Thread Pools

import java.util.concurrent.Callable
import java.util.concurrent.Executors

long ts // timer
def pool = Executors.newFixedThreadPool(THREADS)
def defer = { c -> pool.submit(c as Callable) }

//PLAIN//////////////////////////////////////////

ts = (new Date().time)
doit = { n ->
  def left = { def slp = Math.random()*n*1000+500l as Long; Thread.sleep(slp);  println Thread.currentThread().name + '!!left!!'+slp }()
  def right = { def slp = Math.random()*n*1000+500l as Long; Thread.sleep(slp);  println Thread.currentThread().name + '!!right!!'+slp }()
}
(1..3).each{ n -> println "n=$n => ${doit(n)}" }
println ((new Date().time)-ts)

//POOLED//////////////////////////////////////////////

ts = (new Date().time)
THREADS = 3
fib = { n ->
  def left = defer{ def slp = Math.random()*n*1000+500l as Long; Thread.sleep(slp);  println Thread.currentThread().name + '!!left!!'+slp }
  def right = defer{ def slp = Math.random()*n*1000+500l as Long; Thread.sleep(slp);  println Thread.currentThread().name + '!!right!!'+slp }
}
(1..3).each{ n -> println "n=$n => ${fib(n)}" }
pool.shutdown()
while(!pool.isTerminated()) { Thread.sleep(100) }
println ((new Date().time)-ts)

//FIB//////////////////////////////////////////////////

println "Calculating Fibonacci sequence in parallel..."
CUTOFF = 12    // not worth parallelizing for small n
THREADS = 10
serialFib = { n -> (n < 2) ? n : serialFib(n-1) + serialFib(n-2) }
fib = { n ->
  if (n < CUTOFF) return serialFib(n)
  def left = defer{ println Thread.currentThread().name; fib(n-1) }
  def right = defer{ println Thread.currentThread().name; fib(n-2) }
  left.get() + right.get()
}

(11..16).each{ n -> println "n=$n => ${fib(n)}" }
pool.shutdown()