#597: Dispatch Queue async method inconsistent results
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Reporter: knut.olaf.l...@… | Owner: ernest.prabha...@…
Type: defect | Status: closed
Priority: blocker | Milestone:
Component: MacRuby | Resolution: invalid
Keywords: GCD async method |
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Comment(by lsansone...@…):
Ernie's diagnosis is wrong. The problem here is that the program is
accessing the result variable concurrently. Accesses must be synchronized
by using a serial queue.
The following should work (untested)
{{{
def fib(n=1)
if n < 3
1
else
fib(n-1) + fib(n-2)
end
end
q = Dispatch::Queue.concurrent
grp = Dispatch::Group.new
syncq = Dispatch::Queue.new('sync')
result = []
8.times do |index|
q.async(grp) do
res = fib(ARGV[0].to_i)
syncq.sync { result[index] = res }
end
end
}}}
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Ticket URL: <http://www.macruby.org/trac/ticket/597#comment:4>
MacRuby <http://macruby.org/>
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