From: Erik Veenstra <erikveen@...>
Date: 2008-04-19T03:20:47+09:00
Subject: Re: forkoff - parallel processing for ruby enumerables

Just a word of warning: The construction "Thread.new(i){|i|" is
useless, by definition. Just like "i=i" is useless too.

If i isn't defined outside the loop, you don't have to pas i to
the thread, so "Thread.new{" will do. However, if i is defined
outside the loop (which it isn't, in your code...),
"Thread.new(i){|i|" won't work (see below): It's better to use
"Thread.new(i1){|i2|" instead.

gegroet,
Erik V. - http://www.erikveen.dds.nl/

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 a       = (1..10).to_a
 a1      = a.map{|i|  Thread.new    {    sleep 0.01 ;  i }}.map{|t|
t.value}
 a2      = a.map{|i|  Thread.new(i) {|i| sleep 0.01 ;  i }}.map{|t|
t.value} # Will do.
 i       = nil
 a3      = a.map{|i|  Thread.new(i) {|i| sleep 0.01 ;  i }}.map{|t|
t.value} # Won't do!
 a4      = a.map{|i1| Thread.new(i1){|i2|sleep 0.01 ;  i2}}.map{|t|
t.value}

 p a1    # ==> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 p a2    # ==> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 p a3    # ==> [10, 10, 10, 10, 10, 10, 10, 10, 10, 10]
 p a4    # ==> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

----------------------------------------------------------------