Unexpected Results - Integer v. Double

[dbasnett]

I can never pass up a chance to test my code timer, so when I came across Jon Skeet's Blog about using For or For Each I couldn't resist. My results appear to be similar to his, but why is Double faster than Integer?

http://msmvps.com/blogs/jon_skeet/default.aspx

    03/29/09  08:47:15.847    CPU - 1.794GHz.   Stopwatch(HR) Freq. is 3,579,545
    x86 Family 6 Model 13 Stepping 6    Address width - 32   Memory - 2.0GB
    
    One - For Each
    Two - by Count
    Using Doubles
    Number of Test(NT) = 7    Iterations Per NT(IL) = 262,144
    Times given in ticks.  1 ms. = 10,000 ticks;  1,000 ms. = 1 second.
    
    Ticks / Loop     Fastest? One
    0.0193        	0.4078        	0.4348        	-0.0270
    NT Base IL    	One IL        	Two IL        	 Difference (One - Two)
    1   5,056         	106,621       	113,829       	-7,208
    2   5,056         	107,220       	114,569       	-7,349
    3   5,058         	106,818       	113,727       	-6,909
    4   5,089         	107,120       	114,493       	-7,373
    5   5,056         	106,421       	113,785       	-7,364
    6   5,056         	106,983       	113,752       	-6,769
    7   5,058         	107,225       	113,740       	-6,515
    
     Average
    5,061         	106,915       	113,985       	-7,070    (-0.707 ms./IL)
    
    03/29/09  08:47:16.328   RunMode = CTRL-F5   End Dewayne Relative Speed Test
    Source Code Follows
        '
        Const itms As Integer = 50
        Dim TestData() As Double
        Dim TestList As New List(Of Double)
        '
        Private Function TestCase1() As Boolean 'One
            'Test One Code Follows
            Dim sum As Double = 0
            For Each d As Double In TestData
                sum += d
            Next
            'End Test One Code
            Return True
        End Function
        '
        Private Function TestCase2() As Boolean 'Two
            'Test Two Code Follows
            Dim sum As Double = 0
            For i As Integer = 0 To itms - 1
                sum += TestData(i)
            Next
            'End Test Two Code
            Return True
        End Function
        '
        Private Sub _init()
            'Code needed to get the Test to run.  NOT part of the timing.
            'Only called once!!!
            TestList.Clear()
            For x As Integer = 1 To itms
                TestList.Add(Short.MaxValue) ' + 0.01)
            Next
            TestData = TestList.ToArray
        End Sub

    03/29/09  08:49:51.550    CPU - 1.794GHz.   Stopwatch(HR) Freq. is 3,579,545
    x86 Family 6 Model 13 Stepping 6    Address width - 32   Memory - 2.0GB
    
    One - For Each
    Two - by Count
    Using Integers
    Number of Test(NT) = 7    Iterations Per NT(IL) = 262,144
    Times given in ticks.  1 ms. = 10,000 ticks;  1,000 ms. = 1 second.
    
    Ticks / Loop     Fastest? One
    0.0194        	0.5785        	0.6057        	-0.0272
    NT Base IL    	One IL        	Two IL        	 Difference (One - Two)
    1   5,054         	151,674       	157,853       	-6,179
    2   5,059         	151,893       	157,718       	-5,825
    3   5,055         	151,448       	158,327       	-6,879
    4   5,058         	151,403       	157,754       	-6,351
    5   5,057         	151,319       	159,712       	-8,393
    6   5,057         	152,412       	162,178       	-9,766
    7   5,197         	151,321       	157,835       	-6,514
    
     Average
    5,076         	151,638       	158,768       	-7,130    (-0.713 ms./IL)
    
    03/29/09  08:49:52.232   RunMode = CTRL-F5   End Dewayne Relative Speed Test
    Source Code Follows
        '
        Const itms As Integer = 50
        Dim TestData() As Integer
        Dim TestList As New List(Of Integer)
        '
        Private Function TestCase1() As Boolean 'One
            'Test One Code Follows
            Dim sum As Integer = 0
            For Each d As Integer In TestData
                sum += d
            Next
            'End Test One Code
            Return True
        End Function
        '
        Private Function TestCase2() As Boolean 'Two
            'Test Two Code Follows
            Dim sum As Integer = 0
            For i As Integer = 0 To itms - 1
                sum += TestData(i)
            Next
            'End Test Two Code
            Return True
        End Function
        '
        Private Sub _init()
            'Code needed to get the Test to run.  NOT part of the timing.
            'Only called once!!!
            TestList.Clear()
            For x As Integer = 1 To itms
                TestList.Add(Short.MaxValue) ' + 0.01)
            Next
            TestData = TestList.ToArray
        End Sub

[dbasnett]

I fooled with this a lot yesterday, up until I had to watch the Missouri Tigers. I debated whether or not to post this because I was convinced I had missed something. If anyone wants a little more detail about how I conduct these test I will provide it.

One thing Jon Skeet and I disagree on is what he calls HoistLength, at least we do if my conversion of the code he provided is correct. So, based on his reputation, I must have missed something there.

[Shaggy Hiker]

It shouldn't have been faster, but I have found this before.

The first thing to ask, though, is whether or not you have the checks for integer overflow disabled. That check greatly impacts the performance of integer math. Still, even with the checks off, integer math in .NET is not as fast as it should be.

[dbasnett]

With the checked removed it is better.