I don't have a specific reference and I am not pushing any particular company but Intel has developed some good online resources to help people use their hyperthreading product. They have a lot of pdf files but I guess they want you to buy their intro book, http://softwarecommunity.intel.com/articles/eng/1567.htm Rule 6 here may answer your immediate question, http://softwarecommunity.intel.com/articles/eng/1607.htm I also saw something on google about FFTW that mentions multi-threading. IF you are interested in efficient numerical stuff more generally, their site may be worth some time. Mike Marchywka 586 Saint James Walk Marietta GA 30067-7165 404-788-1216 (C)<- leave message 989-348-4796 (P)<- emergency only marchywka@hotmail.com Note: If I am asking for free stuff, I normally use for hobby/non-profit information but may use in investment forums, public and private. Please indicate any concerns if applicable. Note: Hotmail is possibly blocking my mom's entire ISP - try me on marchywka@yahoo.com if no reply here. Thanks.
From: hal@thresholddigital.com To: boost-users@lists.boost.org Date: Mon, 17 Mar 2008 09:42:46 -0400 Subject: [Boost-users] Threads Don't Take Turns Under Linux (Ubuntu Gutsy Gibbon)
I apologize if this gets posted more than once. I found the group on GMane, tried to post, joined the email list, then tried to post several times but still have yet to see it show up.
I'm learning C++ and found a tutorial on threads with Boost on Dr. Dobb's site. I've copied the code from this url:
http://www.ddj.com/cpp/184401518?pgno=5
It's supposed to fill a buffer with data on one thread and remove data on the other thread. I would expect it to add data and remove at almost the same time but when I run it, it adds 10 items, then removes them, then adds ten again, and so on. It's never adding and removing in an "interleaved" fashion. I've also tried the same with simple counters where both threads count to ten, but it doesn't seem to make a difference. It seems no matter how I set it up, one thread either completes, or runs until it has to stop for a mutex, then the other thread runs. It seems that there is never a case of both threads running at the same time. I've never had trouble doing this in Perl with fork() so I'm not at all sure what could be going wrong.
As I said, it's not just the program below, it seems to be any program that uses more than one thread.
Am I doing something wrong or is there a setting I need to change?
I'm compiling it with "g++ -lboost_thread mthrd.cpp -o mthrd && ./mthrd";
Thanks!
Hal ------ #include #include #include #include
const int BUF_SIZE = 10; const int ITERS = 100;
boost::mutex io_mutex;
class buffer { public: typedef boost::mutex::scoped_lock scoped_lock;
buffer() : p(0), c(0), full(0) { }
void put(int m) { scoped_lock lock(mutex); if (full == BUF_SIZE) { { boost::mutex::scoped_lock lock(io_mutex); std::cout << "Buffer is full. Waiting..." << std::endl; } while (full == BUF_SIZE) cond.wait(lock); } buf[p] = m; p = (p+1) % BUF_SIZE; ++full; cond.notify_one(); }
int get() { scoped_lock lk(mutex); if (full == 0) { { boost::mutex::scoped_lock lock(io_mutex); std::cout << "Buffer is empty. Waiting..." << std::endl; } while (full == 0) cond.wait(lk); } int i = buf[c]; c = (c+1) % BUF_SIZE; --full; cond.notify_one(); return i; }
private: boost::mutex mutex; boost::condition cond; unsigned int p, c, full; int buf[BUF_SIZE]; };
buffer buf;
void writer() { for (int n = 0; n < ITERS; ++n) { { boost::mutex::scoped_lock lock(io_mutex); std::cout << "sending: " << n << std::endl; } buf.put(n); } }
void reader() { for (int x = 0; x < ITERS; ++x) { int n = buf.get(); { boost::mutex::scoped_lock lock(io_mutex); std::cout << "received: " << n << std::endl; } } }
int main(int argc, char* argv[]) { boost::thread thrd1(&reader); boost::thread thrd2(&writer); thrd1.join(); thrd2.join(); return 0; } _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
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