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asio::deadline_timer::expires_at problem when system time changes
by Jeff Gray 09 Dec '08

09 Dec '08

My application is running on an embedded system that has no battery backed up real time clock. So when it starts, it's always 1-1-1970. The first time a client app connects, it synchronizes the time, so the system time will change to 2008. This has drastic consequences on this sort of action: void MyClass::TimerCallback(void) { // do important periodic activity here... myTimer->expires_at(myTimer->expires_at()+ boost::posix_time::milliseconds(100)); myTimer->async_wait(boost::bind(&MyClass::TimerCallback, this)); } Since the expires_at() values is absolute time, it still thinks it's 1970, moving forward 100mS at a time. This causes the timer to expire immediately, and my CPU load goes to 100% as it gets stuck in this repetition. This is not a bug on the part of deadline_timer - it's doing exactly what I told it to. The question is how should I change the code to cope with time changes. I see several options: 1) The API call to set the time on my embedded device is within my application, so I know when an outside party has changed the time. I could send a boost::signal to the rest of the application & wrote code in each module that has a deadline timer used in this way that resets the timer. 2) Before setting a new expires_at value, I could calculate the time period between now() and expires_at(). If it is more than double the periodic delay, then I use expires_from_now() to resync with the new absolute time. 3) I could calculate the periodic time based on absolute time: now() - (now() % milliseconds(100)) + milliseconds(100) This means it would always be aligned with the most recent 100mS time. 4) Only use expires_from_now(). This is the simplest solution, but there are parts of my application where it is preferable to have more accurate timer period. These approaches all have advantages and drawbacks. Does anyone have any comments or experience with this issue? Thanks, Jeff

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Re: [Boost-users] [boost] [review][constrained_value] Review of ConstrainedValueLibrary begins today
by Jesse Perla 09 Dec '08

09 Dec '08

I wasn't sure if anyone was allowed to review, but if so, then all of my questions have been answered: Library Review: > > - What is your evaluation of the design? I can't comment on it as a generic library designer, but as a library user it appears to be an excellent framework. However, the use cases for bounds checking of variables are much more thought through than the more interesting mathematics/set theory and numerics use cases. I think the library seems to be close to supporting these use cases but needs to explicitly address: 1) Floating Points: Enough has been said about this, but it needs to be resolved before the library is completed. Otherwise, all mathematics/numerics use cases are impossible. As a pragmatist about this issue, I would say that a worst case "solution" is to write caveats in the "rationale" section about this problem when using this library. This library is useful for querying bounds on a type, even if it doesn't do any bounds checking. 2) Dynamic Bounded Types: Right now the static bounds are associated globally with a type, and the dynamic bounds are associated with an instance of a type. Since many use cases involve setting dynamic sets and then creating instances, it is crucial that this type of set is implemented. See Robert's rough notes in: http://lists.boost.org/boost-users/2008/12/42959.php 3) Representing Disjoint Sets: Because most of the use cases have been thinking about predicates and bounds checking, the key use cases of unions of bounds has not been addressed. In most of the discussions, people talk about layering constraints on top of each other, which is an intersection. This library needs to also have ways to easily create sets like: (-infinity, 0] union [1,2] union [3,infinity) This would be a union of constraints which could be set or accessed on the type (at runtime or compiletime), hopefully with simple iterators to access this type information. I think that thinking through closed/open/halfopen/etc. intervals as separate objects in themselves is critical, especially to layer this type of bound on. Perhaps it could be integrated with the interval template library in the sandbox for example. 4) Testing with Numerics: This library needs to be tested with key boost numeric packages such as ublas, boost math, accumulators, etc. The key here will also be to verify that it compiles with the static and dynamic bounded types, the storage is identical to the underlying type, and the operations it generates are not any slower. Also that all of the elementary operators on intrinsic types in C++ work as normal for by value/ref/pointer, numeric_limits is thought through, etc. All of the former is performance/storage testing would be conditional on a good compiler of course (gnu and Intel seem to be the main ones to worry about) > - What is your evaluation of the implementation? For the existing constraint types, it looks good. > - What is your evaluation of the documentation? Good for the simple cases here and the bounds checking. Incomplete for the key math/numerics use cases which is where this would be at its best. And the floating point section would need to be rewritten after it is "solved". > - What is your evaluation of the potential usefulness of the library? Extraordinarily useful for generic mathematics/numerics. Even without any bounds checking, managing subsets of intrinsic types with runtime bounds information has a huge value. And having domains/ranges associated with functions would save a huge number of bugs in numeric processing, as well as make the translation from blackboard to program much more elegant. This could be a cornerstone of allowing for safe implementations of mathematical models in disciplines such as economics. For example, an optimizer operating on bounded values could create a grid from just the passed in type, validate if a solution is converging to an open set bound, etc. And higher order functors such as derivatives could generate domain/range information for the functions they are operating on dynamically. > - Did you try to use the library? With what compiler? Did you have any > problems? No. It doesn't yet have the main constraint type I am interested in. > - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? I had previously been writing notes on a library to manage domain/range information for functors that this becomes a superset of, so I have thought through a large number of those use cases. A great deal of time was spent trying to see how this library could fit the use cases I am interested in. > - Are you knowledgeable about the problem domain? > For generic library design: little knowledge. For the bounds-checking, value monitoring use cases: little knowledge. For the mathematics/numerics use cases: A good deal of knowledge as I am working through many of these issues in projects/research and trying to build out domain specific libraries to make future research easier.. > Please state in your review, whether you think the library should be > accepted as a Boost library. Yes, conditional on solving the 1) to 4) design questions above. Robert has posted excellent starting points for many of these topics.

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[random]how to initialise a rng for use in the initialiser list?
by Moritz Beber 09 Dec '08

09 Dec '08

Hello again, sorry for the many questions to this list right now, I'm just beginning to use boost. This time I have some issues regarding the boost.random usage. I have used it just fine for many examples but there's one tricky bit that I was wondering whether anyone of you knows a solution for. I use a class which keeps the random number generator around as a member variable; this class also has a const matrix. Now in the constructor of the class I do something like: my_class::my_class(args) : rng(seed), matrix(initialise()), ... { ... } Of course, I want to use the rng to initialise the matrix and that's where things fail. I guess, I could use a different rng just to fill the matrix, or make it non-const and fill it in the constructor body. But does anyone know a neat trick to do this in the way proposed? Thank you for any answers, Moritz

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boost asio async_read_som
by Chris Freehill 08 Dec '08

08 Dec '08

Never mind... I finally realized io_service.run() exits if there is no work to do. I was misunderstood and thought it stayed running. Thanks, Chris -- =======================

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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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