CODEWITHSUNDEEP
scala
Jason Kim
Jason Kim

Reputation: 19061

Scala: benchmark methods' speed by time: Total runtime for methods

I have two ways of finding factorial using Scala. I want to find out how much slower non-tail recursive way is compared to tail-recursive way.

// factorial non-tail recursive
def fact1(n: Int): Int =
  if (n==0) 1
  else n*fact(n-1)       

// factorial tail recursive
def fact(n: Int): Int = {
  def loop(acc: Int, n:Int): Int =
    if (n==0) acc
    else loop(acc*n, n-1)
  loop(1, n)
}

// a1 = Time.now
fact1(100)
// a2 = Time.now
// a2-a1

// b1 = Time.now
fact(100)
// b2 = Time.now
// b2-b1

I just wrote up Ruby code for Time.now. Basically, how would you write Time.now like code in Scala?

Upvotes: 0

Views: 370

Answers (2)

axel22
axel22

Reputation: 32345

You may use the Scala wrapper method scala.compat.Platform.currentTime which forwards the call to System.currentTimeMillis.

Upvotes: 0

paradigmatic
paradigmatic

Reputation: 40461

You can use the java.lang.System class which provides methods for computing the current time:

  • currentTimeMillis for the current time in milliseconds
  • nanoTime for the current time in nanoseconds (which is recommended now).

However, writing good micro-benchmarks is very difficult and it is recommended to rely on a framework for that. Caliper is really good and there is a nice template for projects in scala.

Upvotes: 3

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