Rob Arthan wrote:
Happy New Year to the Poly/ML User Community!
I am trying to find a fix to a problem where we want to apply a function
that sometimes takes far too long to execute. So I want to abort execution of
the function after a specified time limit. I have a solution that seems to work
by forking a worker thread to execute the function and store the result in a
ref while
the control thread goes into a loop that waits for 100ms and then either (1)
returns the
result from the ref if the worker thread is no longer active, (2) repeats if
the thread
is still active and we haven’t reaced the time limit or otherwise (3) kills the
worker thread
and returns a dummy value.
I am implementing this using Thread.ConditionVar.waitUntil and have two
questions
about that:
1) What does the bool returned by Thread.ConditionVar.waitUntil mean? That
doesn’t seem
to be documented.
While not a Poly/ML -specific answer, this would be the indication of
whether, when execution continues after the wait, it is because the wait
condition was satisfied OR the timeout expired (not 100% which value
means which, but you should be able to determine that rather easily).
2) In addition to the timeout, Thread.ConditionVar.waitUntil has a condition
variable and a mutex
as arguments. I am just creating these using Thread.ConditionVar.conditionVar
and Thread.Mutex.mutex
because I need some values to pass to Thread.ConditionVar.waitUntil. I am not
doing any signalling
or locking or unlocking. Is that going to cause any problems? (The condition
variable and the mutex
are local to the control thread function, so the worker thread function has no
access to them.)
The associated mutex is used to "protect" the condition variable itself,
so that while it is examining the condition, things can't change out
from under it - that's all.
Good luck, and feel free to request further clarification.
Robert Roessler
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