December 2004 - Boost-users

Bug in BGL with num_vertices( filtered_graph )
by Sebastian Weber 20 Dec '04

20 Dec '04

Hello there! I think I found a bug in the BGL concerning the num_vertices function applied to filtered graphs. I use the filtered graph stuff with a vertice predicate. When I loop through the filtered graph with the vertex_iterator, I end up with a loop over all vertices where the predicate is true, just as it is supposed to be. But the function num_vertices on the filtered graph does return me the number of vertices of the original graph and not of the filtered graph. My system: boost 1.32.0, g++ 3.3.4, debian sarge. My graph type is boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS > and boost::filtered_graph<graph_t, boost::keep_all, largest_component<graph_t> > Greetings, Sebastian Weber

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enable_if for class templates
by Agoston Bejo 20 Dec '04

20 Dec '04

Has anyone succeeded in specializing class templates with enable_if under VC++7.1? I have created the simplest example possible and cannot imagine how I could rewrite so that no Internal Compiler Error occurs. I have tried with both the boost 1.31 and 1.32 headers, with no difference. ------------------------------------------------------ #include <iostream> #include <boost/utility/enable_if.hpp> #include <boost/type_traits.hpp> using namespace std; using namespace boost; template<typename T, typename E = void> struct A { enum { X = 0 }; }; template<typename T> struct A<T, typename enable_if< typename is_arithmetic<T> >::type> { enum { X = 1 }; }; template<typename T> struct A<T, typename enable_if< typename is_object<T> >::type> { enum { X = 2 }; }; struct B {}; int _tmain(int argc, _TCHAR* argv[]) { // cout << is_arithmetic<double>::value << endl; typedef A<float> Afloat; cout << Afloat::X << endl; // Internal Compiler Error cout << A<int>::X << endl; cout << A<B>::X << endl; return 0; } ------------------------------------------------------

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Where should STL suggestions go?
by Jim Lear 20 Dec '04

20 Dec '04

I know this is not the correct place to suggest new features to the STL, but I can't find a similar group for STL. Any suggestions? Sorry for the interruption. P.S. In case you're wondering what the suggestion is: Add ability to use random access operators with iterators. E.g. vector<int> intv; ... vector<int>::iterator i=intv.begin(); intv[i]++; It seems odd and confusing that iterators have pointer semantics but not random access semantics. -- Jim Lear

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Return type of boost::bind(...)
by Agoston Bejo 19 Dec '04

19 Dec '04

Hi! Is there an easy way to use the exact type of what boost::bind(...) returns? The example above sheds some light of the source of this question. It would be much better (actually this is what bind is for, isn't it?) if I didn't have to define the plus_5 struct in order to be able to use transform_iterator. I wrote it in the comment what I'm thinking about. I could delve deeply into the bind header files and try to explicitly find what the exact class definition is, but I suspect it would not be too easy. Anyway, I may be forced to do that. Thx, Agoston // ------------------------------------------- #include <iostream> #include <functional> #include <algorithm> #include <boost/iterator/transform_iterator.hpp> #include <boost/bind.hpp> using namespace std; using namespace boost; struct plus_5 : public unary_function<int, int> { int operator()(int i) const { return i + 5; } }; typedef transform_iterator<plus_5, int*> Iterator; //------- *** ---------------------- //typedef transform_iterator< bind_type<plus<5>, _1, 5>, int* > Iterator; // how to easily get the return type of bind(plus<5>(), _1, 5) // in compilation time? //------- *** ------------------------ int _tmain(int argc, _TCHAR* argv[]) { int ia[] = {1,2,3,4,5}; copy(Iterator(ia), Iterator(ia+5), ostream_iterator<int>(cout, " ")); cout << endl; return 0; }

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[range]array of ints
by Duane Murphy 18 Dec '04

18 Dec '04

I am changing a code base that previously was using the no longer supported array_traits. I use the begin() and end() functions in a lot of places with arrays of integers. I have converted everything to using boost::range::begin() and end(). However, there is a severe collision. begin() and more importantly end() are overloaded for wchar_t. Turns out on Mac OS X, wchar_t is the same as an int. This causes end() to look for a null terminator instead of just using the array length template function. Is there a way I can make range::end() work for real array's of int rather than wchar_t? Thanks for any tips, ...Duane

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Re: Trouble using shared_ptr with g++ -O0 and -O2 options
by Bjoern Rasmussen 18 Dec '04

18 Dec '04

Hello Andreas Unfortunately I haven't figured out what causes this, so right now I'm just using the -O0 option for my release version. Do you have a simple code example which provokes this error? Then I can try to test it on previous versions of g++ Kinds regards Bjoern D. Rasmussen >From: akabel(a)stanford.edu >To: "Bear" <bjoern_rasmussen(a)hotmail.com> >Subject: Re: Trouble using shared_ptr with g++ -O0 and -O2 options >Date: Fri, 17 Dec 2004 12:06:37 -0800 > > >Bear wrote: > > Hello there > > > > I'm getting a SIGSEGV when using the boost::shared_ptr in my program >and > > compiling with the g++ -O2 option, whereas if I'm using the g++ -O0 >option > > my programs works the way it should. My program is multi-threaded but >to the > > best of my knowledge it is mutex'ed correctly. > >I have a very similar problem in a (single-threaded) program. I tried >several compilers; Intel icc v8.0 behaves correctly, even for high >optimization level, >gcc 3.4 and gcc 3.3 dump core at -O2 and behave correctly at -O0. Did >you find >out what causes this? > >Thanks, > > Andreas > _________________________________________________________________ Del din verden med MSN Spaces http://spaces.msn.com

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RE: [Boost-users] boost and memory allocations (signals and others)
by Frank Maddin 17 Dec '04

17 Dec '04

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Beman Dawes > Sent: Thursday, December 16, 2004 4:19 PM > To: boost-users(a)lists.boost.org; boost-users(a)lists.boost.org > Subject: Re: [Boost-users] boost and memory allocations (signals and > others) > > At 09:17 AM 12/15/2004, Caleb Epstein wrote: > >On Mon, 13 Dec 2004 09:01:01 -0800, Frank Maddin > <frankmad(a)microsoft.com> > > >wrote: > > > >> We've been thinking about using certain boost functionality on a > project. > > > >> We were trying to keep the number of allocations down. > > > >See the attached test program which makes the Hello class "noisy" and > >runs two different versions of your signals test. One uses object > >copy semantics and the other uses reference semantics. Compare the > >output: > > > >copy test: > >Hello::Hello () @ 0xbfffb950 > >Hello::Hello (const ref) @ 0xbfffb8c0 > >Hello::Hello (const ref) @ 0xbfffb870 > >Hello::Hello (const ref) @ 0xbfffb830 > >Hello::Hello (const ref) @ 0xbfffb7e0 > >Hello::Hello (const ref) @ 0x8050fb0 > >Hello::~Hello @ 0xbfffb7e0 > >Hello::~Hello @ 0xbfffb830 > >Hello::~Hello @ 0xbfffb870 > >Hello::~Hello @ 0xbfffb8c0 > >Hello::Hello (const ref) @ 0x8050fc0 > >Hello::Hello (const ref) @ 0x8050fc8 > >Hello::Hello (const ref) @ 0x8050fd0 > >Hello::~Hello @ 0x8050fc8 > >Hello::~Hello @ 0x8050fc0 > >Hello::~Hello @ 0x8050fb0 > >i = 1968 > >Hello::~Hello @ 0x8050fd0 > >Hello::~Hello @ 0xbfffb950 > > > >ref test: > >Hello::Hello () @ 0xbfffb950 > >i = 1968 > >Hello::~Hello @ 0xbfffb950 > > Wow! That is a pretty substantial difference. > > Seems like the signals docs should make a point of explaining the > efficiency gained by using ref. Or maybe they do, but I didn't find > anything in several minutes of poking around the docs. There is no table > of > contents entry like "Efficiency considerations" or similar. > > --Beman > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users Thanks, that did indeed remove some churn. As Mr. Dawes pointed out, it would be nice to have that info in the docs somewhere. Overall though, I'm not sure that the allocations I'm seeing are acceptable for my application. Ideally, I'd like 1 allocation on connect and 0 allocations on signal send. We will be using an optimized small block allocator, but we still want to reduce memory operations as much as possible. Is there any suggestion to reduce this? I ran my own test putting in _CrtSetAllocHook(MyAllocHook), just copied from msdn. Below are the results (cleaned up a bit for just alloc hook calls). I haven't really looked at memory pools too closely. Would they be useful in any sort of situation with signals? >From the pool docs: >Pools are generally used when there is a lot of allocation and de-allocation of small objects. Another common usage >is the situation above, where many objects may be dropped out of memory. Thanks, Frank ref test before declaration: Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 93) Memory operation in (null), line 0: allocating a 40-byte 'Normal' block (# 95) Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 96) Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 97) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 3240f8 Memory operation in (null), line 0: allocating a 40-byte 'Normal' block (# 98) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 99) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 321688 Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 100) after declaration: before connect: Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 101) Memory operation in (null), line 0: allocating a 20-byte 'Normal' block (# 102) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 103) Memory operation in (null), line 0: allocating a 16-byte 'Normal' block (# 104) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 105) Memory operation in (null), line 0: allocating a 20-byte 'Normal' block (# 106) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 107) Memory operation in (null), line 0: allocating a 4-byte 'Normal' block (# 108) Memory operation in (null), line 0: allocating a 16-byte 'Normal' block (# 109) Memory operation in (null), line 0: allocating a 16-byte 'Normal' block (# 110) Memory operation in (null), line 0: allocating a 40-byte 'Normal' block (# 111) Memory operation in (null), line 0: allocating a 16-byte 'Normal' block (# 112) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 3244e0Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324490Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324340Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 321688Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324290Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 3242e8 after connect: before sig send: Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 113) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 114) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 321688 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324490 after sig send: copy test: before declaration: Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 67) Memory operation in (null), line 0: allocating a 40-byte 'Normal' block (# 69) Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 70) Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 71) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 3240f8 Memory operation in (null), line 0: allocating a 40-byte 'Normal' block (# 72) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 73) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 321688 Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 74) after declaration: before connect: Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 75) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 76) Memory operation in (null), line 0: allocating a 20-byte 'Normal' block (# 77) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 78) Memory operation in (null), line 0: allocating a 16-byte 'Normal' block (# 79) Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 80) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 81) Memory operation in (null), line 0: allocating a 20-byte 'Normal' block (# 82) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 83) Memory operation in (null), line 0: allocating a 4-byte 'Normal' block (# 84) Memory operation in (null), line 0: allocating a 16-byte 'Normal' block (# 85) Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 86) Memory operation in (null), line 0: allocating a 16-byte 'Normal' block (# 87) Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 88) Memory operation in (null), line 0: allocating a 40-byte 'Normal' block (# 89) Memory operation in (null), line 0: allocating a 16-byte 'Normal' block (# 90) Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 91) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 3245f0 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 3245a0 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324560 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324510 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 32439 0Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324340 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 3240f8 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 321688 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324290 Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 3242e8 after connect: before sig send: Memory operation in (null), line 0: allocating a 1-byte 'Normal' block (# 92) Memory operation in (null), line 0: allocating a 24-byte 'Normal' block (# 93) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) Memory operation in (null), line 0: freeing a 0-byte 'Normal' block (# 0) at 324510 after sig send:

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boost::not1(boost::bind(...))
by Agoston Bejo 17 Dec '04

17 Dec '04

This does not seem to work, because the object bind returns does not have an argument_type typedef. Why is that so? Is there a workaround? Thx, Agoston

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RE: [Boost-users] bind and default function parameters
by Mihalicza, Jozsef 17 Dec '04

17 Dec '04

Hello, Attached you can find a modified version of your code snipplet that works. In fact you needn't specify <bool>, but you have to pass as many arguments as the function actually takes, three in this case. Even if you specify a default value for threshold, the compiler treats equ as a function taking three parameters. HTH Best regards, Jocó P.S. to Agoston Bejo: Kicsi a világ :) -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Agoston Bejo Sent: Friday, December 17, 2004 1:01 AM To: boost-users(a)lists.boost.org Subject: [Boost-users] bind and default function parameters Hi! A small example: -------------------------------- template<typename T1, typename T2> bool equ(T1 t1, T2 t2, double threshold) { return t1 == t2; } int _tmain(int argc, _TCHAR* argv[]) { int ia1[] = {1,2,3,4,5}; cout << *find_if(ia1, ia1+5, bind<bool>(equ<int, int>, _1, 5)) << endl; // ERROR return 0; } ----------------------------------- Compiler: VC++7.1 (Intermezzo: another question: why do I have to specify the result type for bind in this case (bool)? Why can't it deduce it from the template function declaration: the return type is non-dependent.) Error message: c:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\boost\bind.hpp(246) : error C2198: 'bool (__cdecl *)(int,int,double)' : too few arguments for call through pointer-to-function ... and the rest (I suppose they are mainly irrelevant) c:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\boost\bind\bind_template.hpp(33) : see reference to function template instantiation 'R boost::_bi::list2<A1,A2>::operator ()<boost::_bi::bind_t<R,F,L>::result_type,bool(__cdecl *)(T1,T2,double),boost::_bi::list1<int &>>(boost::_bi::type<T>,F,A &)' being compiled with [ R=boost::_bi::bind_t<bool,bool (__cdecl *)(int,int,double),boost::_bi::list2<boost::_bi::list_av_2<boost::arg<1>,int >::B1,boost::_bi::list_av_2<boost::arg<1>,int>::B2>>::result_type, A1=boost::_bi::list_av_2<boost::arg<1>,int>::B1, A2=boost::_bi::list_av_2<boost::arg<1>,int>::B2, F=bool (__cdecl *)(int,int,double), L=boost::_bi::list2<boost::_bi::list_av_2<boost::arg<1>,int>::B1,boost::_bi: :list_av_2<boost::arg<1>,int>::B2>, T1=int, T2=int, T=boost::_bi::bind_t<bool,bool (__cdecl *)(int,int,double),boost::_bi::list2<boost::_bi::list_av_2<boost::arg<1>,int >::B1,boost::_bi::list_av_2<boost::arg<1>,int>::B2>>::result_type, A=boost::_bi::list1<int &> ] c:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\algorithm(64) : see reference to function template instantiation 'boost::_bi::bind_t<R,F,L>::result_type boost::_bi::bind_t<R,F,L>::operator ()<int>(A1 &)' being compiled with [ R=bool, F=bool (__cdecl *)(int,int,double), L=boost::_bi::list2<boost::_bi::list_av_2<boost::arg<1>,int>::B1,boost::_bi: :list_av_2<boost::arg<1>,int>::B2>, A1=int ] d:\prog\vcpp\Boost\xBindAndDefFuncArg\xBindAndDefFuncArg.cpp(22) : see reference to function template instantiation '_InIt std::find_if<int*,boost::_bi::bind_t<R,F,L>>(_InIt,_InIt,_Pr)' being compiled with _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Disable Unused Argments
by Duane Murphy 17 Dec '04

17 Dec '04

When using the range libraries size() function, I get an unused argument warning. While I could turn off these warnings explicitly for the project, I would rather not (in order to prevent other potential mistakes). Does boost have a more generalized or compiler specialized mechanism for disabling unused arguments in a function? To complicate matters more, this is a template function so the unused arguments pragma that I would use (with CodeWarrior 8.3) doesn't work. Suggestions welcomed. Thanks, ...Duane

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