Unexpected Results - Integer v. Double

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

Code:

---

    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

---

Code:

---

    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

---

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.

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.

With the checked removed it is better.