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[multi_index_container] Usage Idioms
by Robert Jones 15 Sep '08

15 Sep '08

My head is now exploding with understanding the full power and flexibility of multi-index-container, but still it is not clear to me how best to do the simple things! What is the idiomatically 'correct' way to apply the equivalent functionality of the erase-remove idiom to a multi-index-container? I'm assuming that this, (very much abridged for brevity of exposition) multi_index_container mic; mic.erase( remove_if( mic.begin(), mic.end(), pred ), mic.end() ); is doomed since the remove algorithms overwrite removed elements with copied elements which would cause havoc with other indices, and in any case this kind of modification through iterators is explicitly prohibited. I did think of extracting a vector of references, doing erase-remove on that and then applying rearrange(), but it seems rather inelegant. Is there a better way? Thanks. - Rob.

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Documentation about design and implementation
by Kartik Mahajan 15 Sep '08

15 Sep '08

Hi I have recently installed Boost 1.36. I am right now experimenting with the Boost.thread library primarily for the purpose of learning and I am trying to use them in the project I am working. I also wish to learn to use asio and interprocess libraries in near future. I have gone through the documentation about how to use the thread library, but I guess there is nothing mentioned about its design and implementation. The only reason I am interested in some documentation related to its design and implementation is purely for learning purpose. As Boost libraries are designed mostly by experts, I would like to broaden my horizons "on how to design". I would not like to be just a user of such expertly designed libraries and would like to learn the ins of designing. Also going through the code would I guess improve my skills. I did read some include files and also installed cscope on my linux box so that I can go through code easily but its too hard for me to comprehend why the things ie code is written the way it is. Is some documentation related to implementation of the library available ? I guess no ? Do we just have to comprehend by reading the code ? Are there some tips for reading the code ( I am even unable to find which file to start from, I am still a newbie ) I just need some tips and guidance. Thanks & Regards Kartik Mahajan

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IoStreams: Weird bzip2 behavior?
by Dr. Roland Bock 15 Sep '08

15 Sep '08

Hi, when experimenting with IoStreams a bit, I tried bzip2 compression, too. In contrast to zlib and gzip compression, it did not work as expected. I have a bit weird behavior in two aspects. a) Unknown error code: ====================== The attached code yields: Caught bzip2 error with code: -2 data_error: -4 data_error_magic: -5 config_error: -9 So for some reason, I am catching a bzip2_error with an error code which is not even documented. When I replace gzip2 by zlib, it works fine. b) Empty output of compression: =============================== When I use a std::ofstream instead of the decompressingStream, I get an empty file. This might be the reason for a), but then I would have expected data_error or data_error_magic? Decompressing the content of a valid bzip2 compressed file works fine. Any ideas what might be going wrong? Thanks in advance, Roland

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[Boost][Serialization] CPU bottleneck
by Vjekoslav Brajkovic 14 Sep '08

14 Sep '08

Hi, I am using the serialization library in my project and it has been functioning perfectly thus far. However, when I've scaled up the usage requirements, I had hit a very odd problem. Let me explain the use case. Serialization library is used in a DFS framework, handling large data structures (in terms of size, not complexity) such as std::vector<char> of size 1MB and above. The framework consists of two major components: Chunkserver (server) and a Client. Files are chunked, wrapped in a class, serialized and sent over the wire. Same things is done on the server side, but in a reverse order. The actual binary data is stored in a vector (previously, I've tried using string instead, but I had some issues with it and Robert suggested using some an alternative container). When I was depositing large files to Chunkserver, disk utilization was almost non-existent, whereas the CPU was maxed out. It is important to realize that this problem occurred only on the server side, not client. Upon further investigation using gprof I have concluded that the bottleneck was in the serialization library (it also may be the case that I am misusing it). According to the profiler, above 97% of the CPU time was spent in a singe function. Profiler results can be found at this address: http://www.cs.washington.edu/homes/balkan/gprof.txt For the reference, the signature of that function is: boost::serialization::serialize_adl< boost::archive::text_iarchive, std::vector...> and I am using text archive. I as mentioned before, this issue only occurs on a server side. I would appreciate if anybody could explain why this is happening and more importantly how to circumvent the issue. Thank you! Vjeko

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What's the status of unordered_map.hpp?
by Peng Yu 14 Sep '08

14 Sep '08

Hi, In http://www.boost.org/doc/libs/1_35_0/doc/html/boost_tr1/unsupported.html, it shows the header file is <boost/tr1/unordered_set.hpp> for unordered_set. But I only find the following two files in version 1.36.0. boost/unordered_map.hpp I'm wondering if unordered_map is not stable yet, so that I'd better avoid using it. Or it will be stable from version 1.36.0 on? Thanks, Peng

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Missing MSVCR80.DLL
by Slava D 13 Sep '08

13 Sep '08

guys, please, could you help me. I have installed boost_1_35 with the BoostInstaller (taking the precompiled binaries). When I check any dll-s with the dependency walker (say, release version BOOST_DATE_TIME-VC-MT-1_35.dll or debug version BOOST_DATE_TIME-VC-MT-GD-1_35.dll), it says that it is missing MSVCR80.dll for the release version and MSVCR80D.DLL for the debug version. At the beginning I thought there was something wrong with my PC. I tried on another machine and got the same results. On one machine I have XP with SP2 and on another I have XP with SP3. Some people are saying that this usually shows some mess with the manifest files. But I did not need to generate the manifest file as I took the binaries from the Installer directly. Please, could you help me. Any advice would be greatly appreciated. many thanks, Slava

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Serialization: storing different representations in different archive types
by Simon Fraser 13 Sep '08

13 Sep '08

I have a program that saves program state in both binary and XML archives. I'd like to store one of the model objects in my program in different formats, depending on whether the output archive is XML or binary: for XML archives, I'd like to use a human readable-format, and for binary archives I'd like to use a much more compact representation. I don't see any methods on Archive that let me ask if the output is a textual format (text or XML). I could dynamic_cast in my load/save methods, but that doesn't extend to new kinds of archives that may be implemented in future. Is there a way to do what I want to do? Thanks Simon

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enabled_shared_from_this: bad_weak_ptr exception + online doc explanation
by cxv＠sfu.ca 13 Sep '08

13 Sep '08

Hi all, I have a class called TextTool. In its constructor I initialize a member variable. This member variable needs a pointer to TextTool in *its*constructor. Hence I need to have a pointer to "this" (TextTool) and then pass it to the constructor of the member variable. This is a summery of my code: *TextTool.h* class TextTool : public Tool, public boost::enable_shared_from_this<TextTool> { public: TextTool(QDialog *taskDialogue); private: boost::shared_ptr<ToggleControl> bold; //Member variable that needs a pointer to TextTool in its constructor }; *TextTool.cpp* TextTool::TextTool(QDialog *taskDialogue) : Tool(this->name) { boost::shared_ptr<TextTool> pointerToThis = TextTool::shared_from_this(); //ERROR OCCURS ON THIS LINE bold = boost::shared_ptr<ToggleControl>(new ToggleControl(pointerToThis)); } I get a runtime exception: "boost::bad_weak_ptr at memory location 0x0012fccc" when executing the above mentioned line. On the BOOST online documentation, I dont understand what this line means: "**this* must be a subobject of an instance *t* of type *T* . There must exist at least one *shared_ptr* instance *p* that *owns* *t*.". Do I need to have an instance (t) of TextTool (T) as a member variable of the class TextTool? Won't this lead to loops in my situation (since I want the "this" pointer to be created in the constructor itself)? Any help? Thanks, /C.

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jam environment variables
by Mika Heiskanen 13 Sep '08

13 Sep '08

Hello, Jam documentation mentions that "Jam picks up variable settings from your environment by default". However, I could not find any documentation on what environment variables affect what options. In particular, I am looking for a way to pass on to Jam the --layout and --build-type options via environment variables. Currently I am building a boost rpm for local distribution by using the following command sequence in the rpm .spec file: %build ./configure --prefix=%{_prefix} --libdir=%{_libdir} cat Makefile | sed -e 's/BJAM_CONFIG=/BJAM_CONFIG=--layout=system --build-type=complete/' > Makefile.new mv Makefile.new Makefile make all If I understand correctly, I should be able to define the compile options via environment variables instead of resorting to a hack like above. I'd appreciate any pointers to more detailed documentation on how to accomplish the above with environment variables alone. Thank you in advance, --> Mika Heiskanen / FMI

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what is a vertex_descriptor? (boost graph library)
by Will Chen 13 Sep '08

13 Sep '08

So it looks like it's basically a 0-based integer. When I start adding vertices to an empty graph, the first one comes back as 0, the second as 1, third as 2...etc. Is it always an integer? When is it not an integer? I really want a way to easily convert vertex_descriptor's and edge_descriptor's to and from strings. Any ideas? -- William Yun Chen '09 Hinman Box 1826 Dartmouth College Hanover, NH, 03755

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