相关疑难解决方法(0)

Scala的REPL是交互式测试某些代码片段的绝佳场所.最近,我一直在使用REPL进行一些性能比较,以重复执行操作并相对地测量挂钟时间.

这是我最近创建的一个例子,用于帮助回答SO问题[1] [2]:

// Figure out the perfomance difference between direct method invocation and reflection-based method.invoke

def invoke1[T,U](obj:Any, method:Method)(param:T):U = method.invoke(obj,Seq(param.asInstanceOf[java.lang.Object]):_*) match { 
    case x: java.lang.Object if x==null => null.asInstanceOf[U]
    case x => x.asInstanceOf[U]
}

def time[T](b: => T):(T, Long) = {
    val t0 = System.nanoTime()
    val res = b
    val t = System.nanoTime() - t0
    (res,t )
}

class Test {
  def op(l:Long): Long = (2 until math.sqrt(l).toInt).filter(x=>l%x==0).sum
}

val t0 = new Test

val method = classOf[Test].getMethods.find(_.getName=="op").get

def …