Condition variables used in locks
multi method wait( --> Nil )multi method wait( --> Nil )
Without any predicate, it waits on the condition variable itself; with a predicate, waits until the code returns a truish value.
my = 100;my ;my ;for ^
The condition we obtain from the
$l lock is awaited using a predicate, in this case, check if the counter is still zero. When it takes another value, the program flow continues in the next instruction.
If and only if there are any threads that have previously waited on the condition variable, it unblocks at least one of them. Let's see how it works in this example:
constant ITEMS = 100;for 1..15 ->
We are repeating 15 times the same operation: start 100 threads, every one of which modify a single element in an array. We
protect the modification of a global variable,
$done, and use
signal to wake a up another thread to do its thing. This outputs the first elements of the generated arrays.