Comments on: Improving the Limit Function http://www.pixelwit.com/blog/2007/06/improving-the-limit-function/ Making Flash Go Fri, 03 Feb 2012 01:38:11 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Pixelwit http://www.pixelwit.com/blog/2007/06/improving-the-limit-function/comment-page-1/#comment-7848 Pixelwit Tue, 15 Jan 2008 02:50:12 +0000 http://www.pixelwit.com/blog/2007/06/04/improving-the-limit-function/#comment-7848 Hi Joga, although using an array provides an easy method to sort the limiters, I think the array notation (i.e. limits[0]) decreases performance. I ran a quick performance test and your code seemed about 85% slower than the code I provided. Flash has to look-up a variable twice with array notation, once to find "limits", and then another time to find index "0" within "limits". In contrast, a local variable like "num" only needs to be looked-up once. In AS1 and AS2 looking-up variables can be a fairly slow process, I'm unsure about AS3. Hi Joga, although using an array provides an easy method to sort the limiters, I think the array notation (i.e. limits[0]) decreases performance. I ran a quick performance test and your code seemed about 85% slower than the code I provided.

Flash has to look-up a variable twice with array notation, once to find “limits”, and then another time to find index “0″ within “limits”. In contrast, a local variable like “num” only needs to be looked-up once. In AS1 and AS2 looking-up variables can be a fairly slow process, I’m unsure about AS3.

]]> By: Joga Luce http://www.pixelwit.com/blog/2007/06/improving-the-limit-function/comment-page-1/#comment-7834 Joga Luce Mon, 14 Jan 2008 17:53:47 +0000 http://www.pixelwit.com/blog/2007/06/04/improving-the-limit-function/#comment-7834 what about simple array sorting. maybe i’m wrong, i’m still new to flash. <code lang="actionscript"> function limit(num:Number,limits:Array){ limits.sort(); return (num < limits[0]) ? limits[0] : (num > limits[1]) ? limits[1] : num; } function limitReadable(num:Number, limits:Array){ limits.sort(); if(num < limits[0]) { return limits[0]; } if(num > limits[1]) { return limits[1]; } return num; } </code> what about simple array sorting. maybe i’m wrong, i’m still new to flash.

function limit(num:Number,limits:Array){
    limits.sort();
    return (num &lt; limits[0]) ? limits[0] : (num &gt; limits[1]) ? limits[1] : num;
}

function limitReadable(num:Number, limits:Array){
    limits.sort();
    if(num &lt; limits[0]) {
        return limits[0];
    }
    if(num &gt; limits[1]) {
        return limits[1];
    }
    return num;
}
]]> By: shaun http://www.pixelwit.com/blog/2007/06/improving-the-limit-function/comment-page-1/#comment-186 shaun Tue, 05 Jun 2007 14:06:43 +0000 http://www.pixelwit.com/blog/2007/06/04/improving-the-limit-function/#comment-186 Ah! good to know :) In some languages it is more costly to have complicated "if" forking than simple variable declaration - has something to do with the processor being able to predict likely paths through the code - but that's obviously not the case with actionScript. Also, your "early out" returns probably help in a lot of cases :) Ah! good to know :) In some languages it is more costly to have complicated “if” forking than simple variable declaration – has something to do with the processor being able to predict likely paths through the code – but that’s obviously not the case with actionScript. Also, your “early out” returns probably help in a lot of cases :)

]]> By: Pixelwit http://www.pixelwit.com/blog/2007/06/improving-the-limit-function/comment-page-1/#comment-177 Pixelwit Mon, 04 Jun 2007 21:47:48 +0000 http://www.pixelwit.com/blog/2007/06/04/improving-the-limit-function/#comment-177 Hi Shaun, I originally went the same way as you did with your code, but I decided to use the approach listed above for performance reasons since I frequently use the code in loops which iterate through a large number of objects. The main thing that slows down the code you provided is the creation of the "tmp" variable, which in my tests was only a tiny bit slower, most notably when "hi" was less than "lo". Thanks for your suggestion, interest and perseverance. :D Hi Shaun,

I originally went the same way as you did with your code, but I decided to use the approach listed above for performance reasons since I frequently use the code in loops which iterate through a large number of objects.

The main thing that slows down the code you provided is the creation of the “tmp” variable, which in my tests was only a tiny bit slower, most notably when “hi” was less than “lo”.

Thanks for your suggestion, interest and perseverance. :D

]]> By: shaun http://www.pixelwit.com/blog/2007/06/improving-the-limit-function/comment-page-1/#comment-176 shaun Mon, 04 Jun 2007 20:55:16 +0000 http://www.pixelwit.com/blog/2007/06/04/improving-the-limit-function/#comment-176 How about switching hi and lo if they are in the wrong order? Like such: <code lang="actionscript"> function limit(num, lo, hi) { if (hi < lo) { var tmp = hi; hi = lo; lo = tmp; } if (num < lo) return lo; if (num > hi) return hi; return num; } </code> How about switching hi and lo if they are in the wrong order? Like such:

function limit(num, lo, hi) {
  if (hi &lt; lo) {
    var tmp = hi;
    hi = lo;
    lo = tmp;
  }
  if (num &lt; lo) return lo;
  if (num &gt; hi) return hi;
  return num;
}
]]>