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RE: Problem with graph:johnson_all_pairs_shortest_paths
by keith.briggs＠bt.com 29 Nov '04

29 Nov '04

>So, you get a code like: const int V = n; int D[V][V]; In this case, 'V' is not a compile time constant and the second line >is not valid -- array bounds must be compile time constant. I have no idea why you get the error you get, instead of >error right at the point where array is declared. Most likely, this is diagnostic problem in the rather ancient (;-)) version of >gcc that you're using. Ok, so what's the right say to do this kind of dynamically-sized problem? Keith

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Problem with graph:johnson_all_pairs_shortest_paths
by keith.briggs＠bt.com 29 Nov '04

29 Nov '04

I am using g++ 3.2 on a redhat linux system. I took the johnson_all_pairs_shortest_paths example, (http://www.boost.org/libs/graph/example/johnson-eg.cpp) which works fine, but then changed const int V = 5; to const int V = n; where n has been computed at runtime. This should not change the type of V or D, but I now get the error below. Can anyone explain how to fix this? Thanks, Keith > /usr/bin/g++ -I ~/boost_1_32_0/ graph_stats.cc graph_stats.cc: In function `int main()': graph_stats.cc:46: no matching function for call to ` johnson_all_pairs_shortest_paths(main()::Graph&, int[V][V], boost::bgl_named_params<int*, boost::vertex_distance_t, boost::no_property> )'

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Serialization and source code organization
by Malte Clasen 28 Nov '04

28 Nov '04

Hi, I'm currently trying to use the new Boost 1.32 serialization library to save the state of a medium complex program (about 10.000 lines of code). The problem is that the serialization lib seems to require very close source code coupling: The translation unit that contains the load/save functions for the application has to see all serialize() method definitions (as they are templates). That means that I cannot rely on forward declarations, so I always have to include the respective header file. This slows down the compilation noticably and results in errors such as "C1204: compiler limit : internal structure overflow" and "C1055: compiler limit : out of keys" (VC++ 7.1), as more or less all significant headers are included in this translation unit. The documentation is aware of this kind of problem and recommends manual instantiations of the serialize() methods (in the PIMPL section). Do I get something wrong or is this the only solution? I don't really like manual template instantiations, but in this case I can't imagine another way to deal with it, except waiting for the next VC++ release and hoping for the best. Malte

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help needed on random libary
by Deng Kun 28 Nov '04

28 Nov '04

can someone tell me how to seed the random library? I am having some problem with the following code the seed method won't compile on solaris but works fine on windows especially in the "else" part die->engine().seed((unsigned int)(s)); gives me some error. #ifndef RANDOMBITSET_H #define RANDOMBITSET_H #include <stdlib.h> #include <boost/random.hpp> #include <boost/dynamic_bitset.hpp> class RandomBitset { public: typedef boost::mt19937 EngineType; typedef boost::bernoulli_distribution<> DistType; typedef boost::variate_generator<EngineType, DistType> DieType; EngineType rng; DistType dist; DieType *die; RandomBitset(double p=0.5): rng(), dist(p){ die= new DieType(rng, dist); } RandomBitset(const RandomBitset & r){ rng=r.rng; dist=r.dist; if (die!=NULL) { delete die; } die= new DieType(rng,dist); } virtual ~RandomBitset(){ delete die; } //force reseed //input s<0 will use system time to reseed //otherwise use s as seed void seed(int s=-1){ if (s<0) { long rs=time(NULL); srand(rs); die->engine().seed((unsigned int) rand()); }else { die->engine().seed((unsigned int)(s)); } } void randomBitset(boost::dynamic_bitset<> & bs); }; #endif //RANDOMBITSET_H

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boost and g++-4.0
by Marc Cromme 28 Nov '04

28 Nov '04

I was wondering if Boost does work with g++ 4.0 (on Linux/Unix systems). I have seen that the config files boost/config/compiler/gcc.hpp check up to version 3.4. (boost version 1.31.0-9 on a debian testing system) Does anybody have experiences with g++ 4.0 ?? Is there a gcc.hpp including tests for g++ 4.0 ?? Something else I should know and do not ?? Marc Cromme -- Marc Cromme, cand. polyt, Ph.D Senior Developer, Project Manager Index Data Aps Købmagergade 43, 2 1150 Copenhagen K. Denmark tel: +45 3341 1000 fax: +45 3341 0101 http://www.indexdata.com INDEX DATA Means Business for Open Source and Open Standards

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Can't compile very simple snippet that uses boost::tuple
by Frank Astier 28 Nov '04

28 Nov '04

I am pretty sure it's because of my lack of skills with templates... Still, I don't understand why I can stream a vector if it's on its own, but not if it's stored in a boost::tuple. And it works with a std::pair! Any hint? #include <boost/tuple/tuple.hpp> #include <boost/tuple/tuple_io.hpp> #include <iostream> #include <vector> #include <algorithm> using namespace std; using namespace boost; template <typename T> ostream& operator<<(ostream& out, const vector<T>& v) { copy(v.begin(), v.end(), ostream_iterator<T>(out, " ")); return out; } template <typename T, typename U> ostream& operator<<(ostream& out, const pair<T, U>& p) { return out << p.first << " " << p.second; } int main(int, char**) { vector<float> v; cout << v; // Works fine pair<vector<float>, pair<int, int> > p; cout << p; // Works fine tuple<vector<float> > t; cout << t; // <== WON'T COMPILE } Thanks, Frank

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Another use for apply.
by Paul Elliott 28 Nov '04

28 Nov '04

The bind documentation mentions the apply object as a way to get around the fact that bind does not evaluate its first arguement. There is another use. You can reverse the roles of function and parameters. You can use apply and bind to turn a parameter into a functor, and call it using a function as a parameter! Example. #include <boost/bind.hpp> #include <boost/function.hpp> #include <boost/bind/apply.hpp> #include <fstream> #include <iostream> #include <iomanip> // some sample test functions. (data) int g(int x) {return x+1;}; int h(int x) {return x*x; }; int main(int argc, char * argv) { // want to work with functions of the form int f(int); typedef int P(int); // bind the integer 5 to apply turning // apply into the number 5 into a function! call it five boost::function<int (P)> five = boost::bind(boost::apply<int>(),_1,5); //int y = five(g); // Now call 5 with the "data" g and h. std::cout << "+1=" << five(g) << std::endl << "square = " << five(h) << std::endl; return 0; }; Results: +1=6 square = 25 -- Paul Elliott 1(512)837-1096 pelliott(a)io.com PMB 181, 11900 Metric Blvd Suite J http://www.io.com/~pelliott/pme/ Austin TX 78758-3117

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[Q] Unresolved references when linking against the test libs
by Michael Peterson 27 Nov '04

27 Nov '04

I apologize in advance if this turns out to be a linker problem not related to boost. So here goes: For compatibility/legacy reasons, we can not use the Boost.Build jamfiles to build our application. Accordingly, I've written a set of traditional makefiles to build the project's executables and have run into difficulties. Specifically, when I try to link my test program against the boost test libraries, I get an error message (reformatted for easy reading) saying that the reference to test_main can not be resolved. Here's the spew (formatted to make it easier to read): g++ -g3 -L../long/debug -L/usr/lib -L/usr/local/lib -L/usr/local/lib/stlport -L/usr/local/lib/boost -o "debug/unit_test" debug/longtest.o -lLong -lboost_unit_test_framework-gcc-mt-p -lboost_test_exec_monitor-gcc-mt-p -lpthread -lc /usr/local/lib/boost/libboost_test_exec_monitor-gcc-mt-p.so: undefined reference to `test_main(int, char**)' collect2: ld returned 1 exit status make: *** [debug/unit_test] Error 1 According to nm, the undefined reference, test_main, is defined in the exec_monitor library. I've tried reordering the libraries but no joy. Any advice and/or hints would be very much appreciated. I am using STLPort-4.6.2 and boost_1_32_0 and Linux (I386) Cheers, Michael

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[Q] BBV2 -- How to control naming of libraries...
by Michael Peterson 27 Nov '04

27 Nov '04

This is another getting started question: I noticed that when I staged the build of the boost libraries, unlike BBV1, the lib names were of the form boost_xxx.so. I would like to be able to control the naming (and staging) such that ib names are prefixed with 'lib' and have a version number for a suffix. For example, instead of boost_xxx.so I would like the libs to be named libboost_xxx.so-1.32.0 Must I modify the <lib> target in each Jamfile.v2 to accomplish these ends? Thanks, again Michael P.S. Still haven't solved the unresolved reference to test_main. I now suspect that the libraries did not get built correctly (I used bbv1) because I can take source code directly from the examples and it fails with the same error. Hence, I'm trying to build using BBV2.

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Thread Join/StackTrace
by Fallon, David 26 Nov '04

26 Nov '04

I am having problems debugging an application under Linux using gdb and the boost threads library. The problem I am basically having is the stack trace is only going back to the join statement rather than to point in the program that caused the crash. My application is reasonable complicated so to reproduce it I have created a buggy version of the helloword4 tutorial. The slightly modified the helloworld4 tutorial program to loop 7 times and then crash. The stack trace given in gdb points back to the join statement rather than the source code line that generated the error. Has anyone else come across this problem? // Copyright (C) 2001-2003 // William E. Kempf // // Permission to use, copy, modify, distribute and sell this software // and its documentation for any purpose is hereby granted without fee, // provided that the above copyright notice appear in all copies and // that both that copyright notice and this permission notice appear // in supporting documentation. William E. Kempf makes no representations // about the suitability of this software for any purpose. // It is provided "as is" without express or implied warranty. #include <boost/thread/thread.hpp> #include <boost/bind.hpp> #include <iostream> #include <string.h> void helloworld(const char* who) { for(int i = 0 ; i < 10; i++ ) { std::cout << who << "says, \"Hello World.\" " << i << std::endl; sleep(2); if(i > 7 ) { std::cout << " will crash " << std::endl; char * p = NULL; strcpy(p,"abcde "); // CAUSES Segmentation FAULT here but gdb } } } int main() { boost::thread thrd(boost::bind(&helloworld, "Bob")); thrd.join(); // Stack trace STOPS HERE }

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