July 2010 - Boost-users - lists.boost.org

Statistical Accumulator
by Kraus Philipp 07 Jul '10

07 Jul '10

Hi, I try to calulate the covariance from some data. http://www.boost.org/doc/libs/1_43_0/doc/html/accumulators/user_s_guide.htm… I don't understand the call "acc call". I would like to rebuild the cov command form Matlab for matrix data (http://www.mathworks.com/access/helpdesk/help/techdoc/ref/cov.html ). If this is correct, when I give as the first argument of command data from the first line and second as the data of the first column to the first value to calculate the new matrix? I try try compile the excample, but I get a compiler error on the "acc::tag::covariate1": acc::accumulator_set<double, acc::stats<acc::tag::covariance<double, acc::tag::covariate1> > > xx; xx(1., acc::tag::covariate1 = 2.); xx(1., acc::tag::covariate1 = 4.); xx(2., acc::tag::covariate1 = 3.); xx(6., acc::tag::covariate1 = 1.); std::cout << acc::covariance(xx) << std::endl; The error text: "expected primary-expression befor = token". Sorry, it's a little bit late, so I don't see my mistake Thanks Phil

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[Bind] Placeholders passed by reference?
by Robert Jones 07 Jul '10

07 Jul '10

This works exactly as expected... void f( unsigned & val ) { val *= 2; } unsigned i = 3; boost::bind( f, _1)( i ); with i being doubled. What I don't get is why I don't need to say boost::bind( f, boost::ref( _1 ) )( i ); and conversely how I specify that I want bind to pass by value rather than by reference for the placeholder. Thanks - Rob.

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Thread ID
by Kraus Philipp 07 Jul '10

07 Jul '10

Hi, I need for initialisation the random values on a cluster (64 cores on 8 machines) different seeds. I would like to use the time and thread id: I can't use only the time, because I will get the same random numbers on every core, so I would like to use thread id and time together. I dont' work with boost threads, so I try to read the thread id with boost::thread::get_id(). Compiling works, but on linking I get the error "that boost threads can't linking", but I don't have any library like "boost thread" ? Should I compile the library like the iostream lib? Is this the right way to read the thread id? I need only a value which I can use for the random seed of all cores and the value must be different on every core. Thanks for help Phil

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asio, new connection handler is not called
by Lloyd 07 Jul '10

07 Jul '10

Hi, In our application, inside the "main()" a tcp port made to listen, and the io_service is ran. It receives connection, and reads data from the connection. Then it create a thread and passes the "io_service" and the related "socket" as a reference to the new thread. Further communication are performed inside the thread. So far this works fine. Now inside the thread, I have created a "thread interruption point". This thread interruption point is inside a while loop for testing, and the while loop is inside the "async_read_handler". (That is the read handler never returns - When testing code is execution control is here-). By opening a new "telnet client", I have tried to connect to the listening port, it is connected, but the async_accept handler routine is not called! What could be the reason? How can I rectify this? Thanks, Lloyd ______________________________________ Scanned and protected by Email scanner

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Serialization of boost::gregorian::date
by Nguyen Kim Son 07 Jul '10

07 Jul '10

Hello, Do you know how to serialize class boost::gregorian::date? More generally, is it possible to serialize a class in whose we can't change the code source ? Thanks in advance, Son. -- --------------------------------------------------------- Son NGUYEN KIM Antibes 06600 Tel: 06 48 28 37 47

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Whence Ranges?
by John Dlugosz 07 Jul '10

07 Jul '10

1) Given the existance of <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1871.html>, should <http://en.wikipedia.org/wiki/C%2B%2B_Technical_Report_1#Technical_Report_2> include "Boost Range Library" on the list of things proposed for TR2? 2) Is it going well? That is, should I expect this to be standardized eventually, or have the library workers moved away from it somehow? 3) I've run into various other things like "rangeEx" and "oven" that are what? Extensions? Rewrites? What's out there that I ought to look into, for foundational use in new code? Thanks, --John (stupid footer below) TradeStation Group, Inc. is a publicly-traded holding company (NASDAQ GS: TRAD) of three operating subsidiaries, TradeStation Securities, Inc. (Member NYSE, FINRA, SIPC and NFA), TradeStation Technologies, Inc., a trading software and subscription company, and TradeStation Europe Limited, a United Kingdom, FSA-authorized introducing brokerage firm. None of these companies provides trading or investment advice, recommendations or endorsements of any kind. The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.

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(no subject)
by Long P 07 Jul '10

07 Jul '10

Hi I have problem compiling the example for serialization (boost_asio/example/serialization/server.cpp…) using MS71, does anyone know how to fix this errors? (I don’t have any problem using MS80) Thanks Long Note: including file: C:\OpenSourceSoftware\InternetDownload\boost_1_41_0\boost/serialization/array.hpp Note: including file: C:\OpenSourceSoftware\InternetDownload\boost_1_41_0\boost/serialization/detail/get_data.hpp Note: including file: C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(314) : warning C4003: not enough actual parameters for macro 'min' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(323) : warning C4003: not enough actual parameters for macro 'max' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(314) : error C2059: syntax error : ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(427) : see reference to class template instantiation 'std::valarray<_Ty>' being compiled C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(314) : error C2334: unexpected token(s) preceding ':'; skipping apparent function body C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2143: syntax error : missing ')' before '}' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2143: syntax error : missing '}' before ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2059: syntax error : ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2143: syntax error : missing ';' before '}' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2238: unexpected token(s) preceding ';' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(323) : error C2146: syntax error : missing ';' before identifier '_Ty' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(314) : error C2059: syntax error : ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(1124) : see reference to class template instantiation 'std::valarray<_Ty>' being compiled with [ _Ty=size_t ] C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(314) : error C2334: unexpected token(s) preceding ':'; skipping apparent function body C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2143: syntax error : missing ')' before '}' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2143: syntax error : missing '}' before ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2059: syntax error : ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(323) : error C2334: unexpected token(s) preceding ':'; skipping apparent function body C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(330) : error C2143: syntax error : missing ')' before '}' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(330) : error C2143: syntax error : missing '}' before ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(330) : error C2059: syntax error : ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(330) : error C2143: syntax error : missing ';' before '}' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(330) : error C2238: unexpected token(s) preceding ';' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(332) : error C2146: syntax error : missing ';' before identifier 'valarray' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(314) : error C2059: syntax error : ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(1333) : see reference to class template instantiation 'std::valarray<_Ty>' being compiled with [ _Ty=std::_Bool ] C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(1335) : see reference to class template instantiation 'std::mask_array<_Ty>' being compiled C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(314) : error C2334: unexpected token(s) preceding ':'; skipping apparent function body C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2143: syntax error : missing ')' before '}' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2143: syntax error : missing '}' before ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2059: syntax error : ')' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2143: syntax error : missing ';' before '}' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(321) : error C2238: unexpected token(s) preceding ';' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\valarray(323) : error C2146: syntax error : missing ';' before identifier '_Ty' _________________________________________________________________ Look 'em in the eye: FREE Messenger video chat http://go.microsoft.com/?linkid=9734386

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[hash] hashing of smart pointer types - prevent conversion to bool?
by Alastair Rankine 07 Jul '10

07 Jul '10

Hi Boosters, I'm sure I'm not the first person to be caught out by this. If you try to use Boost.Functional/Hash on a smart pointer type such as boost::shared_ptr, the results may be, well, underwhelming: typedef boost::shared_ptr<int> IPtr; IPtr i1 = IPtr(new int(1234)); IPtr i2 = IPtr(new int(4321)); std::cout << std::hex << "hash(i1): " << boost::hash<IPtr>()(i1) << "\n" << "hash(i2): " << boost::hash<IPtr>()(i2) << "\n"; which produces: hash(i1): 1 hash(i2): 1 This is because the shared_ptr is being silently converted to a boolean type before being hashed. Now maybe this is all documented and so forth but I would argue that it's not really expected behaviour. Or to put it another way, it's very easy to go wrong and use smart pointers in a hashed container such as a boost::unordered_set. The performance of such a set obviously degrades considerably, when compared to a more intelligent hash function. Here's a simple snippet to show the problem: typedef boost::shared_ptr<int> IPtr; template <typename T> struct PtrHash : public std::unary_function<boost::shared_ptr<T>, std::size_t> { std::size_t operator() (boost::shared_ptr<T> const& ptr) const { return boost::hash<T*>()(ptr.get()); } }; template <typename Set> double TimeInserts(int i) { Set s; boost::timer t; while (i--) s.insert(IPtr(new int(i))); return t.elapsed(); } int main() { typedef boost::unordered_set<IPtr> IPtrSetDefaultHash; typedef boost::unordered_set<IPtr, PtrHash<int> > IPtrSetPtrHash; const int iterations = 10000; std::cout << std::dec << "IPtrSetDefaultHash: " << TimeInserts<IPtrSetDefaultHash>(iterations) << "s\n" << "IPtrSetPtrHash: " << TimeInserts<IPtrSetPtrHash>(iterations) << "s\n"; return 0; } Which outputs: IPtrSetDefaultHash: 2.14526s IPtrSetPtrHash: 0.006855s ... a noticable performance difference. OK so obviously it is reasonable to want to question the wisdom of using a smart pointer type in a hashed container like this. But I want to ignore that question for now, and instead ask whether it is possible to *prevent* the conversion of smart pointers to bool for the purposes of calculating hash values. The context for this question is a fairly large codebase with extensive use of hashed containers. Not everyone on the development team is aware of this particular limitation of smart pointers. So not only do I want to detect the use of "dangerous" hashing functions but also prevent them being used in the future. Instead I really want to either fix or prevent the conversion to bool for smart pointers when used in a hashing function (either through the boost:: or tr1:: namespace). One idea is to patch the boost headers to add a hash function for each of the smart pointer types (as per the example above) but there must be a better answer than this? Does this problem affect anyone else? How do people deal with this?

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[unique_ptr] Questions
by dariomt＠gmail.com 07 Jul '10

07 Jul '10

Hi list, I found a C++03 emulation of unique_ptr here http://home.roadrunner.com/~hinnant/unique_ptr.hpp Is there any reason this is not part of Boost? Are there any known issues with this code? Thanks!

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boost serialisation number of global symbols per serializable type
by Avi Bahra 07 Jul '10

07 Jul '10

How can I work out the number of global symbols introduced per serializable type ? Is this fixed or does it vary according to type of serialisation , i.e by ptr, versus by value ? On linux I tried: nm test | grep GLOBAL | grep RepeatDay | wc Which revealed about 26, however this does not seem right ? Is there any way to reduce this overhead? Any help appreciated. Best regards, Ta, Avi

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