Wednesday, 30 September 2015

Barrier in UVM and Usage of uvm_barrier

uvm_barrier can be used to force a set of independently executing processes (e.g. virtual sequences) to wait until they have all reached a particular point.
The barrier provides a flexible synchronization mechanism between the processes: its threshold can be programmed to set the number of processes that must reach the synchronization point before the barrier is 'lifted'.

A barrier is like a semaphore in reverse. It simply blocks until a threshold number of requests.

The uvm_barrier class provides a multi-process synchronization mechanism.  It enables a set of processes to block until the desired number of processes get to the synchronization point, at which time all of the processes are released.

APIs of uvm_barrier class
  1. wait_for : Waits for enough processes to reach the barrier before continuing. 
  2. reset : Resets the barrier. This sets the waiter count back to zero. 
  3. set_auto_reset : Determines if the barrier should reset itself after the threshold is reached. Default is on 
  4. set_threshold : Sets the process threshold. 
  5. get_threshold : Gets the current threshold setting for the barrier. 
  6. get_num_waiters : Returns the number of processes currently waiting at the barrier. 
  7. cancel : Decrements the waiter count by one. This is used when a process that is waiting on the barrier is killed or activated by some other means.
Consider following examples,

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