class Rake::MultiTask


parallel using Ruby threads.
Same as a regular task, but the immediate prerequisites are done in
#########################################################################

def invoke_prerequisites(args, invocation_chain) 

def invoke_prerequisites(args, invocation_chain)
  threads = @prerequisites.collect { |p|
    Thread.new(p) { |r| application[r].invoke_with_call_chain(args, invocation_chain) }
  }
  threads.each { |t| t.join }
end