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In nearly every project you have the need to do some simple profiling. Scala makes this very easy and flexible.
Let's assume we load a potentially large XML file:
def loadDataFile(name:String) = ....
Now instead of adding a lot of timing code to your application we can simple do:
import Profiling._
val data=timed(printTime("loaded XML in ")){
loadDataFile(name)
}
Here is the code of that small utility:
/*
* Copyright (c) 2008-2009, Matthias Mann
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Matthias Mann nor the names of its contributors may
* be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
object Profiling {
def timed[T](report: Long=>Unit)(body: =>T) = {
val start = System.nanoTime
val r = body
report(System.nanoTime - start)
r
}
private val timeUnits = List("ns", "us", "ms", "s")
def formatTime(delta:Long) = {
def formatTime(v:Long, units:List[String], tail:List[String]):List[String] = {
def makeTail(what:Long) = (what + units.head) :: tail
if(!units.tail.isEmpty && v >= 1000)
formatTime(v / 1000, units.tail, makeTail(v % 1000))
else
makeTail(v)
}
formatTime(delta, timeUnits, Nil).mkString(" ")
}
def printTime(msg:String) = (delta:Long) => {
println(msg + formatTime(delta))
}
}
Have fun with Scala |
