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BGL question about districting
by Barend Gehrels 06 Mar '09

06 Mar '09

Hi, We're about an automated districting tool. We want to create Y districts from X polygons, all having a specific value (e.g. area or inhabitants), where the total value of each district is as similar as possible and each district is also as similar as possible. Let's call the value the "potential". Of course this problem is NP-hard so we're glad with the first solution or e.g. the first ten solutions. We thought to implement this by the Boost Graph Library. First we detect neighbour relations with our own Geometry Library (using the still-to-build "touches" relationship). We've a graph then and can divide the graph into subgraphs, each having connected nodes and an (nearly) equal "potential". I've some experience with BGL, having used the "connected_components". But I cannot find an appropriate algorithm for this problem, if it is available. Actually it even could be a "network flow" algorithm dividing the total potential by Y, and starting at some point flowing the potential through the graph. But all network flow algorithms seem to be on directed graphs. This is an undirected graph. It it is not possible with a standard BGL algorithm I think we can still solve it using BGL and e.g. breadth-sort-first, but just want to verify if it is possible or maybe by an unexpected workaround. Thanks, Barend

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Blocking Queue implementation in C++
by Filip Klasson 06 Mar '09

06 Mar '09

Hi, I need to create a Blocking queue implementation in *C++* with the help of Boost libraries and i am looking for some advise. What i need is a queue with linked nodes. The queue needs to be ordered as FIFO (first-in-first-out). I need the following functionality (Functionality from BlockingQueue implementation in Java) INSERT: Insert new items into the queue and if there is no space the queue needs to wait until space is available. RETRIEVE: Retrieve and removes the element that has waited the longest. If there is no elements in the queue it waits until an element becomes available. SIZE: Return the number of elements in the queue. POLL: The same as retrieve but only waits for a specified time for items to become available. I found a messageQueue that looks something like what i need (found here: http://www.boost.org/doc/libs/1_36_0/boost/interprocess/ipc/message_queue.h…) is that correct? /Filip

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[itl] Preview 4 of the Interval Template Library
by Joachim Faulhaber 05 Mar '09

05 Mar '09

Dear list, I am happy to announce that the Interval Template Library (Boost.Itl) converges to a state, that conforms the standards of the boost libraries. It now contains substantial test suites and almost complete quickbook documentation. I hope it will soon be mature for a formal review after a last round of feedback and subsequent improvements. Since the last progress report in November last year the following work has been done. + Interoperability of interval_containers: Addition, subtraction, intersection and symmetric difference are now interoperable for all combinations of interval containers that make sense: You may for instance intersect a split_interval_map with an interval_map, an interval_set an interval or an element. + Added symmetric difference and renamed operators in accordance to other set class templates like e.g. boost::dynamic_bitset. + Introduced infix operators as itl::namespace global functions that are interoperable between interval_maps, sets, intervals and elements, so far as the combinations make sense. + Operators are now +=, +, |=, | : Set union / Map union with aggregation -=, - : Set difference / Map union with aggregation &=, & : Set intersection / Map intersection with aggregation ^=, ^ : Set symmetric difference / Map symmetric difference with aggregation. + Extended the test suite, specifically for the new operators and their overloadings. + Wrote quickbook documentation for the library. Please note that the original ITL as presented in May 2008 has been split into 3 parts and only the *first* part is prepared for boost now: itl : Core library, interval containers, PREPARED FOR BOOST itl_xt : Extensions like histories and generalized crosstables validate: The law based test automaton (LaBatea). A validation tool using laws aka axioms. So please focus on the core part (itl). Download the current version 'preview 4' from the boost vault's containers section: itl.zip http://www.boostpro.com/vault/index.php?action=downloadfile&filename=itl.zi… If you are interested in extended parts or LaBatea you may download all parts as itl_plus.zip http://www.boostpro.com/vault/index.php?action=downloadfile&filename=itl_pl… The quickbook generated documentation is included in the zip files and is also availabe online at http://herold-faulhaber.de/boost_itl/doc/libs/itl/doc/html/index.html Sources are also available form the sandbox: https://svn.boost.org/svn/boost/sandbox/itl/ The documentation has a focus on tree aspects (1) A short introduction, that wants to be easy to understand and to provide good and use case related examples: http://herold-faulhaber.de/boost_itl/doc/libs/itl/doc/html/index.html#boost… http://herold-faulhaber.de/boost_itl/doc/libs/itl/doc/html/boost_itl/exampl… (2) Synoptical representations that allows to see the complete 'picture' of the library. For instance the function matrix http://herold-faulhaber.de/boost_itl/doc/libs/itl/doc/html/boost_itl/interf… is supposed to give a complete overview over the most important functions across all itl containers. (3) A description of the semantics which is characterized by sets of laws that apply for the different interval containers. The semantical analysis, based on sets of laws, was a quite interesting work, where software development sometimes transformed into software discovery guided by the validation tool LaBatea ;) My main finding out of that process was, that the semantics of the aggregating itl::Maps is determined by the semantics of their data or codomain parameter U, so that if U is model of concept C then itl::Map<T,U> is model of C which is stated in section concept induction: http://herold-faulhaber.de/boost_itl/doc/libs/itl/doc/html/boost_itl/semant… All your feedback is welcome. Cheers Joachim

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[time series] What happened to this library?
by Christian Henning 05 Mar '09

05 Mar '09

Hi there, as far as I can tell this lib has been approved but it doesn't show up in boost. Why is it not in there? Thanks, Christian

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Trunk Inspection Report fixed + other reminders
by Beman Dawes 05 Mar '09

05 Mar '09

The trunk Inspection Report is now cycling daily, with a new URL. See http://boost.cowic.de/rc/inspect-trunk.html The release branch Inspection Report also cycles daily. See http://boost.cowic.de/rc/inspect-release.html The links to these and other useful "State of Boost" links are found at http://www.boost.org/development/testing.html --Beman

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Submission of a new application to 'Who's Using Boost'
by Carlo Medas 05 Mar '09

05 Mar '09

Dears, this is a submission of a brand new free application which is using boost. It is also a chance to say thanks to you all. Boost is amazing and thanks to your excellent work we've been able not only to speed up the development but also to make the new app available on several platforms, without a huge effort. Application name: fing Company/team name: overlook App description: Fing is the ultimate command line tool for network and service discovery; born from the ashes of Look@LAN, it takes advantage of a brand new cross-platform network engine and reaches an impressive discovery sharpness and speed. Its network discovery reaches 100% hit in any ethernet-based network. Supported operating systems: Linux, Mac OS, Windows. Boost parts used: thread, system, filesystem, asio, multi-index containers, smart pointers, program options URL: http://www.over-look.com Thank you all once more for your great work, Overlook team Carlo Medas, Daniele Galdi, Marco De Angelis

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Re: [boost] [math] Does any one interesting in calculating derivative for a expression automatically?
by Dongfei Yin 05 Mar '09

05 Mar '09

Hi Bruno, thank you for your interesting, I will try to use proto, I never use it before. yes, It's technically feasible. but the type of all the symbol in the expression can not be the build-in type. and gamma function should be a special version. integral is more difficult than derivative, else, to calculate the volume will be more easier. to simplify the expression is a interesting work. especially in compile time. BTW: I do not know how to upload source to this system, do you know how to do that? Dongfei. > >From my point of view, the main interest would be to compute > expressions containing some compile-time values provided by the user. > For example I want to calculate the volume of a hypersphere which is: > (pi^(N/2)*r^N) / gamma(N/2 + 1), with dimension N known at > compile-time. If the user happens to work only with N=2, that is > circles, I want the resulting expression to be as effective as a > hand-written pi*r^2 (the volume of a hypersphere<2> is the area of a > circle). It's technically feasible. > > Bruno > >

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BoostCon '09 Sessions
by David Abrahams 05 Mar '09

05 Mar '09

Hartmut Kaiser and the BoostCon Program committee have done a stellar job assembling a list of sessions for this year's BoostCon, including everything from C++ compiler developer presentations, to hands-on C++0x development, to talks on eexperimental metaprogramming enhancements, to expression templates for running code on GPUs. I can honestly say I want to go to almost every session. It's going to be hard to choose. Please see the session list at: http://www.boostcon.com/program/sessions and then, of course, head on over to http://www.boostcon.com/registration to register for the conference. Best regards to all. See you there! -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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[serialization] string serialization
by Nikolay Mladenov 04 Mar '09

04 Mar '09

Hi, I the basic_binary_iprimitive.ipp (and I suppose other files) the size of the strings is serialized as std::size_t and not as serialization::collection_size_type. Is that intentional? Thanks, Nikolay Mladenov

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Design conventions; passing functors
by Joachim Faulhaber 04 Mar '09

04 Mar '09

Hi, I am pondering about functor passing. Functors occur in my library (ITL) e.g. for the aggregation of associated values on insertion in interval_maps (aggregation on overlap): template<class Domain, class Codomain, ...> class interval_map{ ... //(1) My current implementation is this: // Combinator is the aggregating functor template, // instantiated at compiletime template<template<class>class Combinator> interval_map& add(const value_type& value_pair) { /*Combinator template passed or instantiated somewhere*/ } ... } //I like this definition, because it's abstract: // The functor has to be a matching template e.g. inplace_max interval_map<int,int> m; m.add<inplace_max>(some); //(1) template<class Domain, class Codomain, ...> class interval_map{ //(2) The more traditional definition template<class Combinator> interval_map& add(const value_type& value_pair) { /*Combinator type passed or called somewhere*/ } ... m.add<inplace_max<int> >(some); //(2) I prefer (1) but both definitions (1) and (2) are purely static denotations. To have adaptable functors or functors that can have states, like in ... m.add(some, max_under(42)); ... I am afraid I have to say sayonara to definition (1) and use this instead: template<class Domain, class Codomain, ...> class interval_map{ //(3) Adaptable functor template<template<class>class Combinator> interval_map& add(const value_type& value_pair, const Combinator<Codomain>& combine) { /*combine functor passed or called somewhere*/ } Now, there seems to be a convention from the STL that functors shall be passed BY VALUE. template<template<class>class Combinator> interval_map& add(const value_type& value_pair, Combinator<Codomain> combine); This is stated in [Sutter & Alexandrecu 2005, C++ Coding Standards] item 89: "Function objects are modeled on function pointers. Like function pointers, the convention is to pass them by value. All of the standard algorithms pass objects by value, and your algorithms should too." I do not really understand this convention and feel some resistance to follow it. In addition the call by value implementation can (and will) lead to heavy inefficiency by unaware usage of fat functors. So I browsed through some boost libraries and found that functors are passed by reference there (e.g. accumulators, fusion). Final question: What is the boost standard on passing functors, that I can adapt to? Cheers Joachim

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