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logfile write/poll mechanism
by Thijs Koerselman 08 Dec '08

08 Dec '08

Hi, This might not be a Boost question. I'm not sure. I have 2 independent applications. One is writing information to a log file somewhere, the other contains a console window. What I would like to do is poll the log file from the application with the console window, and write any new lines (since last poll) to the window. It's seems like a fairly trivial thing to implement, but I don't have a lot of experience dealing with files, and I suspect there are already facilities to do such a thing. Can someone please point me in the right direction? Cheers, Thijs

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Re: [Boost-users] boost asio async_read_some
by Chris Freehill 08 Dec '08

08 Dec '08

Igor, Thanks for the response. I've been out for a few days, so I haven't been able to reply. Here is a self-contained example that illustrates the problem. This example creates a echo server thread that should echo back to the caller anything the caller sends to the thread. (Note that I have a windows Sleep() in there.) The server thread appears to do what I expect. The client thread works until the call to async_read_some(). The call returns, but I never hit the breakpoint I set in my handler, nor do I see any output from the handler. Igor, or anyone, please have a look... Thanks, Chris =============================================START================================================== #include <string> #include <boost/asio.hpp> #include <boost/bind.hpp> #include <boost/smart_ptr.hpp> #include <boost/thread.hpp> const static unsigned int cMaxLength = 512; static const std::string cStopEchoCommand("STOP_ECHO"); static boost::asio::io_service ioService; //needs to have the same life span as socket, or longer static boost::asio::ip::tcp::resolver lResolver(ioService); //------------------------------------------------------------------------------------------------- static int doConnect(std::string& ipAddress, std::string& portNumber, boost::shared_ptr<boost::asio::ip::tcp::socket>& inOutSocket) { using boost::asio::ip::tcp; try { tcp::resolver::query query(tcp::v4(), ipAddress.c_str(), portNumber.c_str()); tcp::resolver::iterator endpoint_iterator = lResolver.resolve(query); tcp::resolver::iterator end; if (inOutSocket == NULL) { boost::shared_ptr<tcp::socket> tmpSocketPtr(new tcp::socket(ioService)); inOutSocket = tmpSocketPtr; } boost::system::error_code error = boost::asio::error::host_not_found; while (error && endpoint_iterator != end) { inOutSocket->close(); inOutSocket->connect(*endpoint_iterator++, error); } if (error) { return -1; } } catch(...) { return -1; } return 0; } //Server routine static void session(unsigned int port) { using boost::asio::ip::tcp; boost::asio::io_service io_service; tcp::acceptor a(io_service, tcp::endpoint(tcp::v4(), port)); tcp::socket sock(io_service); try { bool done = false; a.accept(sock); for (;;) { char data[cMaxLength]; boost::system::error_code error; size_t length = sock.read_some(boost::asio::buffer(data, cMaxLength), error); if (error == boost::asio::error::eof) { // done, stop echoing, wait for another connection break; } else if (error) { std::cerr << "Error while receiving: " << boost::system::system_error(error).what() << "\n"; // TODO report failure break; // closing. } else if (length == cStopEchoCommand.length()) { //See if it's time to end if (cStopEchoCommand.compare(0, cStopEchoCommand.length(), data)) { break; } } else { //boost::asio::write(sock, boost::asio::buffer(data, length)); int bytesWritten = sock.write_some(boost::asio::buffer(data, length)); if (bytesWritten == 0) { std::cerr << "Error while writing to socket: " << boost::system::system_error(error).what() << "\n"; } } } } catch (std::exception& e) { // TODO report failure std::cerr << "Exception in thread: " << e.what() << "\n"; } } class TestClass { public: TestClass(std::string ipAddress, std::string port):mIPAddress(ipAddress), mPort(port) {} void PollReadhandler(const boost::system::error_code& error, size_t bytes_transferred) { mDataReadFromPoll = true; boost::system::error_code e; std::cout << "DELETE ME; PollReadhandler called()" << "\n"; } void testTCPIP() { using boost::asio::ip::tcp; // Start an separate thread which echoes all trafic to the port. std::istringstream i(mPort); unsigned int port; i >> port; mDataReadFromPoll = false; boost::thread echoTcpServer(boost::bind(session, port)); boost::shared_ptr<tcp::socket> socketPtr; int ret = doConnect(mIPAddress, mPort, socketPtr); if (ret) { std::cerr << "Failed to get connection" << std::endl; return; } //------------------------------------------------------------------------------------------------- // test sync. read char buffer[512]; unsigned int bytesRead; std::string test1Str("Test 1"); std::size_t len = socketPtr->write_some(boost::asio::buffer(test1Str.c_str(), test1Str.length())); Sleep(1000); //Windows try { int readError = 0; std::vector<unsigned char> readVectorBuffer(32); //unsigned char readVectorBuffer[512]; boost::system::error_code e; //unsigned int amtRead = socketPtr->read_some(boost::asio::buffer(readVectorBuffer, 512), e); unsigned int amtRead = socketPtr->read_some(boost::asio::buffer(readVectorBuffer, 32), e); if (amtRead != test1Str.length()) { std::cerr << "read_some read an unexpected number of bytes" << std::endl; return; } std::string s(readVectorBuffer.begin(),readVectorBuffer.end()); std::cout << "read_some returned:" << s << std::endl; } catch (...) { std::cerr << "Problem with read_some" << std::endl; } //------------------------------------------------------------------------------------------------- // test async. read std::string test2Str("Test 2"); len = socketPtr->write_some(boost::asio::buffer(test2Str.c_str(), test2Str.length())); Sleep(1000); //Poll while (!mDataReadFromPoll) { socketPtr->async_read_some(boost::asio::buffer(buffer, 512), boost::bind(&TestClass::PollReadhandler, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); Sleep(1000); } //NEVER REACHES HERE mDataReadFromPoll = false; len = socketPtr->write_some(boost::asio::buffer(cStopEchoCommand.c_str(), cStopEchoCommand.length())); // Wait until the server thread is finished. echoTcpServer.join(); } //------------------------------------------------------------------------------------------------- private: std::string mIPAddress; std::string mPort; bool mDataReadFromPoll; }; int main() { TestClass testCase("127.0.0.1", "2222"); testCase.testTCPIP(); } =============================================END==================================================== ---------- Forwarded message ---------- From: "Igor R" <boost.li...(a)gmail.com> Date: Dec 4, 1:44 am Subject: boost asio async_read_some To: BOOST Archives _______________________________________________ Boost-users mailing list Boost-us...@lists.boost.orghttp://lists.boost.org/mailman/listinfo.cgi/boost-users > Here's a simplified version of my call and handler: > unsigned char tmpBuffer[512]; //global > void MyClass::handler(const boost::system::error_code& error, size_t > bytes_transferred) > { > boost::system::error_code e; > std::cerr << "handler called()" << "\n"; > } > void MyClass::test() > { > ... > socketPtr->async_read_some(boost::asio::buffer(tmpBuffer, 512), > boost::bind(&MyClass::handler, this, > boost::asio::placeholders::error, > boost::asio::placeholders::bytes_transferred)); > } > Can anyone give me any idea as to how I can get my handler to be called? Could you please provide some code-excerpt that should compile and work? I.e. code that contains socket initialization, io_service run and your object creation - because the mistake is probably somewhere at those points. > Invocation of the handler will be performed in a > manner equivalent to using boost::asio::io_service::post()." I'm not > sure exactly what this means...what is this equivalent manner that is > mentioned? It means that the handler would be invoked in one of the threads that run the io_service object used by the socked.- Hide quoted text - - Show quoted text -

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Solving sets of interval valued nonlinear equations with Boost Interval?
by Peter H. Hodges 08 Dec '08

08 Dec '08

Does anyone have an example of solving sets of nonlinear interval valued equations using the Boost Interval library functions? Peter Hodges

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boost on windows cmd prompt
by praveen Buddhi 08 Dec '08

08 Dec '08

Hi, I am trying to use boost for my application and builds using command prompt on windows. I am using VC8.0 1) when I invoke build for the my code..i see the following error messages. Any clue?? "Unknown compiler version - please run the configure tests and report the results D:\boost\boost_1_34_1\boost/type_traits/is_integral.hpp(60) : error C2039: 'ulong_long_type' : is not a member of 'boost' D:\boost\boost_1_34_1\boost/type_traits/is_integral.hpp(60) : error C2065: 'ulong_long_type' : undeclared identifier D:\boost\boost_1_34_1\boost/type_traits/is_integral.hpp(60) : error C2913: explicit specialization; 'boost::is_integral' is not a specialization of a class template D:\boost\boost_1_34_1\boost/type_traits/is_integral.hpp(60) : error C2913: explicit specialization; 'boost::is_integral' is not a specialization of a class template D:\boost\boost_1_34_1\boost/type_traits/is_integral.hpp(60) : error C2913: explicit specialization; 'boost::is_integral' is not a specialization of a class template" 2) how to run $BOOST_ROOT/libs/configure on windows command prompt ?? appreciate any help. regards, praveen

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Subject::[boost thread] does a thread block itself when it passes the conditional variable to another thread?
by Lei (oddo) Zhang 08 Dec '08

08 Dec '08

inside a thread, if the conditional variable is changed to satisfy another thread which is on the waiting thread list. Does the current thread give up the global mutex and blocks itself until another thread gives up the mutex? boost::mutex mutex; boost::condition cond; bool data_ready=false; : void thread1(){ boost::mutex::scoped_lock lock(mutex); ...//do some work data_ready=true; cond.notify_one() //assume the condition is satisfied. //do more work -------my question is will this part continue? or thread2 will wake up and block thread 1? } void thread2(){ boost::mutex::scoped_lock lock(mutex); while ( !data_ready) { cond.wait(lock); } ....//do work } -- Lei(Oddo) Zhang 70 Symonds Street Engineering Science Department

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[Graph] call of overloaded 'target(...)' is ambiguous
by Tim Keitt 08 Dec '08

08 Dec '08

I've hit the wall with the Graph library. I cannot seem to resolve the error shown below. This is probably my rather limited experience with complicated template parameters. What is the first thing to try with these sorts of errors? My graph classes do not define source and target, but rely on the template provided in the Graph library. I've tried adding them explicitly to the class without success. The 'target' template is defined as: template <typename G> typename filtered_graph_base<G>::vertex_descriptor target(typename filtered_graph_base<G>::edge_descriptor e, const filtered_graph_base<G>& g) { return target(e, g.m_g); } The ambiguous call to 'target' occurs here: template <class PredEdgeMap, class Tag> struct edge_predecessor_recorder : public base_visitor<edge_predecessor_recorder<PredEdgeMap, Tag> > { typedef Tag event_filter; edge_predecessor_recorder(PredEdgeMap pa) : m_predecessor(pa) { } template <class Edge, class Graph> void operator()(Edge e, const Graph& g) { put(m_predecessor, target(e, g), e); } PredEdgeMap m_predecessor; }; Notice that the 'target' template takes one parameter ('G') and the 'operator()' template takes two parameters ('Edge' and 'Graph'). Notice also below the occurrence of both 'G' and 'Graph' in the 'candidates are' section. Might this be fixed as: template <class Graph> void operator()(typename Graph::edge_descriptor e, const Graph& g) { put(m_predecessor, target(e, g), e); } ??? THK /usr/include/boost/graph/edmunds_karp_max_flow.hpp:232: instantiated from 'typename boost::detail::edge_capacity_value<Graph, P, T, R>::type boost::edmunds_karp_max_flow(Graph&, typename boost::graph_traits<G>::vertex_descriptor, typename boost::graph_traits<G>::vertex_descriptor, const boost::bgl_named_params<P, T, R>&) [with Graph = FlowCapacitySQLDiGraph, P = edge_index_property_map<FlowCapacitySQLDiGraph, double>, T = boost::edge_residual_capacity_t, R = boost::no_property]' postgraph.cpp:1092: instantiated from here /usr/include/boost/graph/visitors.hpp:176: error: call of overloaded 'target(FlowCapacitySQLDiGraph::edge_descriptor&, const boost::filtered_graph<FlowCapacitySQLDiGraph, boost::is_residual_edge<edge_index_property_map<FlowCapacitySQLDiGraph, double> >, boost::keep_all>&)' is ambiguous /usr/include/boost/graph/filtered_graph.hpp:322: note: candidates are: typename boost::filtered_graph_base<G>::vertex_descriptor boost::target(typename boost::filtered_graph_base<G>::edge_descriptor, const boost::filtered_graph_base<Graph>&) [with G = FlowCapacitySQLDiGraph] /usr/include/boost/graph/graph_traits.hpp:154: note: T std::target(std::pair<_ForwardIterator, _ForwardIterator>, const G&) [with T = unsigned int, G = boost::filtered_graph<FlowCapacitySQLDiGraph, boost::is_residual_edge<edge_index_property_map<FlowCapacitySQLDiGraph, double> >, boost::keep_all>] make: *** [postgraph.o] Error 1 -- Timothy H. Keitt http://www.keittlab.org/

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[Asio] Cannot receive a UDP multicast using receive_from
by David Laurie 08 Dec '08

08 Dec '08

Would like to say Hello to all as I've just joined the list today and am also a first time user of the boost libraries. I'm cutting my teeth on asio by trying to receive a UDP multicast message with the boost::asio::ip::udp::socket::receive_from function. I got it going using the windows calls but just cant seem to crack it with boost. My only suspicion is that im getting the wrong IP version in the endpoint, but would guess it has found it from the initialisation, but other than that im a bit stumped. Any suggestions to where I may be going wrong? Cheers David Heres the code: const boost::asio::ip::address listen_address = boost::asio::ip::address::from_string("192.168.1.1"); const boost::asio::ip::address multicast_address = boost::asio::ip::address::from_string("224.x.x.x"); //appropriate address used boost::asio::io_service io_service; boost::asio::ip::udp::socket socket_(io_service); boost::asio::ip::udp::endpoint sender_endpoint_; enum { max_length = 1024 }; char data_[max_length]; // Create the endpoint boost::asio::ip::udp::endpoint listen_endpoint( listen_address, multicast_port); // open the socket socket_.open(listen_endpoint.protocol()); // is this picking up v6 instead of v4? // Join the multicast group. socket_.set_option( boost::asio::ip::multicast::join_group(multicast_address)); // bind it socket_.bind(listen_endpoint); socket_.receive_from( boost::asio::buffer(data_, max_length), sender_endpoint_); This email has been scanned for all known viruses by the MessageLabs Email Security System. Systems Engineering & Assessment Ltd - Beckington Castle, 17 Castle Corner, Beckington, Frome, Somerset, BA11 6TA, UK is registered in England and Wales with the company number 2430846. The contents of this email (including any attachments) are confidential and may be legally privileged. If you are not the intended recipient of this email any disclosure, copying, distribution or use of its contents is strictly prohibited. You should notify the sender immediately and then delete it (including any attachments) from your system. Please help out the environment by only printing this e-mail if absolutely necessary - Thank You.

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Subject::[boost thread] when does the thread start?
by Lei (oddo) Zhang 08 Dec '08

08 Dec '08

When I create a thread object such as : boost::thread thrd1(boost::bind(&function)); does the thread start executing the function immediately? -- Lei(Oddo) Zhang 70 Symonds Street Engineering Science Department

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Build error: "duplicate initialization of gcc"
by Tim Martin 08 Dec '08

08 Dec '08

I downloaded boost 1.37.0, unzipped and ran $ ./configure $ make install It dies reliably with: ------------------ ./tools/jam/src/bin.linuxx86/bjam -sICU_PATH=/usr --user-config=user-config.jam --prefix=/home/timm --exec-prefix=/home/timm --libdir=/home/timm/lib --includedir=/home/timm/include install error: at /home/timm/downloads/boost_1_37_0/tools/build/v2/build/project.jam:846 error: duplicate initialization of gcc with the following parameters: error: version = 4.3.2 error: previous initialization at /home/timm/downloads/boost_1_37_0/tools/build/v2/build/project.jam:846 Not all Boost libraries built properly. ------------------- This is on a relatively unmodified Ubuntu Intrepid linux install. I could only find one other mention of this problem on the web and it was a mailing list post with no answer, so I'm apparently doing something quite unusually wrong. FWIW, the reason I'm building from source rather than using a package is that the Ubuntu packages don't seem to provide a binary lib for MPI - am I missing something here? They provide header files, so it seems eccentric not to provide a package with libs. Tim

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Re: [Boost-users] [boost] [review][constrained_value] Review of ConstrainedValueLibrary begins today
by jesseperla＠gmail.com 07 Dec '08

07 Dec '08

Robert: As a caveat and analogy: I want to use this to represent mathematics rather than just bounds-checking. The constrained value manages the subset within an underlying space (represented by the underlying type int, double, etc.). Then an instantiation of this is an element in this set. And my goal is to be able to take an instantiation/element and access information about the underlying set/type itself (eg managing bounds for optimizers, domain/range for functors, etc. from only an instance of the type passed in to a generic function). And if you use linear operators on elements of the subset, then it always returns members of the underlying space (which is mathematically correct. integers are a subset of reals which is a linear space with the +,-,/,* operators on it. Divide an integer by an integer and you get an element of the superset) More questions: 1) Storage the same as underlying type?::::::: > OK, now it makes a bit more sense. Moreover, I believe it is possible (though > maybe not trivial) to implement something similar with the current library. Cool. This would be necessary for me to use the library, so I hope it is possible to have dynamic bounds associated with the type. If this was completed, would the space/storage taken up by an instantiation of the bounded type be the same as the underlying type? In particular, I would be interested in having a vector of bounded double's have the same storage aa vector of bounded doubles (I would be using ublas for example) so that I could potentially pass on a pointer to a C function for some interoperability (I know... hacky but sometimes necessary for all the C scientific computing libraries out there). And for my numerical work, having an extra parameter or two stored for every value in a big matrix would eat up cache/memory too quickly for no value. If necessary to accommodate consistency of the storage with just the underlying type, perhaps the idea of a bounded value on an instantiation (like it is today for the runtime) vs. a bounded type (modifiable at runtime, but common to all instance) could have a different template... something like: typedef bounded_type<double, "INTEREST RATE"> interest_rate; interest_rate::change_bounds(.8, .99); 2) Casting for underlying numeric type?:::::::::: > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2199.html Thanks for educating me on this. I find the myvar.value() syntax to be a little rough since my functions would want to be able to use both bounded types and intrinsic types in the same function, but perhaps this could work with an explicit cast which seems reasonable considering the C++ limitation. For example, would something like the following work to ensure consistency in my own usage?: template<typname T> void myfunc1(T& t) { cout << std::max(0.0, static_cast<double>(t)); //Note a floating point here } void myfunc2(T& t) { cout << std::max(0, static_cast<int>(t)); //Note integer here. } typedef bounded_type<double, "INTEREST RATE"> interest_rate; interest_rate::change_bounds(.8, .99); interest_rate r = .95; myfunc1(r); //works since casting internal myfunc1(.75); //also works, may be a double to double cast... myfunc2(r); //Would this fail? myfunc2(1); //Should work Note on the last one that it is trying to call max with an integer... My question here is whether this would work? Does the constrained value only have a direct cast to its underlying type, or is there any way to have it cast to any types that the underlying type can cast to? I would guess not for the last case... and this may be where myvar.value() is absolutely necessary? If the casting to the underlying type always works, then I would suggest that the myvar.value() is not the right way to go about things. What we are talking about here really is a cast, like it or not. 3) Bounds including infinity?:::::::: When we are working with bounds, can we use the numeric infinities with both open and closed sets? I am thinking something like: typedef bounded_type<double, "Risk Aversion"> risk_aversion; risk_aversion::change_bounds(1, std::numeric_limits<double>::infinity()); //Might want open or closed depending on if function domain is reals or extended reals. 4) Numeric limits traits?:::::::::::: For numeric processing, we also need to have some association with the numeric limit traits. I realize that there is some kind of conceptual connection between some of the traits here and the bounds themselves, but for practical purposes, these traits are too useful to ignore. Conceptually I think of these traits as being information about how the data is stored, rather than bounds themselves. What would be really useful is if bounded<> and other types would generate traits on their own based on the underlying type... this way, we wouldn't have to create numeric_limits traits for the types ourselves (which is unreasonable for a library user). So what I am thinking of is; typedef bounded_type<double, "Risk Aversion"> risk_aversion; cout << numeric_limits<risk_aversion>::quiet_NaN(); where the numeric_limits<risk_aversion> subclasses directly from numeric_limits<double>..... I don't know enough about generic programming to know how or if this is possible, but this is necessary for generic numeric programming. 5) Testing set inclusion:::::::: While it is nice to have the bounds checking on the () operator, I would also want to be able to ask the type if a value is in the set. For example, in math: Let Y = integers Let X = positive integers y = -1 \in Y Is y \in X? In this: typedef bounded_type<int, "X"> X; X::change_bounds(0, std::numeric_limits<int>::infinity()); int y = -1; cout << X::element_of(y); //would return a boolean? what I really would love to say is is X::element_of() or element_of<X>(y) ? This is a non-failing operation, and would be used all over in my numeric code, especially with wrapping optimizers. 6) No debug only functionality please:::::::::::: On all of the conversations about turning off bounds checking on debug, I would definitely not want this to happen automatically. And a bounds checking failure should be an exception, not a non-recoverable error. I may want to use this with an optimizer that tries to put in values out of bounds, and I would want to catch it and display a message to the console that the optimization failed, then try with a different initial value. 7) Operations consistent with built in C++ numeric types::::::::::::::::::: You have successfully educated me on why you need to overload the ++, --, +, -, etc. operators yourself and can't just revert to the underlying type. But focusing entirely on intrinsic numeric types double, int, etc.: Will we have complete coverage of the operators that are defined for these types in C++? Will the compiler end up generating EXACTLY the same code if I do a whole bunch of read only operations on a bounded<double> vs. a double? And will the overloading of these operators work for cross-type operations (eg multiplying a constrained integer by a constrained double?)? If the answer is no on these, then we probably can't use this library for scientific processing. 8) Multi-bounds:::::::::::::::: In comments such as: http://lists.boost.org/Archives/boost/2008/12/145662.php I think this is getting away from what I would hope this library can achieve: Associating sets(in the mathematical sense) of allowed values with a C++ type. I see what the predicates are used for, but I wouldn't use them very often. So I don't think we can think of the multi-bounds here being orthogonal constraints, but rather being a set of disconnected intervals themselves. Why not orthogonal constraints as described in this link (which essentially means intersections of subsets)? Try to construct X = (-infinity, 0] union [1,2] union [3,infinity) with intersecting intervals.... I would love to have a list of disconnected intervals in the space of the underlying type that could be parsed through from the . I do not see this as primarily a predicate question. If this is done with iterators, it might be even more flexible. For example, say that you only wanted even numbers and wanted to list out the first 10 intervals of this set... it could return an iterator to a list of intervals. In this case, it wouldn't calculate all of the intervals at once, but when you stepped forward, it would give you the next valid interval (a single value in this case). Thanks, Jesse

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