March 2004 - Boost-users - lists.boost.org

[BGL] Finding out what properties exist in a graph?
by Steve Juranich 30 Mar '04

30 Mar '04

Is there an easy way to find out all of, for instance, the vertex properties associated with a graph? What I'm looking for is something like the following: <pseduocode> vector<properties> my_vertex_properties; property_iterator pi, last; for(tie(pi, last) = vertex_property_list(Graph); pi != last; ++pi) my_vertex_properties.push_back(*pi); </pseudocode> How about it? Does anything like this exist or am I just daydreaming again? Thanks. -- Stephen W. Juranich Science Applications Intl. Corp. (SAIC) (520) 570-7706

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Serialization library
by Steve Folly 30 Mar '04

30 Mar '04

Hi, I'm looking using the Robert Ramey's serialization library for our own projects and would like to know it's current status. Obviously, it's not in 1.31.0, so what are the plans for it's future inclusion? Thanks. Steve.

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graph, dfs search
by Peter Aronsson 30 Mar '04

30 Mar '04

Hi. I am having a problem with depth_first_search. The thing I do different is that I do not put any info in a property map and I do not want to bother myself with colormaps etc. The application code does: Graph g; pass2_visitor vis; depth_first_search(g,boost::visitor(vis)); But I get a compilation error, saying that it can not find a suitable operator+ in the property_map... See attached files for complete example. Grateful for all help! (I am running from HEAD on sourceforge cvs ) Regards Peter Aronsson -- _________________________________________________________________ / Peter Aronsson, Phd Student at PELAB (Programming Environments \ | Laboratory ) Department for Computer & Information Science | | Linköping University, Sweden | |=================================================================| | petar(a)ida.liu.se , phone +46 (0)13-28 1737 Room 3B:490 | \_________________________________________________________________/ #include "tg.hpp" int main() { TaskGraph g; pass2_visitor vis; depth_first_search(g,boost::visitor(vis)); } #ifndef _TASKGRAPH_H #define _TASKGRAPH_H #include <boost/config.hpp> #include <iostream> // for std::cout #include <utility> // for std::pair #include <algorithm> // for std::for_each #include <boost/utility.hpp> // for boost::tie #include <boost/graph/graph_traits.hpp> // for boost::graph_traits #include <boost/graph/adjacency_list.hpp> #include <boost/graph/adjacency_iterator.hpp> #include <boost/graph/graphviz.hpp> #include <boost/graph/depth_first_search.hpp> //Task graph types using namespace std; using boost::tie; struct vertex_execcost_t { typedef boost::vertex_property_tag kind; }; struct vertex_unique_id_t { typedef boost::vertex_property_tag kind; }; struct edge_result_set_t { typedef boost::edge_property_tag kind; }; typedef boost::property<boost::vertex_name_t,string, boost::property<vertex_execcost_t,float, boost::property<vertex_unique_id_t, int > > > VertexProperty; typedef boost::property<boost::edge_weight_t, int > EdgeProperty; typedef boost::adjacency_list<boost::listS, boost::listS, boost::bidirectionalS, VertexProperty, EdgeProperty> TaskGraph; typedef boost::graph_traits<TaskGraph>::vertex_descriptor VertexID; class pass2_visitor : public boost::default_dfs_visitor { public: pass2_visitor(/* initialize containers to store stuff in*/) { }; template <typename Vertex, typename Graph> void discover_vertex(Vertex u, const Graph & g) const { // Do some stuff }; }; #endif

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CVS import gotcha - beware!
by Steve Folly 29 Mar '04

29 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 29 Mar '04

29 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 28 Mar '04

28 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 27 Mar '04

27 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 26 Mar '04

26 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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