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Multithreaded Signal Library
by Stephen torri 14 Jan '05

14 Jan '05

Since it has been advise by many people in the past that retrofitting software is troublesome and expense. I am looking at the issues of redesigning the signals library from scratch to keep the same interface. Before providing a new solution to consider I have a few questions. Is the relationship of signals to slots 1 to N where N = 0 to some value? From what I have read I believe this is true. Since signals are not copyable? N processes desiring to signal the M slots (N = 0 to some value N, M = 0 to some value M) will have to do it through the same signal object if the processes are of the same type (class has an signal object as a variable). Right? The second question comes from my initial understanding of the signals library. I was thinking about this scenario: There is a class call Cart which has a signal boost::signal<void()> in_Parking_Lot in it. Since a store will have multiple Carts for customers to use the owner has programmed his carts to signal the front desk computer when they are moved out of the store. class Cart { private: boost::signal<void()> in_Parking_Lot; public: void init (FrontDesk& fd) { in_Store = true; in_Parking_Lot.connect(fd); void process () { for (;;) { Check location (If in store set in_Store = true vice versa if not). if ( ! in_Store ) { in_Parking_Lot(); } } }; So if I have a very small shop with 50 Carts, all 50 Carts be using the same signal object to alert the front desk. If I had a big computer with 51 cpus (50 Carts and 1 FrontDesk) to run each process I have a race condition. Which process gets to alert the front desk when? >From what I understand the relationship of signals to slots is (1:N) where N is 0 to some number. So I have to have some structure in place so that I keep things safe (e.g. no race conditions or starvation) while maintaining throughput when the 50 processes try to send a signal at the same tiem. So given my example I was wondering what are the properties that I need to maintain? For example should each call to the signal's operator() function be blocking (each signaling process must update all the slots listening for the signal before returning) or non-blocking (some other process handles updating the slots while the signaling process returns back to work right away). The final question is that if indeed the relationship of signals to slots is 1:N then the multi-threading problems begins to surface more predominately. That is T threads, where T is a Cart object, use 1 signal to notify N slots. We have a restricted resource, the 1 signal, to update N slots at various times during the lifetime of the T threads. Is this the problem of using the signal library with multiple threads? I will leave things there for now and await your response. Stephen

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newbie question: large multiarray in a mult-file project
by M L 13 Jan '05

13 Jan '05

Hi, I need to declare a large multiarray in a multi-class project, something in the order of 10,000 x 300 x sizeof(a struct of 48 byte), I need to put the matrix in a header file so that other classes can see it. would it be a good idea to put all of the following lines in a header file? or the memory allocation should really be done in a .cpp file while leaving a pointer of some sort in the header? in other words, what would be a better way of declaring a large multiarray in a multi-file project? typedef boost::multi_array<xystruct, 2> xyType; //xystruct is a struct of 6 doubles xyType xy(boost::extents[10000][300]); many thanks mike

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RE: [Boost-users] error in boost/graph/fruchterman_reingold.hpp
by John Wilkinson 13 Jan '05

13 Jan '05

This one works, correcting the "grpah" typo: http://boost-consulting.com/boost/libs/graph/doc/fruchterman_reingold.ht ml -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Welson Sun Sent: Wednesday, January 12, 2005 10:04 PM To: boost-users(a)lists.boost.org Subject: RE: [Boost-users] error in boost/graph/fruchterman_reingold.hpp The link you provided is 404 error. -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Jamie Wilkinson Sent: Wednesday, January 12, 2005 2:16 AM To: Boost-users(a)lists.boost.org Subject: [Boost-users] error in boost/graph/fruchterman_reingold.hpp The doc at http://boost-consulting.com/boost/libs/grpah/doc/fruchterman_reingold.ht ml suggests that there is a 4 argument version of the function, taking only the graph, a position map, width and height; but attempts to compile such a function against the headers from the latest CVS results in a compile error: error: no matching function for call to ` fruchterman_reingold_force_directed_layout(Umbrella::Document&, Umbrella::View::load_from_document()::PositionMap&, double&, double&)' Removing the typenames Param, Tag, and Rest from lines 371-372 of the header allows the compile to continue. Index: boost/graph/fruchterman_reingold.hpp =================================================================== RCS file: /cvsroot/boost/boost/boost/graph/fruchterman_reingold.hpp,v retrieving revision 1.5 diff -u -c -r1.5 fruchterman_reingold.hpp cvs diff: conflicting specifications of output style *** boost/graph/fruchterman_reingold.hpp 29 Dec 2004 16:53:05 -0000 1.5 --- boost/graph/fruchterman_reingold.hpp 12 Jan 2005 09:18:16 -0000 *************** *** 368,375 **** params); } ! template<typename Graph, typename PositionMap, typename Dim, typename Param, ! typename Tag, typename Rest> void fruchterman_reingold_force_directed_layout(const Graph& g, PositionMap position, --- 368,374 ---- params); } ! template<typename Graph, typename PositionMap, typename Dim> void fruchterman_reingold_force_directed_layout(const Graph& g, PositionMap position, _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Date-Time question on seconds since epoch
by Bill Lear 13 Jan '05

13 Jan '05

I'd like to determine the total number of seconds between a date and the epoch ('00:00:00 1970-01-01 UTC'), The date can be in a timezone that has daylight savings. The date should be converted to UTC, with appropriate daylight savings adjustments made, and then the epoch subtracted from it. This should mirror the unix GNU 'date' utility, which can be run as: % TZ="America/New_York" date --date='2004-10-04 12:14:32' +%s 1096906472 I've looked at the doc, but it's not clear how to do this. Could someone give me a few pointers, please? Thanks. Bill

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VC7.1 compile errors using boost::multi_array with template functions
by Thomas A. Seidel 13 Jan '05

13 Jan '05

Hello everybody, I wrote 2 simple template functions for printing the content of arrays which model boost::multi_array. Template functions are necessary to be independent of the exact array type (multi_array_ref, subarrays, array_views and so on), dimension and element type. Here is the corresponding code snippet: ------------------------------------------------------- #include <cstddef> #include <iostream> #include <string> #include <boost/multi_array.hpp> template <typename T, std::size_t Dim, template <typename, std::size_t> class ArrayType> std::ostream& print(const ArrayType<T, Dim>& ma, std::ostream& os); template <typename T, template <typename, std::size_t> class ArrayType> std::ostream& print(const ArrayType<T, 1>& ma, std::ostream& os); template <typename T, template <typename, std::size_t> class ArrayType> inline std::ostream& print(const ArrayType<T, 1>& ma, std::ostream& os) { os << "| "; typename boost::multi_array<T, 1>::size_type ma_size = ma.size(); for (typename boost::multi_array<T, 1>::size_type i = 0 ; i < ma_size; i++) os << ma[i] << ' '; return os; } template <typename T, std::size_t Dim, template <typename, std::size_t> class ArrayType> inline std::ostream& print(const ArrayType<T, Dim>& ma, std::ostream& os) { os << std::string(Dim, '|') << ' '; typename boost::multi_array<T, Dim>::size_type ma_size = ma.size(); for (typename boost::multi_array<T, Dim>::size_type i = 0 ; i < ma_size; i++) { typename ArrayType<T, Dim>::const_reference row = ma[i]; print(row, os); } return os; } int main(int argc, char** argv) { boost::multi_array<unsigned int, 3> test(boost::extents[4][4][4]); for (unsigned int i = 0; i < 4; i++) for (unsigned int j = 0; j < 4; j++) for (unsigned int k = 0; k < 4; k++) test[i][j][k] = k; print(test, std::cout); std::cout << std::endl; print(test[0], std::cout); std::cout << std::endl; return 0; }; ------------------------------------------------------- The code compiles fine under Linux (Suse 9.1, gcc3.3.3) and upon execution produces the following (expected) output: ||| || | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 || | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 || | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 || | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 || | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 | 0 1 2 3 However, compiling the above code with VC7.1 produces 5 errors caused by the wrong deduction of the template parameters (the corresponding build-log is attached - unfortunately only in german language because I do not have an english VC version available, but its highly technical stuff anyway). VC7 always deduces the 'ArrayType'-type for the template function wrong. The type VC7 uses for an instantiation is the direct base class (e.g. multi_array_ref instead of multi_array) instead of the actual argument type and in the end tries to call nonexistent member-functions and constructors. A search in the microsoft compiler-documentation didn't reveal a solution for my problem. So, is this a known bug/error/problem of VC7 and does anybody know an elegant workaround???? Thanks in advance!! Regards, Thomas

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Graph: 2 questions on property maps and subgraphs
by Andrea Olgiati 13 Jan '05

13 Jan '05

Hi, A couple of (newbie) questions on subgraphs and property maps: 1. I tried to re-run the example posted at http://lists.boost.org/MailArchives/boost-users/msg05889.php and I get a segfault whilst trying to assign name1[B1] - according to a follow-up message (http://lists.boost.org/MailArchives/boost-users/msg05891.php) that code snippet was supposed to be working fine. Am I doing something wrong? 2. Maybe it's another symptom of the same problem, but I am seeing runtime failures (invalid pointers) when I write code such as: > Graph *graph = wantFullGraph? rootGraph : subGraph; > MyPropertyMap mymap = get(my_type_t(), *graph); > for( v in all vertices in *graph) { > mymap[v] = blah; > } That is, after reading the docs my understanding is that if I pick up a property map from a (sub)graph, I can use the vertices in that (sub)graph to address into that map - everything should work fine provided that I am consistently using the same (sub)graph. Is this understanding correct? If so, I'm puzzled - the only way I can get this to work is to do: > Graph *graph = wantFullGraph? rootGraph : subGraph; > MyPropertyMap mymap = get(my_type_t(), *rootGraph); > for( v in all vertices in *graph) { > v1 = graph->local_to_global(v) > mymap[v1] = blah; > } I am using - gcc version 3.3.4 (pre 3.3.5 20040809) - Linux myhost 2.6.8-24.10-default #1 Wed Dec 22 11:54:27 UTC 2004 i686 i686 i386 GNU/Linux Can someone enlighten me. please? Thanks, Andrea

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Serialazation compilign under windows.
by Ken Perry 12 Jan '05

12 Jan '05

I am trying to compile Serialization with out cygwin but serialization and other libraries in boost give the error "#error wide char i/o not supported on this platform" When I try to compile under the xp pro Command line. Is there some way this and the other libraries can be compiled under Mingw even if wide char i/o is not supported I don't really need wide char i/o I just want a way to use serialization xml as my base file types under both linux and windows. Ken

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more matrix.hpp
by Becky Bendick 12 Jan '05

12 Jan '05

Here is a more detailed description of the error from the config.log /sw/include/boost/numeric/ublas/vector_expression.hpp:1837: error: due to a defect in the G++ 3.2 ABI, G++ has assigned the same mangled name to two different types In file included from /sw/include/boost/numeric/ublas/matrix.hpp:23, from conftest.cc:67: /sw/include/boost/numeric/ublas/matrix_expression.hpp:5156: error: due to a defect in the G++ 3.2 ABI, G++ has assigned the same mangled name to two different types Thanks again, Becky ------------------------------------------------------------------------ ---------------------- Rebecca Bendick, Ph.D. Bullard Laboratories University of Cambridge Madingley Road CAMBRIDGE CB3 0EZ United Kingdom bendick(a)esc.cam.ac.uk

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C++ Template Metaprogramming - Exercise 2-0
by Trask, Bruce (US SSA) 12 Jan '05

12 Jan '05

Hello, I am going through the book C++ Template Metaprogramming and wanted a sanity check on Exercise 2-0 from the book. My first question is: What would be a motivating example for why one would want a add_const_ref<T> metafunction that returned T if it was a reference and T const& otherwise? My second question is: How did I do? My guess is that the second crack is more correct. Here is crack one: My first crack at the exercise is below (my 2nd crack is below that) #include <iostream> #include <boost/type_traits/is_reference.hpp> #include <boost/type_traits/is_same.hpp> #include <boost/static_assert.hpp> using namespace std; template<typename T, bool> struct add_const_ref { typedef T const& value_type; }; template<typename T> struct add_const_ref<T, true> { typedef T value_type; }; template<typename T> void func(typename add_const_ref<T, boost::is_reference<T>::value >::value_type t) { // .. do something } class BigClass { }; int main() { int i = 0; BOOST_STATIC_ASSERT((boost::is_same<add_const_ref<int&, boost::is_reference<int&>::value >::value_type, int&>::value)); BOOST_STATIC_ASSERT((boost::is_same<add_const_ref<int, boost::is_reference<int>::value >::value_type, int const&>::value)); func<int&>(i); BigClass myBigClass; func<BigClass>(myBigClass); return 0; } After taking a look at add_reference.hpp in boost I modified my answer to the one below: #include <iostream> #include <boost/type_traits/is_reference.hpp> #include <boost/type_traits/is_same.hpp> #include <boost/static_assert.hpp> using namespace std; template<bool> struct const_ref_adder { template<typename T> struct result_ { typedef T const& value_type; }; }; template<> struct const_ref_adder<true> { template<typename T> struct result_ { typedef T value_type; }; }; template<typename T> struct add_const_ref { typedef typename const_ref_adder<boost::is_reference<T>::value >::template result_<T>::value_type value_type; }; template<typename T> void func(typename add_const_ref<T>::value_type t) { // .. do something } class BigClass { }; int main() { int i = 0; BOOST_STATIC_ASSERT((boost::is_same<add_const_ref<int&>::value_type, int&>::value)); BOOST_STATIC_ASSERT((boost::is_same<add_const_ref<int>::value_type, int const&>::value)); func<int&>(i); BigClass myBigClass; func<BigClass>(myBigClass); return 0; } Thanks in advance for your input, Bruce

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matrix.hpp usability
by Becky Bendick 12 Jan '05

12 Jan '05

Hi, I guess this is a 'newbie' question, so I apologize if the answer is obvious to everyone but me. I've just installed boost 1.31 on an apple powerpc using fink. However, when I run compile for the dependent software that needs the boost libraries, I get the following: checking for boost/numeric/ublas/matrix.hpp presence in /sw/include...... yes checking for boost/numeric/ublas/matrix.hpp usability...... no Is there something I can do to matrix.hpp to make it usable? I've confirmed that it exists in the right place, and isn't empty or anything. Thanks, Becky ------------------------------------------------------------------------ ---------------------- Rebecca Bendick, Ph.D. Bullard Laboratories University of Cambridge Madingley Road CAMBRIDGE CB3 0EZ United Kingdom bendick(a)esc.cam.ac.uk

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