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Boost Graph - internal datastructures of graph
by Peter Billen 14 Mar '05

14 Mar '05

Hello all, I was wondering what internal datastructures are used in the different graph concepts (Graph, IncidenceGraph, etc.), to achieve efficient implementations of these different concepts. Is this documented somewhere? I couldn't find anything about the implementations on the website. Is this discussed in the book? I am aware I can browse through the code, but I thought it might be a good idea to ask it first here. Thanks for your replies, -- Peter

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[Boost-bugs] [ boost-Bugs-1163091 ] push_relabel_max_flow may be broken
by SourceForge.net 14 Mar '05

14 Mar '05

Bugs item #1163091, was opened at 2005-03-14 11:06 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1163091&group_… Category: graph Group: None Status: Open Resolution: None Priority: 5 Submitted By: Douglas Gregor (dgregor) Assigned to: Douglas Gregor (dgregor) Summary: push_relabel_max_flow may be broken Initial Comment: The push_relabel_max_flow algorithm seems to be dereferencing past-the-end iterators. The initial bug report is here: http://lists.boost.org/MailArchives/boost-users/msg10032.php Doug ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1163091&group_… ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Boost-bugs mailing list Boost-bugs(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/boost-bugs

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[Boost-bugs] [ boost-Bugs-1163077 ] EdgeListS = setS for adjacency_list does not work
by SourceForge.net 14 Mar '05

14 Mar '05

Bugs item #1163077, was opened at 2005-03-14 10:48 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1163077&group_… Category: graph Group: None Status: Open Resolution: None Priority: 4 Submitted By: Douglas Gregor (dgregor) Assigned to: Douglas Gregor (dgregor) Summary: EdgeListS = setS for adjacency_list does not work Initial Comment: The adjacency_list class template requires the EdgeListS selector to indicate a Sequence container (and may very well require the default listS). setS, for instance, does not work. See http://lists.boost.org/MailArchives/boost-users/msg09557.php ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1163077&group_… ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Boost-bugs mailing list Boost-bugs(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/boost-bugs

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[wiki] New content filtering to reduce spam
by Jeff Garland 14 Mar '05

14 Mar '05

All - I've instituted a new content filter on the Wiki to try and cut off the spamming without going to a login or other user intrusive mechanism. The timing of this feature turned out to be important as a sophisticated spambot that evades the ip banning strategy by using many different ip addresses (presumably using zombie machines) has been attempting to SPAM the wiki all day today. The new content filter has sucessfully stopped this bot. Note that if a spammer is successful I am now reverting all spam content from the Wiki history so that there is no change of googlebot finding it. For the moment, I'm not going to publish the regular expressions I'm using to filter, but suffice to say, normal boost content should be unaffected. If you get an error indicating content has been blocked due to spam, send me and email. Thanks, Jeff

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Hash function review
by John Maddock 14 Mar '05

14 Mar '05

A little late in day, here we go: >What is your evaluation of the design? The design is basically fixed by the TR, so there's not much to review here. The extensions to the TR proposed by Peter Dimov, and implemented here look fine to me as well. >What is your evaluation of the implementation? Modulo the suggestions to the pointer hashing, it looks very good: I spent some time examining the floating point implementation, along with the associated test cases, and everything that could be tested looks like it is. I agree with those opinions expressed here that it's better to have a reliable implementation, that produces good hash values, than an artificially fast version that produces bad hash values. I have one query regarding hashing of integer types, regarding hashing of long long, Daniel says: "Also, it will need a different hash function to the other integer type as the current one won't take account of the higher bits. I want to take my time over things like this and get it right." But I think this is a (mostly theoretical) issue already: type long may have more bits than size_t does. I don't think this is a big issue though, it should effect very few platforms, and shouldn't hold up acceptance of the library. >What is your evaluation of the documentation? Also looks very good, I would like to see some more description of how the implementation differs from the TR (all the bits are there in the docs, it's just not clear which are part of the TR, and which are the extensions). >What is your evaluation of the potential usefulness of the library? Can't believe we haven't had this in Boost already. It's about time. >Did you try to use the library? With what compiler? Did you have any >problems? I've spent some time examining and running the test cases, everything that should pass does so with: gcc-3.3.2 Intel 7, 8.1 and 9Beta VC++ 6, 7, 7.1 and 8Beta. The tests are failing with Borland, due to a problem with Boost.Test. >How much effort did you put into your evaluation? A glance? A quick >reading? In-depth study? A couple of hours reading the code and the docs. >Are you knowledgeable about the problem domain? I don't claim to be any kind of expert in hashing. >Do you think the library should be accepted as a Boost library? Yes, please ;-) John.

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[test] still regressions with IsDebuggerPresent()
by Stefan Slapeta 14 Mar '05

14 Mar '05

There are still regressions caused by a missing definition of IsDebuggerPresent(). These failures have been introduced by the recent changes in boost.test. What is to do here? see http://tinyurl.com/6vdo9 Cheers, Stefan

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Sockets: proposal for a library design
by Boris 14 Mar '05

14 Mar '05

I updated the Wiki pages for a net library at http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?BoostNet. After collecting all the information I found at the Wiki pages for the socket and multiplexing library I try to explain how a net library should basically look like. The proposal includes various I/O models and is based on I/O streams. As usual any comments are appreciated, Boris

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[serialization] current CVS not working for CW
by Joaquín Mª López Muñoz 14 Mar '05

14 Mar '05

Hello, None of the CW compilers being tested seems able to build the serialization lib against the current CVS. I seem to recall there were no problems of this kind a month ago or so. I know the author's probably aware of this, just wanted to know about the status of this problem. Thank you, Joaquín M López Muñoz Telefónica, Investigacion y Desarrollo

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RE : FSM Review : Performance Issues
by jdspalding＠comcast.net 14 Mar '05

14 Mar '05

******************************************************************************* BOOST Re: FSM Review : Performance Issues. I'd like to add some overall comments about the FSM's perceived performance issues. To clarify my bias, previous comments, I have already submitted a positive review, focusing on usage issues. Context: On Sat, 12 Mar 2005 , Dave Garland wrote >On Sat, 12 Mar 2005 15:57:10 -0500, David Abrahams wrote >> >> Haven't a few people been reporting that they won't even begin to >> apply this one because of particular limitations? Anyone who needs >> higher performance won't even get started. >Sure, and on the other hand we've had at least one testimonial that this was >the best fsm library they found -- served them well in a project. I've heard >the same sort of argument from people comparing std::string to a char*. >std::string: Discussion : I believe the discussion of performance in the proposed boost FSM library is going in an unrewarding direction. Undefined design possibilities are being weighed against a working system. (notice : I am going to be sympathetic to the "working system".) On the "design possibilties" side there seem to be a number of major issues. - double dispatch is O(n), we'd like O(1). - overall performance is slow, state transitions in XXX nSec are too slow for a proposed application. - some people have the idea that the techniques used to allow FSM to extend over multiple translation units could be improved. Again and again someone writes in and says the design does not feel right, if we did XXX, FSM is likely to be able to fix YYY. However, the concrete solution is not yet conceived, and for now, a general plausability argument will have to do... Proposal: I think we could adopt a structured approach to evaluate these competing claims. A) One viewpoint of the FSM library is through the filter of application performance tradeoffs. IMHO we have exhausted the qualitative approach, and need the definiteness of the quantitative. I would think the FSM critics have the obligation here to provide support to their view, that FSM performace is inadequate. A.1) It is said that performance considerations will keep FSM from being considered for some applications. => Then could we specifically, and quantitatively define a class of applications for which FSM, as it exists today, would be inadequate? (model app) - in the timed performance area, what are the model app's FSM performace metrics, such as number of states, use of orthogonal states, depth of state nesting, number of events fired per second, number of events handled per second? - what are the model app's non FSM performance metrics, perhaps normalized to FSM metrics, such as lines of code or execution time, per state change, or per event fired? - please also include some details about the context for the app's execution, usage area, etc., to assist the readers from other experience domains. A.2) It is said that O(n) double dispatch is inadequate, that better design is required for acceptance. => To really assert this we really have to have a complete model of FSM's runtime behavior. Since this is different in different usage scenarios, what we really need are several usage scenarios, and an analysis/measurement of where FSM spends its time. I think Andreas has mentioned that he thinks other areas than double dispatch are more important. IMHO this is a quantitative issue, per usage scenario. B) A second viewpoint of the FSM library is that of usage requirements in the application's code. Here there are at least two areas of contention - B.1) The implications of the requirement for compilation in multiple translation units. - B.2) The overal ease of use of the FSM library's API. Finally, here is my submission of data for a model usage of FSM, in the above framework. ****************************************************** Quantitative data : example : from J. Spalding's use of FSM area : industrial control. A.1) Performance metric Number of states : 15-20. maximum state nesting depth : 5. use of orthogonal states : no. maximum number of events per second (burst) : 10. events handled per second (burst) : 10. context : Use of FSM in a machine control application. FSM controls application's execution "mode", and the hardware error monitoring state. remarks : model app not stressing FSM performance. A.2) Runtime behavior profile not carried out. FSM performance trivial component of model application. B.1) Multiple translation units. model application code was broken across multiple translation units, no particular problems occurred. B.2) API Ease of Use. API was expressive, easy to configure to solve the problem. The only difficulties encountered were found in tracing compile time initial useage mistakes. This is also a strength of the approach, incorrectly configured FSM machines will not compile. *********************************************************** My Opinion : per FSM acceptance into Boost: - I like the FSM API, think performance today is adequate for many/most applications, think UML connection is a plus, voted for FSM acceptance. - Seeing statements such as 100 nSec cost per event handled prevents serious use of FSM, does offend me, without a supporting application performance model/context. IMHO Andreas has requsted such info many times, and has not been rewarded with any quantitative data. - IMHO, If we were evaluating FSM for an engineering use today, it would be accepted, due to good API, good documentation. The only way FSM could fail is if FSM code grabbed > (XX) % of the app's compute cycles, or made an unacceptable latency hit. The alternatives, at least in the boost discussion of it, are all proposed concepts requiring evaluation & development. - Further it would be quick work to use FSM to prototype a proposed use, and numerically evalute its time/space/latency cost. Just write the proposed FSM on the target machine, install it with a test harness that puts out events at the required rate, and you have a use/not use decision with hard data. If FSM were included in Boost, then this evaluation might be accomplished a number of times in the future, and the fsm interest group may acquire data justifying a performace oriented new implementation/library. ***********************************************************

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Re: Sockets: proposal for a library design
by Don G 13 Mar '05

13 Mar '05

Hi Boris, Thanks for all the effort and getting something posted! On first blush, my thoughts are as follows: I would suggest that a proposed Boost.Net library should focus on networking in a more abstract manner, and not be merely a socket encapsulation. IMHO, sockets are a terrible API and should be hidden as fast as possible. A socket wrapper class is appropriate, but I would not go to any trouble to change the socket API. Simply wrap the resources and provide portable access to the underlying system. The real end-user part of the Net library should not talk about sockets (unless one provides a method like get_native to return the socket handle, and that method is defined as non-portable). I think all desired I/O models should be available at run-time (see below). In my own work in this area I have seen that this approach does not greatly effect the implementation. In other words, there is virtually nothing to be gained by making async I/O optional at compile-time. As others have also suggested, I would agree that the net facilities not be tied up into I/O streams. It would be better to provide the network facilities and then layer on I/O streams for those that want it. There are really only a few abstract entities to worry about: Url, Address, Stream, Datagram, Acceptor. In my work (not related to Boost), I've also created a Network class to serve as the abstract factory and contain a thread pool for doing the async I/O. I believe your diagrams use "Client" and "Server". I think these terms are a bit too generic. I prefer the term "Acceptor". Usage examples: shared_ptr<Network> net (new SomeSpecificNetwork(some_arguments)); Url some_url = "http://www.boost.org"; shared_ptr<Address> addr = net->new_address(some_url); shared_ptr<Stream> str = addr->new_stream(); str->connect(); // now it's connected (blocking) shared_ptr<Address> localhost = net->new_local_address("ntp://"); shared_ptr<Datagram> dg = localhost->new_datagram(); // on the ntp port localhost = net->new_local_address("ftp://"); shared_ptr<Acceptor> ac = localhost->new_acceptor(); // "ftp" port str = ac->accept(); // blocking accept I've omitted any nonblocking/async methods for brevity. IMHO, blocking, nonblocking and free-threaded-async-w/callback are the only models worth providing. These models can be ported anywhere and can be implemented via whatever mechanism is best for the given platform. A select() based version can be made to work just about anywhere with minimal #ifdef logic, but may be less than ideal when the system supports poll() or NT I/O completion ports. One thing I think is essential when using a blocking model is cancellation. For example, I have a reset() method on Acceptor, Address, Datagram and Stream that can be called at any time to cause blocking methods to terminate with a cancel exception (obviously this must be from another thread). Ironically, these reset() methods meant I could not use blocking socket calls to implement my blocking methods - recv() cannot be canceled once it blocks (at least not portably)! The big issue in nonblocking I/O is how to notify the application that things have changed and now would be a good time to try more I/O. I like the free-threaded callback for this as it fits closely with async I/O and that way the nature of the I/O mechanism can still be encapsulated. Throughout the above I use the term "free threaded callback". By that I mean that the user supplied callback will be invoked directly by a worker thread. The reason for this is that it is the only way to approach the efficiency of a hand-rolled select/poll loop. When select() returns, the fd_set would be examined and steps taken to prepare for the next call to select(). Since multiple operations could complete, whatever state machines exist are pumped inside a processing loop between select() calls. When the abstraction comes in and hides the loop behind callbacks, if the callbacks are made directly, we add only the overhead of making the callbacks. If, on the other hand, all callbacks where marshalled out, the loop would not have the information needed to formulate the next call to select() and would likely have to be interrupted repeatedly to get to the proper state. The dangers of this approach should be obvious (deadlock to say the least). The user code is now forced to understand the execution model in order to properly code a callback. What I found is that a short list of allowed operations is sufficient. Any async I/O methods are OK, as are nonblocking methods, etc.. After that (long winded) explanation, what I have also seen is that very few applications need the performance that free-threaded callbacks provide and would opt out of the complexity if they could. My solution to this was an auto-marshalling callback. I'm not sure what facilities Boost provides for queued function<> calls, but the idea is to provide a callback that queues a callback. The pseudo code for me was something like this: str->async_read(buf, n, channel.bind_async_call(this, &This::foo)); The "channel" was my entity that could enqueue calls. The "(this, &This::foo)" would actually be a function<> object or something. The return from bind_async_call() is a function<> object that performs the actual call to channel.async_call() passing the user callback. Whew! Slightly more than $0.02, I know. :) Best, Don --- Boris <boris(a)gtemail.net> wrote: > I updated the Wiki pages for a net library at > http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?BoostNet. > > After collecting all the information I found at the Wiki pages for > the socket and multiplexing library I try to explain how a net > library should basically look like. The proposal includes various > I/O models and is based on I/O streams. > > As usual any comments are appreciated, > Boris __________________________________ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/

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