail::destructor_impl(Hook&, boost::intrusive::detail::link_dispatch<safe_link>) [with Hook = boost::intrusive::detail::generic_hook<boost::intrusive::get_list_node_algo<void*>, boost::intrusive::default_tag, safe_link, 1>]: Assertion `!hook.is_linked()' failed. class MessageHook : public boost::intrusive::list_base_hook<>{ public: MessageHook(Message* msg) : m_msg(msg) {}; Message* GetMsg() { return m_msg; } private: Message* m_msg; }; class MessageFactory { public: MessageFactory() { } ~MessageFactory() { } ... virtual void destroyMessage( Message* msg ) { MessageHook hook(msg); m_message_list.push_back( hook ); } private: boost::intrusive::list<stockTraderMessageHook> m_message_list; }; Thanks

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[Boost.Graph]: read_graphviz into std::vector
by Sascha Winter 10 Jun '09

10 Jun '09

Hi, I have graphes in the .dot format, with 24 vertex labels d1-d24, each storing one double. I want to use struct Vertex_p { std::string node_id; std::vector<double> d; } as the bundled property for my graph in boost and use read_graphviz to load the graph. How do I have to construct the property_map and the dynamic_properties? This property_map<graph_t, vector<double> Vertex_p::*>::type g_d = get(&Vertex_p::d, graph); g_dp.property("d",g_d); does not work. Is it even possible to do something like this? Thanks for any help, Sascha

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Problem in returning value from DFS vistor class.
by Amanullah Yasin 10 Jun '09

10 Jun '09

Bonjour,Dear all I am facing general programming related logical error. I want to access bolean variable of the class by using get method. but it is not giving the right result. When i read the counter and boolean variable by getcount() and isPathExist() methods. Each time it returns "0" for counter and false for boolean. My code is below #include "AlgoPC.h"#include <boost/graph/depth_first_search.hpp> //=============================Depth First Search===========================class DFSVisitor: public default_dfs_visitor {protected: slBayesianNetwork *pBN; int nodeA, nodeC; bool exist; int counter; public: DFSVisitor(slBayesianNetwork *pBN, int nodeA, int nodeC); ~DFSVisitor(); void discover_vertex(slNode u, const slGraph &g); void resetCounter(); bool isPathExist(); int getCounter(); };//-------------------------------------------------------------------------- DFSVisitor::DFSVisitor(slBayesianNetwork *pBN, int nodeA, int nodeC) { this->pBN = pBN; this->nodeA = nodeA; this->nodeC = nodeC; this->exist = false; this->resetCounter(); }//-------------------------------------------------------------------------- DFSVisitor::~DFSVisitor() { }//--------------------------------------------------------------------------void DFSVisitor::resetCounter() { this->counter = 0; }//-------------------------------------------------------------------------- //--------------------------------------------------------------------------void DFSVisitor::discover_vertex(slNode u, const slGraph &g) { this->counter++; unsigned int varIdx = this->pBN->getVariableIndex(u); if ((varIdx == this->nodeC ) && ((this->counter) > 2)) { this->exist = true; cout<<"\n "<<counter<<" node = "<< varIdx+1; } }//--------------------------------------------------------------------------int DFSVisitor::getCounter() { return this->counter; }//--------------------------------------------------------------------------bool DFSVisitor::isPathExist() { return this->exist; } ====================== main program ======================= cout<< "\n a = "<<a<<" c = "<<c; DFSVisitor vis(this->pBN, a , c); depth_first_search((slGraph&)this->pBN->get_graph(),visitor(vis).root_vertex(vertex(a, this->pBN->get_graph()))); cout<<"\n counter is = "<<vis.getCounter()<<" Path exist = "<< vis.isPathExist(); ======================== out put ========================= counter is = 0 path exist = 0 (false) ------------------------------------------------------- I will be thankful to you for guiding me. Best Regards Amanullah YASIN Master2 (ECD) Ecole Polytechnique Université de Nantes, France. Mob# 06 47 62 89 96 Fix # 02 72 00 26 45 amanyasin(a)gmail.com

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Obtaining base class type
by Robert Dailey 09 Jun '09

09 Jun '09

Hey everyone, I'm using wxWidgets, and as you all may know they have a silly macro used to define an event table... BEGIN_EVENT_TABLE( MainWindow, wxFrame ) EVT_CLOSE( MainWindow::OnClose ) END_EVENT_TABLE() I spend a few hours finding out that wxFrame is the incorrect parameter for parameter #2. This is not the base class that MainWindow derives from. There was no compiler error or warning, nor any errors during runtime. Only weird behavior because events were getting skipped. Because of this error-proneness, I'm looking for a way to have boost help me out with this. I'm looking for a metafunction in Boost that can be used to obtain (at compile time) the base type of MainWindow. For example: BEGIN_EVENT_TABLE( MainWindow, boost::get_base_of<MainWindow>::type ) EVT_CLOSE( MainWindow::OnClose ) END_EVENT_TABLE() Something like that above. I know that type traits has is_base_of, and I'm hoping there is a get version of that too. I've browsed through the reference but I've found nothing helpful.

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assignment operator could not be generated
by Zachary Turner 09 Jun '09

09 Jun '09

When building a project that uses boost on Windows under MSVC 9.0 (VS 2008), I get _tons_ of warnings for "assignment operator could not be generated" all throughout the code. Is this going to cause subtle errors when I run the code, or are the warnings harmless ones that can be disabled with pragmas? One example where I get lots of "assignment operator could not be generated" spam is in boost::detail::addr_impl_ref<T> when I try to use boost::bind. But there are many other places as well. I can produce an explicit sample if requested, but since it happens so frequently and I haven't done anything special AFAIK to make it happen, I suspect someone else will immediately know what I'm talking about.

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