November 2002 - Boost-users - lists.preview.boost.org

[BGL] vc6&7 doesn't support partial specialization,can I still use BGL in vc?
by Jun Zhang 18 Nov '02

18 Nov '02

I can't believe it is vc7!! still missing support for partial specialization. Do you know other method to let vc compile BGL codes used partial specialization? Need your help. Jun Zhang

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adjacency_list going out of memory range?
by Ramón Casero Cañas 18 Nov '02

18 Nov '02

Hi, I'm working with GNU/Linux, Debian Sarge, libboost-graph1.28.0, gcc version 2.95.4 20011002 (Debian prerelease). I'm quite new to this, so I don't know if I'll be able to explain my problem correctly. It seems to me as if when I declare a graph, it writes on memory already used by another data structure. The parts of the code that I consider relevant are (.hpp and .cpp merged) ------------------- | | \|/ ------------------- #include <utility> // for std::pair #include <boost/graph/adjacency_list.hpp>/* for namespace boost * vertex_index_t * edge_weight_t * listS * undirectedS */ using namespace boost; namespace boost { enum vertex_to_be_spanned_t { // used to mark vertices of W vertex_to_be_spanned }; BOOST_INSTALL_PROPERTY(vertex, to_be_spanned); } namespace steiner { typedef std::pair<int,int> Edge; // type of edges /* Steiner Problem Graph: * - multigraph * - add_edge(), ... stability and speed, bad space overhead * - vertex indices, edge weights */ typedef property <vertex_index_t, int, property <vertex_to_be_spanned_t, bool> > VertexProperty; typedef property <edge_weight_t, int> EdgeProperty; typedef adjacency_list <listS, listS, undirectedS, VertexProperty, EdgeProperty > SteinerGraph; } namespace steiner { #define EX_FORMAT "not a valid steiner problem file"; } #include <iostream> // for std::cout #include <fstream> // for std::ifstream using namespace steiner; namespace steiner { int readsteinerORfile(steiner::SteinerGraph& g, char *s); } namespace steiner { inline void skipspaces(std::ifstream& fp, char& c); } namespace steiner { inline int readchar2int(std::ifstream& fp, char& c); } /* int main(int argc, char *argv[]) * -------------------------------- * *argv[] (IN): file names array * -------------------------------- * return n: n files were succesfully read, n > 0 * return 0: no files could be read * return -1: unexpected error * -------------------------------- * read steiner problem from files */ int main(int argc, char *argv[]) { ... SteinerGraph g; nf = steiner::readsteinerORfile(g, argv[i]); ... } /* int readsteinerORfile(VertexListGraph& g, char *s) * -------------------------------- * g (OUT): graph read from file * *s (IN): file name * -------------------------------- * return 1: file successfully read * return 0: file could not be read * return -1: unexpected error * -------------------------------- * read steiner problem from one file */ namespace steiner { int readsteinerORfile(steiner::SteinerGraph& g, char *s) { ... int num_edg=0, num_ver=0, // number of edges, vertices num_verw=0; // number of non-steiner vertices char c; // file reader int i; // counter int x; // temp value int *weight_array=NULL; // edge weights read from file Edge *edge_array=NULL; // array of edges read from file int *w_array=NULL; // vertices of W ... weight_array = new int[num_edg]; if (weight_array == NULL) throw (char *)EX_MEM; edge_array = new Edge[num_edg]; if (edge_array == NULL) throw (char *)EX_MEM; w_array = new int[num_verw]; if (w_array == NULL) throw (char *)EX_MEM; ... *************** HERE ******************* /* creation of graph object */ g.clear(); g = SteinerGraph(num_ver); *************** HERE ******************* ... } } ------------------- | | \|/ ------------------- And what happens? If I print the contents of w_array[] at the first "HERE", I get Puf(W(0)=0 )! Puf(W(1)=1 )! Puf(W(2)=2 )! Puf(W(3)=3 )! but if I print them again at the second "HERE", I get Puf(W(0)=8 )! Puf(W(1)=1 )! Puf(W(2)=2 )! Puf(W(3)=-15 )! Does anybody knows what could be happening? Thank you. Regards, Ramón Casero.

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RE: [Boost-Users] Getting a matrix to the power of n
by Scott Sinclair 17 Nov '02

17 Nov '02

Hi Unless I've missed something, I don't think uBlas provides a way to do this (other than the _very_ inefficient prod(A, A) in a loop). If you need to do this frequently with large matrices and/or large powers (n) then you'll need to look at diagonalizing your matrix using eigenvalue/vector decomposition. This reduces your task to raising the values on the diagonal of a diagonal matrix to the power of n and doing two matrix multiplies and an inverse. Finding the eigenvalues and corresponding eigenvectors of your matrix is a non-trivial task which imposes some restrictions on your matrix. Refer to "Numerical recipes in C" by Press et al. for some guidance as well as any good textbook on linear algebra. Hope this helps, Scott > -----Original Message----- > From: agiatojon [mailto:JonAgiato@nyc.rr.com] > Sent: 14/11/2002 14:17 > To: Boost-Users(a)yahoogroups.com > Subject: [Boost-Users] Getting a matrix to the power of n > > > Hello all, > I am working with a formula which requires me to get the result of a > matrix to the power of n (i.e. pow(matrix, n)) but as expected, the > <cmath> function pow() is unable to convert from type double to > matrix. Does the matrix library have this sort of functionality > built in, or maybe some other part of boost? Thanks! > > Jon Agiato > JonAgiato(a)nyc.rr.com The contents of this email may be confidential. Unauthorised use is prohibited. Umgeni Water does not accept liability for any statements and opinions which are the sender's own view and not expressly made on its behalf.

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Using multi_array/matrix to wrap a SAFEARRAY
by Nick Toze 17 Nov '02

17 Nov '02

Hello, I haven't really used C++ much (more Java and Eiffel), but now I am helping develop a C++ dll that will use matrices alot and will probably need to use SAFEARRAY to interface with Visual Basic (either directly or via COM). Also the group I'm in need to standardize on a matrix representation and it needs to be compatible with NAG. I've been trying to wrap a SAFEARRAY using a multi_array and I've got something that seems to work (see attached), but :-) I'm not sure how to go about passing these (i.e. multi_array, multi_array_ref, const_multi_array_ref) around as function arguments since they don't have any inheritance relationship. Do you have any suggestions on that? Maybe template functions could be used, but I'd like to keep my code fairly simple since I'm no expert. As an alternative the uBLAS container classes look very appropriate since I'll only be passing numbers and some of the algorithms could be useful (although I'll mostly be using NAG), but I couldn't quite see whether it is possible to use a uBLAS matrix as a view onto the data in a SAFEARRAY. Is it possible to attach a pointer to an array to a uBLAS matrix? This is the code I've got as an example for wrapping a SAFEARRAY: typedef boost::multi_array_ref<double, 2> dbl_matrix_ref; typedef boost::multi_array<double, 2> dbl_matrix; __declspec(dllexport) HRESULT __stdcall mmultiply(SAFEARRAY** sa1, SAFEARRAY** sa2, SAFEARRAY** result) { HRESULT hr; if ( result == NULL ) return E_INVALIDARG; if ( (*sa1)->cDims != 2 ) return E_INVALIDARG; if ( (*sa1)->cbElements != 8 ) return E_INVALIDARG; if ( (*sa2)->cDims != 2 ) return E_INVALIDARG; if ( (*sa2)->cbElements != 8 ) return E_INVALIDARG; long m1_dim0_sz, m1_dim1_sz, m2_dim0_sz, m2_dim1_sz; m1_dim0_sz = (*sa1)->rgsabound[0].cElements; m1_dim1_sz = (*sa1)->rgsabound[1].cElements; m2_dim0_sz = (*sa2)->rgsabound[0].cElements; m2_dim1_sz = (*sa2)->rgsabound[1].cElements; hr = SafeArrayLock( *sa1 ); if ( FAILED(hr) ) return hr; hr = SafeArrayLock( *sa2 ); if ( FAILED(hr) ) return hr; dbl_matrix_ref matrix1( (double*)(*sa1)->pvData, boost::extents[m1_dim1_sz][m1_dim0_sz], boost::fortran_storage_order() ); dbl_matrix_ref matrix2( (double*)(*sa2)->pvData, boost::extents[m2_dim1_sz][m2_dim0_sz], boost::fortran_storage_order() ); dbl_matrix matrix_result( boost::extents[matrix1.shape()[0]][matrix2.shape()[1]], boost::fortran_storage_order() ); for (dbl_matrix_ref::index i = 0; i != matrix1.shape()[0]; ++i) { for (dbl_matrix_ref::index j = 0; j != matrix2.shape()[1]; ++j) { double s = 0; for (dbl_matrix_ref::index k = 0; k != matrix1.shape()[1]; ++k) { s = s + matrix1[i][k] * matrix2[k][j]; } matrix_result[i][j] = s; } } SAFEARRAYBOUND rgsabound[2]; rgsabound[0].lLbound = 0; rgsabound[0].cElements = matrix_result.shape()[0]; rgsabound[1].lLbound = 0; rgsabound[1].cElements = matrix_result.shape()[1]; SAFEARRAY* lresult = SafeArrayCreate(VT_R8, 2, rgsabound); lresult->pvData = matrix_result.data(); hr = SafeArrayCopy( lresult, result ); if ( FAILED(hr) ) return hr; hr = SafeArrayDestroy( lresult ); if ( FAILED(hr) ) return hr; hr = SafeArrayUnlock( *sa1 ); if ( FAILED(hr) ) return hr; hr = SafeArrayUnlock( *sa2 ); if ( FAILED(hr) ) return hr; return S_OK; } Then I declare this in VBA with: Declare Function mmultiply Lib _ "D:\multiarray_test\Debug\multiarray_test" _ (a() As Double, b() As Double, c() As Double) As Long

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using 'this' with shared_ptrs
by Stephen Crowley 17 Nov '02

17 Nov '02

How is someone supposed to use 'this' when setting a member of another class to point back to it? Here is an example.. when you run it, this will happen. constructor called 0x804af10 constructor called 0x804af48 destructor called 0x804af48 destructor called 0x804af10 destructor called 0x804af10 The last destructor is called twice! The only way I can think to get around this add a member to the class called "shared_ptr<MyClass> thisptr" which is initialized to "this" in the constructor and over-ride the assignment operator or something.. will that work? ------------------------ #include <boost/shared_ptr.hpp> #include <boost/weak_ptr.hpp> #include <iostream> using namespace std; using namespace boost; class MyClass; typedef shared_ptr<MyClass> MyClassPtr; class MyClass { public: MyClass(); ~MyClass(); MyClassPtr makeCopy(); MyClassPtr original; }; MyClass::MyClass() { cout << "constructor called " << this << endl; } MyClass::~MyClass() { cout << "destructor called " << this << endl; } MyClassPtr MyClass::makeCopy() { MyClassPtr mc(new MyClass); mc->original = MyClassPtr(this); return mc; } main() { MyClassPtr oc(new MyClass); MyClassPtr cc = oc->makeCopy(); // the problem lies here // when cc's reference count is 0 it will be deleted, which will // in turn decrease its 'original' reference count which will be 0, thus // causing it to be deleted as well even though it is still being used by oc! cc.reset(); } ----------------------------------- -- Stephen

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Date_time library question...
by shaneforbes 16 Nov '02

16 Nov '02

With the following line in my Microsoft Vc7 program: std::cout << to_simple_string(d) << std::endl; I get the following linker errors: error LNK2005: "public: __thiscall std::locale::id::id(unsigned int)" (??0id@locale@std@@QAE@I@Z) already defined in stdafx.obj error LNK2005: "private: __thiscall type_info::type_info(class type_info const &)" (??0type_info@@AAE@ABV0@@Z) already defined in LIBCD.lib(typinfo.obj) error LNK2005: "private: class type_info & __thiscall type_info::operator=(class type_info const &)" (?? 4type_info@@AAEAAV0@ABV0@@Z) already defined in LIBCD.lib(typinfo.obj) Clearly I am missing something important! I did put #define DATE_TIME_INLINE in my stdafx.h file and that allowed me to create dates (date d(...)) but clearly something else is needed (for IO related stuff?)... Do I have to for instance recreate the libboost_date_time.lib file with different settings? I just used 'bjam "-sTOOLS=vc7" "- sBUILD=debug release"'. Any help appreciated. Thanks to Jeff Garland and the rest of the Boost group for creating this library - I would really like to use it in my programs from now on but why won't the silly linker oblige!

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Codewarrior 8 and Include Paths
by Roland Weiss 15 Nov '02

15 Nov '02

Hello, I'm trying to compile some simple test programs that use Boost Header libraries (no building required), like any, shared_ptr etc. Using CW8, I have a strange problem. When I add the Boost root to the access path, the compiler finds the according boost headers, but inside the config header the Boost lib looks up some headers using this syntax: #include <user.hpp> and so on. CW8 then fails to find these headers. If I change <user.hpp> to "user.hpp" all works fine (but it fails on the next header in angle brackets). Any help appreciated. Roland

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uBlass outer_product
by Olaf Petzold 15 Nov '02

15 Nov '02

Hi, I can't get the following snipped from the doc examples to work: #include <iostream> #include <boost/numeric/ublas/vector.hpp> #include <boost/numeric/ublas/io.hpp> int main () { using namespace boost::numeric::ublas; vector<double> v1 (3), v2 (3); for (int i = 0; i < std::min (v1.size (), v2.size ()); ++ i) v1 (i) = v2 (i) = i; std::cout << outer_prod (v1, v2) << std::endl; } ublas_cross.cc: In function `int main()': ublas_cross.cc:17: `outer_prod' undeclared (first use this function) ublas_cross.cc:17: (Each undeclared identifier is reported only once for each function it appears in.) What's wrong here? Thanks Olaf

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RE: [Boost-Users] using 'this' with shared_ptrs
by Per Kristensen 15 Nov '02

15 Nov '02

You initialises two shared_ptr with the same raw pointer. As a consequent the destructor is called twice, as you will have two different shared_count object which will calls delete as the count become zero. Try to use weak_ptr as a member: ----------------------------------- typedef shared_ptr<MyClass> MyClassPtr; class MyClass { public: MyClass(); ~MyClass(); void setOriginal(MyClassPtr); MyClassPtr makeCopy(); weak_ptr<MyClass> original; }; MyClass::MyClass() { cout << "constructor called " << this << endl; } MyClass::~MyClass() { cout << "destructor called " << this << endl; } void MyClass::setOriginal(MyClassPtr p) { original = p; } MyClassPtr MyClass::makeCopy() { return MyClassPtr(original); } main() { MyClassPtr oc(new MyClass); oc->setOriginal(oc); MyClassPtr cc = oc->makeCopy(); } --------------------------------- Per -----Original Message----- From: Stephen Crowley [mailto:stephenc@digitalpassage.com] Sent: 15. november 2002 05:37 To: Boost-Users(a)yahoogroups.com Subject: [Boost-Users] using 'this' with shared_ptrs How is someone supposed to use 'this' when setting a member of another class to point back to it? Here is an example.. when you run it, this will happen. constructor called 0x804af10 constructor called 0x804af48 destructor called 0x804af48 destructor called 0x804af10 destructor called 0x804af10 The last destructor is called twice! The only way I can think to get around this add a member to the class called "shared_ptr<MyClass> thisptr" which is initialized to "this" in the constructor and over-ride the assignment operator or something.. will that work? ------------------------ #include <boost/shared_ptr.hpp> #include <boost/weak_ptr.hpp> #include <iostream> using namespace std; using namespace boost; class MyClass; typedef shared_ptr<MyClass> MyClassPtr; class MyClass { public: MyClass(); ~MyClass(); MyClassPtr makeCopy(); MyClassPtr original; }; MyClass::MyClass() { cout << "constructor called " << this << endl; } MyClass::~MyClass() { cout << "destructor called " << this << endl; } MyClassPtr MyClass::makeCopy() { MyClassPtr mc(new MyClass); mc->original = MyClassPtr(this); return mc; } main() { MyClassPtr oc(new MyClass); MyClassPtr cc = oc->makeCopy(); // the problem lies here // when cc's reference count is 0 it will be deleted, which will // in turn decrease its 'original' reference count which will be 0, thus // causing it to be deleted as well even though it is still being used by oc! cc.reset(); } ----------------------------------- -- Stephen Info: < http://www.boost.org> Wiki: < http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> . [Non-text portions of this message have been removed]

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graph question : cycle detection - undirected graph
by Matthew Galati 15 Nov '02

15 Nov '02

Can DFS be used to detect cycles in an undirected graph? Using the code in the example file_dependencies.cpp on an undirected graph - it detects cycles even though there is none. Do we have to do more than simply look for back edges for an undirected graph? or should I convert it to directed then use this function? Thanks, Matt -- Matthew Galati ISE Lehigh University IBM Service Parts Solutions 610.758.4042 (Office) 610.882.0779 (Home) magh(a)lehigh.edu, magal11(a)us.ibm.com http://sagan.ie.lehigh.edu/mgalati/

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