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

Sorting a container of shared_ptr<T>
by alejandro_escalante_medina 29 Aug '02

29 Aug '02

Hello to everyone. I'm starting to take a look on Boost and was happy to find things like better smart pointers. Though, in my tests, I haven't been able to sort, say, a vector of shared_ptr without defining special comparators. I thought that the overload for the < operator would help me for that, but that operator compares pointers, not objects, so it doesn't do the work that I expected. I guess I'm not understanding this well. Could someone explain this to me? Saludos, Alex

2 1

threads and signals question
by lparrab 29 Aug '02

29 Aug '02

Hi all, I guess my question is not specific to Boost.Thread, but to threading in general (I'm new at it)... still hope you can help me out, either directly or by redirecting me to the right place (links are very much appreciated) I'm starting a multi-threaded program using Boost.Thread library: it is a "server", in which a thread loops around a "select" to accept new connections and see when a socket has data to be read, in which case puts the fds in queue from which other threads are taking them out to read the data. The problem I have, is that when a "ReceiverThread" finishes reading the data from the socket, it puts the fd back in the "all connections list", but by this time the other ("main")thread already copied the fds from the list and got into the next "select" loop, which means the socket from which the "receiver" just finished reading, will not be "selected" (monitored) untill the next select loop, which will not be untill a) a new connection comes or b)one of the other connected sockets gets some data that takes makes the main thread return from select. reading the select man, I thought I could just use a signal to force select to return when the "receiver" has put the fd back in the "all connection list": the threads are now executing something like: main_thread { *put all fds from "all sockets" list into a fdset *make a select on the fdset (block till something interesting happens) *take the fds with data out of "all sockets" and put them into "sockets with data" *loop } receiver{ *get a fd from "sockets with data" (if nothing there blocks till the main_thread sends us a fd through the queue) *read from fd *put fd back into "all sockets" (problem: main_thread may be (is!) already into the select) *raise(SIGUSR1) (to force select to return and enter the loop again, but this time with our fd) } the signal handler for SIGUSR1 does nothing, it just serves to force select to return, but the code is not really working as I expected, and I realized that the problem is that each thread has its own pid, so it seems raise is actually sending a signal to the wrong thread.... as I said, I am new to mulithreading, but I thought all threads run in a process, which means, they all have the same pid. ->if I first find out the "pid" of the main_thread and change raise(SIGUSR1) to kill(pid,SIGUSR1) it works ok. so my question: why does each thread have a own pid?? how can then I send signals from one thread to another?? I discovered there is a "pthread_kill" function to send signals to specific threads, the problem is I only have boost::thread objects, no pthread_t structures. or am I talking nonsense and shouldnt be using signals with Boost.Thread? if so, how do I solve the select problem?? thanx! luis

5 5

BGL: adjacency_list: remove_edge problems
by Matthias Kronenberger 29 Aug '02

29 Aug '02

I'm using a undirected grap with hash_setS as the Edge List container and vecS as the Vertex List Container I'm using MSVC60 with SP5 as soon as i'm trying to use remove_edge(vertex1,vertex2,graph) i get the following error message. I dont understand the error message. It means, that my edgelist is a std::vector allthough i compile with boost::hash_setS. Could it be, that some BGL config file detects MSVC and concludes, that hash sets are not available in the MSVC stl?? d:\matthias\programmieren\boost\boost\graph\detail\adjacency_list.hpp(665): error C2039: 'find': Ist kein Element von 'vector<boost::detail::sei_<unsigned int,list<boost::list_edge<unsigned int,boost::property<enum boost::edge_weight_t,float,boost:: no_property>>>::iter,boost::property<enum boost::edge_weight_t,float,boost::no_property>>,allocator<boost::detail::sei _<unsigned int,list<boost::list_edge<unsigned int,boost::property<enum boost::edge_weight_t,float,boost::no_property>>>::iter,boost ::property<enum boost::edge_weight_t,float,boost::no_property>>>>' find is not an element of vector the corresponding code fragment is. template <class Graph, class EdgeList, class Vertex> inline void remove_edge_and_property(Graph& g, EdgeList& el, Vertex v, boost::disallow_parallel_edge_tag) { typedef typename EdgeList::value_type StoredEdge; typename EdgeList::iterator i = el.find(StoredEdge(v)), end = el.end(); if (i != end) { g.m_edges.erase((*i).get_iter()); el.erase(i); } }

3 6

Re: [Boost-Users] threads and signals question
by dick.bridges＠tais.com 29 Aug '02

29 Aug '02

My $.02. Check out the description of the Leader-Follower thread pattern described in Schmidt, et al, Pattern-Oriented Software Architecture, Volume 2, Patterns for Concurrent and Networked Objects. Sure is easy to implement with Boost libraries. Thank you everyone! Luis De la Parra <lparrab(a)gmx.net To: tomhoward(a)users.sourceforge.net, Boost-Users(a)yahoogroups.com > cc: Subject: Re: [Boost-Users] threads and signals question 08/29/2002 09:37 AM Please respond to Boost-Users > IMHO I wouldn't use select. Each time a new connections is initiated, you > can simply start a new thread to receive data from that socket. I don't > know what performance impact this would have, but the code will certainly > be simpler and easier to maintain. as I said, I'm new to threads.. and I know they are much more "leightweighted" than a normal process, but imagine a server, like an application server, which can have *a lot* of clients connected at the same time, but in which the clients are not really all requesting thigs all the time, they are "just connected" I think having a thread waiting on each open connection is not the right approach here, so I thought of going a kind of "production line" approach in which a few threads (5-10) are reading the data from a bunch of open connections (50-100), the only thing they do is read the data, parse it and form a "Request" which they put in a queue for further processing and then go on to service the other connections. Then another group of threads is taking this requests and doing something, and putting Response objects in yet another queue, which another group of threads "Sender" is taking and sending thorugh the socket. I think you get the idea: a frew threads just doing one thing and then passing the processing to another gorup of threads. I know having a thread dedicated to each connection would be much easier, but since this project is mostly for fun (and to learn!) I'd like to take a "better" approach (note that I am not saying the approach I just described is the best one, but right now it sounds more efficient and scalable to me than the one-trhead-per-connection approach) regards, luis.l 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 http://docs.yahoo.com/info/terms/

1 0

tuple and enums
by Tom Matelich 29 Aug '02

29 Aug '02

It appears that an enum cannot be default constructed in the way that tuple does, cons() : head(), tail() {} Any idea on how to get around this (besides using an int in the tuple)? Thanks, Tom <sample_code> #include <boost/tuple/tuple.hpp> #include <string> enum Foo { Willis, Arnold }; void test() { boost::tuple<Foo, std::string> a; } </sample_code> </error compiler="gcc version 2.96 20000731 (Mandrake Linux 8.2)"> /usr/local/eddynet/opt/include/boost/tuple/detail/tuple_basic.hpp: In method `boost::tuples::cons<HT, TT>::cons () [with HT = Foo, TT = boost::tuples::cons<string, boost::tuples::null_type>]': /usr/local/eddynet/opt/include/boost/tuple/detail/tuple_basic.hpp:454: instantiated from `boost::tuples::tuple<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9>::tuple () [with T0 = Foo, T1 = string, T2 = boost::tuples::null_type, T3 = boost::tuples::null_type, T4 = boost::tuples::null_type, T5 = boost::tuples::null_type, T6 = boost::tuples::null_type, T7 = boost::tuples::null_type, T8 = boost::tuples::null_type, T9 = boost::tuples::null_type]' tuple_enum_test.cpp:8: instantiated from here /usr/local/eddynet/opt/include/boost/tuple/detail/tuple_basic.hpp:263: cannot convert `int' to `Foo' in assignment </error> ----------------------------------------------------------------------- DISCLAIMER: Information contained in this message and/or attachment(s) may contain confidential information of Zetec, Inc. If you have received this transmission in error, please notify the sender by return email. -----------------------------------------------------------------------

2 1

shared_ptr const problem
by Olaf Petzold 28 Aug '02

28 Aug '02

Hi, now I have a new problem - const correctness. ---8<--- #include <iostream> #include <algorithm> #include <iterator> #include <vector> #include <boost/shared_ptr.hpp> class Doc { public: virtual ~Doc() { } public: const std::vector<double>& foo() const { return m_foo; } protected: std::vector<double>& foo() { return m_foo; } private: std::vector<double> m_foo; }; using namespace std; int main() { boost::shared_ptr<Doc> lp_doc( new Doc ); std::copy(lp_doc->foo().begin(), lp_doc->foo().end(), std::ostream_iterator<double>(cout, " ") ); cout << endl; } --->8--- `std::vector<double, std::allocator<double> >& Doc::foo()' is protected I hoped std::copy takes the const foo() member function. Thanks olaf

2 2

iterator_adaptors on mipspro 7.3.1.3m
by marcinzalewski 28 Aug '02

28 Aug '02

Hi, I am trying to use iterator adaptors on mipspro and am unsuccessfull as for now. I was wandering if any of you has experience with boost and mipspro. Here are some examples of errors I am getting: ----------- cc-1132 CC: ERROR File = ../../boost_1_28_0/boost/iterator.hpp, Line = 54 The namespace "std" has no member "ptrdiff_t". template <class Category, class T, class Distance = std::ptrdiff_t, ^ or cc-3307 CC: ERROR File = ../../boost_1_28_0/boost/type_traits/array_traits.hpp, Line = 24 Invalid partial specialization--class "boost::is_array<<error-type>>" is already fully specialized. template <typename T, std::size_t N> struct is_array<T[N]> ----------- Please, let me know if you did this before. :) -m ^

2 2

[BGL] undirectedS self-loop add_edge assertion
by Chris Russell 27 Aug '02

27 Aug '02

Just a quick mention: A call to add_edge with u == v causes an assertion if Directed == undirectedS. adjacency_list.hpp line 843: assert( u != v ); // don't allow self-loops ^- boost_1_28_0 Avoiding the assertion is easy enough but this is inconsistent w/section 14.1.1 p.220 of the BGL book: "... Also if u and v are descriptors for the same vertex (creating self loop) and the graph is undirected, then the edge will not be created and the flag will be false." Am having tons of fun - the BGL and the book are super. Thanks! - Chris

2 1

lambda library usage
by khuroth 27 Aug '02

27 Aug '02

I have a View class that has some widgets, and a Controller class that controls the view, so the View class has a GetController() member function that returns a reference to its controller. When the View's constructor is called, GetController() would return a bad ref, but it would return a valid reference by the time a button is clicked... so what I'm trying to do is, inside the View constructor: my_button.on_click = bind( (_1 ->* &A::GetController).DoSomething(), this ); but that obviously doesn't work... I'm even having trouble just saving the first part: my_button.on_click = bind<Controller&>(_1 ->* &A::GetController, this); also doesn't work... I tried defining the on_click member of the button as a boost::function<void> or a boost::function0<void> in the first example, and a boost::function<Controller&> or boost::function0<Controller&> in the second snip... I get immense compiler errors, so I'm not sure where I messed up. What am I doing wrong?

3 8

shared_ptr swap problems
by Olaf Petzold 27 Aug '02

27 Aug '02

Hello, I've trouble with the follwong snippet: #include <iostream> #include <boost/shared_ptr.hpp> struct A { A(const char* n) : name(n) { } const char* name; }; struct B : public A { B(const char* n) : A(n) { std::cout << "construct " << name << std::endl; } ~B() { std::cout << "destruct " << name << std::endl; } }; struct BaseC { virtual void set(const boost::shared_ptr<A>& ptr) = 0; }; struct C : public BaseC { C() : b( new B("C::b") ) { } void set(const boost::shared_ptr<A>& ptr) { b.swap( boost::shared_static_cast<B>( ptr ) ); // L21 } void print() { std::cout << b->name << std::endl; } boost::shared_ptr<B> b; }; using namespace std; int main() { boost::shared_ptr<A> b( new B("b") ); C c; c.print(); c.set( b ); c.print(); } t.cc: In member function `virtual void C::set(const boost::shared_ptr<A>&)': t.cc:21: no matching function for call to `boost::shared_ptr<B>::swap(boost::shared_ptr<B>)' /usr/include/boost/shared_ptr.hpp:234: candidates are: void boost::shared_ptr<T>::swap(boost::shared_ptr<T>&) [with T = B] I did try boost::shared_polymorphic_cast to get a std::bad_cast exception - but it doesn't compile too. How can get it working? Thanks Olaf

3 7