Created
December 18, 2011 06:03
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scala> def time[A](f: => A): A = { | |
| val s = System.nanoTime | |
| val x = f | |
| val e = System.nanoTime | |
| (((e - s) / 1000).toDouble / 1000000).println | |
| x | |
| } | |
time: [A](f: => A)A | |
scala> object Fib { | |
| def unapply(n: Long): Option[Long] = (n >= 2).option(n - 2) | |
| } | |
defined module Fib | |
scala> lazy val fib: Long => Long = { | |
| case 0 => 0 | |
| case 1 => 1 | |
| case Fib(n) => fib(n) + fib(n + 1) | |
| } | |
fib: Long => Long = <lazy> | |
scala> time(fib(40)) | |
4.055657 | |
res6: Long = 102334155 | |
scala> time(fib(43)) | |
16.81403 | |
res7: Long = 433494437 |
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scala> implicit lazy val m = immutableHashMapMemo[Long, Long] | |
m: scalaz.Memo[Long,Long] = <lazy> | |
scala> val memofib = m(fib) | |
memofib: Long => Long = <function1> | |
scala> val memofib = !fib | |
memofib: Long => Long = <function1> | |
scala> time(memofib(40)) | |
4.034974 | |
res8: Long = 102334155 | |
scala> time(memofib(40)) | |
2.8E-5 | |
res9: Long = 102334155 | |
scala> time(memofib(43)) | |
16.980203 | |
res10: Long = 433494437 | |
scala> time(memofib(43)) | |
2.5E-5 | |
res11: Long = 433494437 |
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scala> implicit lazy val m = mutableHashMapMemo[Long, Long] | |
m: scalaz.Memo[Long,Long] = <lazy> | |
scala> lazy val mfib: Long => Long = m { | |
| case 0 => 0 | |
| case 1 => 1 | |
| case Fib(n) => mfib(n) + mfib(n + 1) | |
| } | |
mfib: Long => Long = <lazy> | |
scala> time(mfib(43)) | |
0.002366 | |
res13: Long = 433494437 | |
scala> time(mfib(50)) | |
1.23E-4 | |
res14: Long = 12586269025 |
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scala> val optionMemo = memo[Int, Int] { f => | |
| var o = none[(Int, Int)] | |
| k => { | |
| o some { | |
| case (kk, vv) => (kk === k).fold(vv, f(k)) | |
| } none { | |
| val v = f(k) | |
| o = (k, v).some | |
| v | |
| } | |
| } | |
| } | |
optionMemo: scalaz.Memo[Int,Int] = scalaz.Memos$$anon$3@1dd8a94 | |
scala> val f = optionMemo { i => | |
| Thread.sleep(1000) | |
| i |+| 100 | |
| } | |
f: Int => Int = <function1> | |
scala> time(f(10)) | |
1.002767 | |
res44: Int = 110 | |
scala> time(f(10)) | |
0.001382 | |
res45: Int = 110 | |
scala> time(f(11)) | |
1.000204 | |
res46: Int = 111 |
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