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Re: [boost] Proposal: Monotonic Containers
by joaquin＠tid.es 10 Jun '09

10 Jun '09

Stewart, Robert escribió: > joaquin(a)tid.es wrote: > On Tuesday, June 09, 2009 9:34 AM > >> Stewart, Robert escribió: >> >>> There's a problem with using an allocator for the node based >>> containers: they use the allocator to allocate the elements >>> but not the nodes. That implies free store (de)allocations >>> for the nodes which is contrary to the intended purpose of >>> this proposal. >>> >> Umm, I beg to differ. If we have a node-based container >> >> xxx<T,...,custom_allocator<T> > >> >> and node<T> is the internal node type, the container is required >> to do the allocation using an allocator of type >> >> custom_allocator<T>::rebind<node<T> >::other. >> >> The container is not allowed to do any kind of allocation using >> other means than the custom_allocator<X> family of allocators. >> > > If custom_allocator<node<T> > is not specialized to do the same as > custom_allocator<T>, or to use the same memory pool, then it > doesn't fit the proposal. Point conceded, but how would you do otherwise? Specifying a custom allocator is your only way to affect the container's allocation behavior. Seems like you're implying that the container wrapping approach is in some way more powerful than directly specifying the custom allocator, which is not. Your only chance to solve the problem you mention is to make custom_allocator<node_type<T> > use the same memory pool. There's a way to do this. If you construct the container with custom_allocator<T> a; xxx<T,...,custom_allocator<T> > x(a); then xxx will use an object of type custom_allocator<node<T> > for its allocation needs, which perforce will be an object differnt to the allocator a you've passed; but the container is required to construct this internal allocator as a copy of a: // inside xxx implementation custom_allocator<node<T> > internal_a(a); So you can use this knowledge to pass info around, for instance on the memory pool to be used. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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first review submission of timer_queue.zip
by JohnQ 10 Jun '09

10 Jun '09

Hi, Thanks for pointing me to the submission requirements page... I just uploaded timer_queue.zip to boost vault for first review. Haven't got everything shipshape yet but I'm hoping I've satisfied enough of the requirements so I can start getting some feedback on functionality. If not, let me know so I can rework and resubmit. In essence, timer_queue is a library for creating timers that fire at some arbitrary time in the future and hand you back a void* that you provided when you created the timer. Timers can be deleted before they fire by providing an id (can be non-unique) when you create a timer that can be used to delete particular sets of timers later on. Thanks to any who take the time to review this and help me make it better. John Q.

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[mpl]iter_fold_if Forward Backward rationale?
by Larry Evans 10 Jun '09

10 Jun '09

Why is there both a ForwardOp and BackwardOp template argument to iter_fold_if? https://svn.boost.org/trac/boost/browser/trunk/boost/mpl/iter_fold_if.hpp#L… I would have thought that only 1 was needed. Since iter_fold_if is not documented here: http://www.boost.org/doc/libs/1_38_0/libs/mpl/doc/refmanual/refmanual_toc.h… I assume it's not meant to be used by the user, but is only an implementation detail; however, it, or a variation, might be useful to implement the and_seq mentioned here: http://article.gmane.org/gmane.comp.lib.boost.devel/186204 As shown in that post, the template, while_if_then was used, and it does not require anything like both a ForwardOp and BackwardOp, it just requires the If and Then unary metafunctions. One problem I encountered with while_if_then was moving to the end of the sequence, at which time the Then metafunction couldn't be called; hence, I had to make it lazy to avoid dereferencing the end iterator. Is that somehow related to the need for BackwardOp in iter_fold_if. IOW, because iter_fold_if might reach the end iterator, it has to backup? I'm really asking because in the variadic template version of mpl, I wondering if iter_fold_if could be replaced with something like while_if_then (which may be renamed fold_if to be more consistent with other names with similar function). Any insight about the rationale for the iter_fold_if would probably save me considerable time in deciding whether it can be replaced with the proposed fold_if. -regards, Larry

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[filesytem][1.39.0] basic_path::clear mia?
by Jeff Flinn 10 Jun '09

10 Jun '09

http://www.boost.org/doc/libs/1_39_0/libs/filesystem/doc/reference.html#bas… lists void clear(); as an available modifier on basic_path. Neither I nor MSVC8 seem to be able to find it. Am I doing something wrong? Thanks, Jeff

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Re: [boost] Proposal: Monotonic Containers
by Artyom 10 Jun '09

10 Jun '09

> The space has already been created before the allocator is > requested to > provide for new storage. > > Otherwise, we could never use a vector<char> on a > machine that requires > 16-byte alignment. > This is not correct. Allocators allocate memory as single chunk. So, if you use vector<char> that has size of 10 characters, it would allocate a single chunk of at least 10 bytes, and it's beginning would be aligned to 8 or 16. So if you for example, allocate 3 charrecters that start at 0x100 to 0x102, and then you would try to allocate single integer you need to return pointer with value 0x104, 0x108 or 0x110-- aligned to 4, 8 or 16 according to architecture requirements, if you would return 0x103 it may cause illegal operation on some architectures like ARM, hundreds cycles cost on architectures like IA64 and fault in execution of atomic operations like in shared_ptr. You **must** return aligned pointers from allocators. Artyom

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Re: [boost] [multi_array] Negative strides
by pete＠pcbartlett.com 10 Jun '09

10 Jun '09

>John Reid <j.reid(a)mail.cryst.bbk.ac.uk> wrote:John Reid wrote: >> Either the library was designed with negative strides in mind and it is >> just the assertions that are stopping me using them or they were never >> part of the original spec and are not safe to use. In either case I >> can't find them mentioned in the documentation. Could the owner of the >> library clear this up? >Do libraries have owners? Posts on boost.multi_array don't seem to >provoke many responses. Nearly all libraries have owners (see e.g. http://gitorious.org/boost/svn/blobs/master/libs/maintainers.txt ). There is considerable variation in how closely each owner is monitoring this list. Pete

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Re: [boost] [Christian S] Spirit and ANTLR - Request for example
by Christophe Henry 10 Jun '09

10 Jun '09

> brought an idea to boost and had it shot down [...] I quite agree with Luke's explanation and while Christian's behaviour is not perfect, I'd like to point out that bringing a new idea to boost for the first time is a stressful experience, as I myself remember full well. And having his idea immediately shot down is even less nice (as I also remember full well). It seems to happen quite sometimes that people coming with new ideas are met with (unconsciously) not so friendly behaviour. Perhaps we should think about the way new people are met if we don't want to end as a closed (and thus condemned) community... And in the same time, maybe Christian could take a short break and we could all try to restart on a better basis. I therefore offer to close this thread for now as it clearly brings nothing but spam in our mailboxes. If Christian comes up later with interesting examples, we would all profit from them. Regards, Christophe

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Re: [boost] Proposal: Monotonic Containers
by Artyom 10 Jun '09

10 Jun '09

Hi, Several notes: 1st... This code does not compile with gcc-4.3 (mingw) a) Fix: map.h/set.h --> - set(Predicate P, Allocator const &A) - : Set(P, A) + set(Predicate Pr, Allocator const &A) + : Set(Pr, A) because it shadows template parameter P. b) Fix in ./boost/monotonic/storage_base.h Add #include <boost/cstdint.hpp> 2nd... Never use: #pragma once not portable 3rd... Your allocator is not correct you do not align the pointers as required by most of architectures. You need to provide 8-16 bytes alignment... According to system 4th... Why don't you use boost::pool? It is debugged and tested instead of writing new implementation? 5th... Implement ALL constructors of each container. For example I can call. std::string str="Foo"; std::vector<int> v(str.begin(),str.end()); this is not supported 6th... This is bad idea to derive from std containers. They to do not provide virtual destructors. This may be very error prone. This is just short glance. Artyom --- On Tue, 6/9/09, Christian Schladetsch <christian.schladetsch(a)gmail.com> wrote: > From: Christian Schladetsch <christian.schladetsch(a)gmail.com> > Subject: Re: [boost] Proposal: Monotonic Containers > To: boost(a)lists.boost.org > Date: Tuesday, June 9, 2009, 3:06 PM > Hello, > > That is not what I asked for. I wanted online docs and > code. We are very > >> busy people, and anything that takes extra time is > likely to mean we don't > >> bother. > > > > > OK well on second thought, what? > > I am also busy. > > I gave you a link to code and documentation in the one > archive. > http://www.boostpro.com/vault/index.php?action=downloadfile&filename=Monoto… > > Click on the link, get the code and the documentation. > Sorry that you have > to click into the archive twice, but boost doesn't have a > better way of > doing it ATM that I am aware of. > > Chrstian. > _______________________________________________ > Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost >

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Re: [boost] identifying a string type
by Steven Ross 10 Jun '09

10 Jun '09

Is there a boolean argument that can be used to identify whether a data type is some form of string that has a [] operator that returns an integer data type (preferably 2 or less bytes in size)? I now am using enable_if so that strings and floats are identified and the proper specialized call is made for them when spread_sort is called by the user. It would be nice to automatically identify strings too inside enable_if, so that the user can just call "spread_sort" and the correct specialized and optimized sorting call will be made depending on the data type for integers, floats, and strings, and std::sort will be called for unsupported data types.

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Proposal: Extended Allocators (was Montonic Containers)
by Christopher Jefferson 10 Jun '09

10 Jun '09

It is my belief (but I'm happy to shown wrong) that the idea of 'Monotonic Containers' to provide a new allocator for vector to support a small block of memory is fundamentally not going to work, due to 2 limitations of allocators: 1) There is no support for in-line expansion (effectively, realloc which doesn't move if it can't realloc) 2) There is no support for an allocator to say "No, you can't have X memory, but I could give you Y", so it's hard to "exactly fill" a limited memory buffer. I have been working around this by implementing new special containers, which know about the size of a fixed buffer and therefore can make use of the space. I now think I'm probably going about this the wrong way, a much better way would be to implement: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2045.html , or a variant thereof. The big problem with doing this "within boost" is that it would pull in a basically complete implementation of std::allocator and the containers into boost. In an ideal world, such a small and in my opinion useful extension would have been added to C++0x, but it's far too late for that now. tl;dr : Seeing as we are having a "what would boost accept" couple of days, would adding an (extended) implementation of a substantial part of the standard library be acceptable, or would I be better off trying to get this picked up by one of the existing standard libraries to pick this up (my worry being they may not want, quite sensibly, want to accept code which is not standardised). Chris

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