Question

I m using Math.ceil ( Math.abs (x ) within a loop.

Can anyone realize any optimization for this operation? (Bitwise or what?)

Answer 1

Math.abs don t 更加简单地上网 Javacast Core

case MathObjectImp::Abs:
result = ( arg < 0 || arg == -0) ? (-arg) : arg;

但是,面纱使用C面纱功能

 case MathObjectImp::Ceil:
    result = ::ceil(arg);

so testing on JSpref http://jsperf.com/math-ceil-vs-bitwise bitwise is faster
testing @orangedog s answer http://jsperf.com/math-ceil-vs-bitwise/2 Math.ceil is faster

So I guess your best choice is:

var n = Math.abs(x);
var f = (n << 0),
f = f == n ? f : f + 1;

Answer 2

<代码>x” 0 ? Math.ceil(-x) :Math.ceil(x)

http://jsperf.com/math-ceil-math-abs-x/6”rel=“nofollow”jsPerf page 。 Ignore the "some bitwisemente”bell;以上表述并不使用任何标签。

Answer 3

Javascript isn t a prepared Language such C, so bitwise operations that can work questions in such instruments, aren t so high in JS, as number are Deposit as 64 bitroting Point. 查阅 SO post。

即便如此,你在联合材料中撰写的内容将在一定程度上通过原始浏览器转化为本地的法典,而根据执行情况,这可能会更快或更慢。

自Math.ceil和Math.abs建立以来;我猜测它们重新优化,因此,我怀疑你能通过自己做一些trick,获得更好的业绩。

底线:三个东西阻碍你更快地做到这一点:

number representation in JS
fact that it s an interpreted language
functions you use are "native", so they should be fast enough on their own

Answer 4

parseInt(Math.abs(x)+ 1,在代谢时,其速度为30%左右

由于这一论点总是正面的,Math.ceil()的分支是不必要的。

Answer 5

这里,不需要做任何研究:

((x >= 0 ? x : -x) + 0.5) >> 0

Answer 6

两种最快的计算方法(现代浏览器的速率几乎相同):

function f (n) {
   return (~~n) + 1;
}

// or 

function f1 (n) {
   return (n | 0) + 1;
}

// some tests, ~~ operator seems to work identicaly on numbers:

( 3.3 | 0 ) === 3;   
( 3.8 | 0 ) === 3;   
( -3.3 | 0 ) === -3; 
( -3.8 | 0 ) === -3;

与<代码>Math.底(-3.3)=Math(-3.8)== -4

友情链接