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For a game I'm making with AS3 I've tried to stick with using flat arrays as much as possible because I read somewhere that its faster than using multidimensional arrays. I just need to know if anyone knows or can point me to any place which discusses the speed difference (if there is any).
Using multidimensional arrays would make my coding much easier but if its slower than flat arrays I'm willing to persevere for the better execution time.
Any thoughts?
multi-dim arrays are slower, but not enough to make your life harder by not using them.
It's been years since I've got hung up about speed to the point that I spite myself and make my job harder to save a few ms here and there ( When just plotting image to the screen will take more of your cpu time than 95% of your running code anyway ).
Squize.
I agree with Squize, and since you are using AS3 it's a no-brainer: use multidim arrrays. The reason? AS3 is MUCH faster than previous versions. So the access time to the item in the array won't be a problem.
not sure, i'd say a flat array will always win because you only need one lookup. But i'd say the speed will be unnoticable. So go with whatever makes programming easier.Quote:
Originally Posted by Cortana
Arrays are faster than objects in AS3 as well.
EDIT - what those guys said.
Excellent! Thanks a lot guys :)
Hmm... I've often weighed the possibilities of using a single dimension array, but always dismissed it. My bug was targeting. How does someone target the nth element, n being prime? I would have thought finding the element would be an array[x*y] thing, but I'm starting to think it's more of an array[x*a+y]; 'a' being a set amount that the total number of elements (minus the max value of y) is divisible by. It could be that it's pretty early and I'm tired, but this has always been my beef with 1d arrays.
Yep, using code like array[x*loopIndex+somethingElse] to reference arrays is what I'm doing a lot and its sometimes a pain in the buttocks.
Multidimensional it is!
Yes, but not Dictionaries, sweet, sweet delicious Dictionaries.Quote:
Originally Posted by mr_malee
what are these dictionaries you speak of?
intriguing.
I tried to understand the point in new dictionary object, but it has so far escaped me. Maybe some day I will find out what they are good for.
Dictionaries are just like objects.
dict["string"] = "blah";
trace(dict["string"]);
and:
for each(var i:* in dict)
{
trace(i);
}
So a use for them, say we want to load resources and grab them fast, like some kind of linked list, we can use an array and search through from 0 -> n every time we look for something, or give each resource an 'id' and look it up in a Dictionary.
i'm reading the docs right now. It looks just like an object expect you can pass a reference as an id, and return a value by using the reference.
And you say these are the fastest way to store and retrieve data? testing time :)
it still looks like array wins. Compared with object and dictionary. I know this is a case where array can exist because they key is a number. So i suppose if you had to decide between object and dictionary then i'd go dictionary.
i'll try out a 2 dimensional array. With dictionary having keys as x+yCode:import flash.utils.Dictionary
import flash.utils.getTimer;
var dic:Dictionary = new Dictionary()
var arr:Array = []
var obj:Object = {}
//populate all objects with same data
var len:int = 900000
var i:int = len
var v:String;
while(--i >= 0){
dic[i] = "hello"
arr[i] = "hello"
obj[i] = "hello"
}
//run dictionary
var t:Number = getTimer()
for(i in dic){
v = dic[i]
}
trace(getTimer() - t)
//run array
i = len
t = getTimer()
while(--i >= 0){
v = arr[i]
}
trace(getTimer() - t)
//run object
t = getTimer()
for(i in obj){
v = obj[i]
}
trace(getTimer() - t)
edit - 2D array, dictionary wins when it uses a 1D loop, however Array is by far the fastest when using a 2D loop
Code:import flash.utils.Dictionary;
import flash.utils.getTimer;
var dic:Dictionary = new Dictionary();
var arr:Array = []
var obj:Object = {}
//populate all objects with same data
var lenX:int = 200
var lenY:int = 200
var px:int = 0
var py:int = 0
var i:int;
var v:Array;
for(x = 0; x<lenX; x++){ arr[x] = []
for(y = 0; y<lenY; y++){
dic[x+"-"+y] = ["hello", "goodbye", 0, 1, 2, true]
arr[x][y] = ["hello", "goodbye", 0, 1, 2, true]
obj[x+"-"+y] = ["hello", "goodbye", 0, 1, 2, true]
}}
//run dictionary
var t:Number = getTimer()
for(i in dic){
v = dic[i]
}
trace("dictionary var i in", getTimer() - t)
//run dictionary
t = getTimer()
for(x = 0; x<lenX; x++){
for(y = 0; y<lenY; y++){
v = dic[x+"-"+y]
}}
trace("dictionary x y", getTimer() - t)
//run array
t = getTimer()
for(x = 0; x<lenX; x++){
for(y = 0; y<lenY; y++){
v = arr[x][y]
}}
trace("array x y", getTimer() - t)
//run object
t = getTimer()
for(i in obj){
v = obj[i]
}
trace("object var i in", getTimer() - t)
//run object
t = getTimer()
for(x = 0; x<lenX; x++){
for(y = 0; y<lenY; y++){
v = obj[x+"-"+y]
}}
trace("object x y", getTimer() - t)
Ah nice to see, Dictionaries were faster in the Beta, I hadn't thought to retest.
Either way, they are handy in their own situations.
I think you should try a test with dict[Math.random()*10000] looped a few times though. Iterating is pretty standard.
Also Dictionaries have the insertion/removal cost of next to nothing:
dict[index] = null
vs
Array.splice();
AFIAK, a dictionary has the combined functionality of a numerical array and an associative array. That alone makes it very useful.
If we're going for speed, has anyone tried numerically-named variables:
I seem to remember they're pretty quick too :)
var1
var2
var3
this["var" + x] to retrieve data.
yeah, i think i will have some use for a dictionary array, but just for data that i need keys for.
is the dictionary something special for AS? or do other languages feature such things. Sometimes i wonder why certain structures have not been made accessible for us. Like the linked list in C
Never heard of a Dictionary struct.. interesting.
I'm curious of what you meant, malee.. linked lists are accessible to any programming language, to my knowledge.
You just have to create a Node class and a LinkedList class. And there you have a linked list. I find them very useful when I have a map/array full of empty slots.
Dictionary is an odd duck in AS3. I find it really interesting that it even supports weak references.
sorry, thought that C, C++ came with a native linked list array.Quote:
Originally Posted by AfternoonDelite
How about if you use a onedimensional-array, and save the "width" in another variable..
I actually made a test to compare them... http://www.straleks.com/flash/arraytest/PHP Code://Instead of this:
map1 = [[0,0,1],[0,1,0],[1,0,0]];
//this:
map2 = [0,0,1,0,1,0,1,0,0];
w = 3;
//how to access it:
trace(map1[0][2]); // 1
trace(map2[0*w+2]); // 1
With 10000 cycles i get that flat arrays are about 25 % faster than multidimensional.. Source is available as a link on the page. Could these test-results be reliable?
25% Eh? Probably just your computer. I'm using a turd pc at my fiance's house and I got:
PHP Code:Starting test... Please wait
Times cycled: 10000
Array1: 614
Array2: 626
%: 1.01954397394137
Starting test... Please wait
Times cycled: 10000
Array1: 611
Array2: 628
%: 1.0278232405892
Starting test... Please wait
Times cycled: 10000
Array1: 615
Array2: 622
%: 1.01138211382114
Hmm
Those results are a bit weird cos from that test it looks like the multidimensional array is faster. I think this is because it takes time for Flash to evaluate map2[0*w+j] for the flat array.
Also, I downloaded your Flash 9 source (which is AS2 by the way) and modified it for AS3 and it still looks like the multidimensional array was faster.
Even more argument to use multidimensional then...
Yes, in AS3 accessing multidimensional array is much faster then flat array with width.Quote:
Originally Posted by Cortana