Which function is faster Abs or IIf? - sql

Question

I ran the following test to determine the difference in efficiency between IIf and Abs:
Public Sub TestSpeed()
Dim i As Long
Dim res As Integer
Debug.Print "*** IIF ***"
Debug.Print Format(Now, "HH:mm:ss")
For i = 1 To 999999999
res = IIf(-1 = True, 1, 0)
Next
Debug.Print Format(Now, "HH:mm:ss")
Debug.Print "*** ABS **"
Debug.Print Format(Now, "HH:mm:ss")
For i = 1 To 999999999
res = Abs(-1)
Next
Debug.Print Format(Now, "HH:mm:ss")
End Sub
The results show that Abs is about 12 times faster:
TestSpeed
*** IIF ***
15:59:08
16:01:26
*** ABS **
16:01:26
16:01:37
Can anyone support this or prove that the contrary is true?
EDIT:
One situation in which one may need to decide between the two functions is for doing multiple counts based on criteria in an SQL query such as:
SELECT Sum(Abs(Colour = 'Yellow')) AS CountOfYellowItems, Sum(Abs(Votes>3) AS CountOfMoreThanThreeVotes FROM tblItems
versus
SELECT Sum(IIf(Colour = 'Yellow' ,1 ,0)) AS CountOfYellowItems, Sum(IIf(Votes > 3 ,1 ,0) AS CountOfMoreThanThreeVotes FROM tblItems

Answer 1

I ran a similar test that supports your findings:
Option Compare Database
Option Explicit
Public Sub SpeedTest()
Const LoopLimit = 99999999
Dim Tasked(LoopLimit) As Boolean, i As Long
Dim Total As Long, t0 As Single, Elapsed As Single
For i = 0 To LoopLimit
Tasked(i) = False
Next
Debug.Print "*** IIF ***"
Total = 0
t0 = Timer
For i = 0 To LoopLimit
Total = Total + IIf(Tasked(i) = True, 1, 0)
Next
Elapsed = Timer - t0
Debug.Print "Elapsed time: " & Format(Elapsed, "0.0") & " seconds."
Debug.Print "Average time: " & Format(Elapsed / (LoopLimit + 1) * 1000000000, "0") & " nanoseconds."
Debug.Print "*** ABS ***"
Total = 0
t0 = Timer
For i = 0 To LoopLimit
Total = Total + Abs(Tasked(i))
Next
Elapsed = Timer - t0
Debug.Print "Elapsed time: " & Format(Elapsed, "0.0") & " seconds."
Debug.Print "Average time: " & Format(Elapsed / (LoopLimit + 1) * 1000000000, "0") & " nanoseconds."
End Sub
resulting in
*** IIF ***
Elapsed time: 19.0 seconds.
Average time: 190 nanoseconds.
*** ABS ***
Elapsed time: 2.4 seconds.
Average time: 24 nanoseconds.
In terms of raw execution speed, Abs(BooleanValue) appears to be an order of magnitude faster than IIf(BooleanValue = True, 1, 0).
Whether or not that difference has a significant impact on the overall performance of the code in which the functions may be used depends very much on the context, as illustrated here.

Answer 2

I have had a look at this in SQL for comparison.
DECLARE #i As BIGINT = 1
DECLARE #res As INT
declare #v BIGINT = -1
Print '*** ABS **'
DECLARE #s2 datetime = GETDATE()
Print Format(#s2, 'HH:mm:ss')
SET #i = 1
WHILE #i < 9999999
begin
SET #res = Abs(#v)
SET #i = #i + 1
end
DECLARE #e2 datetime = GETDATE()
Print Format(#e2, 'HH:mm:ss')
Print DATEDIFF(MILLISECOND, #s2,#e2)
DECLARE #i As BIGINT = 1
DECLARE #res As INT
declare #v INT = -1
Print '*** IIF **'
DECLARE #s1 datetime = GETDATE()
Print Format(#s1, 'HH:mm:ss')
SET #i = 1
WHILE #i < 9999999
begin
SET #res = IIf(#v < 0 , #v*-1, #v)
SET #i = #i + 1
END
DECLARE #e1 datetime = GETDATE()
Print Format(#e1, 'HH:mm:ss')
Print DATEDIFF(MILLISECOND, #s1,#e1)
You can't run both statements together to get a fair comparison. I think there is almost no difference. One case where IIF is better is where
#v BIGINT = -2147483648 (or greater), as ABS would just fail with an overflow.