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BGL, swap or move graphs
by Paolo Bolzoni 03 Dec '15

03 Dec '15

Dear list, I am writing a program where I create a graph first and I want to put it inside another class instance (type T). The idea is to keep the two steps separated as possible. Normally, sure-fire way was using swap. Inside the class T you create a default object and swap it with the real one on initialization; this avoids needless copies and just construct a small object. Nowadays, it is also possible to use moveable objects to even avoid that object creation. This is nice and I (think I) understood it, but it is possible to do anything like this with boost graphs? Graphs don't model Assignable, so swap is not possible, and I could not find anything about being Moveable either. Is there really no way to accomplish a swap or a move? I just have to create the graph in the beginning, and keep a reference, or pointer, to it? Cheers, Paolo

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linker errors in vs2012 and boost 1.59...
by Barker, Theo 02 Dec '15

02 Dec '15

Shayne, It's not just VS2012. I'm seeing that exact behavior with VS2008. Theo Please be advised that this email may contain confidential information. If you are not the intended recipient, please notify us by email by replying to the sender and delete this message. The sender disclaims that the content of this email constitutes an offer to enter into, or the acceptance of, any agreement; provided that the foregoing does not invalidate the binding effect of any digital or other electronic reproduction of a manual signature that is included in any attachment.

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[Boost.Container] Need map supporting incomplete type and heterogeneous lookup
by dariomt＠gmail.com 30 Nov '15

30 Nov '15

Hi, I see that boost::container::map has support for incomplete types. However, it does not seem to support heterogeneous lookup. Is this correct? Are there plans to implement it? Is there anywhere in Boost a std::map-like associative container that supports incomplete types *and* heterogeneous lookup? Thanks!

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[statechart]
by Ernesto Rodriguez Reina 30 Nov '15

30 Nov '15

Hi everyone, The statechart search for an event handler in post-order (children first then parent), however when we have orthogonal states involved then the behaviour I am experiencing is different. Let say we have an state X with two children [orthogonal] states Y and W. Assuming none of the handlers discard (or defer) an event, the handler for that event is called in the following order: Y, X, W, X. Note that the handler of X is called twice. The code in the following link shows that behaviour: http://coliru.stacked-crooked.com/a/14cb35ca23e586a5 If there something that I am missing? Best, Ernesto Rodriguez Reina

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[Ublas] Bug in 1.59 in file boost/numeric/ublas/detail/concepts.hpp
by dariomt＠gmail.com 30 Nov '15

30 Nov '15

In the migration from Boost 1.55.0 to 1.59.0 I found a bug in Ublas. For instance, in 1.55.0 function OneElement() declared in boost/numeric/ublas/detail/concepts.hpp line 716 looks like this: template<> double OneElement (double) { return 1.; } However, in 1.59.0 I think there is a copy'n'paste typo, because the corresponding function (which has been refactored) looks like this: template<class T> T OneElement (T) { return T(0.0); } Please note that the latter version returns a *zero*, instead of a *one*. This same bug affects the vector overload of the function, but the matrix version looks correct (it returns identity_matrix). This looks like a copy'n'paste typo, from a similar function called ZeroElement(), that, of course, returns a zero. I'm not sure if there is time to get a fix for this in the 1.60 release... Regards!

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New to Boost
by Gagan Kumar 30 Nov '15

30 Nov '15

I want to contribute to Boost, can you please give me a small task to start contributing.

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variant has non-trivial destructor even when all constituents have trivial destructor
by ☂Josh Chia (谢任中) 28 Nov '15

28 Nov '15

It seems that boost::variant has non-trivial destructor even for something like boost::variant<int32_t, int64_t>. Thus, It cannot be used in situations that call for a POD where calling the destructor is trivial. Particularly, I can't have a boost::lock_free::queue<boost::variant<X, Y>> even both X and Y are trivially destructible. How about making boost::variant trivially-destructible when everything in it is trivially-destructible?

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[BGL] metric_tsp_approx.cpp Error
by Vicky Vergara 28 Nov '15

28 Nov '15

Hello, I am trying to run the metric_tsp_approx.cpp example, but I get an error, I am using the suggested data 3 vertices data, I don't know what I am doing wrong, please help. Vicky. http://www.boost.org/doc/libs/1_58_0/libs/graph/test/metric_tsp_approx.cpp $more graph.txt 1,2 20,4 15,7 I get this error: terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::negative_edge> >' what(): The graph may not contain an edge with negative weight. Aborted (core dumped) Its after all the graph is connected: we can parse the given file Opened file 1,2 20,4 15,7 Closed file (1,2) -> (20,4) = 19.105 (1,2) -> (15,7) = 14.8661 (20,4) -> (15,7) = 5.83095 Conected all terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::negative_edge> >' what(): The graph may not contain an edge with negative weight. Aborted (core dumped) This is what I get when doing a backtrace: (shortened) (gdb) bt #0 0x00007ffff722bcc9 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 #1 0x00007ffff722f0d8 in __GI_abort () at abort.c:89 #2 0x00007ffff7b36535 in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6 #3 0x00007ffff7b346d6 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6 #4 0x00007ffff7b34703 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6 #5 0x00007ffff7b34922 in __cxa_throw () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6 #6 0x00000000004085c8 in boost::throw_exception<boost::negative_edge> (e=...) at /usr/include/boost/throw_exception.hpp:67 #7 0x0000000000408b0f in examine_edge<boost... #8 boost::breadth_first_visit<boost... vis=..., color=...) at /usr/include/boost/graph/breadth_first_search.hpp:82 #9 0x00000000004038ec in breadth_first_visit<boost... at /usr/include/boost/graph/breadth_first_search.hpp:105 #10 dijkstra_shortest_paths_no_init<... (color=..., vis=..., zero=0, combine=..., compare=..., index_map=..., weight=..., distance=..., predecessor=..., s=0, g=...) at /usr/include/boost/graph/dijkstra_shortest_paths.hpp:337 #11 dijkstra_shortest_paths<boost... (color=..., vis=..., zero=0, inf=1.7976931348623157e+308, combine=..., compare=..., index_map=..., weight=..., distance=..., predecessor=..., s=0, g=...) at /usr/include/boost/graph/dijkstra_shortest_paths.hpp:388 #12 dijkstra_shortest_paths<boost... at /usr/include/boost/graph/dijkstra_shortest_paths.hpp:358 #13 dijkstra_dispatch2<boost... at /usr/include/boost/graph/dijkstra_shortest_paths.hpp:431 #14 dijkstra_dispatch1<boost: at /usr/include/boost/graph/dijkstra_shortest_paths.hpp:462 #15 dijkstra_shortest_paths<boost... params=..., s=0, g=...) at /usr/include/boost/graph/dijkstra_shortest_paths.hpp:480 #16 prim_mst_impl<boost at /usr/include/boost/graph/prim_minimum_spanning_tree.hpp:41 #17 boost::prim_minimum_spanning_tree<boost... at /usr/include/boost/graph/prim_minimum_spanning_tree.hpp:72 #18 0x0000000000408bb3 in boost::metric_tsp_approx_from_vertex<boost::... at /usr/include/boost/graph/metric_tsp_approx.hpp:193 #19 0x0000000000402320 in metric_tsp_approx_tour<boost::... o=..., g=...) at /usr/include/boost/graph/metric_tsp_approx.hpp:89 #20 main (argc=<optimized out>, argv=<optimized out>) at metric_tsp_approximation.cpp:249

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Re: [Boost-users] [BGL]Using a function for weightmap to dijkstra_shortest_path
by alex 27 Nov '15

27 Nov '15

>-----Original Message----- >From: Boost-users [mailto:boost-users-bounces@lists.boost.org] On Behalf Of >Amit Prakash Ambasta >Sent: 23 November 2015 08:20 >To: boost-users(a)lists.boost.org >Subject: [Boost-users] [BGL]Using a function for weightmap to >dijkstra_shortest_path > >Hi, > > >I am trying to write use BGL.dijkstra to calculate a shortest path in a time >dependent network where edge.cost C(u, v) is a function of >distance(a)edge.source and a variable wait time dependent on Edge.departure >i.e. > Are you confident that you can use Dijkstra Shortest Paths for this? To me it seems that would only be possible if you knew that delay times are increasing over time, but not when they are fluctuating up and down. The code might be simpler if you put the dynamic part in the combine functor instead of the weight map. using Time = double; using Money = double; struct Distance { Time time; Money cost; }; struct Weight { Time duration; Money cost; Time delay(cost Time& start) const { // delay as a function of start time } }; struct Combine { Distance operator()(const Distance& start, const Weight& weight) const { Distance finish; finish.time = start.time + weight.delay(start.time) + weight.duration; finish.cost = start.cost + weight.cost; return finish; } };

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Boost.Type_erasure: member function return _self
by Yuan Yao 26 Nov '15

26 Nov '15

2 1