September 2009 - Boost-users

Parallel BGL status in Boost
by Mathieu Malaterre 18 Sep '09

18 Sep '09

Hi there, I am getting lost with the status of PBGL in boost. Is it officially in Boost now ? I am reading some documentation such as: http://charm.cs.uiuc.edu/charmWorkshop/slides/2009_PBGL_Lumsdaine.pptx And it appears there are multiple implementations (see slide #54), namely 'the Parallel BGL' (is there only one?) and the (Parallel) BGL-VTK. Documentation links to : http://www.osl.iu.edu/research/pbgl but this page has not been updated in years, and recent commit AFAIK did happen directly within boost, right ? Is there some threads I am missing, I have been following boost users list but could not find any thread relevant. Basically all I am interested in is how do you provide an iterator interface in a parallel environment where vertex/edge are not local to the machine. Thanks -- Mathieu

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[Regex] Problem with optionality operator
by Kay-Michael Wuerzner 18 Sep '09

18 Sep '09

Hello, I have got a problem with the interpretation of the optionality operator '?' in boost::regex. Consider the following example (regex_test.cpp): #include <iostream> #include <boost/regex.hpp> int main ( int argc, char** argv ) { boost::regex test ( "(Apple)? Iphone 3g" ); boost::match_results<std::string::const_iterator> what; std::string input ( argv[1] ); if ( 0 == boost::regex_match ( input, what, test, boost::match_default | boost::match_partial ) ) { std::cerr << "No Match\n"; } if ( what[0].matched ) { std::cerr << "Full Match\n"; } else { std::cerr << "Partial Match\n"; } return 0; } Test runs are: ./regex_test "Apple Iphone" Output: Partial Match (as expected) ./regex_test "Apple Iphone 3g" Output: Full Match (as expected) ./regex_test "Iphone" Output: No Match and Partial Match (Why is that? "Apple" is optional should only be "Partial Match") ./regex_test "Iphone 3g" Output: No Match and Partial Match (Why is that? "Apple" is optional should be "Full Match") Probably, I am only missing a flag but tests with "\A" and friends do not help. Any comments are appreciated. Many thanks in advance. Cheers, Kay

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Can I use Boost.Regex with multilne text to be recognized?
by Ramon F Herrera 18 Sep '09

18 Sep '09

More accurately, my question should be: How hard (or easy) is it to deal with multiple lines of parsed text in Regex? Is there anything special to do? (such as defining an end of line character(s)) Perhaps the best advice is to stay away from Regex and use something more powerful (such as Xpressive)? TIA, -Ramon

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How to compile boost regex
by manish4gupta 18 Sep '09

18 Sep '09

I am compiling the program using the following option g++ -ggdb -lboost_regex -o regex regex.cpp but it is giving error. #include <boost/regex.hpp> #include <iostream> void print_captures(const std::string& regx, const std::string& text) { boost::regex e(regx); boost::smatch what; std::cout << "Expression: \"" << regx << "\"\n"; std::cout << "Text: \"" << text << "\"\n"; if(boost::regex_match(text, what, e, boost::match_extra)) { unsigned i, j; std::cout << "** Match found **\n Sub-Expressions:\n"; for(i = 0; i < what.size(); ++i) std::cout << " $" << i << " = \"" << what[i] << "\"\n"; std::cout << " Captures:\n"; for(i = 0; i < what.size(); ++i) { std::cout << " $" << i << " = {"; for(j = 0; j < what.captures(i).size(); ++j) { if(j) std::cout << ", "; else std::cout << " "; std::cout << "\"" << what.captures(i)[j] << "\""; } std::cout << " }\n"; } } else { std::cout << "** No Match found **\n"; } } int main(int , char* []) { print_captures("(([[:lower:]]+)|([[:upper:]]+))+", "aBBcccDDDDDeeeeeeee"); print_captures("(.*)bar|(.*)bah", "abcbar"); print_captures("(.*)bar|(.*)bah", "abcbah"); print_captures("^(?:(\\w+)|(?>\\W+))*$", "now is the time for all good men to come to the aid of the party"); return 0; } Error message: regex.cpp: In function ‘void print_captures(const std::string&, const std::string&)’: regex.cpp:20: error: ‘class boost::smatch’ has no member named ‘captures’ regex.cpp:26: error: ‘class boost::smatch’ has no member named ‘captures’ How can i avoid that. Please help me. -- View this message in context: http://www.nabble.com/How-to-compile-boost-regex-tp25447212p25447212.html Sent from the Boost - Users mailing list archive at Nabble.com.

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Re: [Boost-users] PBGL vs (Parallel) BGL-VTK
by Randy Heiland 18 Sep '09

18 Sep '09

On Sep 17, 2009, at 1:19 PM, Jeff Baumes wrote: >> Just out of curiosity what are the main differences in between PBGL >> and (Parallel) BGL-VTK ? What I am looking for is why not use PBGL >> directly ? What was the actual issue ? > > The goal of PBGL in VTK is to integrate PBGL with VTK's data > structures and pipeline model. It includes a wrapper around PBGL > algorithms to conveniently use them from VTK, along with extending > vtkGraph to be an implementation of PBGL concepts. > > Will/Randy may have more to say about it. > > Jeff Jeff has summarized nicely. I'd only add that we've not wrapped all of the PBGL algs yet. -Randy

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[mpi] enviroment constructor different from MPI_Init
by alfC 18 Sep '09

18 Sep '09

I am using MPI in combination with BLACS and apparently it works with MPI_Init but not with boost.MPI when I use #include "blacs.h" int main(int argc, char* argv[]) { MPI_Init(&argc,&argv); int nprocs=0; int mype=0; Cblacs_pinfo( &mype, &nprocs ); // overwrites the pointee, that is how Cblacs_pinfo works std::cout<<mype<<" "<<nprocs<<std::endl; the program output (correctly): "0 1" But when I use boost::mpi::environment env(argc, argv); //instead of MPI_Init(argc, argv); the programs outputs (incorrectly): "0 -1". The point being that apparently boost::mpi::environment is not equivalent to MPI_Init/MPI_Finalize. Any idea of what is difference between MPI_Init and boost::mpi::environment? Thank you, Alfredo

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Having trouble with a callback function (converted to a class) in Regex
by Ramon F Herrera 18 Sep '09

18 Sep '09

Hello, This is my first non-trivial, multi-file C++ program with classes and I bumped into a problem. See example from the Regex library below. The problem occurred after I converted the simple code below to a class (called "Pairs"). The troublesome statement is this one, where we attempt to take the address of a function. std::for_each(m1, m2, &regex_callback); My first compilation attempt produces an error message from the compiler, which is nice enough to offer a solution: pairs.cpp:247: error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member func tion to form a pointer to member function. Say `&Pairs::assignment_callback' So, following the compiler's suggestion, I changed the line above to this: std::for_each(m1, m2, &Pairs::assignment_callback); Now, I am getting an inscrutable (for me, anyway) error message: stl_algo.h:158: error: must use .* or ->* to call pointer-to-member function in `__f (...)' Thanks for your kind assistance, -Ramon =================================================== int main(int argc, const char** argv) { std::string text; for(int i = 1; i < argc; ++i) { cout << "Processing file " << argv[i] << endl; std::ifstream fs(argv[i]); load_file(text, fs); // construct our iterators: boost::sregex_iterator m1(text.begin(), text.end(), expression); boost::sregex_iterator m2; std::for_each(m1, m2, &regex_callback); // copy results: cout << class_index.size() << " matches found" << endl; map_type::iterator c, d; c = class_index.begin(); d = class_index.end(); while(c != d) { cout << "class \"" << (*c).first << "\" found at index: " << (*c).second << endl; ++c; } class_index.erase(class_index.begin(), class_index.end()); } return 0; }

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[units] Proposal for generalizing scales
by Manoj Rajagopalan 17 Sep '09

17 Sep '09

Hi boost::units developers I am interested in extending the scale system for units. Here I present a short explanation, my initial hack to get this working, and questions on a small re-engineering issue that will crop up if this proposal is accepted. *** WHY *** Existing boost-units code allows scales which have factors as integral powers of a base, b^e, eg. 10^3, 2^10 etc. I'd like to use scales that have factors of the form a*b^e, Examples: (a) electron-Volt (eV) = 1.602*10^{-19} J (b) bohr = 0.528 Angstroms = 5.28*10^{-11} m In quantum chemistry, for example, such an "atomic units system" is typically used. *** HOW *** To achieve this using templates (which don't (yet) recognize floating point constants), I borrowed the idea from the 'dimnum' package. I, (1) added two more parameters of type long to the scale<> template which are the numerator and denominator of the rational approximation to a, (2) added static const value_type factor() member function which returns the value 'a' evaluated as double, (3) modified the value() static member to return factor() * b^e instead of simply b^e --------------- Code snippet (scale.hpp): template<long Base, class Exponent, long FactorNumerator=1L, long FactorDenominator=1L> struct scale { // ... static const double factor() { return double(FactorNumerator)/double(FactorDenominator); } static value_type value() { return(factor() * detail::static_rational_power<Exponent>(static_cast<double>(base))); } // ... }; ---------------- I modified the defintion of the apply<> template class in the boost::mpl::plus_impl, boost::mpl::negate_impl classes in unscale.hpp so that the scale<> return template-type now includes the correct FactorNumerator and FactorDenominator results based on the operands. This seems to be the place where arithmetic on scales is being performed for inter-conversion of quantities. I couldn't modify boost::mpl::times_impl because I'd have to statically exponentiate the numerator/denominator here and this doesn't fit cleanly into the existing mechanism. *** WHAT *** I do have the following questions/observations - please answer/comment. 1. The current implementation assumes that the scales being multiplied have the same base and differ only in the exponent? I just see T0::base being copied as the new base. This can be fixed with the generalized scale approach where if the bases are different (eg. 2 and 10), the resulting base is a default (10?) with exponent=static_rational<0,1> and a new factor f=(2^e1)*(10^e2). Of course, this will work only if there are no overflows. A conceivable use-case for this feature is when calculating, say, price-per-GB that is incurred in setting up a data-center. $<--->c interconversion will require 10^2 scale along the currency dimension while MB<--->GB<--->TB interconversions will require 2^10 scale along the memory dimension (assume they can be created). Here, currency interconversion will necessitate a generalized scale. 2. For simple scales like the existing one, multiplication of scales leads to addition of the exponents and therefore I can understand the static-overload of the plus_impl template to allow MPL to add the exponents. But with generalized scales we will have to switch to a different mechanism. Could you advise me on what all will need to be changed? I have a fair idea and I could use your input to cross-check. 3. When I complete this, can I submit the patch? I would like to add the atomic units system to the existing list of systems http://en.wikipedia.org/wiki/Atomic_units thanks, Manoj

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hash<pair<...
by John Dlugosz 17 Sep '09

17 Sep '09

I just moved a project that was using VC8, with TR1 supplied via BOOST, to VC9 with its own TR1 implementation. I was surprised that a unordered_map failed to compile with a great deal of verboseness because it didn't like my key type. I used a pair of two primitive types as the key. Boost took that just fine. But looking at the current Boost documentation for the hash object, (<http://www.boost.org/doc/libs/1_40_0/doc/html/boost_tr1/subject_list.html#b…>) I see that the hash specializations include primitive types, strings, but not tuples. Is this something that changed between Boost 1_38 and 1_40, or an undocumented extension, or what? Why would the standard leave out that, when everyone and his neighbor will just supply their own generic definition. That is, is there a good reason for not doing it? --John 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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boost multi-index container find method.
by Ramesh 17 Sep '09

17 Sep '09

Hello Joaquin, I have a class like below that uses mult-index container's find method. I have a record pattern as below initially: Idx : 100 Flag : 5 Idx : 200 Flag : 5 Idx : 300 Flag : 5 Idx : 400 Flag : 5 I modify the flag for index 100 to 6 & take a dump, the change is OK Idx : 100 Flag : 6 Idx : 200 Flag : 5 Idx : 300 Flag : 5 Idx : 400 Flag : 5 I modify the flag for 100 back to 5 and take a dump, which is also fine. Idx : 100 Flag : 5 Idx : 200 Flag : 5 Idx : 300 Flag : 5 Idx : 400 Flag : 5 Now I do a find based on flag value set to 5 I get the results as below: Idx : 200 flag : 5 While find functionally is correct in picking up the correct data, but I am wondering why it doesnt pick the first record (100) which has the flag value set to 5? am I missing something in the indexing definition in the container itself? Thanks /R ========================= using namespace std; #include <boost/lambda/lambda.hpp> #include <boost/multi_index_container.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/member.hpp> #include <iostream> #include <iterator> #include <iostream> #include <string> struct Token { unsigned long mIdx; unsigned char mflag; public: Token(unsigned long pIdx, unsigned char pflag): mIdx(pIdx), mflag(pflag){} void Update(unsigned char pflag) { mflag = pflag; } ~Token() { mIdx = 0; mflag = 1; } }; struct mIdx{}; struct mflag{}; using namespace boost::multi_index; namespace ll = boost::lambda; typedef multi_index_container< Token, indexed_by< ordered_unique< tag <mIdx>, BOOST_MULTI_INDEX_MEMBER(Token,unsigned long,mIdx)>, ordered_non_unique< tag <mflag>, BOOST_MULTI_INDEX_MEMBER(Token,unsigned char,mflag)> > > tToken; class TokenMaster { tToken TokenContainer; public: unsigned long getByFlag(unsigned long useFlag); bool modify(unsigned long idx, unsigned char flag); bool insert(unsigned long, unsigned char); void dump(); }; unsigned long TokenMaster::getByFlag(unsigned long useFlag) { typedef tToken::index<mflag>::type itflag; itflag& mflag_index = TokenContainer.get<mflag>(); tToken::index_iterator<mflag>::type flagit = mflag_index.find(useFlag); if (flagit == mflag_index.end()) { return 0; } printf("Idx : %d flag : %d\n", flagit->mIdx, flagit->mflag); return flagit->mIdx; } bool TokenMaster::modify(unsigned long idx, unsigned char flag) { tToken::iterator itIp=TokenContainer.find(idx); if (itIp == TokenContainer.end()) return false; return TokenContainer.modify(itIp,(&ll::_1)->*&Token::mflag=flag); } bool TokenMaster::insert(unsigned long idx, unsigned char flag) { tToken::iterator it; bool secres; std::pair<tToken::iterator, bool> result = TokenContainer.insert(Token(idx, flag)); it = result.first; secres = result.second; if (secres) return true; else return false; } void TokenMaster::dump() { unsigned long count = 0; printf("\n\n List of indexes\n"); for (tToken::iterator it = TokenContainer.begin(), it_end=TokenContainer.end(); it != it_end; ++it, count++) { printf("Idx : %d Flag : %d\n", it->mIdx, it->mflag); } printf("\n"); } main() { TokenMaster T1; T1.insert(100, 5); T1.insert(200, 5); T1.insert(300, 5); T1.insert(400, 5); T1.dump(); printf("Modifiying 100 to 6\n"); T1.modify(100, 6); T1.dump(); printf("Modifiying 100 back to 5\n"); T1.modify(100, 5); T1.dump(); printf("\n\nGet by flag \n"); T1.getByFlag(5); } ==========================

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