簡短的回答是:你不能得到充分的表現。或者至少我還沒有發現任何能夠提供全面表現的東西。 (並且我已經嘗試了這個用例,正好這個用例;我放棄並寫了一個代碼生成器來代替,特別是因爲你不能處理不同的矢量大小)
我很高興否則會顯示,但迄今爲止,我嘗試過的所有內容都有一小部分(30%)在運行時增加了很多(900%)。
編輯:這裏是一個測試,顯示我的意思。
object Specs {
def ptime[T](f: => T): T = {
val t0 = System.nanoTime
val ans = f
printf("Elapsed: %.3f s\n",(System.nanoTime-t0)*1e-9)
ans
}
def lots[T](n: Int, f: => T): T = if (n>1) { f; lots(n-1,f) } else f
sealed abstract class SpecNum[@specialized(Int,Double) T] {
def plus(a: T, b: T): T
}
implicit object SpecInt extends SpecNum[Int] {
def plus(a: Int, b: Int) = a + b
}
final class Vek[@specialized(Int,Double) T](val x: T, val y: T) {
def +(v: Vek[T])(implicit ev: SpecNum[T]) = new Vek[T](ev.plus(x,v.x), ev.plus(y,v.y))
}
final class Uek[@specialized(Int,Double) T](var x: T, var y: T) {
def +=(u: Uek[T])(implicit ev: SpecNum[T]) = { x = ev.plus(x,u.x); y = ev.plus(y,u.y); this }
}
final class Veq(val x: Int, val y: Int) {
def +(v: Veq) = new Veq(x + v.x, y + v.y)
}
final class Ueq(var x: Int, var y: Int) {
def +=(u: Ueq) = { x += u.x; y += u.y; this }
}
def main(args: Array[String]) {
for (i <- 1 to 6) {
ptime(lots(1000000,{val v = new Vek[Int](3,5); var u = new Vek[Int](0,0); var i=0; while (i<100) { u = (u+v); i += 1 }; u}))
ptime(lots(1000000,{val v = new Veq(3,5); var u = new Veq(0,0); var i=0; while (i<100) { u = (u+v); i += 1 }; u}))
ptime(lots(1000000,{val v = new Uek[Int](3,5); val u = new Uek[Int](0,0); var i=0; while (i<100) { u += v; i += 1 }; u}))
ptime(lots(1000000,{val v = new Ueq(3,5); val u = new Ueq(0,0); var i=0; while (i<100) { u += v; i += 1 }; u}))
}
}
}
和輸出:
Elapsed: 0.939 s
Elapsed: 0.535 s
Elapsed: 0.077 s
Elapsed: 0.075 s
Elapsed: 0.947 s
Elapsed: 0.352 s
Elapsed: 0.064 s
Elapsed: 0.063 s
Elapsed: 0.804 s
Elapsed: 0.360 s
Elapsed: 0.064 s
Elapsed: 0.062 s
Elapsed: 0.521 s <- Immutable specialized with custom numeric
Elapsed: 0.364 s <- Immutable primitive type
Elapsed: 0.065 s <- Mutable specialized with custom numeric
Elapsed: 0.065 s <- Mutable primitive type
...
你可能想看看這個問題:http://stackoverflow.com/questions/4436936/scala-compiler-not-recognizing-a-view-bound/4437336#4437336 – Madoc 2011-01-20 23:57:14