Here's my Histogram based FastSort function for bytes. Unlike normal Sort type algorithms, which require often many passes (the exact number depending on the exact arangement of numbers in the array) over a set of data, while swapping entries in the array, this one takes just 2 passes. The pass to creates the histogram from the input byte array, and the second one reads bytes out of the histogram into the output array. Unfortunately this won't work on Single and Double precision floating point values, as you can't have a histogram array with a fractional index (whole number indices only are allowed), it actually works great on integer data types. The one shown below is intended specifically with the Byte data type, but it should be fairly easy to modify it to work with Integer data type (though with the Long data type there would be a problem unless you limited the range, as it would take 16 gigabytes of ram, and so is not possible to implement in VB6, nor would it work even on most computers, as most computers don't have over 16GB of ram in them, as would be needed to hold both the Windows OS and the huge histogram).
Update:
I have discovered something very interesting. When used with small sized data sets (such as when sorting to find the median value of a 3x3 array of pixels), the byte-swapping Sort algorithm is actually faster than my histogram based FastSort algorithm.
Code:
Private Function FastSort(ByRef ArrayIn() As Byte) As Byte()
Dim ArrayOut() As Byte
Dim Histogram(255) As Long
Dim n As Long
Dim m As Long
Dim m2 As Long
ReDim ArrayOut(UBound(ArrayIn))
For n = 0 To UBound(ArrayIn)
Histogram(ArrayIn(n)) = Histogram(ArrayIn(n)) + 1
Next n
For n = 0 To 255
For m = 1 To Histogram(n)
ArrayOut(m2) = n
m2 = m2 + 1
Next m
Next n
FastSort = ArrayOut()
End FunctionUpdate:
I have discovered something very interesting. When used with small sized data sets (such as when sorting to find the median value of a 3x3 array of pixels), the byte-swapping Sort algorithm is actually faster than my histogram based FastSort algorithm.