July 2014 - Boost-users - lists.preview.boost.org

[boost][sync?] "Distributed" value (or something...)
by Klaim - Joël Lamotte 31 Jul '14

31 Jul '14

I would like to ask Boost developers and users: 1. Am I the only one seeing the following pattern in my concurrent systems code? 2. Is there already some tools available in Boost that does what I describe here and that I am not aware of? 3. If not, would there be any interest in the tool I'm describing here or not? Is it a dumb idea? (I keep getting back to this idea but I'm surprised not finding anything similar online) The pattern that I am seeing occurs when: 1. I have a value or a set of values in an object or several objects which value(s) describe some kind of configuration that several other systems will read and use. 2. The object(s) will be updated only by one thread (at a time). 3. When the object's value is modified, all the systems that rely on the object's value have to be notified so that they update themselves using that value. 4. The systems I am refering to can use different threads for updating and we can assume that they are running concurrently. 5. It is not important that the source object's value is synched with the reader's values at all time, however it is important that the sequence of changes to the source object's value is signaled to the readers exactly in the same order and "as fast as possible", but delay is ok. The simplest solution to solve this is to have a mutex locking the value and the systems checking the value regularly. (that is, using syncrhonized_value for example) However the locking and looping reads might not be necessary if it is done in another way (if I am correct, I still lack experience in the domain). The solution that I am thinking about would look like this. ///////// // The object containing the value used by the other systems. class System_A { distributed_source<int> m_foo_count; // changes to this object will be sent to "readers"... public: System_A() : m_foo_count(42) ... {} //... // thread-safe read-only access distributed_value<int> make_foo_count_reader() const { return distributed_value<int>{ m_foo_count }; } }; ///////// // The different systems acquire a read access to the value. class System_B { distributed_value<int> foo_count; // read-only value reflecting System_A::m_foo_count's value since last update. public: SystemB( const System_A& system_a, ... ) : m_foo_count( system_a.make_foo_count_reader() ) { // setup the initial config... on_foo_count_changed( *m_foo_count ); // trigger some processing when SystemA::foo_count's value have been changed: m_foo_count.on_changed( [this]( int new_value ){ // called after the value have been changed m_work_queue.push( [=]{ // will be executed on the next update cycle for this system... on_foo_count_changed( new_value ); / }); }); } //... private: void update_cycle( const UpdateInfo& info ) { // ... // the following is just to clarify: const int foo_before = *m_foo_count; // the value is not updated yet, but we can still use it m_work_queue.execute(); const int foo_after = *m_foo_count; // the value might have been udpated if( foo_before != foo_after ) { // the value have been updated (though you don't need to do this if you used the callback instead). } //... }; }; //////// // At some point the value is changed by the system owning the source object... System_A::change_foo( int new_value ) { m_work_queue.push( [=]{ // will be executed on the next update cycle of this system... // ... *m_foo_count = new_value; // assign the new value then send the new value to the readers... }); } System_A::something_complex( std::function<void(int&)> some_work ) { m_work_queue.push( [=]{ // ... m_foo_count.update( some_work ); // execute on the current value then send the resulting value to the readers }); } Some notes: a. The names are just invented while I write this email. b. I suppose that the distributed_source might have an interface similar to synchronized_value, anyway I didn't get farther than this idea. c. I see several different ways to implement this idea, some might be more efficient than others but I didn't do any tests yet (by lack of time). Thoughts?

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Re: [Boost-users] [MSM] how to use a compilation firewall around inner state machines
by Mark.Bartosik＠thomsonreuters.com 31 Jul '14

31 Jul '14

Repost from different email client (prior ate linefeeds, sorry again). I have a state machine implemented with MSM (eUML) that currently has 80 transitions, there are two inner state machines. Compilation time is not great, but I have been dealing with it by BOOST_MSM_FAVOR_COMPILE_TIME and using parallel compilation where possible. Slow compilation time is an irritation and productivity killer, but my larger worry is that eventually the compiler will run out of memory. Especially as I will likely have to add another inner state machine with about 40 more transitions. Current we are using VS2008 but planning on moving everyone in the team to the VS2012 toolset but running under the VS2013 environment. I don't know if this will help, I doubt it. Currently compilation memory usage is up to 2.5GB per translation unit. So I would like to use a compilation firewall around the inner state machines. My plan is to implement concrete types for the inner state machines, with a process_event function: boost::msm::back::HandledEnum process_event( const boost::any & event ); Then within this function test for each event type to be handled by the inner state machine, and forward to a regular MSM state machine contained within the inner concrete type. I am hoping that this, plus on_entry and on_exit functions is about all I need to do. I expect that I will be able to get this to work, although an example on how to put a concrete wrapper around an inner state machine would be great, and importantly a list of limitations and work arounds for this technique would be helpful. My problem is that the outer state machine transition table has rows like this: exit_pt_( inner_state, inner_state_some_pseudo_exit_state ) / do_some_stuff() == outer_s2, exit_pt_( inner_state, inner_state_other_pseudo_exit_state ) / do_other_stuff() == outer_s3, If inner_state becomes a concrete type, then I don't know if this can be handled, and if so how? My best idea so far is for the inner_state to call process_event on the outer state machine and rewrite the outer machine's state transition table thus: inner_state + some_synthetic_event / do_some_stuff() == outer_s2, inner_state + other_synthetic_event / do_other_stuff() == outer_s3 The xxxx_synthetic_event's would be generated from within the inner state machine when it reaches one of the pseudo exit states. So in summary I would like to know: 1) Is there a documented example of putting a concrete wrapper around a inner state machine. 2) What is the list of limitations of doing this. e.g. exit_pt_ not working. 3) How should I deal with transitions in the outer state machine that were making use of exit_pt_ P.S. I've got to say that I think MSM is great! thanks - - Mark

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Re: [Boost-users] [serialization] Please help me solve this compile error.
by Brian Wood 30 Jul '14

30 Jul '14

Bjorn Reese writes: On 07/30/2014 04:01 AM, Paul Blampspied wrote: >> boost::archive::binary_ oarchive oa(file); >> oa << PersistentManagedArray<int>(size, capacity, ints); //This line does not compile ! > > The stream operator in Boost.Serialization does not take temporary > objects, so create the PersistentManagedArray<T> object on a separate > line, and then pass it to the stream. The C++ Middleware Writer <http://webEbenezer.net> supports temporary objects. Here's an example: front_messages_middle::Marshal(sendbuf, cmw::marshalling_integer(::strtol(argv[1],0,10))); It doesn't support PersistentManagedArray, but I'm willing to consider adding support for that. More info here - http://webEbenezer.net/about.html -- Brian Ebenezer Enterprises http://webEbenezer.net

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[MSM] how to use a compilation firewall around inner state machines
by Mark Bartosik 30 Jul '14

30 Jul '14

I have a state machine implemented with MSM (eUML) that currently has 80 transitions, there are two inner state machines. Compilation time is not great, but I have been dealing with it by BOOST_MSM_FAVOR_COMPILE_TIME and using parallel compilation where possible. Slow compilation time is an irritation and productivity killer, but my larger worry is that eventually the compiler will run out of memory. Especially as I will likely have to add another inner state machine with about 40 more transitions. Current we are using VS2008 but planning on moving everyone in the team to the VS2012 toolset but running under the VS2013 environment. I don't know if this will help, I doubt it. Currently compilation memory usage is up to 2.5GB per translation unit. So I would like to use a compilation firewall around the inner state machines. My plan is to implement concrete types for the inner state machines, with a process_event function: boost::msm::back::HandledEnum process_event( const boost::any & event ); Then within this function test for each event type to be handled by the inner state machine, and forward to a regular MSM state machine contained within the inner concrete type. I am hoping that this, plus on_entry and on_exit functions is about all I need to do. I expect that I will be able to get this to work, although an example on how to put a concrete wrapper around an inner state machine would be great, and importantly a list of limitations and work arounds for this technique would be helpful. My problem is that the outer state machine transition table has rows like this: exit_pt_( inner_state, inner_state_some_pseudo_exit_state ) / do_some_stuff() == outer_s2, exit_pt_( inner_state, inner_state_other_pseudo_exit_state ) / do_other_stuff() == outer_s3, If inner_state becomes a concrete type, then I don't know if this can be handled, and if so how? My best idea so far is for the inner_state to call process_event on the outer state machine and rewrite the outer machine's state transition table thus: inner_state + some_synthetic_event / do_some_stuff() == outer_s2, inner_state + other_synthetic_event / do_other_stuff() == outer_s3 The xxxx_synthetic_event's would be generated from within the inner state machine when it reaches one of the pseudo exit states. So in summary I would like to know: 1) Is there a documented example of putting a concrete wrapper around a inner state machine. 2) What is the list of limitations of doing this. e.g. exit_pt_ not working. 3) How should I deal with transitions in the outer state machine that were making use of exit_pt_ P.S. I've got to say that I think MSM is great! thanks - - Mark

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equivalent of java.util.properties
by David Frank 30 Jul '14

30 Jul '14

I'm wondering if there is a boost equivalent of the java.util.properties package which can read java properties file. Thanks, Dave.

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revisiting casting a boost::shared_ptr to void*
by Chris Cleeland 30 Jul '14

30 Jul '14

I'm resurrecting this topic: https://groups.google.com/forum/#!searchin/boost-list/shared_ptr$20void*/bo… because there is an unaddressed issue in it that I'm about to run into: "... beware the pointee may be deleted if the last copy of the shared pointer goes out of scope, as the raw pointer won't have incremented the reference count." I cannot be the first person to run into this--a common issue when crossing an API boundary. Has anyone come up with a good, safe solution wherein the reference count gets properly incremented? -- Chris Cleeland

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[Graph] Large Graphs: performace boost
by Sensei 30 Jul '14

30 Jul '14

Dear all, Facing an increasing size in my experiments, I am wondering now if my data structure is still valid. I need to traverse a graph (with my custom A*) that now can easily contain 10M-100M nodes and 100M-400M edges. The graph is (now) without weights, but this may change in the future. The only thing that is guaranteed not to change is that the graph is immutable. The graphs might even be larger, and at some point I will move to parallel BGL, but not now. To spare some memory, I am using a CSR graph: typedef boost::compressed_sparse_row_graph<boost::bidirectionalS> boost_graph; graph_ = new boost_graph(boost::edges_are_unsorted_multi_pass, results.begin(), results.end(), nodelist().size()); I am dubious if this the best solution. I have two objectives right now, optimize with respect to 1) memory consumption, and 2) graph traversal time. The main operation I need to do on graph is just "given a node, find the adjacent ones" (with my A*). Do you suggest to switch to another graph data structure? How do you think I will sacrifice time for memory, and vice versa, if I move for instance to an adjacency list? Thanks for any suggestion!

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Boost Based Proxy
by asim 29 Jul '14

29 Jul '14

In SSl case proxy will become a tunnel so whatever encrypted data i will get from client i have to forward it to server.But i am unable to read content as connection is keep alive (means no end of file exception) and due to encryption no header based reading i can do then how to read it. -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-Based-Proxy-tp4665704.html Sent from the Boost - Users mailing list archive at Nabble.com.

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[Serialization] XML: Necessity of attribute class_id although class_name is given
by Frank Stähr 29 Jul '14

29 Jul '14

Hello everybody, I would like to know what the purpose of the xml attribute class_id is, how it works and in which cases it can be omitted. An example: “Base” is the (abstract) base class of _GMTF_ and _TTF_, and _Hist_ also has got a similar base class. If a pointer of Hist is a member of GMTF and you want to serialize a pointer of Base, you get something like: <filter class_id="0" class_name="GMTF"> <m_bufHalfMaxSize>4</m_bufHalfMaxSize> <m_cutDetector class_id="1" class_name="Hist"></m_cutDetector> </filter> Here, the macros • BOOST_CLASS_EXPORT_GUID(...), • BOOST_CLASS_IMPLEMENTATION(..., boost::serialization::object_serializable) and • BOOST_CLASS_TRACKING(..., boost::serialization::track_never) are used. The problem now is: Although the exact classes are given by human-readable class names (and used!), you cannot omit or change the class_id. If you edit the XML file by hand, it can become invalid (-> exception on reading). It seems that the class ids are just ascending non-negative numbers. What are the rules for choosing the class ids? Why are they necessary? Is there a trick to remove this attribute or at least to ignore it? Thanks, Frank -- Frank Stähr Technische Universität Berlin Communication Systems Group Sekr. EN1 Einsteinufer 17 10587 Berlin, Germany

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Pipe and Filters pattern with boost?
by Journeyer J. Joh 29 Jul '14

29 Jul '14

Hello list! I'd like to find a good approach to implement the Pipe and Filters pattern with boost. Could someone recommend me some useful boost library for this purpose? I only know asio. Is there any known example source code for this - Pipe and Filters pattern with boost. Thank you very much in advance! ---------------------------------------- Journeyer J. Joh o o s a p r o g r a m m e r a t g m a i l d o t c o m ----------------------------------------

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