April 2011 - Boost - lists.preview.boost.org

[Boost.Pool] TR1?
by Phil Bouchard 14 Apr '11

14 Apr '11

Greetings, I see the Boost.Pool is not making its way up to the C++ standards yet an it is very unfortunate given its great use. Boost.Pool provides an is_from() member function that does a simple range check and returns whether a pointer is part of the pool or not. This is a very useful function which I think should be part of the standards because it could be used for the global pool as well; i.e. the one used by operator ::new and ::delete. The benefits outweigh the costs. Thanks, -Phil

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[Parallel BGL] Property access problem
by Cosimo Calabrese 14 Apr '11

14 Apr '11

Hi to all, I'm working on a WinXP, VS2010, boost 1.46.1, openMPI 1.4.3. I've used in the past the BGL lib, and now I would explore the PBGL extension. I've writed a simple program (you can find it in attach), but I've some problem. When I run it with: mpirun -np 1 .\test.exe it works. But if I use 2 or 4 processors the program crash sistematically in the following way, on different machines too: num_vertices: 10 num_edges: 19 A-->B : 1 A-->C : 10 A-->D : 11 B-->D : 13 C-->D : 12 B-->E : 1 C-->A : 14 E-->D : 1 D-->B : 15 D-->A : 1 E-->B : 16 -------------------------------------------------------------------------- Sorry! You were supposed to get help about: odls-default:could-not-kill But I couldn't open the help file: D:\dev\CommesseAperte\Sviluppo\TELLUSXX_CalcServer\lib\openmpi\installed\share\openmpi\help-odls-default.txt: No such file or directory. Sorry! -------------------------------------------------------------------------- Every process allocates 1 GB. The problem disappear only when I eliminate all the property access (get() and put()). Maybe I access to the MPI framework for the first time during the property access, and so could be an MPI problem? Am I using the property in a wrong way? Thanks in advance, Cosimo Calabrese.

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New, powerful way to use enable_if in C++0x
by Matt Calabrese 13 Apr '11

13 Apr '11

I'm not sure if there is much interest in this or if someone else discovered this as well, but I realized today that enable_if can be used in a new way in C++0x. Traditionally when working with enable_if with function templates you invoke it either in the return type or in an additional function parameter of the function. Each of these has advantages and disadvantages. The parameter form has the downside of augmenting the parameter list. The most notable problems with this approach are that it can't be used with overloaded operators that require a fixed number of arguments, and it can't be used after a variadic argument list. The return type use of enable_if is often preferred since it does not involve augmenting the parameter list, meaning that it can be used with most overloaded operators, but you still can't use it for conversion operations and you can't use it all with constructors as they have no explicit return type. However, in C++0x, there is a new way to use enable_if by altering neither the function parameter list nor the specification of the return type. It can be used with operators, constructors, variadic function templates, and even overloaded conversion operations (the latter of which was previously considered impossible). The way to do it is with C++0x default function template parameters. Rather than try to explain any further in English, the following code should demonstrate the approach fairly clearly (tested in GCC 4.5.2): http://codepaste.net/23yo8o There is only one drawback that I can think of off of the top of my head -- you can't refer to the function parameters by name for the enable_if condition, whereas in C++0x if you use the return type form of enable_if along with the new trailing return type form of function declarations you can. I have never personally wanted to do this and I highly doubt that it's common so this is likely entirely a non-issue, plus you can always use std::declval anyway so you aren't actually losing any high-level functionality. Are there any thoughts on this or drawbacks other than what I mentioned? Should such use be added to the docs as supported behavior in 0x compilers? -- -Matt Calabrese

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[config] Local classes as template parameters
by Lorenzo Caminiti 13 Apr '11

13 Apr '11

On Sat, Feb 12, 2011 at 5:50 AM, John Bytheway <jbytheway+boost(a)gmail.com> wrote: > On 11/02/11 22:29, Lorenzo Caminiti wrote: >> On Fri, Feb 11, 2011 at 4:31 PM, Lorenzo Caminiti <lorcaminiti(a)gmail.com> wrote: >>> From: John Bytheway <jbytheway+boost(a)gmail.com> >>> 2. Might anyone care so much about performance that they absolutely must >>> have the code inlined? The answer is probably "yes" (or at least there >>> will be people who *think* they care, which is also a problem). For >>> these people you could, if you choose, provide an alternate >>> implementation which doesn't indirect through local::function<>, and >>> thus will only work in C++0x (or C++03 with non-standard extensions). >> >> Without inheriting from local::function_base<> and then using >> local::function_ref<> the local struct cannot be passed as a template >> parameter in C++. Is this different for C++0x (C++03)? > > Yes, in C++0x local structs can be passed as template parameters. > Obviously, in C++0x there are lambdas too, so you might think your > library is useless, but I'd expect most compilers to support passing > local structs as template parameters before they support lambdas, so > there is some advantage in having this intermediate implementation. > Also, your macros would allow writing code that worked in C++0x and > C++03, with the virtual function business in only those compilers/modes > where it is necessary. Hello all, Is there a Boost.Config macro that indicates if the compiler allows local classes to be passed as template parameters? Thank you. -- Lorenzo

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[GSoC] Boost.Tree and Boost.BloomFilter
by Alejandro Cabrera 13 Apr '11

13 Apr '11

Hello all, I've filed two proposals for this Google Summer of Code. Boost.Tree: http://www.google-melange.com/gsoc/proposal/review/google/gsoc2011/cppcabre… <http://www.google-melange.com/gsoc/proposal/review/google/gsoc2011/cppcabre…> Boost.BloomFilter: http://www.google-melange.com/gsoc/proposal/review/google/gsoc2011/cppcabre… I'd be glad to work on either project. Feedback is welcome. Thanks, -Alej

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Installation fails if env VMS is set
by Dreamcat4 12 Apr '11

12 Apr '11

Hi, Over on the Boost-Users mailinglist we have found that this environment variable (and perhaps unknown but maybe others) will cause bootstrap.sh / Jam failure during the Boost libraries compile and install. Heres the full thread: http://lists.boost.org/boost-users/2011/04/67716.php You (or Jam developement team) may wish to consider taking some kind of action to avoid this as VMS is a very common acronym for "Virtual Machines". Its usage elsewhere is widespread and certainly not Boost-specific. Other choices of course - maybe look towards documenting such usag(es) if they cannot be easily avoided. Or consider ways to detect / warn / clean out the users shell environment variables if they are conflicting. Sorry I cant help any further however as a new user I simply have no experience with the Boost library yet. Many thanks. dreamcat4 dreamcat4(a)gmail.com

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[GSOC]SIMD Library
by Faiçal Tchirou 12 Apr '11

12 Apr '11

Hi everyone, I recently ask documentation about the SIMD Library project here and I receive some guides and references links from Joel Falcou. Now I have some questions about the library itself. Is the goal of the project to build a library similar to libSIMDx86 but more focusing on the AltiVec instruction set ? Joel also advises me to take a look at Proto. I read that Proto is used to build DSEL. Will Proto be used to map high level classes and methods of the library to native SIMD instructions ? What about the library itself ? Which modules have to be developped ? Thanks.

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[trac] Misuse of trac system by spammer
by Joachim Faulhaber 12 Apr '11

12 Apr '11

Hi, I received a ticket today: https://svn.boost.org/trac/boost/ticket/5457 that's only purpose is to distribute a commercial link. Has anyone experienced a similar misuse of the trac system? Are there ideas how to prevent this? Regards, Joachim -- Interval Container Library [Boost.Icl] http://www.joachim-faulhaber.de

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[GSoC] Proposal reviewing
by Andrew Sutton 12 Apr '11

12 Apr '11

Mentors, We need to establish some guidelines for reviewing proposals. They won't be complicated :) I'm opting not to use the mentors mailing list for this announcement. I know that all the mentors are subscribed here. Here's how this should work: 1. Identify the set of proposals for projects that you are interested in mentoring. 2. Evaluate the proposal and write your evaluation as a PRIVATE comment. 3. If you have questions of the student, you can write PUBLIC comments or send them an email. 4. Rank the proposal (I think 5 is the best this year). That would be the project that you want to mentor. Towards the end of the review process, we will select the 10 best proposals. This doesn't guarantee that we'll *fund* 10 proposals, just that I've requested 10 slots. I would like, this year, if all students got feedback regarding their proposals even if they are clearly rejects. The reason for writing evaluations privately, for now, is that it will help me write a public summary for proposals that are not accepted. I'll figure out how this is going to work over the course of the week :) Specific evaluation criteria are up to you (the mentors). You may ask students to modify good proposals. You do not need to ask *all* students to improve their proposals. At the end of the week, you should have a list of 1 or 2 proposals that *you yourself* will mentor. If you are not offering to mentor the project, please don't review it as a 5. Otherwise, we end up with a case where we have to assign a mentor to a project that they aren't interested in. I don't think that this has worked out very well in the past. Also, would prefer that comments regarding specific proposals not be sent to the list. I don't think it would be a good idea for a flood of "this proposal is AWFUL" emails to start popping up. I'm all for transparency, but I don't think airing value judgements would be a beneficial for community development :) Questions or comments involving evaluation criteria and process are fine. Andrew

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[convert] incomplete reference documentation
by Vicente BOTET 11 Apr '11

11 Apr '11

Hi, I was taking a look at the documentation and it seems to me that the reference documentation is incomplete and not ready for review. Do you plan to complete it before review? Thanks, Vicente

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