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Undirected version of dijkstra shortest path on directed graph.
by Jupp Tscheak 04 Feb '13

04 Feb '13

Hello BGL specialists. Is it possible to use an undirected version of dijkstra shortest path function on an /adjacency_list/ which /Directed/ template parameter is set to bidirectional? Thanks in advance :)

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in IOS, thread_info object is being destructed before the thread finishes executing
by Andy Weinstein 04 Feb '13

04 Feb '13

Our project uses a few boost 1.48 libraries on several platforms, including Windows, Mac, Android, and IOS. We are able to consistently get the IOS version of the project to crash (nontrivially but reliably) when using IOS, and from our investigation we see that ~thread_data_base is being called on the thread's thread_info while its thread is still running. This seems to happen as a result of the smart pointer reaching a zero count, even though it is obviously still in scope in the thread_proxy function which creates it and runs the requested function in the thread. This seems to happen in various cases - the call stack is not identical between crashes, though there are a few variations which are common. Just to be clear - this often requires running code which is creating hundreds of threads, though there are never more than about 30 running simultaneously. I have "been lucky" and got it very very early in the run also, but that's rare. I created a version of the destructor which actually catches the code red-handed: in libs/thread/src/pthread/thread.cpp: thread_data_base::~thread_data_base() { boost::detail::thread_data_base* const thread_info=detail::get_current_thread_data(); void *void_thread_info = (void *) thread_info; void *void_this = (void *) this; // is somebody destructing the thread_data other than its own thread? // (remember that its own which should no longer point to it anyway, // because of the call to detail::set_current_thread_data(0) in thread_proxy) if (void_thread_info) { // == void_this) { __builtin_trap(); } } I should note that (as seen from the commented-out code) I had previously checked to see that void_thread_info == void_this because I was only checking for the case where the thread's current thread_info was killing itself. I have also seen cases where the value returned by get_current_thread_data is non-zero and different from "this", which is really weird. Also when I first wrote that version of the code, I wrote: if (((void*)thread_info) == ((void*)this)) and at run-time I got some very weird exception that said I something about a virtual function table or something like that - I don't remember. I decided that it was trying to call "==" for this object type and was unhappy with that, so I rewrote as above, putting the conversions to void * as separate lines of code. That in itself is quite suspicious to me. I am not one to run to rush to blame compilers, but... I should also note that when we did catch this happening the trap, we saw the destructor for ~shared_count appear twice consecutively on the stack in Xcode source. Very doubleweird. We tried to look at the disassembly, but couldn't make much out of it. Again - it looks like this is always a result of the shared_count which seems to be owned by the shared_ptr which owns the thread_info reaching zero too early. Help! Thanks, Andy Weinstein PS I cannot say for sure yet whether this problem occurs on the other platforms, though it looks like Windows is more solid that Mac. Android pretty solid also, though maybe in between Windows and Mac.

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Question regarding circular buffer usage
by Salivar.William 04 Feb '13

04 Feb '13

I am using the circular buffer container to hold up to 10000 std string objects. I am finding that once the buffer has reached max capacity, memory continues to be consumed as I push new strings in. Is there something I'm missing? I stepped into the boost code and it does make a copy of the string using the std string operator so I would think it handles the string copy properly. The size of the strings are variable but I would expect the memory usage to be fairly stable when the buffer is full but that is not the case. Here's basic usage Definition: boost::circular_buffer<std::string> m_message_buffer; Initialization: m_message_buffer.set_capacity (10000); Usage: void myClass::writeToBuffer (const char *message) { m_message_buffer.push_back (string (message)); } Boost code: void push_back(param_value_type item = value_type()) { if (full()) { if (empty()) return; replace(m_last, item); increment(m_last); m_first = m_last; } else { m_alloc.construct(m_last, item); increment(m_last); ++m_size; } } void replace(pointer pos, param_value_type item) { *pos = item; #if BOOST_CB_ENABLE_DEBUG invalidate_iterators(iterator(this, pos)); #endif }

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How to uninstall/reinstall boost by using ./b2 command?
by JIA Pei 04 Feb '13

04 Feb '13

Hi, all: I installed boost by using *./bootstrap.sh* *./b2 install --prefix=/usr* However, I missed two files,* patchlevel.h* and *bzlib.h*: So, afterwards, I have the following two packages installed: *libbz2-dev*and * libpython3.3-dev* . I would like to have a full boost_1_52_0 re-installed. But now, even if I have the files: *libbz2-dev: /usr/include/bzlib.h* *libpython3.3-dev: /usr/include/python3.3m/patchlevel.h* during the re-installation of boost, it still keeps reporting 2 errors: *fatal error: bzlib.h: No such file or directory* *fatal error: patchlevel.h: No such file or directory* So, any suggestions? Cheeers -- Pei JIA Email: jp4work(a)gmail.com cell: +1 604-362-5816 Welcome to Vision Open http://www.visionopen.com

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Re: [Boost-users] in IOS, thread_info object is being destructed before the thread finishes executing (Andy Weinstein)
by Andy Weinstein 04 Feb '13

04 Feb '13

I should note that the boost.sh from Pete Goodliffe (and modified by others) that is commonly used to compile boost for IOS has the following note in the header: : ${EXTRA_CPPFLAGS:="-DBOOST_AC_USE_PTHREADS -DBOOST_SP_USE_PTHREADS"} # The EXTRA_CPPFLAGS definition works around a thread race issue in # shared_ptr. I encountered this historically and have not verified that # the fix is no longer required. Without using the posix thread primitives # an invalid compare-and-swap ARM instruction (non-thread-safe) was used for the # shared_ptr use count causing nasty and subtle bugs. # # Should perhaps also consider/use instead: -BOOST_SP_USE_PTHREADS I use those flags, but to no avail. I also found that there is an alternate implementation inside boost for arm processors which seems also to directly address this issue: spinlock_gcc_arm.hpp The version included with boost 1.48 uses outdated arm assembly. I took the updated version from boost 1.52, but I'm having trouble compiling it. I get the following error: predicated instructions must be in IT block I found a reference to what looks to be a similar use of this instruction here: https://zeromq.jira.com/browse/LIBZMQ-414 I was able to use the same idea to get the 1.52 code to compile by modifying the code as follows (I inserted an appropriate IT instruction) __asm__ __volatile__( "ldrex %0, [%2]; \n" "cmp %0, %1; \n" "it ne; \n" "strexne %0, %1, [%2]; \n" BOOST_SP_ARM_BARRIER : "=&r"( r ): // outputs "r"( 1 ), "r"( &v_ ): // inputs "memory", "cc" ); But in any case, there are ifdefs in this file which look for the arm architecture, which is not defined that way in my environment. After I simply edited the file so that only ARM 7 code was left, the compiler complains about the definition of BOOST_SP_ARM_BARRIER: In file included from ./boost/smart_ptr/detail/spinlock.hpp:35: ./boost/smart_ptr/detail/spinlock_gcc_arm.hpp:39:13: error: instruction requires a CPU feature not currently enabled BOOST_SP_ARM_BARRIER : ^ ./boost/smart_ptr/detail/spinlock_gcc_arm.hpp:13:32: note: expanded from macro 'BOOST_SP_ARM_BARRIER' # define BOOST_SP_ARM_BARRIER "dmb" So that's where thing stand. I am hopefully awaiting your help…. Thanks! On Feb 4, 2013, at 3:38 PM, <boost-users-request(a)lists.boost.org<mailto:boost-users-request@lists.boost.org>> wrote: Send Boost-users mailing list submissions to boost-users(a)lists.boost.org<mailto:boost-users@lists.boost.org> To subscribe or unsubscribe via the World Wide Web, visit http://lists.boost.org/mailman/listinfo.cgi/boost-users or, via email, send a message with subject or body 'help' to boost-users-request(a)lists.boost.org You can reach the person managing the list at boost-users-owner(a)lists.boost.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Boost-users digest..." Today's Topics: 1. in IOS, thread_info object is being destructed before the thread finishes executing (Andy Weinstein) ---------------------------------------------------------------------- Message: 1 Date: Mon, 4 Feb 2013 12:38:29 +0000 From: Andy Weinstein <andyw(a)hyperlync.com> To: "Boost-users(a)lists.boost.org" <Boost-users(a)lists.boost.org> Cc: Moshe Rubin <moshe(a)hyperlync.com>, Ronnie Wulfsohn <roni(a)hyperlync.com> Subject: [Boost-users] in IOS, thread_info object is being destructed before the thread finishes executing Message-ID: <5D324B34-BE82-4B4C-89AD-ED8A0095129B(a)hyperlync.com> Content-Type: text/plain; charset="us-ascii" Our project uses a few boost 1.48 libraries on several platforms, including Windows, Mac, Android, and IOS. We are able to consistently get the IOS version of the project to crash (nontrivially but reliably) when using IOS, and from our investigation we see that ~thread_data_base is being called on the thread's thread_info while its thread is still running. This seems to happen as a result of the smart pointer reaching a zero count, even though it is obviously still in scope in the thread_proxy function which creates it and runs the requested function in the thread. This seems to happen in various cases - the call stack is not identical between crashes, though there are a few variations which are common. Just to be clear - this often requires running code which is creating hundreds of threads, though there are never more than about 30 running simultaneously. I have "been lucky" and got it very very early in the run also, but that's rare. I created a version of the destructor which actually catches the code red-handed: in libs/thread/src/pthread/thread.cpp: thread_data_base::~thread_data_base() { boost::detail::thread_data_base* const thread_info=detail::get_current_thread_data(); void *void_thread_info = (void *) thread_info; void *void_this = (void *) this; // is somebody destructing the thread_data other than its own thread? // (remember that its own which should no longer point to it anyway, // because of the call to detail::set_current_thread_data(0) in thread_proxy) if (void_thread_info) { // == void_this) { __builtin_trap(); } } I should note that (as seen from the commented-out code) I had previously checked to see that void_thread_info == void_this because I was only checking for the case where the thread's current thread_info was killing itself. I have also seen cases where the value returned by get_current_thread_data is non-zero and different from "this", which is really weird. Also when I first wrote that version of the code, I wrote: if (((void*)thread_info) == ((void*)this)) and at run-time I got some very weird exception that said I something about a virtual function table or something like that - I don't remember. I decided that it was trying to call "==" for this object type and was unhappy with that, so I rewrote as above, putting the conversions to void * as separate lines of code. That in itself is quite suspicious to me. I am not one to run to rush to blame compilers, but... I should also note that when we did catch this happening the trap, we saw the destructor for ~shared_count appear twice consecutively on the stack in Xcode source. Very doubleweird. We tried to look at the disassembly, but couldn't make much out of it. Again - it looks like this is always a result of the shared_count which seems to be owned by the shared_ptr which owns the thread_info reaching zero too early. Help! Thanks, Andy Weinstein PS I cannot say for sure yet whether this problem occurs on the other platforms, though it looks like Windows is more solid that Mac. Android pretty solid also, though maybe in between Windows and Mac.

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Re: [Boost-users] [Graph] "Weighted Bacon number" (depth from node) with dijkstra visitor
by Tasos 04 Feb '13

04 Feb '13

Yes, Im just blind, it was so simple. Thanks a lot for your help. Best, Tasos

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[Graph] "Weighted Bacon number" (depth from node) with dijkstra visitor
by The Maschine 04 Feb '13

04 Feb '13

Hi all, In order to find the depth of a source_node from other nodes in my graph, without weights, I use this simple example of the bacon BFS visitor via the tree_edge(). I also count the number of nodes from that source. //////// class bfs_vis : public boost::default_bfs_visitor { public: bfs_vis(unGraph::vertex_descriptor source, boost::shared_ptr< VertexStorage> storage) : s(source), cont(storage) { } template <typename Edge, typename Graph> void tree_edge(Edge e, const Graph& g) const { typename boost::graph_traits<Graph>::vertex_descriptor u = source(e, g), v = target(e, g); cont->depth_from->at(v) = cont->depth_from->at(u) + 1.0; } template <typename Edge, typename Graph> void discover_vertex(Edge e, Graph& g) { cont->node_count = cont->node_count + 1; } private: boost::shared_ptr<VertexStorage> cont; unGraph::vertex_descriptor s; }; //////// What would be an equivalent visitor for Dijkstra? Node count is ok but how do I calculate a "weighted bacon number" with dijkstra (boost::property<boost::edge_weight_t, float>)?? Thanks, Tasos

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Re: [Boost-users] Boost-users Digest, Vol 3349, Issue 1
by Torsten＠Robitzki.de 04 Feb '13

04 Feb '13

Hi Igor, Am 04.02.2013 um 14:15 schrieb boost-users-request(a)lists.boost.org: > Send Boost-users mailing list submit >> >> s.close(); // first time to cancel outstanding handlers >> s.close(); // a second time, later in the d'tor >> But what does 'Bad file descriptor' mean in this context? Is the underlying socket is somehow broken/corrupted? If so, there must be >> a bug in my code. If not, is it save to simply ignore the error? > > > It means that tcp::socket is closed (and the underlying native > descriptor is something like -1). do you think there is something wrong with closing the socket a second time? The documentation doesn't states any precondition. kind regards Torsten

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[function / bind] How to register callbacks using boost::function/bind?
by Olivier Tournaire 04 Feb '13

04 Feb '13

Hi all, I am trying to use a callback mechanism for logging in my app. I thus have a class with : class coordinates_converter { public: coordinates_converter(int id); ~coordinates_converter(); void register_error_callback (const boost::function<void(std::string message)> &callback ) { _error_callback = callback; } private: boost::function<void(std::string message)> _error_callback; } Now, if I want to register a log error callback in another object instance, how should I do this? Cannot find the right syntax ... void another_class::do() { acute_coordinates_converter* converter = new coordinates_converter(2154); converter->register_error_callback( boost::bind(&another_class::log_error, converter, _1) ); } where log_error is a Qt SIGNAL: signals: void log_error(const std::string& error); Hope you could help. Rehads, Olivier

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[asio] How to handle 'Bad file descriptor'
by Torsten＠Robitzki.de 03 Feb '13

03 Feb '13

Hello, I have problems to understand, what might causing a 'Bad file descriptor' exception to be thrown in my application. The exception is most likely thrown by a call to tcp::socket::close. From the logs I have, I'm quit certain, that the last function calls on a socket are: s.shutdown(tcp::socket::shutdown_receive); s.shutdown(tcp::socket::shutdown_send); s.close(); // first time to cancel outstanding handlers s.close(); // a second time, later in the d'tor I'm not sure, whether it's the first or the second call to close(), that causes the exception. But what does 'Bad file descriptor' mean in this context? Is the underlying socket is somehow broken/corrupted? If so, there must be a bug in my code. If not, is it save to simply ignore the error? The program is not single threaded, but there is only one boost::io_service object which is run by a single dedicated thread. Kind reagards Torsten P.S: if someone interested in the code: https://github.com/TorstenRobitzki/Sioux/blob/master/source/server/connecti…; it's open source

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