Computer Science Canada Help with Java Semiphore |
| Author: | lufthansa747 [ Sun Sep 11, 2011 10:43 pm ] |
| Post subject: | Help with Java Semiphore |
ok what i am trying to do with the semiphore is. i want to init it and for every thread i make i want to increase the count by 1. when the thread is done i want to decrease the count by 1. while all this is happening i want the main thread to wait untill the semphore has reached and count of 0 and then continue with the code. how can i do this. |
|
| Author: | lufthansa747 [ Mon Sep 12, 2011 7:39 am ] |
| Post subject: | Re: Help with Java Semiphore |
bump |
|
| Author: | S_Grimm [ Mon Sep 12, 2011 8:29 am ] | ||
| Post subject: | RE:Help with Java Semiphore | ||
http://www.javaworld.com/javaworld/jw-04-1996/jw-04-threads.html?page=2 try using that code but with a counter instead of the boolean variable. eg
and have your other threads increment the counter when they are called. edit: you'd have to stick it in a block of code that isn't mouseDown() |
|||
| Author: | Tony [ Mon Sep 12, 2011 8:35 am ] |
| Post subject: | RE:Help with Java Semiphore |
A semaphore is typically used to block until a resource becomes available (continue with code when a count is above 0), but I suppose you can inverse the condition. The only tricky part to the implementation are atomic increment/decrement operations, but then there's java.util.concurrent.atomic |
|
| Author: | lufthansa747 [ Mon Sep 12, 2011 2:00 pm ] |
| Post subject: | Re: RE:Help with Java Semiphore |
Tony @ Mon Sep 12, 2011 8:35 am wrote: A semaphore is typically used to block until a resource becomes available (continue with code when a count is above 0), but I suppose you can inverse the condition.
The only tricky part to the implementation are atomic increment/decrement operations, but then there's java.util.concurrent.atomic well this is why i want to do that. i have one main thread. that thread spawn off 9 other threads which all do there own math operations. when they are done they update the main thread with numbers and decrement a variable in the main thread which keeps track of alive threads. currently i have my main thread stuck in a while loop with a 1 millisecond sleep waiting for the other threads to finish. i was hopping that using a semphore could optimize the code a bit because it would be more efficient then calling thread.sleep? |
|
| Author: | Tony [ Mon Sep 12, 2011 2:06 pm ] |
| Post subject: | RE:Help with Java Semiphore |
With a semaphore, you would still be busy-waiting. |
|
| Author: | lufthansa747 [ Mon Sep 12, 2011 2:42 pm ] |
| Post subject: | Re: RE:Help with Java Semiphore |
Tony @ Mon Sep 12, 2011 2:06 pm wrote: With a semaphore, you would still be busy-waiting.
but wouldn't it be faster and more efficient |
|
| Author: | Tony [ Mon Sep 12, 2011 2:59 pm ] |
| Post subject: | RE:Help with Java Semiphore |
Than what? How are you checking that other threads have finished now? How is that different from what you plan on doing? |
|
| Author: | lufthansa747 [ Mon Sep 12, 2011 5:58 pm ] |
| Post subject: | Re: RE:Help with Java Semiphore |
Tony @ Mon Sep 12, 2011 2:59 pm wrote: Than what? How are you checking that other threads have finished now? How is that different from what you plan on doing?
the code currently looks like this while(threadCount != 0){ Thread.Sleep(1); } //do something her but i thought that if i could use a semiphore block it would be better because i would not be doing a tight loop. lol idk i just though it would be better. |
|
| Author: | DemonWasp [ Mon Sep 12, 2011 8:47 pm ] | ||
| Post subject: | RE:Help with Java Semiphore | ||
In Java, if you want to wait for another thread to complete, use .join() on the thread you want to wait for. See: http://download.oracle.com/javase/6/docs/api/java/lang/Thread.html Your main then looks like:
Join puts the calling thread to sleep until the target thread is done. This is done without a busy-wait. |
|||