Why are SINGLE variables faster than INTEGER variables ?

[SMcNeill]

I get comparable times on this with all my variable types.  I certainly don't see a difference of three times the performance with SINGLE over LONG.

Code: (Select All)

T0 = Timer



For chiffreetudie = 2 To 14000

    premier = 1

    For diviseur = 2 To chiffreetudie - 1

        ' Print "chiffre etudie = "; chiffreetudie; "Diviseur = "; diviseur; chiffreetudie / diviseur

        If chiffreetudie / diviseur = Int(chiffreetudie / diviseur) Then

            premier = 0

        End If

    Next diviseur

    'If premier = 1 Then

    '    Print chiffreetudie;

    'End If

Next chiffreetudie



Color 12: Print: Print "Duration (SINGLE) : "; Timer - T0; " seconds."



T0 = Timer



For chiffreetudie = 2 To 14000

    premier = 1

    For diviseur = 2 To chiffreetudie - 1

        ' Print "chiffre etudie = "; chiffreetudie; "Diviseur = "; diviseur; chiffreetudie / diviseur

        If chiffreetudie / diviseur = chiffreetudie \ diviseur Then

            premier = 0

        End If

    Next diviseur

    'If premier = 1 Then

    '    Print chiffreetudie;

    'End If

Next chiffreetudie



Color 12: Print: Print "Duration (SINGLE, INT DIVISION) : "; Timer - T0; " seconds."









Dim premier As Long ' SINGLE faster than INTEGER !!! Why ?

Dim chiffreetudie As Long ' SINGLE faster than INTEGER !!! Why ?

Dim diviseur As Long ' SINGLE faster than INTEGER !!! Why ?



T0 = Timer



For chiffreetudie = 2 To 14000

    premier = 1

    For diviseur = 2 To chiffreetudie - 1

        ' Print "chiffre etudie = "; chiffreetudie; "Diviseur = "; diviseur; chiffreetudie / diviseur

        If chiffreetudie / diviseur = Int(chiffreetudie / diviseur) Then

            premier = 0

        End If

    Next diviseur

    'If premier = 1 Then

    '    Print chiffreetudie;

    'End If

Next chiffreetudie



Color 12: Print: Print "Duration (LONG) : "; Timer - T0; " seconds."



T0 = Timer



For chiffreetudie = 2 To 14000

    premier = 1

    For diviseur = 2 To chiffreetudie - 1

        ' Print "chiffre etudie = "; chiffreetudie; "Diviseur = "; diviseur; chiffreetudie / diviseur

        If chiffreetudie / diviseur = chiffreetudie \ diviseur Then

            premier = 0

        End If

    Next diviseur

    'If premier = 1 Then

    '    Print chiffreetudie;

    'End If

Next chiffreetudie



Color 12: Print: Print "Duration (LONG, INT DIVISION) : "; Timer - T0; " seconds."

Here's a quick test code though that will show a nice way to improve this and make it much quicker for you -- especially with integers.   Hint:  Swap out INT(x/y) for integer division with x \ y...

---

integer division is notoriously slow, if I am not mistaken, integer division promotes a 32-bit  dividend to 64-bit before division and likewise a 64-bit  dividend is promoted to 128-bit before division
[edit]
integer division could possibly be sped up significantly by using invariant integers, see https://gmplib.org/~tege/division-paper.pdf

Integer Division (the \ division) is much faster than taking the integer value of normal division, as shown above.

x \ y is faster than INT(x / y).   At least, it always has been for me on Windows with the math processors on my PCs and Laptops.  Perhaps Linux or Mac handles them differently somehow?