Barriers are a synchronization tool that causes threads to wait at a specific location in the program until every thread has reached the same location. In this example, the first barrier is used to make sure that before any thread performs its calculations, every thread correctly sees that the value of diff is 0. The second barrier is used to ensure that every thread has been able to make its update to diff so that it can properly check for the tolerance. The last barrier is needed in the event that the some threads already performed the check and needed to perform the loop again that they do not set diff to 0 to change the result of the check for other threads.
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mitraraman
Another important part of this program that is not highlighted is the LOCK and UNLOCK on the diff variable. Since diff is a global variable that is being accessed and updated by all threads, the user must lock the variable before updating it so that there are no concurrency issues. For instance, when thread 0 locks diff to update it, then other threads will not be able to access diff until thread 0 is completed updating and unlocking diff.
Barriers are a synchronization tool that causes threads to wait at a specific location in the program until every thread has reached the same location. In this example, the first barrier is used to make sure that before any thread performs its calculations, every thread correctly sees that the value of diff is 0. The second barrier is used to ensure that every thread has been able to make its update to diff so that it can properly check for the tolerance. The last barrier is needed in the event that the some threads already performed the check and needed to perform the loop again that they do not set diff to 0 to change the result of the check for other threads.
This comment was marked helpful 0 times.
Another important part of this program that is not highlighted is the LOCK and UNLOCK on the diff variable. Since diff is a global variable that is being accessed and updated by all threads, the user must lock the variable before updating it so that there are no concurrency issues. For instance, when thread 0 locks diff to update it, then other threads will not be able to access diff until thread 0 is completed updating and unlocking diff.
This comment was marked helpful 0 times.