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

RE: [Boost-users] Looking for some help with boost::thread::sleep()
by Kutch, Patrick G 03 Aug '04

03 Aug '04

Has nobody else experienced this? Patrick Kutch Life is too short to drink bad coffee. -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Kutch, Patrick G Sent: Thursday, July 22, 2004 8:07 PM To: boost-users(a)lists.boost.org Subject: [Boost-users] Looking for some help with boost::thread::sleep() I am used to putting in quick sleep() statements in my worker threads, usually a sleep(0) just to give up a timeslice, or maybe a sleep(1). Of course boost::thread::sleep takes an xtime object not a milliseconds value, so I wrote a small routine to simulate the sleep() statement using boost::thread::sleep: void inline UtilitySleep(long milliSeconds) { const int NANOSECONDS_PER_MILLISECOND = 1000000; if (0 == milliSeconds) { boost::thread::yield(); // just do a yield return; } boost::xtime time; int sec = 0; // if larger than 1 sec, do some voodoo for the boost::xtime struct if (milliSeconds >= 1000) { // convert ms > 1000 into secs + remaining ms int secs = milliSeconds /1000; milliSeconds = milliSeconds - secs*1000; sec += secs; } milliSeconds*=NANOSECONDS_PER_MILLISECOND; // normal boost time sleep stuff // get current time boost::xtime_get(&time,boost::TIME_UTC); // add # of desired secs and ms time.nsec+=milliSeconds; time.sec+= sec; // sleep until that time boost::thread::sleep(time); } It seems to always work fine unde Windows, however occasionally under Linux it appears that if I use a small value, such as sleep(2) that sometimes it takes longer to setup the values and call boost::thread:sleep() and I end up passing an xtime value that has already passed, basically blocking the thread forever. Anybody have any advice for me? Thanx! - Patrick _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Looking for a simple example of instantiating normal_distribution from the random library correctly
by Kuntz, David A 03 Aug '04

03 Aug '04

> I am instantiating normal_distribution from the random > library incorrectly and looking for a simple example of how to do it > correctly. > > I compiled, built and ran random_test.cpp and can see > when I step through the normal_distribution () operator that _r1 and > _r2 have values < 1. > > Here are the relevant excerpts from my incorrect attempt > at instantiation and calling the () operator: > > typedef boost::mt19937 base_generator_type; > > boost::uint32_t x = 42u; > Ideal4045EsmModel::base_generator_type > base_generator(x); > > double randomDrawResult; > > boost::normal_distribution<double> boostNormalRand; > > boostNormalRand.reset(); > > randomDrawResult = boostNormalRand(base_generator); > > This compiles, builds, and runs, but when I step through > the normal_distribution () operator, _r1 and _r2 have very large > positive values, resulting in an attempt to take the log of a > negative number and an Indefinite value being returned. > > I am a relatively inexperienced C++ developer. I have > built and stepped through random_test.cpp > (http://www.boost.org/libs/random/random_test.cpp) and can see that > its gets correct results, but I found it quite difficult to follow. Is > there anyone out there who could show me a simpler way? > > Thanks, > > Dave > > > >

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Bidirectionnal filtered multigraph
by Robert weldon 03 Aug '04

03 Aug '04

I've created a bidirectional filtered multigraph from an adjacency_list with vectorS and listS as containers for the vertices and egdes respectively. It seems the function edge(u,v,g) does not work properly for this kind of graph. I can detect the existence of an edge (u,v) if I iterate explicitly through the out_edges of the filtered graph but not if I use edge() directly on the filtered graph. Also, I get an exception when I remove an edge that was invisible to the edge(u,v,g) function while the bidirectionnal version of remove_edge for adjacency_list is erasing the edge ID form the in_edge list of the graph. Any idea why edge() does not work in this case? Patrick --------------------------------- Do you Yahoo!? New and Improved Yahoo! Mail - Send 10MB messages!

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Print all routes in a graph
by Daniele Carlucci 03 Aug '04

03 Aug '04

Hi all, I have seen the mail with dijikstra algorithm, there is a way to print all the routes in a graph from a node A and a node B? Thanks Daniele Carlucci

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Function Adaptor that takes an Address
by Ewan Mellor 03 Aug '04

03 Aug '04

I have a function T & foo() and I wish to use a function adaptor to turn this into T * foo2() In other words, I want a function adaptor that takes the address of its given function's result. Does such a thing exist in boost? TIA, Ewan Mellor.

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[BGL] Importing adjacency list from a txt file
by Rui Carvalho 03 Aug '04

03 Aug '04

Hi, I've got a file with the adjacency list of a graph, where each line contains the node index followed by the index of nodes that are adjacent to it (comma-separated). One of the lines of this file could read like: 1,3,4 This would mean that node '1' is adjacent to nodes '3' and '4' (undirected & unweighted graph). I'm declaring it as: typedef adjacency_list < vecS, vecS, undirectedS, no_property, no_property > Graph; Graph g; My question is: is there a simple way of reading the adjacency list into the graph from my txt file? I found Kevin_Bacon, but was looking for something more powerful. Then I found adjacency_list_io.cpp (is it documented?), but it wouldn't compile on MSVC. Am I missing something obvious? Thanks, Rui

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bind and weak pointers
by Jeff Williams 02 Aug '04

02 Aug '04

What is the prefered method of creating a boost::function<void()>, via boost bind, that is calling a member function of a class, and that class instance is held inside the bind object as a weak ptr. Thus, when the function is called, it will try to lock the shared_ptr, if successful it calls the bound function, otherwise it does nothing. Is there an standard way of doing this? Or do I have to write my own custom intermediate function? (which is how I do it now). Jeff

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execution order of slots (signals)
by oliver.kowalke＠t-online.de 02 Aug '04

02 Aug '04

Hello, if I create a signal sig with n slots (slots are ordered by group). What happens if : - I call sig(); and the first called slot removes the slot which is its successor - I call sig(); and the first slot connects a new slot to signal which has a higher priority (group -> higher values are executed at first) with best regards, Oliver -- "Der Spezialist ist ein Barbar, dessen Unwissenheit nicht allumfassend ist." Master's Voice, S.LEM

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RE: [Boost-users] Window API
by Ben Hutchings 02 Aug '04

02 Aug '04

Dr Jekyll <drjekyll(a)empirics.net> wrote: > Hi, > I use a library, which itself use Boost. This library define > > #define Handle boost::shared_ptr Ugh. > But because I intende to use WINAPI , this definition results > in a conflict > > c:\Program Files\Microsoft Visual Studio .NET > 2003\Vc7\PlatformSDK\Include\WinUser.h(3282): error C2751: > 'boost::shared_ptr' : the name of a function parameter cannot > be qualified <snip> > What should I do, if I have to keep the #define line in my library... Don't use that library. Its code quality is so low that you will probably waste more time working around its bugs then you can save by using it. If you disagree with this assessment, perhaps you could write and use a wrapper header that does something like: #ifndef LIBRARY_WRAPPER_H #define LIBRARY_WRAPPER_H #include "library.h" #undef Handle // undefine any other unwanted macros #endif // !defined(LIBRARY_WRAPPER_H)

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lambda and shared_ptr
by Vladimir Krasovsky 02 Aug '04

02 Aug '04

Hello boost-users(a)lists.boost.org, It seems to me that currently lambda's bind does not support shared_ptr as a second argument to bind, when first argument is a pointer-to-member. But boost::bind handles it perfectly. It would be nice for me to be able to write something like this: using namespace boost::lambda; struct SomeClass { int member1; }; boost::shared_ptr<SomeClass> ptr(new SomeClass); (bind(&SomeClass::member1, ptr) = _1)(5); Is it possible with current implementation of lambda? Or I have missed something important? -- Best regards, Vladimir mailto:vkrasovsky@yandex.ru

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