src/Pure/General/timing.scala

support for completion within the formal context;
tuned signature;

/*  Title:      Pure/General/timing.scala
    Module:     PIDE
    Author:     Makarius

Basic support for time measurement.
*/

package isabelle


object Timing
{
  val zero = Timing(Time.zero, Time.zero, Time.zero)

  def timeit[A](message: String, enabled: Boolean = true)(e: => A) =
    if (enabled) {
      val start = System.currentTimeMillis()
      val result = Exn.capture(e)
      val stop = System.currentTimeMillis()

      val timing = Time.ms(stop - start)
      if (timing.is_relevant)
        System.err.println(
          (if (message == null || message.isEmpty) "" else message + ": ") +
            timing.message + " elapsed time")

      Exn.release(result)
    }
    else e
}

sealed case class Timing(elapsed: Time, cpu: Time, gc: Time)
{
  def is_relevant: Boolean = elapsed.is_relevant || cpu.is_relevant || gc.is_relevant

  def + (t: Timing): Timing = Timing(elapsed + t.elapsed, cpu + t.cpu, gc + t.gc)

  def message: String =
    elapsed.message + " elapsed time, " + cpu.message + " cpu time, " + gc.message + " GC time"

  override def toString = message
}