- Boost-users - lists.boost.org

CVS import gotcha - beware!
by Steve Folly 30 Mar '04

30 Mar '04

Hi, Most of you are probably aware of this, but I just thought I'd share my experience with trying to import the new version of boost into our CVS repository using 'cvs import': It wasn't recognising new folders - e.g. boost/spirit/core and all it's contents. I was puzzling it for a while until I realised the import output was showing 'I' next to boost/spirit/core. Aha - it's ignored. DOH! Well, core files are ignored, aren't they! To all those who have been long suffering with this : don't forget to include '-I !' in the command to include all files!! I'll be happy if it helps at least one person! :) -- Regards, Steve.

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RE: [Boost-users] Defining less on member variables/functions
by Chris Jurney 30 Mar '04

30 Mar '04

In this case, I could have used pair's operator<, but if I have a class by value as the second item of the pair that doesn't have a meaningful operator<, I want to ignore it in the sort. Thanks for all the help, guys. Chris -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Victor A. Wagner Jr. Sent: Friday, March 26, 2004 8:40 AM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Defining less on member variables/functions why do you want to sort ONLY on the 1st element of the pair? At Thursday 2004-03-25 11:34, you wrote: >content-class: urn:content-classes:message >Content-Type: multipart/alternative; > boundary="----_=_NextPart_001_01C41297.D800D40A" > >I've had this same pattern come up 4 or 5 times now, and each time I've >been unable to find a stl + boost solution that allowed me to do what I >want without writing my own less function. Basically, I want something >that will let me do a sort, or define a map on structs or pairs without >writing a less that compares the member variable or ..first. My last attempt: > >vector<pair<float, float>> myVector >std::sort(myVector.begin(), myVector.end(), _1.first < _2.first); > >No such luck. It looks like I can do operator * and & on lambda objects, >but not access members through them. Is there anything in boost, stl, or >elsewhere that lets me not write this: > >class myLess >{ > bool operator() (pair<float, float> a, pair<float, float>b) > {return a.first < b.first;} >} > >Thanks for any help, >Chris > > >_______________________________________________ >Boost-users mailing list >Boost-users(a)lists.boost.org >http://lists.boost.org/mailman/listinfo.cgi/boost-users Victor A. Wagner Jr. http://rudbek.com The five most dangerous words in the English language: "There oughta be a law" _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Microsoft Managed C++
by Roger Wilco 29 Mar '04

29 Mar '04

I have a somewhat large (~100K lines) C++ server application. It uses Boost (lots of smart pointer use, thread use, regex), Xerces XML libraries, some MFC for GUI, and ADO for database access. I tried to build a test build of my application using Microsoft's Managed C++. I got all my code to compile, but I can't link to either Boost or Xerces XML. Is this possible? Has anyone done this? If I ultimately go the .NET route, I would replace Boost and Xerces with functionality provided by the native .NET runtime libraries. However, that would be a massive time consuming undertaking. At this point, I just want to dip my toes in the water and observe pros/cons of .NET, and have the option of migrating to .NET piecemeal. I have solid experience with C# and Java and I am extremely experienced with C++ (10 years). My main problems with C++ are: - Compile times. On my 2.8GHz dev system, a rebuild takes ~20 minutes and even a build after making a minor change takes 45 seconds. It's amazing how VC++ build speeds really have remained so stagnant despite increases in hardware speed. I realize VC++ is the slower of the IDEs for build times. - Debugging memory corruption or thread concurrency issues. This is much easier in Java/C# and the tools for assisting are much easier to use. I spent many days trying tools such as Purify for C++ and couldn't produce any fruitful results. - Diagnosing memory usage. My server application uses lots of memory. After running for several hours under production conditions it will reach around 400MB-1.3GB depending on the tasks its doing. I'd like to get a general overview of where this memory is being used. I don't suspect blatant memory leaks (new with no delete) but instead runaway caches or legitimate usage. These issues are of course still present in C#/Java but the diagnostic tools to address these issues seem to be much better. I haven't found any usable C++ tool for this issue and I rely on manually logging data points and manually trying to infer an idea of what is happening. - Java/C# is overall a better (easier/faster to develop/maintain) development platform for this type of server application work. However, I will happily stick with C++ if I can resolve these other issues. And I am of course, concerned about any performance hit when migrating to Java/C#. We max out CPU and RAM use, so these factors aren't important. I couldn't take more than a 25% drop in efficiency. Any other suggestions on my situation?

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SQLite
by Witz 29 Mar '04

29 Mar '04

I don't know if this is the forum for bringing this up but ... I was wondering if anyone thinks SQLite might make a good addition to Boost - www.sqlite.org - if the author would agree to it. Ian Whittley

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boost::format with non-standard string class
by Scott Lamb 28 Mar '04

28 Mar '04

Hi, I'm not real happy with std::string, largely because it seems poorly suited to UTF-8. I'm happier with other classes such as Glib::ustring. [1,2] Is it possible to use boost::format with such a class? I'd previously thought that boost as a whole expected you to use std::string, but the recent discussion of boost::regex + Glib::ustring gave me some hope. It seems the requirements for boost::regex are more simple - a bidirectional, read-only character (not byte) iterator. That should be easy enough to provide for any UTF-8 string class. I do see explicit mention of std::basic_string in the boost::format headers, but I thought I'd ask anyway. (I likely will find or make another class to avoid pulling in all of glib. But it would be similar to Glib::ustring.) [1] - more in-depth discussion of Glib::ustring vs. std::string at <http://www.gtkmm.org/gtkmm2/docs/reference/html/ classGlib_1_1ustring.html#_details> [2] - additional reasons for disliking std::string at <http://www.sgi.com/tech/stl/string_discussion.html> Thanks, Scott

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boost/graph/push_relabel_max_flow::is_flow() bug?
by Arun Bhalla 27 Mar '04

27 Mar '04

Hi, I'm not really a user of Boost, but I've been referring to the Boost Graph Library code for another project. In particular, I've been looking at push_relabel_max_flow.hpp. I was writing a unit test which followed the same ideas of the is_flow() test, and it was failing on what should be a flow network with a valid maximum flow. The code in question: // a is an edge_descriptor if (capacity[a] > 0) if ((residual_capacity[a] + residual_capacity[reverse_edge[a]] != capacity[a]) || (residual_capacity[a] < 0) || (residual_capacity[reverse_edge[a]] < 0)) return false; I contend the test should actually be: // a is an edge_descriptor if (capacity[a] > 0) if ((residual_capacity[a] + residual_capacity[reverse_edge[a]] ! != capacity[a] + capacity[reverse_edge[a]]) || (residual_capacity[a] < 0) || (residual_capacity[reverse_edge[a]] < 0)) return false; I refer to an example network in CLR (1st ed.), p.589. There are several vertices, but I focus on vertices v1 and v2. In this graph, we have capacities c(v1,v2) = 10 c(v2,v1) = 4 and residual capacities cf(v1,v2) = 11 cf(v2,v1) = 3 With the above (original) test, it would fail because 11 + 3 (the sum of residual capacities) != the capacity of either edge. This would hold true if the sum of residual capacities were compared with the sum of capacities. Ordinarily this test would work if reverse_edge[a] has a capacity of 0, which would be the case if the edge (a) is in the flow network, but its reverse is not. I'm not a graph theory expert, though, so I defer to anyone who is. :) Thanks, Arun

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Defining less on member variables/functions
by Chris Jurney 27 Mar '04

27 Mar '04

I've had this same pattern come up 4 or 5 times now, and each time I've been unable to find a stl + boost solution that allowed me to do what I want without writing my own less function. Basically, I want something that will let me do a sort, or define a map on structs or pairs without writing a less that compares the member variable or .first. My last attempt: vector<pair<float, float>> myVector std::sort(myVector.begin(), myVector.end(), _1.first < _2.first); No such luck. It looks like I can do operator * and & on lambda objects, but not access members through them. Is there anything in boost, stl, or elsewhere that lets me not write this: class myLess { bool operator() (pair<float, float> a, pair<float, float>b) {return a.first < b.first;} } Thanks for any help, Chris

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Re: [Boost-users] MAC OS X installation of boost libs
by Michael Short 26 Mar '04

26 Mar '04

Hello I am using MAC OS X 10.3.3. First I done find the bjam tool? Second when I build the bjam tool myself I get the following error. Jamfile:71: in module scope rule unless unknown in module. I think if you could please just give me a quick step by step of what you did to setup the libs with the correct directorys you used then that would probably fix the problems. I did try following the instructions on the page you stated but just did not help. thanks Michael On Tuesday, March 23, 2004, at 09:25PM, James Mastro <jmastro(a)rochester.rr.com> wrote: >On Mar 22, 2004, at 5:12 PM, Michael Short wrote: > >> The only problem is that I am having problems installing and building >> the libs on my MAC OS X system. > >What kind of problems? What version of OS X? I built boost 1.31.0 on >OS X 10.3.2. I think the regex library gave me some problems, but I >believe everything else built OK. > >I just followed the directions here: > >http://www.boost.org/more/getting_started.html > >-jim > > >

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MultiArray questions
by Dr Mark H Phillips 25 Mar '04

25 Mar '04

Hi, I've recently found out about the existence of MultiArray and I am quite impressed! I was thinking of implementing something similar myself but now hopefully I don't have to! However I have a few questions that I'm hoping someone can answer. Question 1 ---------- In the user documentation there is an example which has some example code: for(index i = 0; i != 3; ++i) for(index j = 0; j != 4; ++j) for(index k = 0; k != 2; ++k) A[i][j][k] = values++; Why can't you change the != into <? Ie, do: for(index i = 0; i < 3; ++i) for(index j = 0; j < 4; ++j) for(index k = 0; k < 2; ++k) A[i][j][k] = values++; or can you? This would be more efficient I should think, and requiring that index types be ordered shouldn't be too onerous should it? Question 2 ---------- If I use the built-in "no-frills" C array type to represent a 2-dimensional array in row-major order, then I would access an element (i, j) by doing: a[ &a[0] + i*n + j ] where a is my m by n array. And if I wish to traverse a, in row-major order, I can do: for (int* ip=&(a[0]); ip<&(a[n*m]); ip+=n) { for (int* ijp=&(ip[0]); ijp<&(ip[n]); ++ijp) { visit(ijp); } } These are a very efficient ways of doing things, but it lacks somewhat in ease-of-generalization and in readbility. This is where the MultiArray library is useful. But do I lose in efficiency by going to MultiArray? Ie, in the simple case where base is 0, stride is 1, and when we traverse in row-major order, is the MultiArray library smart enough to do compile-time optimizations to generate code which is as efficient as the above? I am guessing that this sort of approach is what the Blitz++ library does?? Question 3 ---------- Is it possible to construct a new multi_array/multi_array_ref/const_multi_array_ref from an array_view by doing a deep copy of the view? A view is a nice way of looking at different parts of a MultiArray object in a readable way, but sometimes you might wish to turn this view into a more-efficiently represented object. Is this easy to do in the MultiArray library? Question 4 ---------- Sometimes you might have an object starts off being mostly accessed in row-major order, so you want a representation which works efficiently for this use. But down the track you might wish to change to mostly column-major access. Does MultiArray provide easy ways to transform from one underlying representation to another? Thanks, Mark Phillips.

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RE: [Boost-users] boost::filesystem::exists() & GetfileAttributesA
by Ben Hutchings 25 Mar '04

25 Mar '04

Sebastian Orfino <sorfino(a)lanacion.com.ar> wrote: > I am experiencig a problem with exists() and its Windows > implementation with GetFileAttributes API. I am using exists() prior > to the scan of a directory to see if it exists; the fact is that on > W2K (just tested it on that OS) after a day or two > GetFileAttributesA() returns INVALID_FILE_ATTRIBUTES but the path > does exists (it is a UNC-style path). > After a restart of the app, all works fine. <snip> It couldn't possibly be related to this bug, could it: <http://support.microsoft.com/default.aspx?scid=kb;en-us;325929>? I know that that talks about Windows XP clients and NT 4 servers but MS does not always test thoroughly whether a bug found in one version of a product exists in other versions. The bug is supposed to be fixed in Windows XP SP2, by the way.

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