[MacRuby-devel] [MacRuby] #597: Dispatch Queue async method inconsistent results

[MacRuby]

#597: Dispatch Queue async method inconsistent results
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 Reporter:  Knut.Olaf.Lien@…          |        Owner:  ernest.prabhakar@…        
     Type:  defect                    |       Status:  closed                    
 Priority:  blocker                   |    Milestone:                            
Component:  MacRuby                   |   Resolution:  invalid                   
 Keywords:  GCD async method          |  
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Comment(by lsansonetti@…):

 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/>