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

error in boost_serialization of static variable
by ashish srivastava 24 Mar '10

24 Mar '10

Hello I am having some problem in executing the code of boost_serialization. I'm trying to serialize the static class member variable. For that purpose I have wrapped the int static variable to tracked_int static variable. Please find the code attached with this mail. This is how I'm running the code and getting the segmentation fault. --------------------------------------------------------- $ g++ test_serialization_linklist.cpp -l boost_serialization $ ./a.out do u want to continue adding more nodes into the link list (y/n) ??y do u want to continue adding more nodes into the link list (y/n) ??y do u want to continue adding more nodes into the link list (y/n) ??n 5 6 6 6 the number of nodes present in the list = 4 Segmentation fault ----------------------------------------------------------------------------- The INTERNET now has a personality. YOURS! See your Yahoo! Homepage. http://in.yahoo.com/

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boost::thread SIGABRT when starting thread?
by Sean McAllister 24 Mar '10

24 Mar '10

So I'm trying to get some throughput measurements on an I/O library I'm working on, and I'm currently testing a synchronous mode so that I need two threads, one to read data and one to write. The code is quite simple: template <typename T> void sync_read_loop(pf_istream *in_sock, T *buffer, uint32_t iters) { for (int ii=0; ii < iters; ii++) { (*in_sock) >> buffer; } } template <typename T> void sync_write_loop(pf_ostream *out_sock, T *buffer, uint32_t iters) { for (int ii=0; ii < iters; ii++) { (*out_sock) << buffer; } } template <typename T> void TEST_READ_WRITE(const char* msg, t_pf_type pf_type, bool &all_passed, T (*randnum)(), bool throughput, bool sync) { const size_t BUFF_SIZE = 1024*1024; const size_t ITERS = 32; T* write_buffer = (T*)(new char[BUFF_SIZE*sizeof(T)]); T* read_buffer = (T*)(new char[BUFF_SIZE*sizeof(T)]); if (sync) {

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BoostTest: Is BOOST_MESSAGE is not thread safe?
by Dmytro Ovdiienko 24 Mar '10

24 Mar '10

Guys, I've just noticed BOOST_MESSAGE is not thread safe instruction. It is unbelievable!! I do not want to believe it!!! Try this: #define BOOST_TEST_MAIN #include <boost/test/unit_test.hpp> #include <boost/thread/thread.hpp> void foo() { for( size_t i = 0; i < 100000000; ++i ) { BOOST_MESSAGE( "111111122222222223333333333" ); } } BOOST_AUTO_TEST_CASE( testBoost ) { size_t const SIZE = 2; boost::thread t[ SIZE ]; for( size_t i = 0; i < SIZE; ++i ) { t[ i ] = boost::thread( &foo ); } for( size_t i = 0; i < SIZE; ++i ) { t[ i ].join(); } } windows XP SP3 32bit VS 2008 SP1 boost 1.42 -- Dmytro Ovdiienko

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Problem regarding downloading Boost 1.42.0
by Wasik Mursalin Rushafi 24 Mar '10

24 Mar '10

Hi, I am trying to download the latest boost library from here<http://sourceforge.net/projects/boost/files/boost/1.42.0/>but failing. is there any problem? isn't it available or I am the only one facing this problem? -- Rushafi ps. I am not sure for which mailing list this mail would be appropriate. if this isn't the correct one then it would be great if the moderators give me some direction.

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Linking with Boost on x64
by Iskandar Prins 24 Mar '10

24 Mar '10

Hi all, I have build the bjam tool and then I run the following: bjam toolset=sun stdlib=sun-stlport address-model=64 stage When I try to link with the generated libboost_thread.so I get the following error: ld: fatal: file <my_path>/libboost_thread.so: wrong ELF class: ELFCLASS64 Does this mean that the libraries are compiled for 32bit instead of 64bit? And how can I fix this? Regards, Iskandar

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[Lambda] Lost in lambda land!
by Robert Jones 24 Mar '10

24 Mar '10

Hi Folks, Can anyone tell me why this is wrong? My intention is to call A::f() for each A constructed on-the-fly from the elements of v. Thanks, Rob. #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> #include <boost/lambda/construct.hpp> #include <algorithm> #include <vector> struct A { A( int ); void f( ); }; int main( ) { using namespace boost::lambda; std::vector< int > v; std::for_each( v.begin( ), v.end( ), bind( & A::f, bind( constructor<A>(), _1 ) ) ); }

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[Bind] Is this how to write it?
by Robert Jones 24 Mar '10

24 Mar '10

Hi All In this bit of code.... #include <algorithm> #include <vector> #include "boost/bind.hpp" struct A { int double_it( int i ) { return i * 2; } } a; std::vector< int > v; int main( ) { for ( std::vector< int >::iterator i = v.begin( ); i != v.end( ); ++ i ) { a.double_it( * i ); } // Write it as a for_each/bind std::for_each( v.begin(), v.end(), boost::bind( & A::double_it, boost::ref( a ), _1 ) ); } Is that last line the idiomatic way of writing the bind expression? Thanks, Rob.

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shared_memory_object constructor
by Just C 24 Mar '10

24 Mar '10

I find shared_memory_object constructor semantics to be rather inconvenient for embedding it into another class. Consider the following class A { public: A(int type) : shm_(pass params to the shared_memory_object ctor) { } private: shared_memory_object shm_; }; If my class A is such that a shared_memory_object needs to be called with either create_only or open_only based on the type passed to A's constructor, I can't do it easily. i.e. some thing like A(int type) : shm_(type == something ? create_only : open_only) {} This won't work because create_only & open_only are different types & this will call 2 different overloaded constructors, hence the above code will not compile. Alternatives here are 1) make A a templated class instead of having type as a ctor param. i.e. template <class T> class A { public: A() : shm_(T(), other params) {} }; then use A<create_only> a; A<open_only> b; OR 2) Keep a shared_memory_object ptr inside non-templated class A instead of an actual object and create it dynamically. Assuming, I don't want to use either of these options, is there any other nifty trick anyone can think of to achieve what I want to do?

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shared_memory_object & managed_shared_memory
by Just C 24 Mar '10

24 Mar '10

This is what I am trying to do - I have to 2 processes in the same box. - I need to send a buffer of data from one process to another. - The other process reads the data & may want to send something back. - At any time there is only one such buffer in process - i.e. no queue of data to send. - the process will send a new buffer only when it gets acknowledgement back from the other process that it's finished reading it. I am a little unclear as to what I should use here - shared_memory_object or managed_shared_memory - it's not very clear what's the difference between the two. I tried out a sample from the condition_variable example here & it seems to work. http://www.boost.org/doc/libs/1_36_0/doc/html/interprocess/synchronization_… However, in the example the size of the shared memory is based on the size of the trace_queue object. In my case, the size needs to be configurable. so I am thinking of something like this - no data array inside the struct. struct data { data(void * p) : message_in(false), actualdata(p) {} //Mutex to protect access to data boost::interprocess::interprocess_mutex mutex; boost::interprocess::interprocess_condition cond_empty; boost::interprocess::interprocess_condition cond_full; void * actualdata; bool message_in; }; then shared_memory_object shm (create_only ,"shared_memory" ,read_write ); shm.truncate (sizeof(data) + myconfiguredsize); actual data is beyond the struct which holds the condition variable i.e. when i write data, i will do mapped_region region (shm ,read_write ); void * addr = region.get_address(); data * d = new (addr) data(addr); then //Use the condition_variables to protect the write & then memcpy memcpy(d->actualdata, thedataiwanttocopy, sizeofthedataiwanttocopy); Am I doing this the right way or is there a better way to go about this?

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A question on boost mpl used by MTL. Can any one with kindness help me?
by fmingu 24 Mar '10

24 Mar '10

I am using MTL(Matrix Template Library) 4 (the version is mtl4-beta-1-r6916) 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 1.34.1. The sample code is : #include <boost/numeric/mtl/mtl.hpp> int main(int argc, char* argv[]) { using namespace mtl; using namespace mtl::matrix; const unsigned xd= 2, yd= 5, n= xd * yd; dense2D<double> A(n, n); compressed2D<double> B(n, n); hessian_setup(A, 3.0); laplacian_setup(B, xd, yd); typedef std::complex<double> cdouble; dense_vector<cdouble> v(n), w(n); for (unsigned i= 0; i < size(v); i++) v[i]= cdouble(i+1, n-i), w[i]= cdouble(i+n); v+= A * w; w= B * v; std::cout << "v is " << v << "\n"; std::cout << "w is " << w << "\n"; return 0; } But the complier tolde me that : ……………………………… F:\CB2009\boost_1_34_1\boost_1_34_1/boost/mpl/apply_wrap.hpp:81:31: error: missing binary operator before token "(" F:\CB2009\boost_1_34_1\boost_1_34_1/boost/mpl/apply_wrap.hpp:173:31: error: missing binary operator before token "(" ……………………………… And the code in the corresponding lines of apply_wrap.hpp are: …………………………. #elif BOOST_PP_ITERATION_DEPTH() == 1 ……………………… #elif BOOST_PP_ITERATION_DEPTH() == 2 And I do not know how to solve it. Can any one with kindness help me?

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