Re: wait vs. yield?
On 05/30/2010 02:25 PM, Marcin Rodzik wrote:
On May 29, 9:42 pm, Eric Sosman<esos...@ieee-dot-org.invalid> wrote:
Thread.sleep()
Thread.yield()
Both techniques are *vastly* inferior to wait().
So whay does yield() exist? Is there any case in which it can be
preferred?
Anyway, thanks, I really appreciate your answers.
wait and notify are the Java equivalent to Posix condition
variables--they cause the thread to not run until some condition is met.
Sleep, on the other hand, can be used when you need the thread to not
run for a short while. Yield means to let another thread run if it can
run. The idea is that you might be doing a computationally expensive,
but necessarily synchronous task: every once in a while, you want to
explicitly tell someone else to run.
Sleep is occasionally useful for some timing stuff, and it can be used
in some circumstances to "suggest" certain thread orderings in examples.
Yield is probably much more rarely used, since thread scheduling is
typically rather fair. I can imagine using it before doing something
that would cause a disk cache to be thrashed, or perhaps to tell the
scheduler that it's better to wait for a bit before resuming execution
in heavy usage situations.
--
Beware of bugs in the above code; I have only proved it correct, not
tried it. -- Donald E. Knuth