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Performance comparison of using a List as opposed to an Array

, 17 Jun 2010
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Benchmark both List and string[].

Introduction

The objective of this article is to elucidate you, fellow developers, to really evaluate the need of using a generic List<T> instead of an old string[], since usually the cost is overlooked.

Using the Code

I've built a simple example to compare the performance for reading and writing to a List<string> and a string[]. Concerning the writing time in milliseconds, for 100000 randomly generated items, the string[] outperformed the List<string> by approximately 8ms.

//Write
const int size = 100000;
Stopwatch startList = new Stopwatch();
startList.Start();
List<string> listString = new List<string>(size);
for (int i = 0; i <= size; i++)
{
    string toAdd = Guid.NewGuid().ToString();
    listString.Add(toAdd);
}
startList.Stop();
TimeSpan durationList = startList.Elapsed;

Stopwatch startArray = new Stopwatch();
startArray.Start();
string[] arrayString = new string[size];
for (int i = 0; i < size; i++)
{
    string toAdd = Guid.NewGuid().ToString();
    arrayString[i] = toAdd;
}
startArray.Stop();
TimeSpan durationArray= startArray.Elapsed;

When reading, the string[] outperforms the List<string> by approximately 2.5 times faster!!

//Read
Stopwatch startListRead = new Stopwatch();
startListRead.Start();
for (int i = 0; i <= listString.Count - 1; i++)
{
    string str = listString[i];
}
startListRead.Stop();
TimeSpan durationListRead = startListRead.Elapsed;

Stopwatch startArrayRead = new Stopwatch();
startArrayRead.Start();
for (int i = 0; i <= arrayString.Length - 1; i++)
{
    string str = arrayString[i];
}
startArrayRead.Stop();
TimeSpan durationArrayRead = startArrayRead.Elapsed;

And you can still do this with LINQ to Objects with an array, as you do with your List<string>:

//Perform our LINQ query on an Array just like a List<T>
var result = from i in arrayString
         where i.StartsWith("a")
         select i;

Results:

benchmarkres.png

So, bottom line, you should consider if you really need the List<T> as opposed to an array because there are serious performance costs that will affect your application.

Points of Interest

Creating concerns on performance of instructions being used in your applications.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

ricrodrigues
Software Developer (Senior) Truphone
Portugal Portugal
No Biography provided
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Comments and Discussions

 
Questionlist<>.Count Kills Reading Performance PinmemberMountainGhost30-Aug-12 6:41 
GeneralMy vote of 5 PinmemberDan Randolph8-Jul-12 6:17 
GeneralRe: My vote of 5 PinmemberDan Randolph8-Jul-12 7:00 
GeneralMy vote of 1 Pinmemberkrishnabhargav16-Jun-10 13:50 
GeneralRe: My vote of 1 Pinmemberricrodrigues16-Jun-10 23:33 
AnswerAbout accuracy PinmemberNiklas Lindquist17-Jun-10 2:48 
GeneralRe: About accuracy Pinmemberricrodrigues17-Jun-10 3:21 
GeneralRe: About accuracy Pinmemberricrodrigues17-Jun-10 3:33 
Generalhad similar results ... BUt Pinmemberkrishnabhargav16-Jun-10 13:29 
GeneralRe: had similar results ... BUt Pinmemberricrodrigues16-Jun-10 23:33 
GeneralRe: had similar results ... BUt Pinmemberricrodrigues17-Jun-10 3:34 
GeneralMy vote of 1 PinmemberYaroslav Tatarenko16-Jun-10 10:26 
GeneralRe: My vote of 1 Pinmemberricrodrigues16-Jun-10 23:31 
GeneralRe: My vote of 1 Pinmemberricrodrigues17-Jun-10 3:36 
GeneralRe: My vote of 1 PinmemberYaroslav Tatarenko17-Jun-10 7:18 
GeneralRe: My vote of 1 Pinmemberricrodrigues17-Jun-10 7:29 
GeneralMy vote of 1 PinmemberJason McBurney16-Jun-10 6:17 
GeneralRe: My vote of 1 Pinmemberricrodrigues16-Jun-10 23:31 
GeneralRe: My vote of 1 Pinmemberricrodrigues17-Jun-10 3:35 
GeneralThoughts PinmvpPIEBALDconsult15-Jun-10 18:19 
GeneralRe: Thoughts Pinmemberricrodrigues15-Jun-10 22:28 
GeneralRe: Thoughts Pinmemberricrodrigues17-Jun-10 3:35 
GeneralRe: Thoughts PinmvpPIEBALDconsult17-Jun-10 14:38 
GeneralRe: Thoughts Pinmemberricrodrigues17-Jun-10 22:29 
GeneralRe: Thoughts PinmvpPIEBALDconsult18-Jun-10 3:38 

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