For Vs Foreach - Benchmark 2013

• Download ForVsForeach2.zip 

Update (23/02/2017)

There is another benchmark result published on 13 May 2016 at [C#: For Vs ForEach Vs While] which the benchmark tested with more data type and more details findings. You might want to have a read on it. The benchmark shows different times consumed for different data type.

Introduction   

I have seen lots of arguments and different points of view about which is better practice among For Loop and Foreach Loop. 

Year	Researcher	Article	.NET Based
2004	Chester Ragel	FOREACH Vs. FOR (C#) - CodeProject.com	.NET 1.1
2004	Codecutter	To foreach or not to foreach that is the question - blogs.msdn.com	.NET 1.1
2006	Dustin Campbell	Performance of foreach vs. List.ForEach - diditwith.net	.NET 2.0
2008	Adrian Vintu	Foreach Loop VS For Loop - adrianvintu.com	.NET 3.5
2013	steinkrauz	Once upon a time there was a difference between 'for' and 'foreach' - lj.rossia.org	.NET 4.0
2016	David Lozinski	C#: For Vs ForEach Vs While - cc.davelozinski.com	Not specified.

From the outcomes of the findings from the previous programmers, some of the conclusions of the researches were conflicting each other, and thus, this shows that the way .NET work with For Loop and Foreach Loop has changed from years to years. It seems that the development team of .NET Framework has improved and modified the workout logic of For Loop and Foreach throughout different version of milestone of .NET Framework releases.

After reading the valuable information from the articles, I have decided to do benchmark, to compare the performance between For Loop and Foreach Loop in figures. 

The Benchmark Result (2013)

Measured in miliseconds.  Default collection length: 30000000 . I try to increase the length, but receive exception of System.OutOfMemoryException. 

 

Data Type	Collection Type	Loop Type	Test 1	Test 2	Test 3	Average
int	int[]	For	88.0051	83.0047	83.0048	84.672
int	int[]	Foreach	83.0047	82.0047	81.0047	82.005
int	List<int>	For	89.0051	84.0048	83.0048	85.338
int	List<int>	Foreach	98.0056	98.0057	98.0056	98.006
int	ArrayList<int>	For	188.0107	182.0104	182.0104	184.011
int	ArrayList<int>	Foreach	445.0254	444.0254	445.0254	444.692
class	class[]	For	98.0056	92.0052	92.0053	94.005
class	class[]	Foreach	93.0053	93.0053	92.0052	92.672
class	List<class>	For	107.0061	107.0061	108.0062	107.339
class	List<class>	Foreach	136.0078	138.0078	137.0079	137.008
class	ArrayList<class>	For	195.0111	195.0111	196.0112	195.344
class	ArrayList<class>	Foreach	446.0255	443.0254	446.0255	445.025

Chart 

Conclusion

Speed of Collections

 

1. Array (Fastest)
2. List 
3. ArrayList (Slowest) 

 

Data Type - Operation 

Array

Almost no difference between For Loop and Foreach Loop. Foreach Loop seems to be a bit faster. 

List

For Loop is slightly faster than Foreach Loop

ArrayList

For Loop is about more than 2 times faster speed than Foreach Loop. 

Codes Used to Run the Test 

Declare Collections: 

static int[] intArray = null;
static List<int> intList = null;
static ArrayList intArrayList = null; 
static SampleClass[] scArray = null;
static List<SampleClass> scList = null;
static ArrayList scArrayList = null; 
static int LengthTest = 30000000; 

Initializing Collection: 

// int  
byte[] ba = new byte[LengthTest];
Random rd = new Random();
rd.NextBytes(ba);
intArray = new int[ba.Length];
for (int h = 0; h < ba.Length; h++)
{
    intArray[h] = ba[h];
} 
intList = new List<int>();
intList.AddRange(intArray);
intArrayList = new ArrayList(intArray); 

// class object 
DateTime scStart = DateTime.Now;
scArray = new SampleClass[LengthTest];
for (int i = 0; i < scArray.Length; i++)
    scArray[i] = new SampleClass();
scList = new List<SampleClass>(scArray);
scArrayList = new ArrayList(scArray); 

 

A StringBuilder to collect information:

StringBuilder sb = new StringBuilder(); 

Sample of For Loop Test: 

static void TestIntArrayFor()
{
    string section = "int[] For Loop Test - Length = " + intArray.Length; 
    List<TimeSpan> lstTimespan = new List<TimeSpan>();
    sb.AppendLine(section);
    for (int round = 0; round < Round; round++)
    {
        DateTime start = DateTime.Now;
        int total = 0;
        for (int i = 0; i < intArray.Length; i++)
        {
            total += intArray[i];
        }
        lstTimespan.Add(DateTime.Now - start);
        sb.AppendLine("Test " + (round + 1) + " : " + lstTimespan[round].TotalMilliseconds.ToString()); 
    }
    double ds = 0;
    for (int b = 0; b < lstTimespan.Count; b++)
    {
        ds += lstTimespan[b].TotalMilliseconds;
    }
    sb.AppendLine("Average: " + (ds / 3).ToString("0.###") + " miliseconds");
    sb.AppendLine();
} 

Sample of Foreach Loop Test 

static void TestClassArrayForeach()
{
    string section = "Class[] Foreach Loop Test - Length = " + scArray.Length;
    List<TimeSpan> lstTimespan = new List<TimeSpan>();
    sb.AppendLine(section);
    for (int round = 0; round < Round; round++)
    {
        DateTime start = DateTime.Now;
        long total = 0;
        foreach(SampleClass sc in scArray)
        {
            total += sc.Number;
        }
        lstTimespan.Add(DateTime.Now - start);
        sb.AppendLine("Test " + (round + 1) + " : " + lstTimespan[round].TotalMilliseconds.ToString()); 
    }
    double ds = 0;
    for (int b = 0; b < lstTimespan.Count; b++)
    {
        ds += lstTimespan[b].TotalMilliseconds;
    }
    sb.AppendLine("Average: " + (ds / 3).ToString("0.###") + " miliseconds"); 
}