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Re: [BGL]edge connectivity code won't compile
by Vladimir Prus 30 Mar '05

30 Mar '05

> Hi, I ran into problems trying to compile the BGL example code, > edge_connectivity.cpp. (There are two codes, this is the short one with > underscore, the other is hyphen edge-connectivity.) I used VC7. I have > been running other codes without any problem. Hi, > Basically, I got two errors: > 1)C1076--I have changed from /Gm to /Zm1000, and it went way. > 2) C2039--it flagged error "reference is not a member of property map" and > points to boost/property_map.hpp in boost-1-29-0. I have no idea how to > fix this one. I think that in order for somebody to look into the problem, you should provide *exact* error messages. The property_map.hpp file is big, and guessing what line upsets VC7 is impossible. In first case, you did not even say where error occurs. BTW, could you also try with CVS version? - Volodya

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RE: [boost] Call for Volunteers: the Synopsis project
by Stefan Seefeld 30 Mar '05

30 Mar '05

Hi Volodya, > From: Vladimir Prus [mailto:ghost@cs.msu.su] > Sent: September 30, 2004 03:04 > Count me as interested. Are you going to base that parser on > OpenC++, which, > IIRC, was used by Synopsis some time ago? Last time a looked > at OpenC++, it > did not even distinguish between ordinary names and > typenames, which makes me > wonder if it's a good parser. You are right, there remains a lot of work to be done. The C++ parser backend of synopsis which we are talking about here is indeed based on OpenC++, but has already undergone lots of improvements. In its original design the parser didn't contain any form of semantic analysis such as symbol lookup to disambiguate certain expressions. For what it had been used so far it was good enough. I'm now working on the features that allow it to get closer to the standard, i.e. constant expression evaluation, symbol (type) lookup, etc. As I said, any help would be very appreciated ! Regards, Stefan

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boost::tree advice?
by Dan Rosen 30 Mar '05

30 Mar '05

Hi all, Over the past few weeks I've been slowly working on (what I hope to be) a candidate for a boost::tree. I've reviewed the comments on previous submissions by Kasper Peeters (http://www.damtp.cam.ac.uk/user/kp229/tree) and Justin Gottschlich (http://nodeka.com/TreePart1.pdf) and I'm trying to put together a set of concepts to address some of the issues that were discussed here. Of the two "how to design a generic tree container" camps, I'm finding myself mostly in the one where individual nodes are not exposed to users, and the tree is an opaque structure. Also, nodes are not identical to iterators, and the iterator concept is not extended in any significant way from the standard. (Anybody who would like more detail, I'm happy to provide my draft of the concepts, but I don't want to get into that detail here -- it's not particularly relevant to my questions that follow.) I feel like I've been making decent progress so far, mostly working on paper, just documenting the concepts, and doing some coding exercises for proofs of concept. But I don't have anything I'd consider ready for primetime yet -- not even remotely -- and in fact as I progress more solidly into the coding phase, I'm finding myself getting somewhat mired in the details. So I thought I'd solicit opinions from experienced Boosters here on some of the issues I'm trying to work through. I'm primarily finding myself conflicted about what degree of flexibility the concepts and their concrete implementations need to offer. I thought it would be useful to allow clients of tree<> to be able to specify the container type for a node's children. In the code I'm currently playing with, I have a couple "selector" structs, basically identical to Boost Graph Library's vecS, listS, etc, and the tree<> class template takes one of these selectors as a template parameter. That much is all well and good, but I quickly run into trouble once I start dealing with nodes and iterators. First of all, I'd like to provide access to the children of a given node as a sequence of the type specified by the client. So if you have an iterator to an element in the tree (the structure of the tree being otherwise opaque), I want to be able to say something like: tree<foo, list_selector> t; tree<foo, list_selector>::some_kind_of_iterator i; // assume t contains something useful and i points to an element in t std::list<foo> children = t.children(i); At this point, I've got a problem: internal to the tree<>, the lists representing child sequences contain not instances of type "foo" but instances of something like node<foo>. So I can't simply provide access like this unless I can guarantee that my nodes are convertible in all contexts to their stored data. That seems like a rat hole. Another thing I'm stuck on is, even if I don't expose the container structure like this, I still have a problem with iterators. The above example omits the actual iterator type, but to get into some specifics, one type of iterator I'd like to provide is a pre-order traversal iterator. In my current code, this iterator is basically just a wrapper for iterators into the flat sequences I've been instructed to use, and some minimal code that knows how to jump between these sequences appropriately (for example: if a node has children, operator++ yields the first child of that node). It's easy to get an iterator into the sequence containing a node's children (internally, it's just something like node.children.begin()), but it's not so easy to get an iterator into the sequence containing a node's parent, unless a node contains not a pointer to its parent but an iterator instead. And that scheme breaks down for children of the root node, which is not in any sequence, as it has no siblings. I'm sure there are other options for how to implement the node structure and iterator relationships, but none jump out at me. In short, although I'd like my concepts for trees to allow users to specify and access the sequences representing the children of a node, my implementation of this is proving very clumsy. So I'm wondering two things: 1. Is this a good idea in the first place? Are there really any compelling use cases, where you'd want one tree to store its node structure in vectors and another in lists? Or is this a case where a policy-based approach is misplaced effort? 2. If this actually is a good idea (which I'm starting to get the feeling is not the case), my experience so far is that there's some significant overhead -- both in terms of the size of the structures, and in terms of speed (extra pointer traversals when doing anything with iterators). Does anybody have any brilliant ideas about how to minimize this overhead? If these questions are too vague, or lacking in context, I'm more than willing to provide the rough draft I've got of the structural concepts, and the very incomplete code (such as it is). Thanks in advance for your expert advice! dr

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Re:[serialization] Private ctor again
by Vladimir Prus 30 Mar '05

30 Mar '05

Robert Ramey wrote: >> binary_oarchive oa(...); >> Data data(....); >> oa << data; > >>Now, how do I deserialize it? I can't write > >> Data data; >> ia >> data; > >>Since ctor is private. I would guess it's still possible to deserialize >>this class, but I don't know how. > > what's the matter with > > Data data(....); > ia >> data; The wrong is that when I create and serialize data, I have something to pass as ctor parameter. But when deserializing, I don't have that something. Let's be more specific: the ctor parameter includes parse tree. I can't serialize it because it requires *lots* of work. > I don't see how the fact you want to construct different ways is related > serialization. Unless its a pointer, serialization presumes the > instance has already been constructed. How this is done is > outside the influence of the serialization library. What I'm after it telling to serialization lib: "hey, I know this data was not serialized via pointer, but I want to restore it into pointer variable, so that serialization lib creates it itself". Specifically, I look at this code from collection_load_imp.hpp: stack_allocate<type> t;^M load_construct_data(ar, t.address(), 0U);^M ar >> make_nvp("item", t.reference());^M Can the same trick be use from user code? I'm not all all sure it's better than saving Data as pointer in the first place, but I'm exploring possibilities. - Volodya

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Mailing list archive change and list downtime
by Beman Dawes 30 Mar '05

30 Mar '05

DongInn Kim, Jeff Squyres, and the other sysadmins at Indiana University are planning to switch all the Boost mailing list archives they host from MHonArc to Hypermail. They report "Hypermail seems to be much more stable, faster, and more efficient than MHonArc. We've been quite pleased with it, and have deployed it across most other lists on the listserver already (the boost lists were saved until last)." The old archives will still be available, and DongInn and Jeff have made various plans to minimize disruptions. All the listservers will be down during the transition, which is planned to start at 11 PM Saturday night (Eastern US time). Thanks to all the folks at IU for their help with Boost list hosting, --Beman

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[boost] [Assign] list_inserter.hpp missing include for boost::begin, boost::end
by Douglas Gregor 30 Mar '05

30 Mar '05

The BGL GraphViz test is failing on GCC 3.4.3 with this error message: In file included from /boost/head-regression/boost/boost/assign/std/map.hpp:19, from ../libs/graph/test/graphviz_test.cpp:17: /boost/head-regression/boost/boost/assign/list_inserter.hpp: In member function `boost::assign::list_inserter<Function, Argument>& boost::assign::list_inserter<Function, Argument>::range(const SinglePassRange&)': /boost/head-regression/boost/boost/assign/list_inserter.hpp:260: error: `begin' is not a member of `boost' /boost/head-regression/boost/boost/assign/list_inserter.hpp:260: error: `end' is not a member of `boost' Date: 2005-03-29 12:25 It looks like we need to include something from the range library to get these functions. Thorsten? Doug

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set_property on reverse_graph fails
by Manish Mangal 30 Mar '05

30 Mar '05

Hi I am not able to use set_property function for reverse Graphs. I am using C++7.0 on .Net2003 compiler. I read an earlier question posted at http://lists.boost.org/MailArchives/boost-users/msg06970.php This sounded similar to my problem. The solution posted by Jeremy http://lists.boost.org/MailArchives/boost/msg66361.php runs fine on my machine . So I decided to use get_property instead of set_property as suggested in the solution. This did not solve my problem So I took Jeremy's solution and replaced subgraph by reverse_graph. Even that code generated: error C2784 could not deduce template argument list.. The code is: #include <string> #include <iostream> #include <boost/cstdlib.hpp> #include <boost/graph/adjacency_list.hpp> #include <boost/graph/reverse_graph.hpp> int main() { using namespace boost; using std::string; typedef adjacency_list<vecS, vecS, directedS,no_property, property<edge_index_t, int>, property<graph_name_t, string> > graph_t; graph_t g; get_property(g, graph_name) = "graph"; std::cout << "name: " << get_property(g, graph_name) << std::endl; typedef reverse_graph<graph_t> reverse_graph_t; reverse_graph_t sg = reverse_graph_t(g); get_property(sg, graph_name) = "Reverse graph"; std::cout << "name: " << get_property(sg, graph_name) << std::endl; return exit_success; } Can anyone suggest how to make this work? Much appreciated Manish Mangal Stratagen Systems 1-425.821.8454 ext. 136

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Re: Asynchronous I/O
by Don G 29 Mar '05

29 Mar '05

Of the mechanisms discussed, I am not sure I understand what you mean by async I/O with only one thread. I can imagine a nonblocking/select style approach that has no extra threads, but as soon as the main thread is not waiting on I/O itself (my interpretation of "async"), there needs to be threads to do the waiting. Unless I am missing something (which happens often<g>) or we are having terminology problems (also a frustratingly frequent occurrence). Best, Don --- Caleb Epstein <caleb.epstein(a)gmail.com> wrote: > I'd say coupling asynchronous I/O to multi-threading would be a > mistake. It is at its most useful IMHO in single-threaded cases. > > -- > Caleb Epstein > caleb dot epstein at gmail dot com __________________________________ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/

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Warnings in Boost.Thread
by Janusz Piwowarski 29 Mar '05

29 Mar '05

Hi all, When Boost.Thread is compiled in release mode, there are a lot of warnings about unused variable 'int loop_count' in read_write_mutex.cpp. They comes from code like: int loop_count = 0; while (m_state == -1) { BOOST_ASSERT(++loop_count == 1); ++m_num_waiting_readers; m_waiting_readers.wait(l); --m_num_waiting_readers; } If loop is for second evaluation of condition only, i think it would be better to write: if (m_state == -1) { ++m_num_waiting_readers; m_waiting_readers.wait(l); --m_num_waiting_readers; BOOST_ASSERT(m_state != -1); } Regards, Janusz

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Re: [boost] Re: Classpath to C++ conversion
by Iain Hanson 29 Mar '05

29 Mar '05

> Do I understand this to mean that "ClassPath" is the entire Java > API? If not, you've failed to answer Dave's query on what > "Classpath" actually is. I have no idea what it is, so I > cannot discuss the merits of the idea for Boost. > Classpath is the GNU project for the full Java API. > > You didn't explain what GCJ is, and given that you used the term "GCJ > > classes" I'm beginning to think I don't really know what you mean by > > GCJ. > > I also don't know what "GCJ" is. IOW, I have no idea what this > proposal is for and can't comment on whether it is useful. > GCJ is the Java part of gcc. /ikh

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